Recently, the labeling of the currently preferred renographic test compound, o-iodohippurate,5 with a newly available radioisotope, I125, has allowed a simplification of equipment used for the radioisotope renogram. Formerly, sodium o-iodohippurate (Hippuran)-I131 was the test agent of choice for renography in all ages. The high-energy γ-rays of I131 plus the resultant "Compton effect" scattering made necessary the use of heavy lead collimators around thick scintillation crystals in order to achieve a high kidney/contiguous tissue radiation ratio. Although the test was applicable to any age group, the bulky scintillation probes made it difficult, geometrically, to obtain close proximity to the infant's kidneys. This problem is obviated with the use of I125 8,9
The decay scheme of I125 produces soft x-rays and low-energy γ-rays with a narrow energy spectrum between 27-35 kev compared with the wide energy spectrum for I131 of from
WINTER CC. Radioisotope Renography Refinement in Pediatrics. Am J Dis Child. 1963;105(5):475–477. doi:10.1001/archpedi.1963.02080040477009
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