99mTc-DTPA gamma-camera renography: Normal values and rapid determination of single-kidney glomerular filtration rate

Abstract

A method for 99mTc-diethylenetriaminepentaacetate (DTPA) gamma-camera renography is presented. From each renogram, an uptake index (UI) proportional to the single-kidney glomerular filtration rate (SKGFR) is defined. If the proportionality factor between UI and SKGFR is the same in all patients, UI can be used as an accurate measure of SKGFR. In order to test this, 99mTc-DTPA renography was performed in 101 patients with glomerular filtration rates (GFR) varying between 4 and 172 ml/min. The sum of the right- and left-kidney UIs correlated well with the total GFR calculated from the simultaneously measured plasma clearance of 99mTc-DTPA after a single injection. The correlation coefficient was 0.97. The method was tested in a prospective study of 57 patients. The total GFR estimated from the renograms was not significantly different from the GFR calculated from the plasma clearance of 99mTc-DTPA. The coefficient of variation--a combination of inaccuracy and imprecision in the estimates as well as in the reference values-was 11.8% at a GFR of 100 ml/min. It is concluded that, in adults, the SKGFR can be calculated as part of the clinical routine from 99mTc-DTPA gamma-camera renography without determining the injected dose or collecting urine or blood samples. Normal values for some parameters of the renogram obtained in 25 normal subjects are given.

Studies on Renal Function in Patients with Cystinuria

“…Background subtraction was applied in all renographic studies. A side distribution o f renal function exceeding 44/56% was regarded as abnormal [18], In the comparison between early and late renographic examinations, a change in RRF o f 10% or more was regarded as significant [19]. Only renograms performed in situations without suspicion o f acute urinary obstruction were used in the evaluation.…”

“…We con structed an estimate o f the normal ranges o f separate GFR using a computer simulation based on the normal mean and standard devia tion for total GFR [23]. in addition to the 95% confidence interval of RRF among healthy subjects reported by Rchlinget al [ 18], The esti mated standard deviation was calculated to be 6. …”

Scintigraphic Imaging of Renal Function

“…Any of equations 6–8 can be used to measure single kidney GFR [27, 28]. Whilst these equations are based on absolute values (i.e., ml and MBq), gamma camera units are simply counts per minute (cpm) and therefore need to be converted to absolute units.…”

“…So Z is the rate of increase in renal activity at t divided by the arterial concentration at t [27]. …”

“…Whilst these equations are based on absolute values (i.e., ml and MBq), gamma camera units are simply counts per minute (cpm) and therefore need to be converted to absolute units. A region of interest can be placed over the heart and a time-activity curve obtained and calibrated with a single timed peripheral venous sample taken at about 20 min after injection [27, 28]when the arteriovenous concentration gradient across the forearm has essentially disappeared [29]. The count rate from the kidney can be converted to MBq of activity by applying a correction for photon attenuation based on measurement of kidney depth and a knowledge of gamma camera sensitivity (cpm/MBq) [27, 28].…”