Talia Yeshua1, Ori Gleisner2, Richard Lederman3, Victor Neeman2, Mordechai Duvdevani4, Isaac Leichter2,3. 1. The Applied Physics Department, The Jerusalem College of Technology, Jerusalem, Israel. yeshua@g.jct.ac.il. 2. The Applied Physics Department, The Jerusalem College of Technology, Jerusalem, Israel. 3. Radiology Department, Haddasah Medical Center, Jerusalem, Israel. 4. Urology Department, Haddasah Medical Center, Jerusalem, Israel.
Abstract
PURPOSE: Partial obstruction of the upper urinary tract is a common urological pathology that leads to progressive atrophy and dysfunction of the kidney. Most methods for evaluating the urine drainage rate, to assess the severity of partial obstruction, involve injection of markers into the blood stream and therefore the filtration rate from the blood effects the drainage rate. This study presents a novel method for assessing the drainage rate from the upper urinary tract by analyzing sequential fluoroscopic images from a routine nephrostogram, in which contrast material is introduced directly into the renal collecting system. METHODS: Fluoroscopic images from 36 nephrostograms, following percutaneous nephrolithotomy, were retrospectively evaluated, 19 with a dilated renal pelvis. A radiological model for calculating the radiopacity of the renal pelvis, which reflects the amount of contrast material in each sequential image, was developed. Using this model, an algorithm was designed for generating a drainage curve and calculating the "drainage time" t1/2 in which half of the contrast material has drained from the renal pelvis. RESULTS: Analysis of images of a step-wedge phantom made of an increasing number of contrast material layers showed that the calculated radiopacity of each step was proportional to the amount of contrast material, independent of the background attenuation. Analysis of the nephrostograms showed that the drainage curves highly fitted an exponential function (R = 0.961), with a significantly higher t1/2 for dilated cases. CONCLUSION: The developed method may be used for a quantitative and accurate estimation of the urine drainage rate.
PURPOSE: Partial obstruction of the upper urinary tract is a common urological pathology that leads to progressive atrophy and dysfunction of the kidney. Most methods for evaluating the urine drainage rate, to assess the severity of partial obstruction, involve injection of markers into the blood stream and therefore the filtration rate from the blood effects the drainage rate. This study presents a novel method for assessing the drainage rate from the upper urinary tract by analyzing sequential fluoroscopic images from a routine nephrostogram, in which contrast material is introduced directly into the renal collecting system. METHODS: Fluoroscopic images from 36 nephrostograms, following percutaneous nephrolithotomy, were retrospectively evaluated, 19 with a dilated renal pelvis. A radiological model for calculating the radiopacity of the renal pelvis, which reflects the amount of contrast material in each sequential image, was developed. Using this model, an algorithm was designed for generating a drainage curve and calculating the "drainage time" t1/2 in which half of the contrast material has drained from the renal pelvis. RESULTS: Analysis of images of a step-wedge phantom made of an increasing number of contrast material layers showed that the calculated radiopacity of each step was proportional to the amount of contrast material, independent of the background attenuation. Analysis of the nephrostograms showed that the drainage curves highly fitted an exponential function (R = 0.961), with a significantly higher t1/2 for dilated cases. CONCLUSION: The developed method may be used for a quantitative and accurate estimation of the urine drainage rate.
Authors: Marie-Claire Rassweiler-Seyfried; J J Rassweiler; C Weiss; M Müller; H P Meinzer; L Maier-Hein; J T Klein Journal: World J Urol Date: 2019-05-09 Impact factor: 4.226