title: Low-dose MDCT urography: feasibility study of low-tube-voltage technique and adaptive noise reduction filter.
abstract: OBJECTIVE
  The purpose of this study was to investigate the feasibility of performance of MDCT urography with low tube voltage and an adaptive noise reduction filter.
  
  
  METHODS
  Thirty-one patients underwent excretory phase (300 seconds after administration of 100 mL of iopamidol) 40-MDCT of the urinary tract at 120 and 80 kVp. The 80-kVp images were postprocessed with an adaptive noise reduction filter. Using a 3-point scale for homogeneity of the urinary tract and sharpness of contour, streak artifacts, and overall image quality, two radiologists evaluated coronal multiplanar reconstruction images generated from 120-kVp, unfiltered 80-kVp, and filtered 80-kVp images. Attenuation values of the abdominal aorta, renal pelvis, renal cortex, psoas muscle, vertebral body, and retroperitoneal fat and image noise of the psoas muscle were measured. The effective radiation dose was estimated for each patient.
  
  
  RESULTS
  At visual evaluation of images of the upper urinary tract, the quality of filtered 80-kVp images was comparable with that of 120-kVp images. At evaluation of images of the lower urinary tract, however, filtered 80-kVp images were of inferior quality. Except for those of fat tissue, attenuation values were significantly higher on 80-kVp than on 120-kVp images (paired Student's t test, p < 0.01). Noise values did not differ significantly between 120- and filtered 80-kVp images (Dunnett test, p = 0.37). The mean effective doses for 120- and 80-kVp scans were 7.0 and 2.9 mSv.
  
  
  CONCLUSIONS
  MDCT urography is feasible with a low-tube-voltage technique and an adaptive noise reduction filter. The technique allows reduction in radiation dose without marked degradation of image quality and can be used in clinical assessment of the renal collecting system and upper ureter. For evaluation of the pelvic ureter and urinary bladder, however, image quality is not sufficient, and a compensatory increase in tube current may be necessary.
authors.affiliation: Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto, 860-8556, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Yanaga
authors.forename: Kazuo
authors.initials: K
authors.lastname: Awai
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Funama
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakaura
authors.forename: Toshinori
authors.initials: T
authors.lastname: Hirai
authors.forename: Sebastien
authors.initials: S
authors.lastname: Roux
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamashita
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D003287:Contrast Media / Q000008:administration & dosage; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007479:Iopamidol / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D014567:Urography / Q000295:instrumentation / Q000379:methods*; D014570:Urologic Diseases / Q000000981:diagnostic imaging*
chemical_list: D003287:Contrast Media; D007479:Iopamidol