Improved visualization of the urinary tract in multidetector CT urography (MDCTU): analysis of individual acquisition delay and opacification using furosemide and low-dose test images.
OBJECTIVE
To retrospectively analyze the reliability of opacification and image quality of a modified MDCTU examination protocol using furosemide and an individual acquisition delay by low-dose test images


METHODS
Excretory phase images obtained from 4-row and 16-row MSCTU examinations in 103 patients (69 men, 34 women) were independently reviewed by two radiologists. MDCTUs were performed by using a low-dose furosemide iv injection. No fixed delay for urographic image acquisition was applied. Urographic timing was individually adjusted by performing low-dose test images of the distal ureters to display their current opacification. Image analysis included grading of opacification and image quality of the segmented collecting system. Average urographic delay was calculated. Stratified comparisons of mean scores were assessed. Interobserver kappa values were calculated.


RESULTS
Calculated median scan delay for patients with normal creatine levels (n = 92) was 420 sec (mean 453 sec; SD, 121 sec). The median number of acquired test images was 2 (range 1-6 images). The analysis of opacification demonstrated that 97% of the ICS, 89% of the proximal, 86% of the middle, and 81% of the distal ureter segments showed opacification greater than 90%. 7.8% of the distal ureteral segments could not be visualized. Statistics did not show significant differences of opacification between proximal, middle, and distal ureteral segments (P > 0.05). Overall image quality of MSCTU showed to be high when latest test images indicated homogeneous bilateral contrasted ureters (Pearson correlation coefficient r= 0.81). Interobserver kappa values were 0.8 and 0.78.


CONCLUSIONS
Furosemide and scan delay timing by means of test images for MDCTU proved to be a reliable procedure to reach improved opacification of the upper urinary tract. It features the individual adaption of MDCTU to the excretory rate of the kidneys.
Kemper
Joern
J
University Medical Center Hamburg-Eppendorf, Clinic of Diagnostic and Interventional Radiology, Hamburg, Germany. jkemper@uke.uni-hamburg.de
Regier
Marc
M
Stork
Alexander
A
Adam
Gerhard
G
Nolte-Ernsting
Claus
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000008:administration & dosage; D004232:Diuretics; D005260:Female; D005665:Furosemide; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives; D007674:Kidney Diseases / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014567:Urography / Q000379:methods*; D014570:Urologic Diseases / Q000175:diagnosis*
D003287:Contrast Media; D004232:Diuretics; D007472:Iohexol; C038192:iopromide; D005665:Furosemide