ABSTRACTS PRESENTADOS AL 11th INTERNATIONAL SYMPOSIUM "RADIONUCLIDES IN NEPHRO-UROLOGY", REALIZADO EN MONTEREY, CALIFORNIA, 13-17 MAYO 2001.

22. DETERMINATION WITHOUT DECONVOLUTION OF MEAN TRANSIT TIME INDICES IN THE 99mTc-DTPA RENOGRAPHY USING ONLY AN EARLY AND A LATE SERIES OF RENAL IMAGES.

Ove Carlsen.
Department of Clinical Physiology and Nuclear Medicine.
Vejle Hospital, DK-7100 Vejle, Denmark.

ove-carlsen@get2net.dk

The analysis makes use of early of an images (0-2 1/2 min postinjection) and a late series of images (the last 5 min). Regions of interest (ROIs) over the kidneys, the renal parenchyma and renal backgrounds were created in both sets images of images. A robust method for the determination without deconvolution of mean transit time indices for the whole kidney and the renal parenchyma was established based on the pooled results of two renal transport models.

Simulation studies and studies in patients with normal and delayed renal outflow show a close relationship between the whole kidney and the renal parenchymal mean transit times and the mean transit time indices.

The method presented has several advantages over the conventional analysis of the 10 sec/frame dynamic series of images recorder for 20-30 min.: a) The method is tolerant to movement of the patient on the couch during the examination (pediatric patients need not be under an anaesthetic); b) In fact, the patient need not even be lying on the couch in the time interval between the early and the late images (an ideal situation for pediatric patients), c) It permits a pixel by pixel background correction of the early image for determination of the fractional renal clearances and the estimation of total glomerular filtration rate, d) The mean transit time index is believed to be less sensitive to outflow irregularities than the mean transit time based on deconvolution methods, e) Since the renal ROIs in the early image are drawn around the renal parenchyma, the renal volumes can be estimated using a geometrical method; f) In order to further investigate the possible occurrence of obstruction in a very dilated renal pelvis, the late image can easily be replaced by a separately recorded image of the kidneys after the completion of the 99mTc-DTPA renography.