-. ,.. .... / 6. : . .. . .... . . $ I OFI. ORNL P 1405 . . L '. j .. . . . I . . . 1. K 7 1 . - - . 1 . .. . . . . . . . . . . .. -.,. A.. ....... ... .... .. .. . 5 50 > i 1..25 .1.4 LS .. MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS - 1963 .... po . - inais 0 F 3 - LEGAL NOTICE This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representa- tion, expressed or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, appa- ratus, method, or process disclosed in this report may not infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report. As used in the above, “person acting on behalf of the Commission" includes any em- ployee or contractor of the Commission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any information pursuant to his employ- ment or contract with the Commission, or his employment with such contractor. : ... . ORNUP-1400 ÚdulF-52373- 'JUL 2 0 1965 "Ep 27:-1778" ABSORBED DOSE FROST:0X-BETA-EMITTING RADIONUCLIDES C. Craig liúrris Oak Ridge l'ationai. Laboratory Oak Ridce, Tennessee Radionuclides that decay by electron capture and/or isomeric tran- sitions are being increasingly used in nuclear medicine. These radio- nuclides, though they emit no actual beta particles, can produce in a patient energy deposition similar to that produced by beta particles. This energy deposition is the result of absorption of soft x-rays and Auger electrons following electron capture, and of absorption of these LEGAL NOTICE - The report wo propared u an account of Government sposored work, Neluter the United Sutos, dor the Commission, por any person ucunc on beball of the Commutulon: A. Makes uy w:ranty or representatoa, expressed or implied, with respect to the accu- racy, completeness, or usefulness of tbe talcrmation conuloed la tato report, or that be we of any information, apparatus, qethod, or procos: dixcloud la this report may oot iniringe B. Asnacs any liabiliuos wild respect to the use of, og for damages resuung from wie Un of Lay lalorasulon, apparatus, metbod, or proceu disclosed in this report. As used in the above. "person acting on beball of the Commisslon" includes any en- ployse or coolriclor of obye Commission, or employee of such contractor, w the extent that such employee or contractor of ebe Commission, or employee of such contractor prepares, dicmemintes, or fejvideo scens Lo, any informator pursount to his cap'ogorot or cootract with the Commission, or his employment with aucb contractor, I princely owned rigble; or radiations and conversion electrons following internal conversion of gamina rays. Because these radionuclides produce less absorbed dose per disinte- cration than radionuclides that emit beta particles, and because many of them have short physical half-lives, a larger number of millicuries can be administered to a patient for the same absorbed dose in the patient (compared with beta-emitting nuclides). For this reason the absorbed dose should be estimated with more care and in more detail than has been done in the past. In 1956 Loevinger et al (1) gave simple expressions that can be used to estimate, from decay-scheme data, the amount of local energy deposition from the electron capture and gamma ray conversion processes. These formu- las are adequately accurate for most radionuclides, though their simplicity causes them to yield a slightly pessimistic figure in some instances. With Research sponsored by U. S. Atomic Energy Commission under contradas with Union Carbide Corporation. PATENT CLEAP.ANCE OBTARTEra FASE TO THE PUBLIC 13 APPROVED. PROCEDURES ARE ON FILE IN THE RECEIVING SECTION -2- some radionuclides, however, inclusion of the often-neglected "littie bits and pieces" modifies the result considerably. Certain nuclides, because of their unusual decay schemes, must be handled with more detail. There: has been derived a set of expressions (2) that are extensions of those given by Loevinger and which make possible a very careful estimation of local energy deposition per disintegration from electron capture and Cannia ray conversion. These expressions also yield numbers of x- and gamma photons per disintegration. The equations themselves are not of great concern to the clinician, but the answers that they produce will be useful in estimating the absorbed dose from internal administration of these radionuclides. Table I gives values of E, for several radionuclides that either have rut been tabulated before, or have been inadequately treated. These values are the total energy deposition from Auger electrons, conversion electrons, L x-rays, and K x-rays below 11.3 keV. The values for mercury-197 and selenium-75 are of special interest. The decay parameters for mercury-197 are not as well established as one would desire. There has been considerable uncertainty in published valdes of Ē, for mercury-197, but we believe the value of 80 keV per dis- integration is as accurate as present decay-scheme data will support. Di- Giulio and Beierwaltes, using the best decay information available at the time, reported a value of 11 keV for selenium-75 (3). The value of 19.2 keV reported here provides an example of energy deposition not accounted for uniess basic information is complete and great care taken. For a more complete treatment of this subject, the reader is referred to reference 2. TABLE I Vales or for several radionuclides, in key per disintegration Nuclide T 1/2 Eg (rounded-off) Cesium-131 7.47 6.1 Chromium-51 Cobalt-57 9.70 28 d 267 C 63.89 120 Mercury-197 Selenium-75 19.2 Strontiim-85 14 Strontium-870 80 h 6 81, 82.8* 14, 15.5** Technetium-99m Eq, if 1.8 keV/disn. from " 15 keV K x rays included as "on-site" depsoition. ** **Eg, if 1.5 kev/disn. from m 19 keV K: rays included as "on-site" deposition. *Includes no component from K x rays. . •. • REFERENCES 1. Loevinger, R., Holt, J.G., and Hine, G. J., in Radiation Dosimetry, Academic Press, New York, 1956, pp 842-847. 2. Smith, E.M., Harris, C.C., and Rohrer, R.H., Calculation of Local Energy Deposition Due to Electron Capture and Internal Conversior., subnitted to J. Nucl. Med. 3. DiGiulio, W., and Beirwaltes, W.H., Parathyroid Scanning with Selenium-75 Labelled Methionine, J. Nucl. Med. 5:417, 1964. -- - ------... -- - -- ----- -- -- ---- : -- - - ... -- --.-- - - - - - ---- - END DATE FILMED 9 / 16 / 165 - De m.