title: Comparison between low (3:1) and high (6:1) pitch for routine abdominal/pelvic imaging with multislice computed tomography.
abstract: OBJECTIVE
  The purpose of this study was to compare the performance of low helical pitch acquisition (3:1) and high helical pitch acquisition (6:1) for routine abdominal/pelvic imaging with multislice computed tomography (CT).
  
  
  METHODS
  Three hundred eighty-four patients referred for abdominal/pelvic CT were examined in a breath-hold on a multislice CT scanner (LightSpeed QX/I; General Electric Medical Systems, Milwaukee, WI). Patients were randomized and scanned with pitch of 3:1 or 6:1 using a constant 140 peak kV and 280-300 mA. Images were reconstructed at a 3.75-mm slice thickness. Direct comparison between the two pitches was possible in a subset of 40 patients who had a follow-up scan performed with the second pitch used in each patient. A comparison was also performed between standard dose CT using a pitch of 6:1 and 20% reduced radiation dose CT using a pitch of 3:1. Two readers performed a blind evaluation using a three-point scale for image quality, anatomic details, and motion artifacts. Statistical analysis was performed using a rank sum test and the Wilcoxon signed rank test.
  
  
  RESULTS
  Overall image quality mean scores were 2.5 and 2.3 for a pitch of 3:1 and a pitch of 6:1, respectively (P = 0.134). Likewise, mean anatomic detail and motion artifact scores were 2.5 and 2.6 for a 3:1 pitch and 2.3 and 2.5 for a 6:1 pitch, respectively (P > 0.05). In patients with a direct comparison of the two pitches (with the standard radiation dose as well as with a 20% reduction in milliamperes), no statistically significant difference in the performance of the two pitches was observed (P > 0.05).
  
  
  CONCLUSIONS
  Image quality with a high pitch (6:1) is acceptable for routine abdominal/pelvic CT.
authors.affiliation: Division of Abdominal Imaging and Intervention, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA. dsahani@partners.org
authors.forename: Dushyant
authors.initials: D
authors.lastname: Sahani
authors.forename: Sanjay
authors.initials: S
authors.lastname: Saini
authors.forename: Roy V
authors.initials: RV
authors.lastname: D'Souza
authors.forename: Mary Jane
authors.initials: MJ
authors.lastname: O'Neill
authors.forename: Srinivasa R
authors.initials: SR
authors.lastname: Prasad
authors.forename: Mannudeep K
authors.initials: MK
authors.lastname: Kalra
authors.forename: Elkan F
authors.initials: EF
authors.lastname: Halpern
authors.forename: Peter
authors.initials: P
authors.lastname: Mueller
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003955:Diagnostic Tests, Routine; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010388:Pelvis / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted; D011860:Radiography, Abdominal; D014057:Tomography, X-Ray Computed