key: cord-0727053-q25ipbdn authors: nan title: Abstracts of Original Contributions ASNC2021 The 26th Annual Scientific Session of the American Society of Nuclear Cardiology date: 2021-09-13 journal: J Nucl Cardiol DOI: 10.1007/s12350-021-02760-1 sha: a6362d99cde6f4d3c04bc809c0d2ad68e6eaefd9 doc_id: 727053 cord_uid: q25ipbdn nan Introduction: Cardiac involvement can be the first manifestation of sarcoidosis even in patients with systemic disease. Positron emission tomography (PET) imaging is an important diagnostic tool as it is able to detect active disease but is also useful in guiding therapy by detecting non-responsiveness or relapse. With the absence of randomized trials, first-line treatment with corticosteroids has been recommended by most experts during the past 50 years, but it is unknown if all patients should be treated nor for how long. We aimed to evaluate the incidence of relapse and patient characteristics associated with relapse after stopping initial therapy with steroids in patients with cardiac sarcoidosis (CS). Methods: Consecutive newly diagnosed, treatment naive patients with clinically manifest cardiac sarcoidosis were prospectively recruited. All patients were treated with 0.5 mgÁkg prednisone up to a maximum dose of 40mg OD. All patients had a follow-up PET scan after 3-6 months of therapy (FU PET1). Patients were then classified as responders or non-responders. In the responders, the prednisone was then weaned over 6 months and stopped. Three months after stopping, the PET was repeated to look for disease relapse (FU PET2). Evaluation with PET/CT included whole-body and dedicated cardiac imaging for the presence of extra-cardiac sarcoidosis using 18F-FDG, and myocardial perfusion at rest using 82Rb or 13N-ammonia to evaluate perfusion and LV function. Parameters evaluated included 18F-FDG distribution pattern in the myocardium (focal or focal on diffuse), LV SUVmax, LV SUVmean, RV uptake and summed rest score (SRS). Results: Twenty patients were included and 19/20 were responders. Of these 14/19 relapsed after prednisone was stopped. There was no significant difference between age at presentation and patient's sex among the two groups. Non-relapser patients had steroids for a longer time compared to the relapsers (529 ± 184 days vs 393 ± 110 days, P = 0.03, respectively). Focal myocardial uptake was the predominant pattern of 18F-FDG distribution both at baseline and after disease relapse. Twenty percent of the non-relapsers had RV uptake at presentation compared to 42% of the patients who had a relapse. Comparing the non-relapse and the relapse groups, SUV max was (mean ± SD): 11.1 ± 7.7 and 8.9 ± 0.2 (P = 0.2); 3.0 ± 1.1 and 3.7 ± 1.3 (P = 0.15) and 2.9 ± 1.0 and 7.8 ± 3.7 (P = 0.004) at baseline, FU PET 1 and FU PET2, respectively. Conclusion: Therapy guided by serial PET scanning can identify a subset of patients with clinically manifest cardiac sarcoidosis who do not require chronic therapy. DEEP LEARNING FOR THE DETECTION OF ATTR CAR-DIAC AMYLOIDOSIS ON CARDIAC SCINTIGRAPHY IMAGING R. M. Wehbe*, 1 S. Dutta, 1 S. Barutcu, 1 F. S. Ahmad, 1 J. D. Thomas, 1 P. M. McCarthy, 1 P. Kansal, 1 T. A. Holly, 2 A. K. Katsaggelos, 1 S. J. Shah 1 ; 1 Northwestern University, Chicago, IL, of Calgary, Calgary, AB, Canada, 3 Department of Imaging, Medicine, and Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA Introduction: 99m Tc-pyrophosphate (PYP) scintigraphy is a highly sensitive and specific non-invasive method to diagnose transthyretin cardiac amyloidosis (ATTR-CM). However, the correlation between abnormal myocardial PYP activities with disease burden has not been well described. Cardiovascular magnetic resonance (CMR) provides robust quantitative evaluation of disease burden and its impact on myocardial deformation. We performed a retrospective study to examine the relationship between PYP and CMR quantitative parameters in ATTR-CM patients. Methods: Consecutive patients (N = 36) who underwent clinical PYP (imaged with GE NM Discovery 670) and CMR imaging diagnosed with ATTR-CM were included. PYP activity was quantified in myocardial segments according to the 17-segment model from SPECT images using dedicated research software, normalized to background activity. Native myocardial T1 (N = 20), extracellular volume (ECV, N = 8) were assessed in patients imaged with a 3T CMR scanner (Prisma or Skyra, Siemens Healthineers, Erlangen, Germany). 3D CMR strain analysis was also available in a subset (N = 25). We assessed the correlations between PYP uptake and CMR quantitative parameters. Results: The mean age was 70.4 ± 1.4 years. There were no significant correlations between segmental or overall normalized radiotracer counts and left ventricular ejection fraction (LVEF) or left ventricular mass (P[ 0.1 for all). There was significant correlation between normalized radiotracer counts with native myocardial T1 ( Figure) and ECV (P \ 0.05 for all). Mean radiotracer counts from the mid-segments correlated with longitudinal, circumferential, and radial strain (P \ 0.05 for all). Conclusions: Quantitative PYP measures correlate with CMR markers of disease burden. While there was no correlation with LVEF, there was correlation with measures of myocardial deformation. Quantitative PYP imaging may potentially be a useful marker of disease burden in ATTR-CM. HIGH PREVALENCE OF MICROVASCULAR DYSFUNC-TION IN CARDIAC ATTR AMYLOIDOSIS: A CZT SPECT STUDY R. A. Nieves*, 1 J. Dietz, 2 K. Hynal, 2 J. Ibrahim, 1 P. Soman 1 ; 1 University of Pittsburgh Medical Center, Pittsburgh, PA, 2 UPMC Cardiovascular Institute, Pittsburgh, PA Introduction: Cardiac ATTR amyloidosis (CA) is a disorder characterized by amyloid fibril infiltration of the myocardial extracellular space. A positron emission tomography study has suggested that microvascular dysfunction maybe prevalent in CA. Solid state SPECT myocardial perfusion imaging (MPI) can measure myocardial blood flow (MBF). We evaluated MBF in CA patients using a CZT SPECT system. Methods: Patients with ATTR CA who underwent stress MPI were included. Regadenoson stress, and Tc-99m sestamibi (MIBI) injection were performed with the patient under the camera. The protocol consists of 9mCi and 30mCi of MIBI in 2 ml saline for the rest and stress studies, respectively, with the tracer injection performed 50 s after regadenoson stress using an automated injector, followed by a 40 mL saline flush. Data acquired in list mode were processed on the Cedars platform. Rate pressure product (RRP) and residual subtraction corrections were applied. Results: Fourteen patients with available SPECT flow were included with average age of 75.8 years, 81.2% male, LVEF 48% ± 14.6 and LV septal thickness 1.68 cm ± 0.41. MPI did not show reversible perfusion defects in any patient. RRP corrected rest flow ranged from 0.27 to 1.04 mlÁgmÁmin (0.58 ±0.26, median: 0.58). Peak stress flow (PSR) ranged from 0.63 to 2.6 mlÁgmÁmin (1.38 ± 0.54, median: 1.45) with 13 (92%) patients having abnormal PSR (\ 2 mlÁgmÁmin) indicative of microvascular disease. All patients showed a vasodilator response, with MFR ranging from 1.89 to 4.32 (2.76 ± 0.86, median: 2.47). Conclusions: Microvascular disease as determined by SPECT MBF quantification is prevalent in cardiac ATTR amyloidosis. Its mechanistic and therapeutic implications should be explored. TREATMENT RESPONSE AND ADVERSE CARDIOVASCU-LAR EVENTS IN PATIENTS WITH BIOPSY-PROVEN VERSUS NON-BIOPSY PROVEN SARCOIDOSIS C. Rojulpote*, 1 A. Bhattaru, 1 P. Karambelkar, 1 H. Lee, 2 V. Patel, 1 J. Rodriguez, 1 P. E. Bravo 1 ; 1 University of Pennsylvania, Philadelphia, PA, 2 Department of Radiology, University of Pennsylvania, Philadelphia, PA Introduction: Patients with suspected cardiac sarcoidosis (CS) undergo FDG-PET imaging to assess disease activity. However, there are a paucity of data in the understanding of treatment response and major adverse cardiovascular events (MACE) amongst individuals with and without biopsy-proven disease. Methods: We identified 83 patients with suspected CS (53 ± 1.8 years, 71% males, 69% white) who had evidence of myocardial inflammation at baseline, were treatment naïve, and underwent repeat PET imaging after treatment initiation. Our cohort was divided into three groups as follows: Group (1) biopsy-proven sarcoidosis (N = 51); Group (2) non-biopsyproven sarcoidosis with extra-cardiac inflammation at baseline (N = 18); Group (3) non-biopsy-proven sarcoidosis without extra-cardiac inflammation (N = 14). Follow-up PET scans were reported as complete myocardial suppression (CMS), partial myocardial suppression (PMS), or no suppression (NS). Treatment response was defined as CMS/PMS. Patients were also followed for the occurrence of MACE defined as sustained ventricular tachycardia/ventricular fibrillation (VT/VF), heart failure (HF) admission, and death with Cox regressions compared to Group 1 as the reference. Results: Biopsy-proven patients with suspected CS were most likely to achieve suppression after treatment when compared to both non-biopsyproven suspected CS with extracardiac features and isolated CS (80.4% vs 61.1% vs 50%, P = 0.048). Risk for MACE was not significantly different between the three groups (Hazardgroup 2 1.9; Hazardgroup 3 1.7; P = 0.11, Figure 1 ). However, there was a trend for better outcomes amongst biopsy-confirmed patients. Conclusion: A difference in myocardial FDG suppression rates was noted in biopsy-proven suspected CS patients in comparison to nonbiopsy-proven patients, irrespective of prednisone dose. Moreover, isolated CS patients had inferior suppression rates in comparison to the remaining cohort. SPECT/CT QUANTIFICATION OF 99MTC-PYP UPTAKE TO ASSESS TAFAMIDIS TREATMENT RESPONSE IN ATTR CARDIAC AMYLOIDOSIS C. Godoy Rivas, 1 M. Elsadany, 2 S. Arora, 1 A. Jaiswal, 1 A. Weissler-Snir, 1 W. Duvall* 1 ; 1 Hartford Hospital, Hartford, CT, 2 Cardiology department, Hartford Hospital, Hartford, CT Background: Tc-99m-PYP is commonly used to diagnose transthyretin (ATTR) cardiac amyloidosis employing only limited quantification with a visual score and a heart to contralateral lung ratio. SPECT/CT acquisition and analysis with dedicated software can provide volumetric assessment and quantification of cardiac tracer uptake. While therapy for ATTR cardiac amyloid is available with tafamidis, there are no data regarding the longitudinal assessment of 99mTc-PYP imaging findings to determine if treatment with tafamidis results in any change in quantitative measures of tracer uptake. Methods: A prospective, single-center, study of patients with ATTR cardiac amyloid being treated with tafamidis who had baseline and follow-up 99mTc-PYP studies. SPECT/CT quantification software was used to quantify heart, lung, and bone tracer uptake and generate standardized uptake values (SUVs). Comparison of baseline (before treatment) total SUVs, mean SUV value, percentage of the injected dose, mean SUV of heart to mean SUV of bone ratio, and to mean SUV of right lung ratio was made to the values obtained at follow-up. Measurements were obtained from the whole heart and the isolated left ventricle by 2 physicians and the results averaged. Results: Seventeen patients were analyzed with a mean age 75.6 ± 8.7, 82% were males, and a mean length of tafamidis therapy at repeat imaging of 9.8 ± 3.7 months. At follow-up, there was an average change in left ventricular total SUV counts of -7.9 ± 18.9%, in the mean SUV value of -0.7 ± 19.9% and in the percentage of injected dose of -8.4 ± 18.2%. Less pronounced changes were seen in the whole heart measurements. Heart to bone and heart to lung ratios showed a mixed response to therapy. Detailed results are provided in the table. Conclusion: The quantitative SUV measurements showed mild, although mixed improvement with tafamidis treatment. The length of time on treatment was relatively short, and continued assessment is warranted. This new technique offers a potential method for following tafamidis therapy and assessing the cardiac amyloid burden. SERIAL QUANTITATIVE 99MTC PYROPHOSPHATE IMAG-ING IN TRANSTHYRETIN AMYLOID CARDIOMYOPATHY PATIENTS TREATED WITH TAFAMIDIS S. Gill*, 1 P. Chandrashekar, 2 S. Warner, 1 L. Al-Rashdan, 1 Y. Burton, 1 A. Masri 1 ; 1 Oregon Health & Science University, Portland, OR, 2 Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR Introduction: Our group recently evaluated 2D LV myocardium to descending aorta mean counts ratio (2D TBR) as a quantitative method for myocardial 99mTc-PYP tracer uptake on SPECT imaging. It is unknown if tafamidis use affects PYP uptake. In this report, we describe the longitudinal change of 2D TBR in patients with transthyretin amyloid cardiomyopathy (ATTR-CM) on tafamidis as compared to controls. Methods: Six patients with known ATTR-CM on tafamidis therapy and 4 controls who each underwent two serial PYP SPECT scans were included. PYP uptake was quantified using 2D TBR and change in uptake was compared using Mann-Whitney U test. Results: Six ATTR-CM patients (100% male, 100% wtATTR; mean age 72 ± 3.4 years) received tafamidis therapy for a median of 1.2 (range 0.6-2.2) years before the second PYP scan. Five were ESC Stage 1 (other ESC Stage 3), and 50% were on diuretic therapy. Controls were 75% female (all were ATTR variant carriers undergoing screening for ATTR-CM), mean age of 53 ± 9.6 years at first PYP scan with mean septum thickness of 9.2 ± 2.7 mm. Their 2nd PYP scan was performed a median of 2.1 years later. PYP quantification was not significantly different between two consecutive scans among ATTR-CM patients on tafamidis (Fig 1) . All PYPs among ATTR-CM demonstrated Perugini Grade 3 uptake, with only a single scan changing from Grade 3 to 2. Conclusions: Use of tafamidis in ATTR-CM was associated with stable 99mTc PYP uptake on SPECT imaging without evidence of regression. Larger studies are needed to confirm these findings and investigate if transthyretin silencers affect quantitative 99mTc PYP myocardial uptake. A PRACTICAL 99M TC PYROPHOSPHATE QUANTIFICATION METHOD WITH SEVERITY OF DISEASE AND ECHOCARDIOGRAPHIC FEATURES OF TRANSTHYRETIN AMYLOID CARDIOMYOPATHY P. Chandrashekar*, S. Gill, S. Warner, L. Al-Rashdan, Y. Burton, A. Masri; Oregon Health & Science University, Portland, OR Introduction: There are no current accepted methods for PYP quantification of SPECT imaging. It is unclear if the degree of 99m Tc-PYP uptake on SPECT imaging correlates with the severity of disease or echo characteristics. We investigated the correlation of two methods of SPECT imaging quantification with clinical and echocardiographic markers of severity disease. Methods: Approach to quantifying PYP uptake in 30 patients with ATTR-CM is summarized in Figure 1 . We calculated the correlation with clinical and echocardiographic variables using Pearson's or Spearman's correlation coefficient as appropriate. Results: Clinical markers of severity of ATTR-CM (NYHA class, NAC ATTR Stage, and NT-proBNP) were not found to significantly correlate with quantified PYP uptake using the 2 different TBR methods (Table 1) . There was a weak negative correlation between 2DTBR-LV-DAo with left atrial volume index (r = -42; P = 0.02) as well as stroke volume index (r = -0.37; P = 0.05). Conclusions: In this pilot study, quantification of PYP uptake on SPECT was not found to strongly correlate with most clinical or echo variables in ATTR-CM. Larger studies are warranted to further investigate this as well as estimate correlation with clinical outcomes. Introduction: Most common types of cardiac amyloidosis (CA) are light chain amyloidosis (AL) and transthyretin amyloidosis (ATTR). Differentiation between AL CA and ATTR CA is of high therapeutic and prognostic importance. An algorithm of noninvasive diagnosis of ATTR CA, based on bone scintigraphy (SCINT), has been proposed (Gillmore's algorithm) (Gillmore et al, Circulation 2016).[Aim:\/b[To describe the exploitation and evaluate the utility of [ 99m Tc]Tc-DPD (DPD) SCINT in the differential diagnosis of cardiomyopaties in patients (pts) with a suspicion of CA in a single cardiac center. Methods: During 2.5 years since the introduction of DPD SCINT for routine diagnostics (Aug 2018) in our cardiac center, the test was performed in 100 pts (69M,31F) with a cardiomyopathy and with a suspicion of CA based on the clinics and ECHO and/or CMR. Wholebody, chest planar, and chest SPECT (if planar was positive) imaging was performed 3 hours after DPD injection. Semi-quantitative visual grading of myocardial DPD uptake by comparison to bone (rib) uptake was performed according to four-grade Perugini scale (grade 0-no uptake, grade 3-uptake grater than rib uptake with mild/absent rib uptake). Images were assessed by 2 independent observers experienced in nuclear medicine and in case of discrepancy the result was established by consensus. In all the points, the assay of a monoclonal protein in blood and urine (MPb/u) was performed. Extended diagnostics (DIAG-EXT) included histology and hematological examination. Results: Cardiac uptake of DPD was observed in 26 pts (26%): grade 3in 22 pts, grade 2 -in 2 pts, and grade 1 -in 2 pts. The inter-observer variability was 0% in cases of grade 0 and grade 3 (agreement of 100%). In cases of grade 1 or 2, the result was established by consensus. In 14 of 24 pts with grade 2 or 3 ('high') DPD cardiac uptake and no evidence of MPb/u, ATTR was diagnosed according to Gillmore's algorithm. On the basis of DIAG-EXT, (a) in all the remaining 10 pts with grade 2 or 3, ATTR was recognized, (b) in both pts with grade 1, AL was recognized, (c) among 73 pts without DPD cardiac uptake, no ATTR was recognized. Altogether, ATTR was diagnosed in all the 24 pts with grade 2 or 3 and ATTR was not diagnosed in any of the 76 pts with grade 0 or 1. Conclusions: DPD SCINT is a method easy in terms of acquisition and highly reproducible in terms of image interpretation for CA. In 58% of pts with ATTR CA, the result of SCINT (high DPD cardiac uptake) in conjunction with lack of MPb/u allowed to make a diagnosis of ATTR CA without additional diagnostics, on the basis of Gillmore's algorithm. However, as our population of pts referred for an examination for CA consisted of 24% of pts with ATTR CA, it concerned only 14% of the whole population studied. Methods: Consecutive patients referred for PYP cardiac scintigraphy at a single center (10/2018-10/2020) were identified. Data on patient demographics, baseline characteristics, PYP scan interpretation, subsequent utilization of cardiac imaging studies, heart failure hospitalizations, and death were retrospectively collected through review of electronic medical records. Scans were interpreted as ''strongly suggestive,'' ''equivocal,'' or ''non-suggestive'' based on combined input from semi-quantitative (Perugini Grade) and quantitative-expressed as heart to contralateral lung ratio (H/L)-myocardial uptake, according to published guidelines. Results: A total of 149 unique patients underwent PYP imaging (mean age 68.4 ± 12.3 years; 52.3% women). SPECT was used in 35.6% of the studies and SPECT/CT in 63.1%. Overall, 40 (26.8%) patients were deemed to have ''strongly suggestive'' scans, 77 (51.7%) had ''equivocal scans, while the rest were deemed to have ''non-suggestive'' studies. Conclusion: In this single-center experience, half of the patients referred for cardiac amyloidosis screening were found to have equivocal PYP studies. This finding was associated high rates of downstream testing but no increase in subsequent cardiac amyloidosis diagnosis, heart failure hospitalization, or death. Introduction: Display the use of pyrophosphate ( 99m Tc-PYP) scintigraphy in patients with suspected cardiac amyloidosis. Cardiac amyloidosis can be divided into two main groups, the first being the light chain (AL) and the second transthyretin (ATTR), with completely different prognoses and treatments. Methods: Retrospective analysis of consecutive exams between October 2017 and March 2021 with 99m Tc-PYP scintigraphy. The diagnostic criteria included visual analysis (grade 0 -without myocardial uptake / grade 1 -myocardium uptake less than the rib uptake/ grade 2 -myocardium uptake equal to the rib uptake / grade 3 -myocardium uptake greater than the rib with reduced or absent rib uptake), analysis of the heart to contralateral lung ratio at 1 hour (H/CL) and SPECT-CT images. Suggestive studies for ATTR amyloidosis were those that had grade 2 or 3, H/CL ratio[ 1.5 and that in SPECT-CT with myocardium uptake. Results: A total of 43 scintigraphies were performed the studied period. There were 11 studies performed from January to March 2021 versus 10 in 2020 and 13 in 2019. There were 15 women and 28 men (62.74% male) with an average age of 77.8 ± 12 years. Scintigraphic criteria for ATTR amyloidosis were met in 19 patients (44.18%) with a predominance of males, with only 2 women (17 vs 2, P = 0.002). The comparison of visual analysis and H/CL ratio showed good correlation between the methods, grades 0 and 1 showed H/CL ratio values of 1.13 and 1.10 respectively, and grades 2/3 showed average H/CL ratio CL of 1.68 (P\ 0.001). Of the total of 43, in 2 cases, the SPECT-CT changed the interpretation of the final report. In one patient with grade 2 uptake, the SPECT-CT showed blood-pool uptake and in the second patient with costochondritis SPECT-CT images confirmed myocardial uptake. Conclusions: The use of 99m Tc-PYP scintigraphy for cardiac amyloidosis is crucial, it allows to differentiate AL and ATTR amyloidosis and can be a substitute for endomyocardial biopsy in those patients who have suspected echocardiogram and/or Magnetic resonance imaging and also have the AL amyloidosis excluded. The assess of monoclonal protein is of great importance for the correct interpretation of the 99m Tc-PYP scintigraphy and to avoid imaging pitfalls. Scintigraphy is a simple, inexpensive, reproducible exam that can reduce costs and morbidity for patients compared to endomyocardial biopsy. SUNY@Buffalo, Buffalo, NY, 2 Michael E. Merhige M.D., L.L.C., Tonawanda, NY, 3 ECP of Western New York, Amherst, NY Introduction: Noninvasive augmentation of diastolic blood pressure with external counterpulsation (ECP) has been shown to improve collateral flow index in man. We sought to measure coronary collateral flow capacity (CCFC) noninvasively, in patients with chronic total coronary occlusion (CTO), treated with ECP using PET myocardial perfusion imaging (MPI). We hypothesized that flow into the ischemic bed measured with vasodilator stress (DIP), which reduces supply side pressure causing coronary steal, would improve with dobutamine stress (DBT) which maintains supply-side pressure, identifying the presence and adequacy of collateral circulation. Methods: Seven patients with CTO, treated with 35 one-hour sessions of ECP, were studied with both DIP and DOB stress PET MPI. Absolute flows and coronary flow capacity (CFC), which integrates absolute rest and stress flow with coronary flow reserve on a per pixel basis, were measured objectively with FDA approved HeartSee software. Results: The figure shows CFC in the same patient with CTO of both the right and LAD coronary arteries after ECP therapy, imaged with DIP (top row) and DBT (second row). Both global and regional CFC into the ischemic bed, improved significantly during demand ischemic stress compared to vasodilator stress (KS = 0.93; P \ 0.001), identifying successful collaterogenesis. All 7 patients demonstrated a decrease in the size of the ischemic zone at risk, defined as moderate or severely reduced CFC, when CFC with DIP was compared with DOB: 28% LV mass vs 5%; P \ 0.02. Absolute stress flow into the ischemic zone (lowest myocardial quadrant) improved significantly in ECP-treated patients during demand ischemia compared with vasodilator stress (1.9 vs 1 mlÁminÁg; P \ 0.02). One of two patients who did not improve global CFC significantly, despite ECP treatment, underwent coronary arteriography demonstrating a new flow limiting stenosis in the supply-side vessel, which was successfully stented. Conclusion: Quantitative PETMPI identifies coronary collateral flow capacity in patients with CTO, treated with ECP. Cardiology, St. Luke's' Mid America Heart Institute, Kansas City, MO Introduction: Relative perfusion assessment with MPI often underestimates the extent of ischemia in patients with balanced ischemia from high-risk CAD. Non-perfusion high-risk markers on PET such as reduced myocardial blood flow reserve (MBFR), LVEF, LVEF reserve (LVEF-R), and transient ischemic dilation (TID) contribute to increased sensitivity and diagnostic accuracy of PET. We aimed to study the relative contribution of perfusion and non-perfusion high-risk markers on PET in diagnosis of high-risk CAD. Methods: Out of 1282 patients who underwent coronary angiogram within 6 months of Rb-82 PET MPI between 2010 and 2016, we included patients with significant left main (C 50% stenosis, LM) and multi-vessel CAD (C 2 epicardial stenosis C 70%, MVD). Rates of LM and MVD were estimated among patients with normal (0%), mild (1-10%) and moderate-severely abnormal ([ 10%) perfusion. For patients with high-risk CAD and normal perfusion, prevalence of non-perfusion high-risk markers on PET were estimated. Results: Significant LM stenosis was present in 91 (7%) and MVD in 478 (37%). Overall, 82% had [10% perfusion defect, 28% had transient ischemic dilation, 32% had LVEF \ 50%, 48% had LVEF-R\ 0%, 69% had MBFR \ 2 and 87% had stress MBF \ 1.6 mlÁminÁg. Of patients with LM, 2% (N = 2) had normal perfusion, 20% (N = 18) mild and 78% (N = 71) had moderate-severely abnormal perfusion. Both patients with LM and normal perfusion had at least 2 non-perfusion high-risk markers. Of patients with MVD, normal, mild, and moderate-severely abnormal perfusion was present in 3% (N = 15), 15% (N = 70), and 82% (N = 393), respectively (Figure) . Of the 15 patients with normal perfusion and MVD, 2 (13%) had no high-risk markers, and 8 (53%) had at least two. Conclusion: The rate of high-risk CAD resulting in normal perfusion on PET is 3%. Non-perfusion high-risk markers on PET helped identify high-risk CAD in 99.6% of these patients. High-risk CAD is unlikely to be missed if PET MPI is used as a gatekeeper for catheterization GOING BEYOND SUMMED STRESS SCORES: CORRELAT-ING GLOBAL AND TERRITORIAL CORONARY FLOW RESERVE BY SINGLE-PHOTON EMISSION TOMOGRAPHY WITH ROUTINE MYOCARDIAL PERFUSION IMAGING A. S. Koh*, 1 B. M. Keng, 2 X. Teng, 2 R. Tan, 1 L. Baskaran, 2 T. Chua, 3 F. Keng 1 ; 1 National Heart Centre Singapore; Duke-NUS Medical School, Singapore, Singapore, 2 National Heart Centre Singapore, Singapore, Singapore, 3 Cardiology, National Heart Centre Singapore; Duke-NUS Medical School, Singapore, Singapore Introduction: The ability to use single-photon emission tomography (SPECT) to measure myocardial blood flow (MBF) through dynamic acquisition represents a major advance for SPECT laboratories in this decade, providing greater sensitivity towards coronary health assessment, beyond semi-quantitative myocardial perfusion imaging (MPI). We determined global and territorial MBF in absolute quantitation by dynamic SPECT, in relation to grades of abnormality on routine MPI. Methods: We studied SPECT MPI images of consecutive clinical subjects who underwent vasodilator gated MPI stress and rest studies. Measurements of routine static myocardial perfusion were compared with dynamic measurements of MBF for each subject using standard software package. For MBF, we computed global and territorial [i.e., left anterior descending (LAD), left circumflex (LCX), right coronary artery (RCA)] coronary flow reserve (CFR). CFR was calculated by dividing stress MBF with rest MBF. Coronary flow reserve cut-off value of \ 2.5 for each coronary territory is used to define abnormality. Results: Of 90 subjects (mean age 67 ± 8 years; 68 (76%) males), 44 (49%) had normal MPI (summed stress score (SSS) \ 3; LV ejection fraction [ 50%). There was a graded reduction in global and territorial CFR in all coronary arteries across SSS categories from normal, mildly to moderately, to severely abnormal MPI ( Figure 1 ). Table 1 shows mean MBF values for each SSS category. Among normal MPI scans, patients who had abnormal global CFR had lower LAD CFR (1.94 ± 0.27 vs 2.96 ± 0.59, P.0001), LCX CFR (1.92 ± 0.46 vs 3.19 ± 0.47, P.0001), RCA CFR (2.14 ± 0.37 vs 3.52 ± 0.51, P \ 0.0001), and were older in age (69 ± 7 vs 62 ± 9 years, P = 0.034). Correlation of CFR with age was significant with LAD, LCX, and RCA CFR ( Figure 2 ). Conclusions: We present global and territorial MBF values corresponding to SSS categories determined by dynamic SPECT. Abnormal CFR values in otherwise normal MPI scans may suggest a particular role for dynamic SPECT in certain higher risk populations such as older adults, enabling finer risk stratification. MECHANICAL MYOCARDIAL DYSYNCHRONY EVALU-ATED WITH GATED SPECT PHASE ANALYSIS FOR CARDIOVASCULAR RISK PREDICTION L. Gutierrez*, 1 F. A. Pen˜afort 2 ; 1 Instituto de Diagnostico y Resonancia de Mendoza, Mendoza, Argentina, 2 Penta Medicina Cardiovascular, Mendoza, Argentina Introduction: Through functional images, we found several variables for the appropriate stratification of cardiovascular risk in patients (p) with ischemic heart disease. Through Phase Analysis (PA) from MPI, we can assesses Mechanical Myocardial Dysynchrony (MMD) and given incremental prognostic value simultaneously with perfusion and function We analyze the predictive value of MMD in MPI by Phase Analysis, (PA) identifying groups of risk Methods: We retrospectively evaluated an outpatient population of 1041(p) with a prospectively telephone follow-up. We analyze MPI MMD parameters and clinical events in their evolution. MMD analysis groups by PA were created; G1: Absence of MMD; G2: MMD only Rest; G3: MMD only Stress; G4: MMD in Stress and Rest. Combined Outcome (O.CV) of Cardiac Death (CM) ? Heart Failure Hospitalization was analyzed. Statistical analysis was performed using frequency analysis, multivariate Cox regression to identify predictors, and Kaplan-Meier survival curves in follow-up. A P value of \ 0.05 was considered statistically significant. Results: The follow-up period was a median of 27 months with ranges of (1 month-114 months). G1: 946p (90.8%); G2: 32p (3.2%); G3: 18p (1.7%); and G4: 45p (4.3%). Incidence of O.CV was for G1: 26p (2.7%); G2: 4p (12.5%); G3: 2p (11.1%); G4: 12 p (26.7%) P: \ 0.001. During our follow-up, we observed an event-free survival time mean for O.CV G1: 108 ± 1.2 months; G2: 69 ± 5.7 months; G3: 78 ± 8.6 months; G4: 68 ± 6.5 months P: \ 0.001. Independent variables for O.CV were quantification of Moderate Scar OR: 8.2 (95% CI 3.78-18.07) P \ 0.001 and Severe Scar OR: 3.4 (95% CI 1.24-9.8) P:.018. Regarding the groups analyzed, we observed that G2 presented an OR: 4.4 (95% CI 1.5-12.9) P: 0.007 and G4 presented an OR: 4.4 (95% CI 1.76-11, 4) P: 0.002 Conclusions: The evaluation of the Mechanical Myocardial Dysynchrony by Phase Analysis from Gated SPECT allowed to incorporate a robust parameter of risk stratification of the combined event for Cardiac Outcome.CV in our registry. IMPACT OF GLYCOSYLATED HEMOGLOBIN HBA1C ON MYOCARDIAL PERFUSION AND FUNCTION BY GATED MYOCARDIAL PERFUSION SPECT IMAGING H. Nasr*, 1 H. Alsomali 2 ; 1 Nuclear Medicine Unit, Faculty of Medicine, Cairo University, Cairo, Egypt, 2 Radiology Department, Security Forces Hospital Program (SFHP), Riyadh, Saudi Arabia Introduction: Glycosylated hemoglobin (HbA1c) allows for long-term blood glucose level monitoring and may be helpful for early detection of cardiovascular complications related to diabetes mellitus or abnormal glucose homeostasis. Our aim is to assess the relation of HBA1C to perfusion and function parameters on GMPS imaging. Methods: We retrospectively reviewed 200 patients who had GMPS studies. Data collected included patients' demographics, clinical data, and lab findings (HTN, smoking, dyspnea, chest pain, DM, HA1C, total cholesterol, HDL and LDL), perfusion parameters (SSS, SRS, SDS, and TPD), function, and gated parameters (EF, EDV, ESV and wall motion abnormalities (WMA)). We used unpaired student T-test to compare mean values of continuous variables. ROC analysis was used to define the cutoff values for HA1C that best identifies patients with abnormal GMPS parameters. Chi-square test was used to compare difference in frequency between categorical variables. Pearson correlation was used to assess the correlation between continuous variables. Results: The study included 200 patients (mean age of 58.21±11.53 years; 102 (51%) males). Study included 132 (66%) diabetic patients. The mean HBA1C in diabetic patients was significantly higher compared to non-diabetic group (7.92±1.99 vs 6.05±0.99; P \ 0.001). HBA1C% was negatively correlated to EF% and HDL (r = -0.262; P \ 0.001 and r = -0.316; P.001, respectively) while it was positively correlated to EDV and ESV (r = 0.291; P \ 0.001 and r = 0.221; P = 0.002, respectively). The mean EF% and HDL were significantly lower in patients with HGA1C%[6.5 (53.17 ± 14.55 vs 57.8 ± 12.61; P = 0.017) and (1.046 ± 0.262 vs 1.196 ± 0.295; P.001). Patients with HGA1C% [ 6.5 had more frequency of EF \ 50% (30.0% vs 15.6%; P = 0.017), more incidence of WMA (24.5% vs 12.2%; P = 0.027) and more ESV [ 44 ml (38.2% vs 20.0%; P = 0.005). Patients with HGA1C% [ 6.5 had more prevalence of hypertension (77.3% vs 54.4%; P = 0.001) and more frequency of dyspnea (27.3% vs 15.6%; P = 0.047); however, with less prevalence of chest pain (70.9% vs 83.3%; P = 0.039). In diabetic patients subgroup again, there was lower mean EF% and HDL in patients with HGA1C%[7.5 (52.0 ± 14.59 vs 57.6 ± 11.55; P = 0.018 and 1.005 ± 0.239 vs 1.148 ± 0.273; P.002, respectively). Also HGA1C%[7.5 revealed more frequent EF \ 50% (33.3% vs 14.5%; P = 0.011), WMA (30.2% vs 11.6%; P = 0.008), more ESV [ 44 ml (41.3% vs 20.3%; P = 0.009) and in addition more EDV[100 ml (34.9% vs 18.8%; P = 0.037). No statistically significant relation could be found between HBA1C% and GMPS perfusion parameters including SSS, SRS, SDS, and TPD%. Conclusions: A higher HBA1C% was associated with multiple function parameters abnormalities including lower EF, more WMA and larger ESV in addition to larger EDV in diabetic patient population. Unfortunately no significant association was found between HBA1C% and perfusion parameters. Luke's Medical Center, Quezon City, Philippines Introduction: LV diastolic dysfunction is prevalent among obese but remained undiagnosed with echocardiography alone. Evaluation of LVDD using GSPECT is rarely done. Studies reported that diastolic dysfunction evaluated by echocardiography correlated with LVDD by GSPECT. Addition of cardiac stress may unmask diastolic abnormalities that are not evident at rest. Early diagnosis and management of LVDD may prevent the development of overt heart failure. Methods: 160 Filipino patients who underwent one-day rest/stress (treadmill or dipyridamole) 99mTc-sestamibi myocardial perfusion imaging with GSPECT between January 2016 and January 2020 in our institution were included in the study given that they have a normal MPI, resting systolic, and diastolic parameters. Patients with known CAD, hypertension, diabetes, heart failure, pericardial disease, and moderate to severe valvular heart disease were excluded. Included patients were grouped into 3 BMI class: Normal weight, overweight, and obese. The % rest-to-stress difference of the G-SPECT diastolic parameters (PFR, MFR/3, TTPF) was determined and compared among groups and among different stressors (Treadmill exercise vs Dipyridamole). Data were analyzed using ANOVA and Kruskal-Wallis test. Tukey test and Dunn's test were used for post-hoc analysis. Results: Findings showed no significant differences in PFR and TTPF among the BMI classes at baseline and after stress test. The resting MFR/ 3 was significantly lower among obese patients compared to the other two groups (P = .027). The % rest-to-stress decrease of MFR/3 was lower in normal BMI patients than in overweight or obese patients (P = .009). Conclusions: No significant differences in PFR and TTPF among the BMI classes at baseline and after stress test. The resting MFR/3 was significantly lower among obese patients compared to the other two groups (P = .027). The % rest-to-stress decrease of MFR/3 was lower in normal BMI patients than in overweight or obese patients (P = .009). (MPI) is the only modality capable of non-invasively measuring absolute myocardial blood flow (MBF) in patients with coronary artery disease (CAD). Recent guidelines for PET MPI advocate for a 17-segment evaluation of coronary flow reserve (CFR), which is the ratio of stress MBF (sMBF) to rest MBF (rMBF). However, this methodology does not track artery-specific perfusion, and CFR can be misleading under certain physiological conditions. Developed to overcome these limitations, coronary flow capacity (CFC) is a categorical measure utilizing a two-dimensional scatterplot of CFR and sMBF to classify different levels of ischemia burden at the pixel level. Prospective observational studies in stable CAD patients have suggested that CFC is a superior metric for predicting major adverse cardiovascular events (MACE) and improved post-revascularization survival compared with CFR, sMBF, and relative flow. This hypothesis could profoundly affect clinical practice if verified in randomized studies. Methods: We are conducting the first randomized clinical trial using PET CFC to guide enrollment prior to revascularization (PETREVASC). The study's primary objective is to assess whether optimal medical therapy (OMT) can reduce the extent of myocardial perfusion abnormalities as effectively as immediate revascularization in stable CAD patients who have reduced CFC. Patients will be randomized 1:1 to receive OMT with immediate revascularization (active) or OMT without immediate revascularization (control). Patients will undergo PET MPI at Screening, Day 105, and Day 365. Patients in the control group will have the option to receive revascularization any time after Day 105. The study population includes patients who have C 10% of left ventricle (LV) with CFCgreen (sMBF 0.83 to 1.09 mlÁminÁg and CFR 1.27 to 1.60) and at least one pixel with CFCblue (sMBF B 0.83 ml min g and CFR B 1.27) OR C 2% of LV with CFCblue. Observational data suggest that these patients are at substantial risk of MACE. Patients with a large myocardial scar (rest relative defect in [ 5% of LV) are excluded. The primary endpoint of the study is change from baseline to Day 105 in the % of LV with CFCblue plus CFCgreen. This endpoint was chosen as a surrogate for MACE and death. Secondary endpoints include changes from baseline to Day 105 and Day 365 in other PET perfusion metrics (e.g. CFR), MACE rate, and adverse event rate. We will also assess whether PET processing differs significantly between a secondary care practice and a tertiary academic core laboratory. We plan to randomize 104 patients (D = 15, SD = 20, a = 0.05, power = 90%). The study has been reviewed and approved by WCG IRB. Recruitment is currently ongoing at Gramercy Cardiac Diagnostic Services, a secondary care practice in New York. University of Texas Health Science Center at Houston is the study sponsor. Hartford Hospital, Hartford, CT, 2 University of Connecticut, Farmington, CT, 3 Internal Medicine, University of Connecticut, Farmington, CT, 4 Nuclear Cardiology, Hartford Hospital, Hartford, CT Introduction: Thousands of patients undergo stress testing for risk stratification and evaluation of coronary artery disease annually. The risk of exercise and pharmacologic stress testing of patients with carotid artery disease has never been defined, but it is thought to increase the risk of ischemic stroke and transient ischemic attack. We sought to understand the risk of stress testing in patients with different degrees of carotid artery stenosis (CAS). Methods: We retrospectively reviewed records of all patients with either ultrasound or CT evaluation of their carotid arteries from 2015 to 2020 who also underwent stress testing within 180 days without carotid intervention in the interim. We performed a manual chart review of all patients looking for any adverse events that occurred within 24 hours of the stress test. We defined the primary end point as any cerebrovascular event or syncope. Secondary endpoints included death, myocardial infarction, urgent angiography, urgent revascularization, or exaggerated hemodynamic response (SBP drop [ 20 mmHg). Patients were stratified based on the level of CAS into either severe (greater than 80%), moderate (50%-79%), or mild/no (less than 49%) stenosis. Patients with severe CAS were compared to those with mild/no stenosis. Propensity matching was performed, using the following patient risk factors: history of diabetes, hypertension, hyperlipidemia, smoking status, coronary artery disease, gender, and age. Results: A total of 4457 patients underwent carotid ultrasound, 10,644 CT, and 16,011 stress testing during this time period, with 514 having both a carotid evaluation and a stress test within 6 months of one another. After propensity matching, 62 patients with severe CAS were matched to 170 patients with mild/no CAS. In the non-propensity matched cohort, patients with severe CAS were older, more likely to smoke, have diabetes, hyperlipidemia, or known coronary artery disease. All patients with severe CAS underwent pharmacologic stress compared to those with mild/no CAS. There were no primary endpoints and only three adverse events occurring in two patients -both patients requiring urgent angiography, one of whom required urgent revascularization with coronary artery bypass grafting. Both of these patients were in the group with mild/no CAS. The proportion of exaggerated hemodynamic response to stress was similar in both groups, 21.0% in the CAS group and 31.2% in the group without CAS (P = 0.17). Conclusions: In our study, there were no primary and few secondary outcome events with no events occurring in patients with severe CAS. This small cohort study suggests that stress testing bares no increased risk in patients with severe CAS but continued care should be taken in this cohort. Background: Splenic switch-off (SSO) is a phenomenon describing a decrease in splenic radiotracer activity from rest to stress. Previous studies have shown that adenosine-and dipyridamole-induced splenic switch-off can be used to assess vasodilator response. The prior study using cardiac magnetic resonance perfusion stated that regadenoson does not show evidence of splenic switch-off, which was suggested to be specific to adenosine. The aim of this study is to assess whether regadenoson vasodilator stress is associated with splenic switch-off in Rubdium-82 Positron emission tomography (PET) myocardial perfusion imaging (MPI). Methods: Patients were selected from an institutional registry of Regadenoson Rb-82 PET MPI between August 2020 and April 2021. A total of 100 consecutive patients with normal regadenoson PET MPI studies having no perfusion defects (SDS = 0), normal myocardial blood flow, no wall motion abnormalities, and calcium score of zero were selected. Radiotracer activity concentrations (BqÁml) were measured in region of interests (ROIs) from the spleen, liver, and myocardium both at rest and stress. Each study was evaluated by two investigators blinded to the others results. Results: A significant decrease was observed between spleen activity from rest to stress (79.9 kBqÁml vs 69.1 kBqÁml, respectively, P.001). Inversely, there was a significant increase in blood flow to the liver (P \ 0.001) along with an expected increase in blood flow to the myocardium (P \ 0.001). This was consistent among young vs elderly patients, men versus women or among patients with or without hypertension or dyslipidemia. There was a strong inter-rater reliability of radiotracer activity concentrations across the spleen, liver, and myocardium (ICC [ 0.95) Conclusion: Patients with normal regadenoson vasodilator stress in PET MPI studies exhibit significant decrease in splenic radiotracer activity from rest to stress. ADDED PROGNOSTIC ROLE OF COMPUTED TOMOGRA-PHY-DERIVED FRACTIONAL FLOW RESERVE A. Ahmed*, 1 Y. Han, 1 T. Alnabelsi, 1 M. Al Rifai, 2 F. Nabi, 1 S. Chang, 1 J. J. Mahmarian, 1 M. A. Chamsi-Pasha, 1 W. Zoghbi, 1 M. H. Al-Mallah 1 ; 1 Houston Methodist DeBakey Heart and Vascular Center, Houston, TX, 2 Baylor College of Medicine, Houston, TX Introduction: Cardiac-computed tomography angiography (CCTA)derived fractional flow reserve (FFRCT) adds incremental diagnostic value by providing functional severity of coronary lesion in patients with coronary artery disease (CAD). We aimed to assess the incremental prognostic value of FFRCT on a CCTA-based anatomic assessment. Methods: Consecutive patients who had clinically indicated CCTA and FFRCT determination were included. FFRCT was determined off-site using a Food and Drug Administration (FDA) approved commercially available tool. Segment involvement score (SIS), the total number of coronary artery segments with plaque on CCTA irrespective of stenosis, was used to quantify the burden of CAD. Patients were followed for major adverse cardiovascular events (MACE, inclusive of all-cause death, non-fatal myocardial infarction, hospitalization for chest pain/ unstable angina and percutaneous coronary intervention (PCI)/coronary artery bypass grafting (CABG) 90-days after imaging test.) Results: A total of 667 patients with at least coronary artery disease reporting and data system (CAD-RADS) 2 were included (mean age 68 ± 10 years, 37% women, 73% hypertension, 12% diabetes, and 61% dyslipidemia). More than half (57%) of the patients had moderate (CAD-RADS 3) stenosis. FFRCT \ 0.8 was found in 59% of patients, with an increasing percent across categories of CAD-RADS. After a median follow-up of 9 months, 52 patients (7.2%, 6.7 events per 1000 person-year) experienced MACE. In multivariable Cox regression models adjusted for age, sex, CCTA obstructive stenosis, and SIS, FFRCT \ 0.8 was not significantly associated with outcomes (HR 1.63, P = 0.185). Results were the same on sensitivity analysis using lower thresholds of FFRCT. Conclusion: We have shown that in this real-world cohort of patients with suspected CAD and at least 30% stenosis on CCTA, FFRCT provides no significant incremental prognostic value over an assessment of stenosis and plaque burden. One hundred and forty-seven patients (55.7%) received adenosine while 117 patients (44.3%) received dipyridamole. Adverse effects were graded using a four-point scale as follows: 0 = no adverse effects; 1 = less than 3 adverse effects (mild); 2 = 3-6 adverse effects (moderate); 3 = more than 6 adverse effects (severe) or side effects requiring reversal with intravenous aminophylline. Results: The overall prevalence of adverse effects was 62.1%, the majority of which were (Grade 1) adverse effects. Only 3 patients (1%) developed Grade 3 adverse effects. The most common adverse effects reported by patients who received adenosine were chest pain and dyspnea while headache was more common in the dipyridamole group. Adenosine was three times more likely to cause adverse effects compared to dipyridamole (OR 3.23; 95% CI 1.93-5.43; P \ 0.001). However, dipyridamole showed a greater propensity to cause higher grade adverse effects as all participants with Grade 3 adverse effects received dipyridamole (P \ 0.001). Compared to dipyridamole, adenosine was also associated with a more significant drop in systolic blood pressure from baseline to end of infusion (P \ 0.009). Conclusions: Although both vasodilators show an overall satisfactory safety profile, adenosine has demonstrated a marginally better tolerance profile than dipyridamole which was associated with more severe adverse effects. Artificial intelligence may improve the diagnostic accuracy of myocardial perfusion imaging (MPI); however, it will likely be implemented as an aid to physician interpretation. Explainable deeplearning (DL) model has high diagnostic accuracy for obstructive coronary artery disease (CAD), but its influence on physician interpretation is unknown. We assessed whether access to explainable DL predictions improves physician interpretation of SPECT MPI. Methods: We selected a representative cohort of patients imaged with conventional or solid-state camera systems with reference invasive coronary angiography. Obstructive CAD was defined as stenosis C 50% in the left main artery or C 70% in other coronary segments. We utilized an existing explainable DL model (CAD-DL), developed in a separate patient population. CAD-DL estimates the probability of CAD and highlights regions of the polar map contributing to predictions. Three physicians interpreted studies with clinical history, stress results, and perfusion but without the explainable DL results, then with all the data plus the explainable DL results. Diagnostic accuracy was assessed using area under the receiver-operating characteristic curve (AUC). Results: In total, 240 patients were included with median age 65 (IQR 58-73) and 120 (50.0%) having obstructive CAD. The diagnostic accuracy of physician interpretation with access to CAD-DL results (AUC 0.779) was significantly higher compared to physician interpretation without CAD-DL (AUC 0.747, P = 0.003) and stress TPD (AUC 0.718, P \ 0.001). All readers had numerically higher accuracy with the use of CAD-DL, with improvement in AUC ranging from 0.018 to 0.049. Interpretation with explainable DL resulted in net reclassification improvement of 17.5% (95% CI 9.8-24.7%, P.001). Conclusion: Access to explainable DL results leads to meaningful improvements in the accuracy of physician interpretation. This technique could be implemented clinically as an aid to physician diagnosis in order to improve the diagnostic accuracy of SPECT MPI. Introduction: Rest/stress myocardial perfusion imaging (MPI) with single-photon emission-computerized tomography (SPECT) is used to diagnose significant obstructive coronary artery disease (CAD). Rest MPI assists interpretation of stress MPI and helps differentiate artefacts from ischemia or scar. Stress first MPI may help avoid rest MPI if the stress MPI is interpreted as normal. Cancelling rest MPI reduces radiation dose to the patient and staff and camera time. We have developed and validated the SPECT technique of myocardial blood flow (MBF) measurement which has high diagnostic accuracy for obstructive CAD. Our objective was to explore the potential value of stress MBF to increase certainty of the clinical diagnosis of a normal stress MPI and facilitate cancelling of rest MPI. The purpose was to determine the change in the number of stress MPI studies interpreted as normal when stress MBF data are added to the conventional approach. Methods: The study was approved by the University of Ottawa Research Ethics Board. All patients provided informed consent. Patients were referred for evaluation of suspected or known CAD. Patients underwent dipyridamole stress MPI with dynamic imaging during stress injection and delayed gated imaging using a cardiac SPECT camera (Discovery NM530c, GE HealthCare). Stress global and regional MBF were calculated using inter-frame motion correction and a previously validated 1tissue-compartment model. Stress MPI images were interpreted by 1 reviewer with and without stress MBF data. Clinical data including referral information, stress testing results and gated images were available at time of stress MPI review. Results were compared using McNemar's test for paired nominal data. Results: The study population included 31 patients with a mean age of 57 years, 22 males and 3 with known CAD. Stress MPI studies were identified as normal on the first interpretation without stress MBF in 8/31 patients (26%) and on the second interpretation with stress MBF in 23/31 patients (74 %, P \ 0.001). The additional 15 patients identified as normal using stress MBF data on the second interpretation underwent rest MPI since the first interpretation did not identify them as normal and were reported as normal after including the rest MPI. Conclusion: This pilot study demonstrated incremental value of stress MBF data for classifying stress MPI studies as normal and reducing need for rest MPI. A larger study is necessary to confirm the initial results, compare the predictive value of stress MBF to other available clinical ECG and imaging data and provide follow-up for cardiac outcomes in patients not undergoing rest MPI. Introduction: 99m Tc-PYP SPECT imaging is superior to planar imaging in the diagnosis of ATTR-CM. We aimed to investigate a practical method of PYP quantification on SPECT imaging. Methods: PYP uptake was quantified in 44 SPECT and planar scans (29 ATTR-CM; 15 controls) using 3 methods: 2DTBR (Target-Background Ratio)-LV-DAo, 3DLV-TBR, and free form H/CL. (Fig 1) Their diagnostic performance was compared to conventional planar H/CL ratio. TBR (paraspinal muscle to spine) was used as control. Results: 2DTBR-LV-DAo was associated with the highest AUC of 0.995 (Fig 2A) . Control TBR was similar between groups ( Fig 2B) . The difference between 2DTBR-LV-DAo between groups appeared to persist across NYHA classes (Fig 2C) . Five scans considered equivocal were correctly reclassified as negative using the 2DTBR-LV-DAo method. Conclusions: 2DTBR-LV-DAo is a practical and simple method of PYP quantification on SPECT imaging. Further studies are needed to understand the relationship between PYP SPECT uptake and natural history of ATTR-CM as well as response to therapy. , which is more severe in patients with bicuspid aortic valve (BAV), as opposed to tricuspid aortic valve (TAV). The treatment of CAVD remains limited to valve replacement for advanced disease, in part because of a lack of representative animal models for human disease. Fluorine-18 sodium fluoride ([ 18 F]-NaF) PET can detect the calcification process in vivo. Pursuing the observation that Discoidin, CUB, and LCCL domain-containing protein 2 (DCBLD2) are reduced in patients with AS, we observed that DCBLD2-deficient mice develop BAV. The purpose of this work was to address the feasibility of [ 18 F]-NaF PET/CT and evaluate valvular stenosis and calcification in Dcbld2-/-mice in comparison with wild-type (WT) animals. Methods: Aortic valve leaflet separation and transvalvular jet velocities were determined by echocardiography in cDcbld2-/-(N = 49) and agematched WT mice (N = 6) at the age of [ 9 months. Valvular calcification was detected in vivo by [ 18 F]-NaF PET/CT in Dcbld2-/-mice at 3-4 months (young, N = 4) and [ 9 months (old, N = 4). The animals were injected with 28.3 ± 5.4 MBq of [ 18 F]-NaF and underwent a 30 minutes long PET acquisition starting at 1 hour post-injection. Contrastenhanced CT images were also obtained. The mean SUV values were determined in regions of interest drawn over the aortic valve region and the left ventricle, as identified by CT, and normalized to the blood SUV values measured in the left ventricle to determine target to blood ratios (TBR). Valvular calcification was confirmed by quantitative autoradiography ex vivo. Dcbld2-/-mice at [ 9 months (old, N = 9), and agematched WT (N = 4) animals were injected with 16.3 ± 4.9 MBq of [ 18 F]-NaF, and the aorta and aortic valve were dissected after 1 hour, and aortic valve tracer uptake was quantified. Results: Fifty three percent (26/49) of Dcbld2-/-mice had a BAV. Mice with BAV had a significantly higher aortic valve velocity compared to those with TAV (Dcbld2-/-BAV: 2838 ± 1383; TAV: 1781 ± 759 mmÁs, P \ 0.05) and WT animals (1060 ± 173 mmÁs, P \ 0.001), and lower leaflet separation versus TAV (P \ 0.01) and WT (P \ 0.0001) mice. The aortic valve [ 18 F]-NaF signal was clearly visible in a subset of PET/CT images. Aortic valve TBR was significantly higher in older Dcbld2-/-mice compared to younger animals (1.32 ± 0.05 vs 1.18 ± 0.08, P\ 0.05). Ex vivo autoradiography showed higher uptake of [ 18 F]-NaF in old Dcbld2-/-mice relative to age-matched WT controls (P \ 0.05). Conclusion: [ 18 F]-NaF PET/CT is feasible in murine CAVD. Older Dcbld2-/-mice develop AS and valvular calcification. In addition, AS is more severe in older Dcbld2-/-mice with BAV. This combination of a new animal model of CAVD and small animal [ 18 F]-NaF PET/CT to track the aortic valve calcification process can accelerate pathophysiology research and facilitate the development of novel therapeutics for CAVD. Methods: We prospectively enrolled 73 subjects (mean age 62 ± 8 years, 45.5% women) with biopsy-proven AL amyloidosis into 3 study groups: Active AL-CMP (abnormal cardiac biomarkers, N = 41), Active AL-non-CMP (normal cardiac biomarkers and normal left ventricular wall thickness, N = 14), and Remission-AL-CMP (hematalogical remission for C 1 year, N = 18). All subjects underwent 18F-florbetapir PET/CT (8-10 mCi) and gadolinium enhanced cardiac magnetic resonance imaging (CMR). RV amyloid burden was estimated on a voxel level by 18Fflorbetapir activity concentration (kBq/cc) in RV from static images (4-30 minutes) using PMOD software; voxels with activity concentration more than two times mean left atrial activity concentration were considered abnormal. RV function was quantified by RVEF on CMR. RV amyloid in the study groups was compared using one-way ANOVA with post-hoc Bonferroni testing and correlated to RVEF using a Pearson's R. Results: RV amyloid was present in 11/14 patients without CMP ( Fig A) . Mean RV 18F-florbetapir activity was highest and RVEF was lowest in the active AL-CMP cohort (Fig. A and B) . RV amyloid activity was significantly lower in the remission-AL-CMP cohort (Fig. A) compared to active-AL-CMP, yet RVEF was similarly reduced (Fig. B) . RV amyloid was moderately and inversely correlated to RVEF in both AL-CMP cohorts (Fig. C) . Estimated RV systolic pressure was 33 ± 13, 28 ± 12, and 10 ± 12 mmÁHg, respectively, in the three groups. Conclusions: This is the first study, to our knowledge, to evaluate RV amyloid using a molecularly targeted amyloid tracer. Notably, we found (1) RV amyloid deposits in most patients without known cardiac involvement and (2) persistent AL amyloid deposits in the right ventricle after successful AL therapy with remission; these may contribute to persistent RV dysfunction and functional limitation. Vancouver, BC, Canada, Los Angeles, CA, 9 St. Paul's Hospital, University of British Columbia, Vancouver, BC, Canada Introduction: As well as developing graft vasculopathy, coronary artery bypass grafts (CABG) have been proposed to accelerate native coronary atherosclerosis. We aimed to describe the potential of 18 F-sodium fluoride positron emission tomography ( 18 F-NaF PET) to identify graft vasculopathy and to investigate the influence of CABG surgery on native coronary artery disease activity and progression. Methods: Patients with established coronary artery disease underwent baseline 18 F-NaF PET, coronary artery calcium scoring, coronary CT angiography, and one-year repeat coronary artery calcium scoring. We quantified the whole-vessel 18 F-NaF PET coronary microcalcification activity (CMA) and change in calcium scores in those with and without CABG surgery. Results: Among 293 participants (65 ± 9 years; 84% male), 48 (16%) had CABG surgery 2.7 [1.4-10.4] years previously. Although all arterial and the majority (120/128, 94%) of vein grafts showed no 18F-NaF uptake, 8 saphenous vein grafts in 7 subjects had detectable CMA. Bypassed native coronary arteries had 3 times higher CMA values (2.1 (0.4-7.5) versus 0.6 (0-2.7), P.001) and greater progression of oneyear calcium scores (118 [48-194] versus 69 [21-142] AU, P = 0.01) compared to those who that had not undergone CABG: an effect largely confined to native coronary plaques proximal to the graft anastomosis. In sensitivity analysis, bypassed native coronary arteries had higher CMA Conclusions: Native coronary arteries that have been bypassed, demonstrate increased disease activity and more rapid disease progression than non-bypassed arteries, an observation that appears independent of the baseline atherosclerotic plaque burden. Microcalcification activity is not a dominant feature of graft vasculopathy. . This allows for a combined anatomic (CAC) and functional (ischemia) assessment of coronary artery disease (CAD) burden. We evaluated the independent prognostic value of ischemia and CAC in patients undergoing PET MPI. Materials and Methods: Consecutive patients who underwent PET with CAC scoring between 2008 and 2018 were identified. Patients with known CAD and those who underwent revascularization within 90 days of PET were excluded. Ischemia and CAC were quantified during clinical reporting. Our primary outcome was major adverse cardiovascular events (MACE) including all-cause mortality, myocardial infarction (MI), admission for unstable angina (UA), and late revascularization. Associations with MACE were assessed using multivariable Cox proportional hazards models adjusted for age, sex, medical history, symptoms, and fixed perfusion defects. Results: In total, 3055 patients were included with median age 70 (interquartile range [IQR] 62-78) and 50.3% female. During median followup of 4.1 (IQR 2.2-6.5) years, 755 patients experienced at least one MACE (death 613, MI 52, UA 22, and late revascularization 68). Increasing ischemia and CAC were associated with an increased risk of MACE. In multivariable analysis, both increasing log CAC (adjusted hazard ratio [aHR] 1.09, 95% confidence interval [CI] 1.06-1.13, P \ 0.001) and increasing ischemia (aHR 1.13 per 5%, 95% CI 1.03-1.24, P = 0.013) continued to be associated with an increased risk of MACE. The addition of log CAC and ischemia to the multivariable model improved fit compared to the addition of log CAC or ischemia alone (log-rank P \ 0.01 for both). S. Berman, 1 P. J. Slomka 1 ; 1 Cedars-Sinai Medical Center, Los Angeles, CA, 2 Institute of Cardiology, Warsaw, Poland, 3 University of Calgary, Calgary, AB, Canada Introduction: We aimed to develop and evaluate a novel explainable deep-learning (DL) network for the prediction of all-cause mortality (ACM) directly from perfusion and myocardial blood flow (MBF) polar maps and evaluate it in simulated prospective regimen. Methods: A total of 4784 consecutive patients undergoing rest/pharmacologic stress 82Rb PET from 2010 to 2018 were followed for allcause mortality (ACM) for mean 4.4 ± 2.6 years. DL network utilized stress and rest polar maps of raw perfusion, MBF, myocardial flow reserve (MFR) and spillover fraction, cardiac volumes, singular indexes, age, and sex. 3,568 patients scanned from 2010 to 2016 were used as a training set, and internal validation was performed with the training set. The network was validated in the remaining 1137 patients scanned from 2017 to 2018 (age 70 ± 11 years, 38% female), after excluding early revascularization, to simulate prospective implementation. The output of DL was ACM probability along with an attention map highlighting the polar map regions contributing DL prediction. Summed stress and difference scores (SSS, SDS) were obtained during clinical reading. Quantitative parameters including stress and ischemic total perfusion deficit (TPD), stress MBF, and MFR were obtained with standard software. ACM prediction of DL was compared to visual and quantitative assessment in a prospective temporal validation set. Background: Splenic switch-off (SSO) is a phenomenon describing a decrease in splenic radiotracer activity from rest to stress. Adequate stress response is imperative for the detection of ischemia in positron emission tomography (PET) myocardial perfusion imaging studies (MPI); therefore, inadequate vasodilatory response may result in falsenegative studies. The aim of this study is to explore the diagnostic utility of visual splenic switch-off and splenic response ratio (SRR) in Regadenoson Rubdium-82 PET MPI studies. Methods: The splenic response ratio was calculated with spleen and liver radiotracer concentrations obtained from a derivation cohort defined as Regadenoson Rb-82 PET MPI patients with normal MPI studies and no perfusion defects: SRR = (Spleen stress/Liver stress)/(Spleen rest/Liver rest). SRR was used to classify splenic responses from a validation group formed from patients who had undergone both PET-MPI studies and invasive coronary angiography (ICA). Based on the results of the coronary angiographies, false-negative and true-positive PET-MPI studies were used to assess clinical utility of visual SSO ( fig.1 ) and SRR. Results: Using the derivation cohort (N = 100), a splenic response ratio cut-off of 0.88 was established. Patients with an SRR B 0.88 were classified as splenic responders while patients above that were non-responders. When applied to the validation cohort (N = 323), 72% were classified as splenic responders and 28% were splenic non-responders compared to visual assessment (85% and 15%, respectively). MFR was significantly lower in splenic non-responders defined by SRR (1.5 vs 1.7 P = 0.01) or visual assessment (1.4 vs 1.7 \ 0.001). Moreover, patients with undetected ischemia on PET (as confirmed by ICA) were more likely to be splenic non-responders especially with corrected MFR \ 1.5 based on SRR (62% vs 27% P = 0.02) or visual assessment (80% vs 30% P = 0.006). Conclusion: Patients with inadequate vasodilatory response in Regadenoson Rb-82 PET MPI studies can be identified using visual splenic switch-off or splenic response ratio. University -LHSC, London, ON, Canada, 4 Western University -LHSC, London, ON, Canada, 5 Cardiology, Cook County Health, Chicago, IL Introduction: SPECT improves diagnostic specificity of Technetium-99m pyrophosphate (PYP) scintigraphy and is recommended to be performed whenever there is evidence of tracer uptake on planar imaging. Given the ability to co-localize tracer activity, hybrid SPECT/CT could provide superior diagnostic accuracy when compared to SPECT-only. Methods: This retrospective, quality assurance study was performed on imaging data from patients who underwent PYP SPECT/CT between 2017 and 2021 at Western University. All images were reviewed by two experienced independent readers. Reader 1 reviewed planar and PYP SPECT with CT, while reader 2 was blinded to CT, and reviewed planar and SPECT-only PYP data. Imaging was performed at 1 hour after tracer injection and data were processed by a nuclear medicine technologist and not reprocessed by the two readers. Demographic, clinical, and other testing data were obtained from the electronic medical records. Results: PYP scintigraphy was performed in 120 Caucasian patients (mean age 76 ? 11 years), of whom 63% were men. Of these, 37 (29%) were considered to be positive based on myocardial uptake on SPECT/ CT, with 86% of the patient with grade 3 uptake on planar imaging. There was excellent correlation between the two readers on the visual score (94%, P \ 0.0001) and tomographic uptake (98%, P \ 0.0001) by SPECT-only and SPECT/CT. Only one study was categorized as being falsely negative by SPECT only and was noted to have focal myocardial uptake on SPECT/CT (Figure) . Both readers reported high confidence in their reads in 97% of the studies, with reader 2 reporting a low level of confidence in only 2 studies. Conclusions: When read by experienced readers, SPECT-only reconstruction of PYP scintigraphy has near perfect concordance with PYP SPECT/CT. In cases with only focal myocardial uptake that may be seen in early cardiac amyloidosis, SPECT/CT is likely to provide greater diagnostic certainty. Cedars-Sinai Medical Center, Los Angeles, CA, 2 Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA Introduction: We aimed to evaluate inter-scan and inter-rater agreement of Coronary Calcium (CAC) scores obtained from ECG-gated CAC scans and low-dose, ungated computer tomography attenuation correction (CTAC) scans obtained routinely during myocardial perfusion PET imaging. Methods: From the patients who underwent Rb-82 cardiac positron emission tomography (PET/CT and gated CAC scans without prior revascularization, we have studied 200 cases selected randomly after stratification for the calcium scores categories. Both dedicated gated CAC and ungated CTAC scans were scored for coronary calcium with the quantitative clinical software by two experienced readers. The score agreement was assessed using 5 CAC categories (no CAC: 0, very low: 1-10, low: 11-100; moderate 101-400; and high [ 400). The absolute inter-reader differences in scores (bias) between CAC scans and ungated CTAC maps were compared with the Wilcoxon signed-rank test. Results: Median age of included patients was 70 (inter-quartile range 61-77), 51% were male. The inter-reader concordance index and Cohen's Kappa were 0.9 and 0.87, respectively, for CAC scans and 0.86 and 0.8 for CTAC scans respectively. Class agreement is shown in figure. Interreader bias was larger for CTAC than for gated CAC scans: 16.74 (95% confidence interval [CI] -1.13, 34.61) vs -5.06 (95% CI -14.93,4.82), P \ 0.0001. Inter-reader levels of agreement (LOA) were wider for CTAC compared to CAC scans: (-233.81 to 267.29) vs (-143.47 to 133.36) . The inter-scan concordance index and Cohen's Kappa for reader 1 and 2 were 0.7; 0.62 and 0.74; 0.67, respectively. Conclusion: The overall concordance in 5 classes of CAC scores was good for both gated CAC and CTAC scans. Overall, inter-scan (CTAC vs gated CAC) agreement was comparable to inter-reader agreement in terms of bias and LOA. However, inter-reader agreement was worse on the ungated CTAC maps with significantly larger bias. Cedars-Sinai Medical Center, Los Angeles, CA Introduction: Coronary 18 F-sodium fluoride ( 18 F-NaF) on uptake positron emission tomography/computed tomography (PET/CT), determined by coronary microcalcification activity (CMA), displays excellent observer reproducibility and interscan repeatability. We wanted to test whether we could quantify CMA using non-contrast PET/CT with similar precision. Methods: Patients underwent 18 F-NaF PET/CT scanning on 2 occasions in close succession. Subjects were administered 125 MBq 18 F-NaF and underwent PET/CT (Biograph mCT; Siemens) 60 minutes later. We used 3 methods to evaluate coronary 18 F-NaF activity: the maximum standard unit value (SUVmax); the maximum target-to-background (TBR) approach; and the CMA which represents the integrated coronary activity in SUV units exceeding blood-pool activity in the right atrium (mean blood-pool SUV plus 2 standard deviations. We calculated intraobserver, interobserver, and interscan reproducibility using Bland-Altman analysis repeatability coefficients and coefficients of variation. Results: Fifteen patients (73 ± 7 years, 67% men) had 2 scans, 3.9 ± 3.3 weeks apart. 40 (89%) coronary arteries were analysed in total; vessels with no visible uptake were not assessed. Table 1 with interscan coefficients of reproducibility showing of 0.45, 0.40, and 2.72, respectively, and coefficients of variation of 34%, 35%, and 135%: Similar results were observed for interobserver and intraobserver reproducibility. Conclusion: The precision of coronary 18 F-NaF PET quantification (SUV, TBRmax and CMA) is sub-optimal when using non-contrast, ECG-gated CT scans. Nuclear Medicine, Hospital Procardiaco, rio de janeiro, Brazil Introduction: Integrating multiple specialties in a single meaningful report requires coordinated multispecialty collaboration. To meet this need, we developed a new strategy: a multidisciplinary cardiovascular integrated report (MCIR). In this report, we provide the first analysis of this experience in a tertiary cardiology hospital. Methods: Our Multidisciplinary Cardiovascular Imaging Reporting Team (MCIRT) includes specialists in cardiovascular medicine and surgery, echocardiography, nuclear medicine, and radiology. MCIRT is organized as a team discussion that meets weekly in-person or online (as social distancing is needed) and generates a single integrated report of cardiovascular imaging studies (MCIR) as demanded by requesting physicians or by the imaging team. The online tool used was TEAMS by Microsoft. We prospectively obtained clinical, diagnostic aspects, and decision-making data during the first 10 months of experience. Results: In 10 months, there were 56 clinical cases that were reported as MCIR. Coronary artery disease (CAD) was the most common etiology demanding integrated reports (23 cases -41%), most frequently including coronary CT angiography and myocardial perfusion scintigraphy. The second commonest disease was cardiac infectious endocarditis (IE) in 8 cases (14%). The other diagnosis reported was cardiac amyloidosis (CA -5), dilated cardiomyopathies (5), myocarditis (4), valvar diseases (3), hypertrophic cardiomyopathy (2), pulmonary hypertension (2), coronary fistula (1), COVID-19 complication (1), cardiac tumor (1), and pacemaker complication (1). The online discussion was limited because of internet instability in less than 5% of cases. The impact in decision making and clinician satisfaction was significant with some physicians bringing cases from other institutions for discussion. Conclusions: We report a novel method to communicate cardiovascular imaging results as a single integrated report. This report was produced by a multidisciplinary team that engages multiple clinical/surgical and imaging specialists contributing to delivering efficient, organized, and evidence and value-based care. MCIR was technically successful in almost all cases, and it was mostly used in diseases that demand difficult decision making like CAD, IE, and CA. Houston Methodist DeBakey Heart and Vascular Center, Houston, TX Introduction: Single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has an established role in both the accurate detection of ischemia and identification of patients at high risk of future cardiovascular events. We aimed to assess the incremental prognostic role of SPECT to a coronary computed tomography angiography (CCTA) anatomic assessment in patients with suspected coronary artery disease (CAD). Methods: Consecutive patients with suspected CAD who underwent CCTA and SPECT MPI within 180 days of each other were reviewed. Anatomically obstructive CAD by CCTA was defined as C 50% in the left main artery and C 70% stenosis severity in proximal, mid, and distal branches of the left anterior descending, left circumflex, and right coronary artery without including side branches. Ischemia and scar on SPECT were defined as summed difference score and rest score [ 0, respectively. Patients were followed from the date of first imaging to incident major adverse cardiovascular events (MACE -composite of allcause death, myocardial infarction (MI), and unplanned revascularization -percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) occurring more than 90 days after index imaging). Results: Our study population consisted of 956 patients (mean (SD) age 61.1 ± 14.2 years, 54.1% men, 89% hypertension, 81% diabetes, and 84% dyslipidemia). After a median follow-up of 31 months (IQR 12-65 months), 102 patients (10.7%, 29.2 events per 1000 person-year) experienced the primary outcome. In multivariable Cox regression models adjusted for several CAD risk factors, the addition of SPECT variables to CCTA obstructive stenosis significantly improved model C-statistic (P = 0.037) and net reclassification (P \ 0.001). Conclusion: In this high-risk cohort of patients with suspected CAD, SPECT added incremental prognostic value to CCTA anatomic assessment. Recent societal guidelines recommend stress-first and stress-only if normal myocardial perfusion imaging (MPI) as a means of improving laboratory efficiency, reducing radiation and minimizing patient and staff interaction times to lower the risk of COVID-19 transmission. This protocol could be further enhanced if the post-injection delay could also be reduced. This study tested a rapid and early postinjection stress-only Tc-99m tetrofosmin (TETRO) protocol using attenuation-corrected CZT SPECT to establish comparability of images acquired early (Early) versus the standard (Late) 45-60 minute delay post-injection. Methods: A total of 95 patients (61 male, BMI = 29 ± 5 kmÁm 2 ) referred for MPI were examined as part of a quality improvement project. Patients were imaged upright and then supine on a Spectrum Dynamics, D-SPECT CZT system following injection of 16.7 ± 0.7 mCi of TETRO at peak stress. All had both early and late post-injection images acquired for 106 myocardial counts (approx. 2-5 minutes). Supine images were reconstructed using CT-based attenuation correction. Early and late images were interpreted in random sequence by a blinded panel of three expert readers for image quality (excellent, good, fair, poor), reader confidence (Low, Moderate, High), overall diagnosis (Normal, Abnormal) and need for follow-up rest imaging. Results: The average time delay between tracer injection and start of imaging was 17 ± 4 minutes (Early) and 67 ± 15 minutes (Late). Image quality was good or excellent in 86% Early vs 94% Late (P = 0.001), with 63% of Early and Late images judged equal in quality. Reader confidence was high for Early (78%) and Late (76%) images (P = ns). Diagnosis was identical for 86% of Early vs Late images, and perceived need for a rest image was the same (12% for both). Conclusions: Acquiring images much earlier after injection of Tc-99m tetrofosmin than is standard in practice appears feasible using CZT instrumentation and attenuation correction. Despite small differences in image quality, the rates for needing follow-up rest imaging were identical and there was a very high degree of agreement in overall diagnosis. There are limited data for their application in obese patients. The purpose of this study was to investigate the effect of delayed imaging time and carbonated water on extracardiac activity in obese patients. Methods: Consecutive patients referred for MPI with pharmacological stress using 99mTc tetrofosmin (Myoview, GE Healthcare) were assigned to three different groups: A -imaging 60 min after radiopharmaceutical injection, B -delayed imaging (75-90 min postinjection), C -delayed imaging and drinking of 200 ml of carbonated water. Patients with BMI C 30 kg/m 2 were considered obese. Patients were imaged in the sitting position using a CardiusÒ X-ACT camera (Digirad, California, USA). The extracardiac activity adjacent to the inferior myocardial wall was determined visually by two experienced readers who accepted MPI for interpretation or decided for repeated acquisition. The proportion of accepted scans was collected prospectively. Results: We studied 490 patients (60% women, age 69.5 ± 10.5 years) and 213 obese (BMI 34.3 ± 3.5). Figure 1 shows the proportion of accepted MPI scans. Obese patients in group A had significantly lower acceptance rate than non-obese patients while there were no differences between them in groups B and C (Figure 1 ). In obese patients, delayed scanning time was shown to increase the acceptance rate by 86% versus a regular scanning time (HR 1.86, 95% CI 1.3-2.6; P = 0.0006). The addition of carbonated water to delayed scanning time further improved the success rate by 20% (HR 1.20, 95% CI 1.0-1.4; P = 0.04). Conclusions: A combination of delayed image acquisition and drinking of carbonated water led to a significant and clinically important decrease of interfering extracardiac activity in obese patients referred to MPI with pharmacological stress. with previous PCI or CABG, were excluded. AC images were processed by the same nuclear technologist with the routine 5 mm low-dose attenuation scan and with a 5 mm CT reformatted from the CAC score acquisition. These perfusion images were reviewed by two board certified nuclear cardiologists for image quality (1-4, with 4 = excellent), subdiaphragmatic tracer uptake (1-4, with 4 = severe), summed stress (SSS), summed rest (SRS), and summed difference scores (SDS). Any datasets with large discrepancies were reprocessed and re-reviewed to exclude processing errors. Results: A total of 20 patients (mean age 62.6 ± 8.3, and 65% male) were included. The average coronary artery calcium score was 636 ± 1251 with four patients having a calcium score of 0. The average image quality of the AC CT scan images was 3.2 ± 0.5 compared to 2.9 ± 0.5 (P = 0.02) and the average GI tracer uptake was 2.3 ± 0.9 vs 2.4 ± 1.0 (P = 0.19). The average difference in the SSS between groups was 0.7 ± 4.3, in the SRS was -0.6 ± 4.8, and in the SDS was 1.4 ± 3.6 ( Figure) . Three patients had a summed score difference greater than 5 when using the CAC score for AC versus the standard AC CT. Conclusion: In this small patient cohort, use of the CAC score CT for attenuation correction was feasible, but further study to confirm the consistency of perfusion findings and interpretation is necessary. Cardiac single-photon emission-computed tomography (SPECT) studies commonly use computed tomography (CT)-based attenuation correction (AC) to improve diagnostic accuracy. However, this is unavailable for SPECT-only scanners and increases radiation exposure to the patient. We developed a method to simulate CTAC images from non-corrected (NC) myocardial perfusion imaging (MPI). Methods: SPECT-MPI was performed using Tc-99m sestamibi or Tc-99m tetrofosmin on scanners with solid-state multi-pinhole detectors. We developed Conditional Generative Adversarial Neural Network (cGAN) which generates simulated attenuation-corrected images (PseudoAC). The model was trained using 798 (train 700: validation 98) pairs of noncorrected and CT-AC MPI studies performed at a single site. We tested the model using studies from an external dataset (N = 178). We assessed the agreement of measures obtained automatically with using quantitative clinical software: stress total perfusion deficit (S-TPD) and stress volume (S-VOL) as well as perfusion change for AC vs PseudoAC and NC scans. Wilcoxon rank-sum test was used to compare median values of S-TPD and perfusion change. Results: The median (IQR) of S-TPD was 4.54 (1.39, 11.29) for AC and 5 5.50 (2.02, 11.69) for Pseudo-AC scans (P = 0.4 from dynamic PET myocardial perfusion imaging (MPI). However, frame-by-frame manual correction is time consuming and is not reproducible. Therefore, we aimed to develop and validate an automated algorithm to perform motion correction in dynamic PET MPI. Methods The algorithm uses simplex iterative optimization of a countbased cost function customized to different dynamic phases for performing frame-by-frame MC. Two experienced operators performed MC in 224 consecutive patients undergoing dynamic rest/stress 82 Rb PET MPI across 16 frames for stress and rest images in three directions (inferior-superior, septal-lateral, apex-base). The third operator reconciled the MC results by a consensus with each operator. 224 patients were split into a tuning group (N = 112) and a validation group (N = 112). Automated and manual MC were compared in the early (first 2 minutes) and late phases for the validation group. Additionally, operators performed MC on a population undergoing 82 Rb PET and invasive angiogram within 18 days (N = 112) which is separate from the tuning and validation groups. MFR was obtained by fitting the corresponding timeactivity curves for each polar map region using QPET software (Cedars-Sinai). The per-patient diagnostic performance for the detection of obstructive coronary artery disease (CAD) by minimal 17-segment MFR was compared for automated MC in the angiographic group. Obstructive CAD was defined as C50% stenosis in the left main trunk or C 70% stenosis in any of the main coronary arteries. Results The automated algorithm generates the corrections in \ 12 seconds per case (stress and rest). The mean/max manual shifts in any direction were 0.8/16 mm at stress and 0.5/14 mm at rest in early phase, and 0.3/8 mm at stress and 0.2/13 mm at rest in late phase. Manual shifts C 5 mm at stress and rest, respectively, were made in 10% and 7% in septal-lateral, 51% and 17% in anterior-inferior, and 27% and 15% in apex-base directions. The frequency of motion differences C 5mm between manual and automated MC in septal-lateral and anterior-inferior directions were \ 5% across all frames at stress and rest. In baseapex direction, motion differences C 5mm were observed still in 14% in frame 3 at stress and \ 5% in remaining frames at stress and rest. There was no significant difference in area under the curve for obstructive CAD detection by MFR between operator MC and the automatic MC ( In patients with suspected coronary artery disease (CAD), evaluation using coronary computed tomography angiography (CCTA) and Single-Photon Emission-Computed Tomography (SPECT) Myocardial Perfusion Imaging (MPI) provide complimentary information on the anatomical extent and functional significance of disease. We aimed to assess the prognostic significance of concordant vs discordant test findings in patients who were investigated with both tests. Methods: Consecutive patients with suspected CAD who underwent CCTA and SPECT MPI within 180 days of each other were reviewed. Anatomically obstructive CAD by CCTA was defined as C 50% in the left main artery and C 70% stenosis severity in proximal, mid, and distal branches of the left anterior descending, left circumflex, and right coronary artery without including side branches. Ischemia on SPECT was defined as summed difference score [ 0. Patients were followed from the date of first imaging to incident major adverse cardiovascular events (MACE -composite of all-cause death, myocardial infarction (MI), and unplanned revascularization -Percutaneous Coronary Intervention (PCI) or Coronary Artery Bypass Graft (CABG) occurring more than 90 days after index imaging.) Results: Our study population consisted of 956 patients (mean (SD) age 61.1 ±14.2 years, 54.1% men, 89% hypertension, 81% diabetes, and 84% dyslipidemia). Obstructive stenosis on CCTA and any ischemic defect on SPECT were present in 14% of patients. After a median follow-up of 31 months (IQR 12-65 months), 102 patients (10.7%, 29.2 events per 1000 person-year) experienced the primary outcome. The highest event rates were in patients with both stenosis on CCTA and ischemia on SPECT (Figure 1) . Patients with abnormal test on either CCTA or SPECT had higher event rates compared to those with normal tests. Conclusion: In this analysis, we have shown that in our high-risk cohort of patients with suspected coronary artery disease, stenosis on CCTA and ischemia on SPECT can be used to identify patients at higher risk of incident cardiovascular outcomes. VISUAL PATTERNS OF BREAST ATTENUATION ARTI-FACTS IN WOMEN AND MEN WITH AN UPRIGHT AND SUPINE CADMIUM-ZINC-TELLURIDE CAMERA F. Waqar*, 1 M. Athar, 1 A. Dwivedi, 2 S. Ahmad, 1 S. Sanghvi, 3 E. Scott, 4 N. Khan, 1 M. Gerson 1 ; 1 University of Cincinnati College of Medicine, Cincinnati, OH, 2 Texas Tech University Health Sciences Center El Paso, El Paso, TX, 3 University of Illinois College of Medicine at Chicago, Chicago, IL, 4 University of Cincinnati Medical Center, Cincinnati, OH Introduction: Breast attenuation is a common source of artifacts in single-photon emission-computerized tomography-based myocardial perfusion imaging. Breast attenuation artifacts occurring with upright Cadmium-Zinc-Telluride (CZT) cardiac imaging systems have not been well characterized. Methods: 216 consecutive patients with Single-Photon Emission-Computerized Tomography myocardial perfusion imaging and no angiographically significant obstructive coronary artery disease were identified. All upright and supine SPECT images as well as coronary angiograms were reviewed and analyzed in blinded fashion. Patients were sub-grouped as obese or non-obese. Comparisons of visual defects between anterior and inferior myocardial territories were evaluated for rest and stress conditions and separately for each gender. All stress and rest images were acquired in upright as well as supine position. Results: In women imaged upright, more visual false-positive defects were noted in the inferior wall compared to the anterior wall (26 vs 10 at rest, P = 0.006, and 33 vs 13 at stress, P \ 0.001). Visual inferior wall defects were more common in the upright than supine position at stress (33 vs 23, P = 0.018) and rest (26 vs 14, P = 0.011), and most apparent in non-obese women (13 vs 8, at stress, P = 0.059 and 11 vs 5, at rest, P = 0.014). Conclusions: With upright CZT myocardial perfusion imaging, women often have visible inferior wall attenuation artifact defects, likely from pendant breast tissue. These inferior wall attenuation artifacts may be seen in non-obese female patients. Introduction: Respiratory and bulk motion frequently reduce the interpretability of cardiac PET images. This study utilized a prototype datadriven motion correction (DDMC) algorithm to generate corrected images, and evaluated image quality and change of perfusion defect size and severity by comparing DDMC images Methods: Rest and stress images with NMC and DDMC from 40 consecutive patients with motion were rated by 2 blinded investigators on a 4-point visual ordinal scale (VOS) (0: no motion; 1: mild motion; 2: moderate motion; 3: severe motion/uninterpretable). DDMC tracks heart motion at a high spatiotemporal resolution from list mode PET data. Resulting motion vectors can be used to quantify the severity of motion Results: A total of 40 patients had mild, moderate, and severe motion, respectively. Fig.1 shows example NMC (1A, VOS = 3) and DDMC (1B, VOS = 0) images from the same patient. All corrected images showed an improvement in quality and were interpretable after processing (Fig 1C) Conclusions: The novel DDMC algorithm improved quality of cardiac PET images with motion. Correlation between data-driven motion quantification and physician interpretation was significant PRIOR SARS-COV-2 INFECTION IS ASSOCIATED COR-ONARY VASOMOTOR DYSFUNCTION AS ASSESSED BY CORONARY FLOW RESERVE FROM CARDIAC POSI-TRON EMISSION TOMOGRAPHY Baseline and stress hemodynamics were obtained, and the CFR was calculated as the ratio of myocardial blood flow (mlÁminÁg) at peak stress over rest. Results: We studied 15 COVID-19 patients and 43 matched controls (median 3 per case) (Table). The median time from SARS-CoV-2 PCR to cardiac PET was 4 (IQR 1.2-5.6) months. 9/15 (60%) of patients were previously hospitalized for COVID-19 infection. Baseline cardiac risk factors were common, and 8 (53%) patients in the COVID-19 group had abnormal perfusion (defined as summed stress score [3). CFR was abnormal (\ 2) in 46% (7/15) of the COVID-19 patients compared to 16.2% (7/43) of matched controls (P = 0.041). The mean CFR was 16 Myocardial infarction (MI) is complicated by post-MI remodeling, which is mediated in part by matrix metalloproteinase (MMP) activation. Intramyocardial injections of hydrogels post-MI can mitigate remodeling Methods: A one-pot reaction was developed to radiolabel 10 mg doxycycline hyclate with [99mTcO4], ascorbic acid, and SnCl2. A range of conditions were tested to optimize specific activity (SA) and radiochemical purity (RP) of Tc-DOX. Quality-control testing was performed via radio-TLC and radio-HPLC. Ad-HA was dissolved in iohexol solution, while CD-HA was dissolved in equal volume of Tc-DOX and combined into HG in Eppendorf tubes. Saline was added to mixture to define Tc-DOX effusion from hydrogel over 24 hours. Supernatant was assayed for radioactivity and exchanged with saline at 1, 2, and 4 hours after gel formation, and HG serially imaged via SPECT/CT. Results: The optimal SA of Tc-DOX was 100 MBqÁlmol, with RP [ 95%. Tc-DOX is stable at room temperature 6 hours after labeling, while precursor was stable for labeling for 2 mon at -80°C. Once in HG, Tc-DOX is slowly released with * 50% HG retention over 24 hours. Conclusion: DOX can be labeled with [99mTcO4 015-09, 015-10, 125-04 C Cacko 112-04 H Hainer 212-01 I Ibrahim 125-04 M MacAskill 212-03 N Nabi, F.; 112-09, 112-11 112-12 R Rabyschoffsky 125-01, 125-02, 125-03 S Saad 207-01, 212-02 U Uman, S.; 212-14 V van Beek 212-12 Y Yee, A.; 125-06 Z Zhang ASNC2021 Keyword Index Acute Coronary Syndrome Calcium Scoring Computer Processing Diastolic Function: 112-06 Fluorodeoxyglucose Hybrid Imaging Image Processing Molecular Probes Myocardial Perfusion