^99mTc-DTPA dynamic SPECT and CT volumetry for measuring split renal function in live kidney donors

Split renal function (SRF) estimated from the posterior view of ^99mTc-diethylenetriaminepentaacetic acid planar scintigraphy (DTPA/P) is not sufficiently accurate even after correction for kidney depth by computed tomography (CT). To obtain more accurate SRF using ^99mTc-DTPA, dynamic SPECT method was carried out for the initial 5 min after bolus injection of ^99mTc-DTPA (DTPA/SPECT). Also SRF was evaluated from the renal volume measured by CT. We compared the results with ^99mTc-dimercaptosuccinic acid SPECT (DMSA/SPECT).

In 60 consecutive live kidney donors, 30 DTPA/P, 30 DTPA/SPECT, 60 ^99mTc-DMSA/SPECT, and 60 CT studies were performed. In the DTPA/P studies, SRF was calculated from the posterior image recorded during 2–3-min postinjection with attenuation correction for kidney depth measured by CT. In the DTPA/SPECT studies, SPECT images were acquired continuously for 5 min with a dual-headed gamma camera. In ^99mTc-DMSA scintigraphy, DMSA/SPECT images were acquired 3-h postinjection. The SRF on both SPECT studies was calculated from the total counts of each kidney. In the DTPA/SPECT study, SRF was evaluated on the three images summed for 1 min: 1–2 min (DTPA/SPECT1–2), 2–3 min (DTPA/SPECT2–3), and 1–3 min (DTPA/SPECT1–3). In the CT examination, to assess the global renal volume, the axial images in the excretory phase were chosen. Renal contours were identified on each image, and the areas (cm²) of these regions were summed and multiplied by the slice thickness (10 mm) to yield global renal volume (ml). Right renal function from DTPA/P, DTPA/SPECT, and CT were compared with that from DMSA/SPECT as a reference.