title: Low-dose abdominal computed tomography for detection of urinary stone disease - Impact of additional spectral shaping of the X-ray beam on image quality and dose parameters.
abstract: OBJECTIVE
  To evaluate a novel tin filter-based abdominal CT protocol for urolithiasis in terms of image quality and CT dose parameters.
  
  
  METHODS
  130 consecutive patients with suspected urolithiasis underwent non-enhanced CT with three different protocols: 48 patients (group 1) were examined at tin-filtered 150kV (150kV Sn) on a third-generation dual-source-CT, 33 patients were examined with automated kV-selection (110-140kV) based on the scout view on the same CT-device (group 2), and 49 patients were examined on a second-generation dual-source-CT (group 3) with automated kV-selection (100-140kV). Automated exposure control was active in all groups. Image quality was subjectively evaluated on a 5-point-likert-scale by two radiologists and interobserver agreement as well as signal-to-noise-ratio (SNR) was calculated. Dose-length-product (DLP) and volume CT dose index (CTDIvol) were compared.
  
  
  RESULTS
  Image quality was rated in favour for the tin filter protocol with excellent interobserver agreement (ICC=0.86-0.91) and the difference reached statistical significance (p<0.001). SNR was significantly higher in group 1 and 2 compared to second-generation DSCT (p<0.001). On third-generation dual-source CT, there was no significant difference in SNR between the 150kV Sn and the automated kV selection protocol (p=0.5). The DLP of group 1 was 23% and 21% (p<0.002) lower in comparison to group 2 and 3, respectively. So was the CTDIvol of group 1 compared to group 2 (-36%) and 3 (-32%) (p<0.001).
  
  
  CONCLUSIONS
  Additional shaping of a 150kV source spectrum by a tin filter substantially lowers patient exposure while improving image quality on un-enhanced abdominal computed tomography for urinary stone disease.
authors.affiliation: University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt, Germany.
authors.forename: Patricia
authors.initials: P
authors.lastname: Dewes
authors.affiliation: University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Frellesen
authors.affiliation: University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt, Germany.
authors.forename: Jan-Erik
authors.initials: JE
authors.lastname: Scholtz
authors.affiliation: University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Fischer
authors.affiliation: University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt, Germany.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Vogl
authors.affiliation: University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt, Germany. Electronic address: ralfwbauer@aol.com.
authors.forename: Ralf W
authors.initials: RW
authors.lastname: Bauer
authors.affiliation: University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt, Germany.
authors.forename: Boris
authors.initials: B
authors.lastname: Schulz
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging; D000328:Adult; D016477:Artifacts; D005260:Female; D005374:Filtration / Q000295:instrumentation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D016658:Psoas Muscles / Q000000981:diagnostic imaging; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000379:methods*; D011860:Radiography, Abdominal / Q000295:instrumentation / Q000379:methods*; D059629:Signal-To-Noise Ratio; D014001:Tin; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D014545:Urinary Calculi / Q000000981:diagnostic imaging*
chemical_list: D014001:Tin
keywords: CT; Low-dose abdominal CT; Spectral shaping; Tin filter; Urinary stone disease