Biomedical subjects

Wigbert Stefan Rau

Publications and source records attributed to Wigbert Stefan Rau.

3 recordsLinked to original sources

PubMed2003

Glomerular filtration rate measured by using triphasic helical CT with a two-point Patlak plot technique.

PURPOSE: To determine the accuracy of the two-point Patlak plot in the calculation of glomerular filtration rate (GFR). MATERIALS AND METHODS: Fifty patients without acute renal disorder were included. GFR was calculated by using a two-point Patlak plot technique. The computed tomography (CT) protocol consisted of a plain examination followed by two contrast material-enhanced examinations in the arterial and portovenous phase. Each examination included the entire kidneys and was performed after injection of 120 mL iopromide and 300 mg of iodine per milliliter given per 75 kg of body weight. All examinations were performed with a standard abdominal protocol. Section thickness was 4 x 2.5 mm, and table advance was 12.5 mm. Bolus triggering commenced 10 seconds after the start of contrast medium injection. Twelve dynamic scans were obtained with reduced tube current every 3 seconds to obtain sufficient arterial input function data. Correction for hematocrit level was made by using the unenhanced attenuation of the aorta. As a reference method, plasma clearance of the contrast medium injected for CT was calculated from three iodine plasma concentration measurements obtained 3, 4, and 5 hours after injection. Linear correlation was performed. RESULTS: GFR was calculated from CT data in 48 patients. Two patients were excluded because of breathing errors. Mean GFR was 80 mL/min (range, 17-153 mL/min) as measured with iopromide plasma clearance and 82 mL/min (range, 28-148 mL/min) as measured with CT. Linear correlation between the two methods was r = 0.889; GFR calculated with the two-point Patlak plot was equal to 15 plus 0.83 times GFR (plasma clearance). The mean difference between GFRs as determined with the two methods was -1.2 mL/min (95% CI: -27.1, 24.6). CONCLUSION: Total GFR can be measured accurately with minimally extended triphasic CT in patients without acute renal disorder by using a two-point Patlak plot technique.

Adult↗

PubMed2003

Measuring single-kidney glomerular filtration rate on single-detector helical CT using a two-point Patlak plot technique in patients with increased interstitial space.

OBJECTIVE: We measured the single-kidney glomerular filtration rate (GFR) with a two-point Patlak plot technique based on multiphasic CT in patients with hydronephrosis or pyelonephritis or both. The question we sought to answer in our study was, Does increased interstitial space as measured with the Patlak plot technique cause overestimation of GFR? SUBJECTS AND METHODS: Twenty adult patients treated with percutaneous nephrostomy were studied. The CT protocol consisted of an unenhanced scan and three subsequent scans obtained 38, 71, and 102 sec after the initiation of the contrast medium injection. Plasma clearance of the contrast medium was determined and used as the reference. Additionally, single-kidney excretory clearance was determined by separate urine collections from the left and right kidneys. A three-compartment model calculation was made using all data available to estimate volume and transfer rate constant of the interstitial space. RESULTS: The GFR determined using plasma clearance correlated well with the GFR determined using excretory clearance, with a correlation coefficient of r = 0.94 and a regression line of y = -6 + 0.97 x x. GFR of both kidneys as measured using CT was overestimated according to the GFR determined using plasma clearance, with a correlation coefficient of r = 0.80, and a regression line of y = 35 + 0.79 x x. Single-kidney excretory clearance GFR was similarly overestimated using single-kidney CT GFR, with a correlation coefficient of r = 0.81 and a regression line of y = 20 + 0.84 x x. Single-kidney parenchymal volume was used as an indicator of interstitial space enlargement. The overestimation of excretory clearance GFR using CT correlated significantly with the parenchymal volume of the individual kidneys. A high correlation was also found between overestimation of total GFR determined with CT and interstitial space estimated using a three-compartment model calculation. Relative interstitial space was estimated to be 25% (range, 9-46%) of total kidney volume. CONCLUSION: Using the interstitial space as a third compartment may introduce an error into the measurement of GFR with the Patlak plot technique. We found that the CT protocol in our study resulted in considerable overestimation of GFR as determined with the Patlak plot in patients with increased interstitial space.

Contrast Media↗

PubMedDate not supplied

Sonography of the common bile duct and the gallbladder during ceruletid infusion.

In the present study, we investigated a new sonographic test to confirm or exclude partial common bile duct (CBD) obstruction, hereinafter called "dynamic cholangio-cholecysto sonography (DCCS)." Healthy controls (6) and patients with low- to intermediate probability for partial CBD obstruction (17) were investigated. DCCS started with three baseline masurements of gallbladder volume and CBD diameter, which were then repeated every 2 to 3 min for 45 min during a 30-min infusion of ceruletid. According to CBD diameter change during gallbladder contraction, DCCS was considered positive (> 1 mm), negative (< 0.5 mm) or equivocal (remainder). After DCCS, all patients underwent endoscopic retrograde cholangiography (ERCP) and all but one patient had endoscopic sphincterotomy (EST). A follow-up examination was performed at least 4 weeks after ERCP. Based on these results, an outcome score was calculated to classify the patients as having a flow-relevant CBD obstruction or not. DCCS was true positive in 4 patients (sensitivity 66%, positive predictive value 100%). DCCS was false-negative in 1 patient and equivocal in another patient. DCCS was true-negative in 9 patients (specifity 82%, negative predictive value 90%). Two patients without flow-relevant CBD obstruction had equivocal DCCS test results. DCCS might be used as a noninvasive test for further workup of patients with low- to intermediate probability of flow relevant CBD obstruction, helping to avoid unnecessary ERCP and to serve as an additional indication for ERCP and EST.

Adult↗