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A method for I131 conversion ratio utilizing the plasma inorganic I131 fraction
  1. H. Oyamada,
  2. E. Irene Pentz
  1. Radioisotope Section, Department of Therapeutic Radiology, Chicago Wesley Memorial Hospital, Chicago, Illinois, U.S.A.
  2. Department of Research, Chicago Wesley Memorial Hospital, Chicago, Illinois, U.S.A.
  3. Department of Radiology, North Western School of Medicine, Chicago, Illinois, U.S.A.


    A method for calculating I131 conversion ratios by utilizing the inorganic I131 counts in the plasma at 24 hours is presented. Its chief advantage over previously used methods is that in cases of low conversion ratio it eliminates the large error introduced by fluctuations in the background of the counting equipment. The principle of the method depends upon the ability of silver to precipitate iodine (I131) in the presence of a slight excess of carrier iodine. Data are presented which show that low conversion ratios are frequently found in euthyroid patients, as has been the finding of other investigators.

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    • 1 This work was supported (in part) by U.S. Public Health Service general research support grant no. 1-GS-70.