[Clinical evaluation of 99mTc-MAG3 as a radiotracer to assess the function of transplanted kidney: comparison with 123I-OIH].

99mTc-MAG3 (mercaptacetyl glycilglycilglycine) is a newly developed radiopharmaceutical for the functional imaging of kidneys. We evaluated the clinical usefulness of 99mTc-MAG3 in 12 cases (7 men and 5 women, aged from 18 to 57 years old) with transplanted kidney, and compared it with 123I-OIH (o-iodohippurate). Immediately after bolus injection of 300 MBq of 99mTc-MAG3, first pass images (1 frame/3 sec for 1 min) and dynamic renal images (1 frame/60 sec for 30 min) were recorded. In 10 of 12 cases, the same examination was carried out using 37 MBq of 123I-OIH within 2 weeks. Because of its larger dose and suitable gamma-ray energy, 99mTc-MAG3 provided much better images than 123I-OIH, particulary among first pass images. Effective renal plasma flow (ERPF) calculated from the clearance of 99mTc-MAG3 was less (about 70%) than that of 123I-OIH, however, a strong correlation (r = 0.98, p < 0.001) was observed between the ERPF values of the two radiotracers. No adverse effects were caused by 99mTc-MAG3. Our data suggested that 99mTc-MAG3 was a promising radiopharmaceutical with which to evaluate regional dynamic renal function.