Original Article
Glomerular filtration rate measured by 99mTc-DTPA Gates method is not significantly affected by the premature or delayed initiation of image acquisition
Abstract
Background: This study was performed to examine the effect of non-synchronization of the radiotracer injection and image acquisition on estimates of the glomerular filtration rate (GFR) by the Gates’ method.
Methods: A total of 218 volunteers were selected as the research subjects. Two-sample method (GFRdt) and 99mTc-DTPA dynamic renal imaging (GFRGates) were used for determination of the GFR. We took GFRdt as the reference method, and then took the peak time of blood perfusion phase as the new time origin to ensure that all patients were unified on the time-radioactivity count rate curve. We moved the radioactivity curve on 9 time points to simulate premature (+20/+15/+10/+5 seconds), synchronous (0 seconds), and delayed (−20/−15/−10/−5 seconds) image acquisition in relation to the completion of tracer injection; we then acquired 9 GFRGates. The correlation and consistency of GFRGates and GFRdt were analyzed. Variance analysis compared the differences between different GFRGates.
Results: All 9 GFRGates had good correlation with GFRdt. GFRdt and GFRGates derived from −5, −10 and −15 s had the best correlation (r=0.827, P<0.01). The consistency between GFRGates derived from +20 s and GFRdt was the worst, and GFRGates derived from –15 s and GFRdt was the best. There were no significant differences between the 9 GFRGates.
Conclusions: Non-synchronization of the radiotracer injection and image acquisition has no significant effect on the estimates of the GFRGates if the premature or delayed time between image acquisition and tracer injection is not more than 20 seconds.
Methods: A total of 218 volunteers were selected as the research subjects. Two-sample method (GFRdt) and 99mTc-DTPA dynamic renal imaging (GFRGates) were used for determination of the GFR. We took GFRdt as the reference method, and then took the peak time of blood perfusion phase as the new time origin to ensure that all patients were unified on the time-radioactivity count rate curve. We moved the radioactivity curve on 9 time points to simulate premature (+20/+15/+10/+5 seconds), synchronous (0 seconds), and delayed (−20/−15/−10/−5 seconds) image acquisition in relation to the completion of tracer injection; we then acquired 9 GFRGates. The correlation and consistency of GFRGates and GFRdt were analyzed. Variance analysis compared the differences between different GFRGates.
Results: All 9 GFRGates had good correlation with GFRdt. GFRdt and GFRGates derived from −5, −10 and −15 s had the best correlation (r=0.827, P<0.01). The consistency between GFRGates derived from +20 s and GFRdt was the worst, and GFRGates derived from –15 s and GFRdt was the best. There were no significant differences between the 9 GFRGates.
Conclusions: Non-synchronization of the radiotracer injection and image acquisition has no significant effect on the estimates of the GFRGates if the premature or delayed time between image acquisition and tracer injection is not more than 20 seconds.
