Effect of background region of interest and time-interval selection on glomerular filtration ratio estimation by percentage dose uptake of 99mTc-DTPA in comparison with 51Cr-EDTA clearance in healthy cats

Evaluation of glomerular function is a useful part of the diagnostic approach in animals suspected of having renal disease. Time-interval and background region of interest (bg ROI) selection are determining factors when calculating the glomerular filtration ratio (GFR) based on percentage uptake of 99mtechnetium-labelled diethylene triamine penta-acetic acid (99mTc-DTPA). Therefore, three different time intervals (60–120 s, 120–180 s, 60–180 s) and three different bg ROIs (C-shape, caudolateral, cranial + caudal) were investigated. In addition, global GFRs based on percentage dose uptake of 99mTc-DTPA for the different time-intervals and bg ROIs were compared with the global GFR based on 51chromium-ethylene diaminic tetra-acetic acid (51Cr-EDTA) plasma clearance in nine healthy European domestic shorthair cats. Paired Student’s t-tests and linear regression analysis were used to analyse the data. Different time intervals seemed to cause significant variation (P