RESUMO
We have compared several techniques for measuring [99mTc]DTPA plasma clearance following single injection to estimate glomerular filtration rate (GFR). Half hourly measurements of disappearance of plasma activity were used to calculate a reference GFR corrected for one-pool assumption and body surface area. Alternative methods involving (i) single blood sample, (ii) two blood samples, (iii) external detector clearance rate, and (iv) a combination of (i) and (iii) were then compared. Closest correlations were obtained with (i) two blood samples at 2 hr and 4 hr (s.e.e. 2.8 ml/min) and (i.v.) external rate constant from 2-5 hr with a blood sample at 3 hr (s.e.e. 3.0 ml/min). Correlations with single blood sample were closest at 3 hr and 4 hr postinjection (s.e.e. 5.4 and 4.5 ml/min, respectively). External detector disappearance rate constant alone was least accurate (s.e.e. greater than 10 ml. min).
Assuntos
Taxa de Filtração Glomerular , Ácido Pentético , Renografia por Radioisótopo/métodos , Tecnécio , Humanos , Cinética , Matemática , Taxa de Depuração Metabólica , Ácido Pentético/sangue , Tecnécio/sangue , Pentetato de Tecnécio Tc 99m , Fatores de TempoRESUMO
A comparison has been made between three gamma camera methods for estimation of glomerular filtration rate (GFR) using 99mTc-DTPA in a group of 27 patients with widely different renal function. Plasma clearance of 99mTc-DTPA by multiple blood sampling was used as the reference. Percentage uptake of chelate in the bladder and kidneys at 20 min after injection gave the lowest standard error of 8.0 ml/min. Techniques using early uptake of isotope in the kidneys at 2 min after injection gave less accurate estimates. Correction for the vascular activity in the renal region of interest improved the results for the 2 min uptake technique. Gamma camera techniques provide rapid estimates of GFR which are less accurate than those obtained by plasma clearance of labelled chelate.
