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Kwabenya shadow shield whole body counter for clinical diagnosis and medical research

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by Garbrah, B.W. (Ghana Atomic Energy Commission, Accra)

The construction of a shadow shield whole body counter, using 5.08 cm thick interlocking lead bricks and a 12.7 cm x 10.16 cm NaI(Tl) detector, is described. The final shielding reduced the 100% background, (corresponding to the unshielded detector) to 4.2% in the energy range 1 – 2 MeV. The sensitivity of the counter for the isotopes Iron 59, Cobalt 59, Calcium 47, Sodium 22 and Iodine 131 was 3.5 x 10-3, 4.9 x 10-3, 4.1 x 10-3 and 2.8 x 10-3 microcuries, respectively, using a water phantom for 30-minute scans. The sensitivity for Iron 59 in human subjects was found to be 3.3 x 10-3 microcuries. The redistribution effect on count rates was also studied using point sources placed in wooden phantoms. The maximum longitudinal variation in sensitivity was found to be less than 2%, while the lateral variation had a maximum of approximately 14%. Periodic scanning of three normal Ghanaians for up to a maximum of seven hours after oral administration of Iron 59 showed a maximum variation of activity of 4% approximately, even where two of the subjects had had a meal of rice and chicken one hour after the isotope was administered. (author)

Source/Report: Ghana Medical Journal; p. 24-32; Mar 1976

Publ. Year: 1976

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