title: Helical versus conventional CT in detecting meniscal injuries.
abstract: OBJECTIVE
  We compared volumetric helical and conventional CT in the study of meniscal injuries.
  
  
  METHODS
  Thirty-three patients with suspected meniscal tear underwent helical and conventional CT. Common parameters were 512 x 512 matrix, 14-15 cm FOV, 120 kV and 175 mA; helical CT was performed with 2 mm beam thickness, 1.5 mm/s table feed, 1 mm reconstruction index and conventional CT with 2 s scan time, 1 mm slice thickness and 1 mm table feed. All scans were photographed with a Laser printer using the same window (180/100). All patients also underwent sagittal and coronal T2* GE MRI at .5-T; slice thickness was 5 mm and interslice gap 1 mm. Nonparametric scales were used to study the menisci, as follows: for CT we had A = no visible injury; B = diffuse hypodensity (degenerative condition); C = questionable meniscal tear; D = unquestionable meniscal tear. For MRI, we had A = no visible injury; B = grade 1 or 2 injury; C = grade 3 injury; D = grade 4 injury. We used the 1-4 MR grading by Lotysch et al. and by Crues et al. MRI was used as the gold standard. The agreement between helical CT, conventional CT and MRI was calculated with kappa statistics.
  
  
  RESULTS
  Helical and conventional CT found 23 and 15 patterns A, 6 and 10 B, 3 and 1 C and 1 and 7 D, respectively. MRI found 15 A, 8 B, 3 C and 7 D. There was no agreement between helical CT and MRI and between helical CT and conventional CT because of the meniscal tears underestimated by the former. Agreement was very high between conventional CT and MRI (p < .001).
  
  
  CONCLUSIONS
  The main result of our experience is that helical CT appears less sensitive than conventional CT in detecting meniscal tears. The helical CT section profile (more roundish than that of conventional CT) and the lower radiation dose used by helical CT (with increased quantum noise) may have played a key role in its underestimation of meniscal tears.
authors.affiliation: Department of Radiology, University of Genoa School of Medicine, San Martino Hospital, Italy.
authors.forename: R C
authors.initials: RC
authors.lastname: Parodi
authors.forename: F
authors.initials: F
authors.lastname: Sardanelli
authors.forename: A
authors.initials: A
authors.lastname: Castaldi
authors.forename: G
authors.initials: G
authors.lastname: Cittadini
authors.forename: G
authors.initials: G
authors.lastname: Rescinito
mesh_terms: D000293:Adolescent; D000328:Adult; D003627:Data Interpretation, Statistical; D003937:Diagnosis, Differential; D005069:Evaluation Studies as Topic; D005260:Female; D050724:Fractures, Cartilage / Q000175:diagnosis / Q000000981:diagnostic imaging*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008592:Menisci, Tibial / Q000000981:diagnostic imaging* / Q000473:pathology; D008875:Middle Aged; D008962:Models, Theoretical; D011829:Radiation Dosage; D000070600:Tibial Meniscus Injuries; D014057:Tomography, X-Ray Computed / Q000379:methods*