86 TABLE 32. TIONS Wij VaLUES OBTAINED UNDER Various ConpI- OF COLLIMATION, DEPTH, DISTANCES Distance AND Sovurce-To-Rop Pilot ¥Y 2in. X Distance 2 ft Pilot B 2 in. X¥ 2 ft between two Absorher between ; consecutive| hickness,| source EfficienEfficienleadbricks, em. and rod, Resolu- cy,/Resolu-| cy,“ : cm tion,| 10° tion,|! 103 width, cm cm cpm/ cm cpm/ pCi pCi No collimation 3.0 0.0 0.0 10.5 — 8.5 — 0.0 10.5 8.8 — 6.3 $= 3.0 3.0 0.0 2.0 18.5 12.5 &.8 8.8 — —_ 6.3 6.3 — 3.8 3.0 4.0 14.5 8.8 —_— 6.3 —_ 3.0 8. Qt) 18.5 '§ 9.2 1.3 6.3 1.3 0.0 0.0 2.0 4.0 8.0 0.0 14.5 18.5 12.5 14.5 18.5 10.5 . | | | 9.2 9.2 9.2 9.4 10.0 — — 3.5 5.5 4.5 2.0 —_ 8.0 8.0 8.0 8.0 8.0 5.3 3.0 5.0 5.0 5.0 5.0 5.0 5.0 L.0 0.0 0.0 14.5 8.8 10.5 ; 9.2 28 — 63) 8.0 — 9.0 — — 6.8 5,2 2.9 1.5 @) Cs? point source. ®) Cs? 54 cm long distribution. ‘) 7.5 em of polyethylene + 0.5 em of plaster of Paris “tissue .’” TABLE 33. Rod dimensions, cm 5 dia. X 61 L, round of Figure 69 show that the solution can lead ° gerated peaks and valleys and that their locati be seriously misplaced. Preliminaryresults with cylindrical plastic roc tically collimated with sources at realistic p depths are shown in Table 32; from the few expc made we conclude that the resolutions attainab! simulated clinical conditions are of the order of less and that the results obtained with the samc mensional source are similar to those obtained + crystal. With larger prismatic rods, but without ef improve the ensuing crude light piping, the re: of the kernel gets worse (Table 33); hence, one limited with present technology to 5- x o-cm about 100-cm length. It must be noted, howev: faster and more transparentscintillators and mo) tive P.M.’s are alreadyavailable and that better tions are expected. It is our intention, however, to investigate fi mathematical and collimation problems with 2 mensional camera byusing a set of six square roc: feet in length to look at constructional deta: practical model capable of dealing with a twosional phantom. The actual construction of thitype is well under way. Errecr or Rop Cross Section DIMENSION ON RESOLUTION OF PrLoT B Rop‘®) Resolution, cm Resolution, psec Rod dimensions, cm Resolution, cm Co = 3.2 Cs = 4.3 460 630 5 dia. x 91 L, round Co = 3.9 Cs = 5.1 530 700 5 x 5 x 91 L, square Co = 4.6 630 5 x 10 x 91 L, rectan- Co = 7.5 Cs = 9.0 1170 10 x 10 x 91 L, square with light pipe Co = 8.7 Cs = 10.4 1175 1400 gular with light pipe Cs = 6.0 Resolutio! 820 960 (s) All wrapped in black paper. not much could be done by varying /; within the inter- vals considered, kh = 5 cm seemsthe best. We conclude provisionally, that A should be around }4 Wi,;., but recognize that more experimentation is needed onthis point. A preliminary inquiry has been made on the possible success of the iterative method of solving Fredholm’s equation for the distribution considered above. Results REFERENCES 1. Bender, M. A. The digital autofluoroscope, Medical isotope Scanning, Intern. Atomic Energy Agency, V 1964, Vol. 1, pp. 391-399. 2. Ogata, A., Tao, 8. J., and Green, J. H. Reeent develoy in measuring short time intervals by time-to-am} converters. Nucl. Inst. Methods, 60, 141-150 (1968). 3. Potter, R. J. A theoretical and experimental study.