Prostate depiction at endorectal MR spectroscopic imaging: investigation of a standardized evaluation system.
OBJECTIVE
To investigate the accuracy and interobserver variability of a standardized evaluation system for endorectal three-dimensional (3D) magnetic resonance (MR) spectroscopic imaging of the prostate.


METHODS
The human research committee approved the study, and all patients provided written informed consent. Endorectal MR imaging and MR spectroscopic imaging were performed in 37 patients before they underwent radical prostatectomy. For the 22 patients with good or excellent MR spectroscopic imaging data, step-section histopathologic tumor maps were used to identify spectroscopic voxels of unequivocally benign (n = 306) or malignant (n = 81) peripheral zone tissue. Two independent spectroscopists, unaware of all other findings, scored the spectra of the selected voxels by using a scale of 1 (benign) to 5 (malignant) that was based on standardized metabolic criteria. Descriptive statistical, receiver operating characteristics (ROC), and kappa statistical analyses of the data obtained by both readers were performed by using two definitions of cancer: one based on a voxel score of 3-5 and the other based on a score of 4 or 5.


RESULTS
The scoring system had good accuracy (74.2%-85.0%) in the differentiation between benign and malignant tissue voxels, with areas under the ROC curve of 0.89 for reader 1 and 0.87 for reader 2. Specificities of 84.6% and 89.3% were achieved when a voxel score of 4 or 5 was used to identify cancer, and sensitivities of 90% and 93% were achieved when a score of 3-5 was used to identify cancer. Readers demonstrated excellent interobserver agreement (kappa values, 0.79 and 0.80).


CONCLUSIONS
The good accuracy and excellent interobserver agreement achieved by using the standardized five-point scale to interpret peripheral zone metabolism demonstrate the potential effectiveness of using metabolic information to identify prostate cancer, and the clinical usefulness of this system warrants testing in prospective clinical trials of MR imaging combined with MR spectroscopic imaging.
Jung
Juyoung A
JA
Department of Radiology, University of California-San Francisco, San Francisco, CA 94143, USA.
Coakley
Fergus V
FV
Vigneron
Daniel B
DB
Swanson
Mark G
MG
Qayyum
Aliya
A
Weinberg
Vivian
V
Jones
Kirk D
KD
Carroll
Peter R
PR
Kurhanewicz
John
J
D000328:Adult; D000368:Aged; D019540:Area Under Curve; D003430:Cross-Sectional Studies; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D009682:Magnetic Resonance Spectroscopy / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011467:Prostate / Q000473:pathology; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000473:pathology; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity