title: Prostate cancer: endorectal MR imaging and MR spectroscopic imaging--distinction of true-positive results from chance-detected lesions.
abstract: OBJECTIVE
  To retrospectively investigate size criteria for the identification of chance-detected lesions at endorectal magnetic resonance (MR) imaging and MR spectroscopic imaging of prostate cancer.
  
  
  METHODS
  Approval of the committee on human research and written informed consent were obtained. This study was HIPAA compliant. Endorectal MR imaging and MR spectroscopic imaging were performed with a 1.5-T MR imager in 48 men with a mean age of 59 years (age range, 47-75 years) prior to radical prostatectomy. Two independent readers recorded the size and location of all suspected peripheral zone tumor nodules on MR images alone and on images obtained with combined MR imaging and MR spectroscopic imaging. Nodules detected at MR imaging were classified as matched lesions if tumor was present in the same location at step-section histopathologic review. For all matched lesions, kappa values were calculated to examine agreement between measured and actual tumor size. Lesions that were overmeasured at MR imaging with a kappa value of less than 0.2 were considered chance-detected lesions.
  
  
  RESULTS
  At MR imaging, two of 27 and four of 35 matched lesions for readers 1 and 2, respectively, were chance-detected lesions. The corresponding numbers of lesions at combined MR imaging and MR spectroscopic imaging were one of 21 and one of 31, respectively. In all but two cases, the measured diameter of chance-detected lesions was more than twice that of the diameter at histopathologic analysis. By using this diameter threshold to distinguish true-positive results, the mean diameter of detected tumors at histopathologic analysis was 15 mm compared with 4 mm for both undetected and chance-detected tumors (P < .05).
  
  
  CONCLUSIONS
  To ensure uniformity in the comparison of scientific studies, peripheral zone tumors detected at MR imaging and MR spectroscopic imaging of the prostate that are in the same location as tumors detected at histopathologic review should be considered chance-detected lesions if the MR transverse diameter is more than twice the histopathologic transverse diameter.
authors.affiliation: Department of Radiology, University of California, Box 0628, M-372, San Francisco, CA 94143-0628, USA.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Hom
authors.forename: Fergus V
authors.initials: FV
authors.lastname: Coakley
authors.forename: Jeffry P
authors.initials: JP
authors.lastname: Simko
authors.forename: Aliya
authors.initials: A
authors.lastname: Qayyum
authors.forename: Ying
authors.initials: Y
authors.lastname: Lu
authors.forename: Lars
authors.initials: L
authors.lastname: Schmitt
authors.forename: Peter R
authors.initials: PR
authors.lastname: Carroll
authors.forename: John
authors.initials: J
authors.lastname: Kurhanewicz
mesh_terms: D000368:Aged; D003627:Data Interpretation, Statistical; D003937:Diagnosis, Differential; D006801:Humans; D007091:Image Processing, Computer-Assisted; D033162:Incidental Findings; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000601:surgery; D012007:Rectum; D012189:Retrospective Studies; D012680:Sensitivity and Specificity