137 RADIOIODINE UPTAKE MEASUREMENT In order to investigate the potential acceptance of a calibration method, alargeseries of instruments has been set up in Oak Ridge. Most of the methods of doing thyroid uptake measurements can now be duplicated in Oak Ridge, and the methods of intercalibra- tion can be tested on a fixed-geometry training table. This allows for the substitution of various manikins and standardsin a fixed geo- metry with three representative types of ins- trumentation. A series of conferences has been held so that those who have participa- ted in the survey can calibrate their own instrumentation. To assit in the calibration problem a series of calibration kits has been desig- ned. The calibration kits contain the long- life mock-iodine; and when used in con- junction with a carefully designed phantom, the spectrum emitted by the calibration elements will be within the range of the spectra emitted by the necks of patients. Two simulated thyroid glands are included, one at 5 and one at 50 microcuries. Five mocktesttubes with activities ranging from 50 to 0.01 microcuries and 5 simulated capsules with activities ranging from 10 to 0.001 microcuries are included. Thus, it is possible to intercalibrate almost all kinds of instrumentation from highly sensitive well-scintillation counters to very insensitive thin-walled Ec. = - (0005 PAPER CUP” IODINE (St DIFFERENCE 4 “ST TauF tic preie. Counts FEM BEceee Vol. VIT, N? 3-4 Ses TERT OTHER . - f3cc SEARER . BEATA SPECTRA TAMPLE STAN DAMPED SHOCT Fan 0 Tae . 90sec TUSE Mo yMasTOS Oe . AEROT TAOID LAP zray J uStTe . FOLaE stant F G. 8. The first order difference spectra standards compared. of various tient is used. This patient cannot be standardized in any way; however, a selection of patients can afford a reasonable kind of stan- dardization. The kinds of patient in which the newly divised standard technique is valid are only those in which the thyroid gland is in its usual anatomical position and in which the thyroid gland is of reasonablesize. The words “usual” and “reasonable” are used in order to cut out of consideration sublin- gual thyroid tissue, substernal thyroid glands, or metastases in the range of “vision” of the detector. The word “usual size” is defined as follows: Any thyroid gland that can be com- pletely hidden by a 4” by 4” square thyroid eclipse shield is considered to be of usualsize. Geiger-Muller tube external counters. (Nar- row-window spectrometers are always an exception when mock-iodine is used.) Over a two-year period Dr. Hirotake Kakehi, from Chiba University, Tokyo, Japan, used nineteen different kinds of thyroid uptake measuring equipment in Oak Ridge to investigate the problems of thyroid uptake measurement. The results of this very extensive investigation showed that there were a number of major sources of error that were always present in every kind of thyroid uptake measurement. Figure 9 shows a tem- plate that was devised to illustrate almost all of the methods of doing thyroid uptake. In every thyroid uptake measurement a pa- iY STAMBARTIZATION $3 FALNLESS QB sercniacinrion Mubts Soeuegoay Fic. 9. Template for investigating methods of doing thy roid uptake and the individual sources of error contained therein, Reading from left to right on the upper row are the patient, the “B’’-filter, the “A’’—-filter, the collimator, detector, and the scaler. Any method of standardization must include statements on hall of these individual pieces of a calibration method.