Diagnostic performances and clinical usefulness of comprehensive non-commercial software for renogram analysis: Values of renal output efficiency and normalized residual activity in suspected kidney outflow obstruction
Introduction/Objective. Nuclear Medicine Section of IAEA has developed the software for dynamic renal scintigraphy, which allows calculation of advanced parameters of drainage: renal output efficiency (OE) and normalized residual activity (NORA). The aim of this study was to validate IAEA software by comparing results of parameters of renal drainage in normal subjects against their established reference values and to assess diagnostic accuracy of OE and NORA in distinguishing between obstruction/unobstruction. Methods. 55 patients with suspected obstruction and 36 kidney donors were investigated. Group A consisted of 24 obstructed kidneys, Group B of 37 kidneys with dilated urinary tract and Group C of 72 normal kidneys. 40min acquisition was applied. Furosemide was administered after 20min. Post-micturition image was acquired at 50min. Parameters analyzed were: OE at 20min (OE20) and at the end of furosemide test (OE40), NORA at 20min (NORA20) and after micturition (NORAPM). One-way ANOVA was used for evaluating differences between Groups. Ability of OE40 and NORAPM to distinguish between obstruction/unobstruction was determined by ROC curve analysis. The sensitivity, specificity, area under the curve and cutoff values were analyzed. Results. Excellent agreement of our results with established OE and NORA values was found. Difference between Groups was significant for OE20, OE40 NORA20 and NORAPM (p < 0.001). Cut-off values for obstruction were 82% and 0.11 for OE40 and NORAPM, respectively. Conclusion. IAEA software gives reliable analysis of diuretic renography and helps to better diagnose obstruction. IAEA should be encouraged to produce final version of the software and to release it through Web site.