title: Elimination of the influence of total renal function on renal output efficiency and normalized residual activity.
abstract: One of the potential limitations in the usefulness of both renal output efficiency (ROE) and normalized residual activity (NORA) is their residual dependence on total renal function. The purpose of this study was to present and examine a new quantitative method whereby the effects of this dependence may be removed.
  
  
  METHODS
  The analytic method involves the determination of a retention function using an unconstrained matrix algorithm deconvolution technique followed by reconvolution with a chosen standard input function to yield a new secondary renal activity time (A/T) curve from which normalized values of ROE and NORA, denoted as N_ROE and N_NORA, respectively, can then be obtained using conventional definitions. The method has been applied in a series of 50 patient studies, which had been acquired using (99m)Tc-mercaptoacetyltriglycine (99(m)Tc-MAG3) and a standard F+18 furosemide protocol, with values of the ratio of plasma clearance to plasma volume (C/V) in the range 0.013-0.242 min(-1).
  
  
  RESULTS
  Pre- and postnormalization values of NORA, calculated at 30 min after injection, showed a significant difference in mean values (paired t test; P < 0.001), with a maximum observed difference, DeltaNORA(30), of -4.82 (-482%) and with a SD on the paired differences, DeltaNORA(30), of 0.56 (56%) or 0.63 (63%) if background subtraction on the input function (BSIF) had been performed. In contrast, corresponding values of ROE showed a nonsignificant difference in means (P > 0.05) and a SD on the paired differences, DeltaROE(30), of 3.7% or 3.2% with and without BSIF, respectively. The normalized parameters N_ROE and N_NORA were found to be strongly linearly correlated (r = -0.99; P < 0.001), in agreement with theoretical predictions.
  
  
  CONCLUSIONS
  These results suggest that renal function affects NORA significantly more than ROE. The effects can be corrected by our normalization technique, resulting in equivalent values of normalized ROE and normalized NORA.
authors.affiliation: Chiang Mai, Thailand. Institute of Nuclear Medicine, 1st Faculty of Medicine, Charles University Prague, Prague, Czech Republic. hermescn@cscoms.com
authors.forename: Cyril C
authors.initials: CC
authors.lastname: Nimmon
authors.forename: Martin
authors.initials: M
authors.lastname: Sámal
authors.forename: Keith E
authors.initials: KE
authors.lastname: Britton
mesh_terms: D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007668:Kidney / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008297:Male; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D011786:Quality Control; D011866:Radioisotope Renography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D017263:Technetium Tc 99m Mertiatide / Q000493:pharmacokinetics*; D014570:Urologic Diseases / Q000097:blood / Q000000981:diagnostic imaging* / Q000378:metabolism*
chemical_list: D019275:Radiopharmaceuticals; D017263:Technetium Tc 99m Mertiatide