I-123 whole body scanning: case report and discussion.
OBJECTIVE
In managing differentiated thyroid carcinoma, concern over the stunning that may occur with traditional whole body imaging using I-131 has fostered an interest in using I-123 for this purpose. A case is presented as a focus for discussion of the issues, with special reference to accuracy and the effect thereon of technical factors.


METHODS
A 43-year-old man with papillary carcinoma of the thyroid was scanned after thyroidectomy using 10 mCi I-123. Images at 24 and 48 hours demonstrated foci including multiple regional metastases. They were less well demonstrated in images 7 days after therapeutic I-131, and negative imaging 1 year later implied therapeutic success.


CONCLUSIONS
I-131 has the advantages of a longer half-life, facilitating delayed imaging and lower price. I-123 has the advantages of favorable gamma-ray energy and less useless radiation to thyroid tissue and the whole body. Despite its short half-life, with a sufficient amount, images at 48 hours are practical. In the case presented, there are several possible reasons why superior lesion detection occurred in diagnostic I-123 images. In any case, the outcome demonstrates that I-131 posttherapy images are not an absolute "gold standard" for accuracy. Investigations comparing I-123 with I-131 imaging have been subject to biases, including insufficient dose of I-123, lack of delayed I-123 imaging, suboptimal collimation for I-131, and the relatively high dose of I-131 in posttherapy scanning.


CONCLUSIONS
The evidence, although not definitive, strongly suggests that I-123 is at least as accurate for diagnostic whole body imaging as I-131.
Klein
Herbert A
HA
Department of Radiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15240, USA. herbert.klein@med.va.gov
DiSibio
Kenneth J
KJ
Sims
Diane
D
Singleton
Helen C
HC
Worthy
Lois J
LJ
D000328:Adult; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging* / Q000532:radiotherapy / Q000556:secondary*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D014915:Whole-Body Counting / Q000379:methods*
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals