title: Prevalence and nature of excluded findings at reduced scan length CT angiography for pulmonary embolism.
abstract: BACKGROUND
  Scan length reduction effectively decreases radiation dose at CT pulmonary angiography (CTPA) for pulmonary embolism (PE) but may exclude important incidental scan findings.
  
  
  OBJECTIVE
  We aimed to determine the prevalence and nature of excluded findings with the use of reduced scan length CTPA.
  
  
  METHODS
  We reviewed 335 consecutive emergency department CTPA studies performed on 16- or 64-detector row scanners with the use of a standard scan range. A scan length of 14.2 cm that was centered 4.1 cm below the carina has been shown to be adequate for PE diagnosis. Boundary slices for this scan range were determined. All pertinent and incidental findings within and outside the reduced scan range were noted. To determine the significance of newly detected excluded findings, we reviewed medical records and all relevant imaging studies before and 9-11 months after the reference CTPA.
  
  
  RESULTS
  We found 374 pertinent findings in 192 patients, including 28 (8%) cases of PE. All except 3 (0.8%) were adequately seen with the reduced scan range, among which only one finding altered clinical management. There were a total of 230 incidental findings in 165 patients, 60 (26%) of which were excluded; 23 (10%) of the 60 were newly detected, including 10 thyroid nodules, 6 liver lesions, and an 8-mm pulmonary nodule. The reduced scan length decreased z-axis coverage by 49% ± 6%.
  
  
  CONCLUSIONS
  Substantial scan length reduction at CTPA may not compromise the diagnostic yield for pertinent alternative diagnoses.
authors.affiliation: Department of Diagnostic Imaging, Rhode Island Hospital, Warren Alpert School of Medicine, Brown University, Providence, RI 02903, USA. atalay_99@yahoo.com
authors.forename: Michael Kemal
authors.initials: MK
authors.lastname: Atalay
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Walle
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Egglin
mesh_terms: D000328:Adult; D000368:Aged; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging* / Q000453:epidemiology; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D012237:Rhode Island / Q000453:epidemiology; D014057:Tomography, X-Ray Computed / Q000379:methods*