The glomerular filtration rate determined with 99mTc-DTPA and a portable cadmium telluride detector.

In twenty-two patients with 51Cr-EDTA renal clearance (glomerular filtration rate) values of 36-141 ml/min, the final plasma disappearance rate constant of i.v. injected 99mTc-DTPA (Sn) was found to be very close to that of 51Cr-EDTA determined from 180 to 300 min after injection. The disappearance of i.v. injected 99mTc-DTPA (Sn) was also recorded from the body surface by means of a low weight cadmium telluride detector (CRN, Strasbourg, France) and commercially available stationary or portable tape recorders. The disappearance rate constant of 99mTc-DTPA as determined externally from 30 min was comparable to that in plasma determined from 180-300 min. The external rate constant could be converted to plasma clearance by means of one plasma 99mTc-activity determination 180 min after injection. The calculated values agreed with the conventionally determined 51Cr-EDTA clearance values. The portability of the detector system allows it to be used to estimate alterations in GFR during the measurement due to changes in physical conditions such as posture, exercise, etc.