title: Detection of focal hepatic lesions with spiral CT: comparison of 4- and 8-mm interscan spacing.
abstract: OBJECTIVE
  The objective of this study was to determine if spiral CT with 4-mm interscan spacing results in increased confidence in or rate of detection of focal hepatic lesions when compared with spiral CT with 8-mm interscan spacing.
  
  
  METHODS
  Spiral CT scans of the liver of 42 consecutive patients with suspected hepatic disease were independently reviewed by three senior radiologists in two sets: one set was reconstructed with 8-mm interscan spacing and one set was reconstructed with 4-mm interscan spacing. The slice thickness was 8 mm for both data sets. The number and sizes of focal hepatic lesions were documented.
  
  
  RESULTS
  Thirty-three of the 42 patients had least one focal lesion. The lesion size varied from 2 mm to 21 cm. When 8-mm interscan spacing was used, 297 lesions were detected (212 were considered definite). When 4-mm interscan spacing was used, 318 lesions were detected (258 were considered definite). Therefore, 7% more lesions were detected with 4-mm interscan spacing than with 8-mm interscan spacing (p = .05), and 22% more were diagnosed definitively (p < .01). If lesions larger than 4 cm are excluded, 10% more lesions were detected with 4-mm interscan spacing, and 33% more were diagnosed definitively. Of the lesions detected exclusively with 4-mm interscan spacing, 69% were less than 1.0 cm in diameter.
  
  
  CONCLUSIONS
  Spiral CT with smaller interscan spacing (4 instead of 8 mm) results in increased confidence in and rate of detection of focal liver lesions. The additional benefit is most significant with smaller lesions.
authors.affiliation: Department of Radiology and Radiological Science, Johns Hopkins Hospital, Baltimore 21205.
authors.forename: B A
authors.initials: BA
authors.lastname: Urban
authors.forename: E K
authors.initials: EK
authors.lastname: Fishman
authors.forename: J E
authors.initials: JE
authors.lastname: Kuhlman
authors.forename: A
authors.initials: A
authors.lastname: Kawashima
authors.forename: J G
authors.initials: JG
authors.lastname: Hennessey
authors.forename: S S
authors.initials: SS
authors.lastname: Siegelman
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed / Q000379:methods*