[Calculation of renal clearance by dynamic measurement of excreted activity].
OBJECTIVE
In this paper we present a new method to measure the renal slope-clearance of Tc-99m-MAG-3 in a single-shot model (Excretion-clearance).


METHODS
A renal scintigraphy with Tc-99m-MAG-3 was performed in 22 patients. The excreted activity of the tracer in the kidneys and the bladder was dynamically measured using a double-head gamma-camera. Additionally the total absorption over the kidneys and the bladder was determined. The Excretion-clearance was calculated in a differential and an integral variant. Simultaneously the 2-compartment-clearance (Sapirstein-clearance), the Oberhausen-clearance and the Bubeck-clearance were calculated.


RESULTS
The Sapirstein-clearance is considered as the "gold standard" in a single-shot model. The correlation of the Bubeck-clearance and the Oberhausen-clearance ranged from r = 0.96 to r = 0.97, the Excretion-clearance (differential-method) correlated with r = 0.90. The absolute difference of the clearance-values was lowest comparing the Bubeck-clearance with the Sapirstein-clearance with an average difference of 11%, whereas the Excretion-clearance revealed at least an average difference of 21% and the Oberhausen-clearance of 24%.


CONCLUSIONS
The Excretion-clearance requires a more complicated protocol measuring the clearance in comparison to the Bubeck-clearance. The results of the excretion-clearance differ more from the Sapirstein-clearance with regard to the examined patient population than the Bubeck-clearance. Regarding the theoretical basis of the methods, we expect advantages of the Excretion-clearance compared with the Bubeck-Clearance in patients with compartmental disproportion or with a low clearance. We are going to prove this in combination with the above mentioned methodical improvements in a further study.
Hackstein
N
N
Klinik für Nuklearmedizin des Zentrums für Radiologie, Justus-Liebig-Universität Giessen, Deutschland.
Bauer
R
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging* / Q000503:physiopathology; D007674:Kidney Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D008954:Models, Biological; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012044:Regression Analysis; D012079:Renal Circulation; D017263:Technetium Tc 99m Mertiatide / Q000493:pharmacokinetics; D001743:Urinary Bladder / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014563:Urodynamics
D019275:Radiopharmaceuticals; D017263:Technetium Tc 99m Mertiatide