In-vivo evaluation of standard man model absorbed fractions using /sup 99m/Tc-sulfur colloid

Results are reported from a study performed to check how well the calculated absorbed radiation dose fraction data (S-factors) given in MIRD Pamphlet No. 5 and related reports apply to living patients administered radionuclides. An external target region was defined on the skin of the Snyder-Fisher phantom, anterior to and overlaying the center of the liver. This target was a 5 cm square by 0.089 cm thick slab of LiF, and the S-factors were computed for this target and uniform distributions of /sup 99m/Tc in the liver and spleen. Experimentally, this target was represented by placing thirteen LiF TLD's of the same thickness in a correspondingly positioned 5 cm square area. An experiment performed with the Mr. Adam phantom showed good agreement between the measured (TLD) and calculated (S-factor) doses. In the patient studies, the group of thirteen TLD's was correspondingly positioned, and the measured TLD dose compared to that calculated from the patient cumulated activity and the Snyder-Fisher phantom S-factors. In most cases, these doses agreed to within 30 percent, although larger discrepancies were observed with non-standard sized patients. Based upon these results, it is desirable to make further investigations of this type, especially with lower energy gamma emitters, and the methods of dose and activity measurement used in this study should be useful unless the photon energy is too low, or the source activity changes rapidly with time