The half maximum time of (99m)Tc-DTPA renography measured in healthy kidney donors, compared to (131)I-OIH.

Technetium-99m-diethylene triamine pentaacetic acid ((99m)Tc-DTPA) has been widely used after (131)I-ortho-hippurate ((131)I-OIH) for renography and to test renal function. Only a few reports refer to normal values range of (99m)Tc-DTPA renography half maximum time (HMT). We have measured the normal value range of (99m)Tc-DTPA renography HMT in our department, of 433 healthy kidney donors from 2007 to 2010, and compared these results with those of (131)I-OIH renography. There were 326 men and 107 women, 18y-69y (median age 29y), subjects were measured before the donation of their kidneys operation and their biochemical, ultrasound and renal function tests were normal. All subjects drunk at least 1 litre of tap water before renography. The (99m)Tc-DTPA dynamic scintigraphy was performed in the posterior view by injecting intravenously as a bolus 185-296MBq. Dynamic imaging was performed immediately after the injection, using a high-resolution low-energy general purpose collimator and a large field of view dual-detector gamma-camera (Hawkeye; General Electric Medical Systems, USA). Matrix was 64Χ64, the phase acquisition time of blood perfusion was 1s/frame and 30 frames were collected. Dynamic acquisition was 30s/frame and 39 frames were collected. Total acquisition time was 20min. We defined as background two regions of interest around the kidneys and the aorta, for radioactive decay correction. We also compared (99m)Tc-DTPA renography HMT values with the HMT values of (131)I-OIH, between the two kidneys, and between men and women. The findings were evaluated by using frequency distribution analysis, paired Sample Student's t-test and one sample t test, with a level of significance P<0.05. We used the SPSS 10.0 statistical software. Since values beyond a high boundary were regarded as unusual, we used the P(95), i.e. " 95% of HMT reference ranges value" to determine the medical reference range of values, as the HMT normal limit. This reference value is used especially when the data shows a skewed distribution. For the HMT (P(95) value), the normal reference values found between mean values of the left and the right kidney were: 10.76±4.14min and 10.89±4.55min, respectively and P=0.416, two tailed. For the left kidney HMT, there was no significant difference between men: 10.90±4.31min and women: 10.33±3.57min, (t=1.235, v=432, P=0.2186, two tailed), and similar findings were found between men's right kidney HMT: 11.02±4.89min and women's right kidney HMT: 10.49±3.32min, (t=1.253, v=266.59, P=0.211, two tailed). By comparing the mean value of (99m)Tc-DTPA renography HMT measured (10.76min, 10.89min) with the mean value of (131)I renography HMT that we found in the literature as referring to both left and right kidneys (4min). We found a significant difference (P=0.000, two tailed). Renography may be used to diagnose urinary tract obstruction, estimate the split renal function and is useful.