title: Pulmonary nodules: effect on detection of spiral CT pitch.
abstract: OBJECTIVE
  To compare spiral computed tomography (CT) performed at increased pitch with spiral CT performed at standard pitch in the detection of pulmonary nodules.
  
  
  METHODS
  Spiral CT scanning of the thorax was performed with a pitch of 1.0 in 109 patients with pulmonary nodules due to metastases. The patients were also randomly assigned to undergo further scanning with a pitch of 1.2 (n = 34), 1.5 (n = 37), 2.0 (n = 38) at the same scanning session. The scan pairs were analysed for number, size, and distribution of nodules.
  
  
  RESULTS
  A bias toward undercounting was noted on scans with a pitch of 1.5 and 2.0; however, this was not statistically significant. Correlation coefficients were r = .982, r = .977, and r = .989 for scans of pitch 1.2, 1.5, and 2.0, respectively. Disease in one patient would have been prospectively understaged from findings on a scan of pitch 2.0 because of poor conspicuity of a small solitary nodule.
  
  
  CONCLUSIONS
  Findings from scans with increased pitch generally agree well with those from scans with standard pitch; however, there is a greater risk of understaging of disease in patients with solitary nodules as pitch increases. Pitch should be limited to no greater than 1.5 for initial staging of pulmonary metastatic disease.
authors.affiliation: Department of Radiology, Western General Hospital, Edinburgh, Scotland.
authors.forename: A R
authors.initials: AR
authors.lastname: Wright
authors.forename: D A
authors.initials: DA
authors.lastname: Collie
authors.forename: J R
authors.initials: JR
authors.lastname: Williams
authors.forename: B
authors.initials: B
authors.lastname: Hashemi-Malayeri
authors.forename: A J
authors.initials: AJ
authors.lastname: Stevenson
authors.forename: C M
authors.initials: CM
authors.lastname: Turnbull
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000556:secondary*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013902:Radiography, Thoracic / Q000295:instrumentation / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*