Combined use of diffusion-weighted MRI and 1H MR spectroscopy to increase accuracy in prostate cancer detection.
OBJECTIVE
The objective of our study was to establish the sensitivity and specificity for prostate cancer detection using a combined 1H MR spectroscopy and diffusion-weighted MRI approach.


METHODS
Forty-two men (mean age +/- SD, 69.3 +/- 4.7 years) with prostate cancer were studied using endorectal T2-weighted imaging, 2D chemical shift imaging (CSI), and isotropic apparent diffusion coefficient (ADC) maps. Regions of interest (ROIs) were drawn around the entire gland, central gland, and peripheral zone tumor, diagnostically defined as low signal intensity on T2-weighted images within a sextant that was biopsy-positive for tumor. Lack of susceptibility artifact on a gradient-echo B0 map through the slice selected for CSI and no high signal intensity on external array T1-weighted images confirmed the absence of significant hemorrhage after biopsy. CSI voxels were classified as nonmalignant or as tumor (ROI included > or = 30% or > or = 70% tumor). Choline-citrate (Cho/Cit) ratios and average ADCs were calculated for every voxel. A plot of Cho/Cit ratios versus ADCs yielded a line of best separation of tumor voxels from nonmalignant voxels. Receiver operating characteristic (ROC) curves were plotted for Cho/Cit ratios alone, ADCs alone, and a combination of the two.


RESULTS
The Cho/Cit ratios were significantly higher (p < 0.001) and the ADCs were significantly lower (p < 0.006) in tumor-containing voxels than in non-tumor-containing voxels. When voxels containing 30% or more tumor were considered positive, the area under the ROC curves using combined MR spectroscopy and ADC (0.81) was similar to that of Cho/Cit alone (0.79) and better than ADC alone (0.66). When voxels containing 70% or more tumor were considered positive and cutoffs to achieve a 90%-or-greater sensitivity chosen, a combination of Cho/Cit and ADC achieved a significant improvement in specificity compared with Cho/Cit alone (p < 0.0001) or ADC alone (p < 0.0001).


CONCLUSIONS
When voxels containing > or = 70% tumor are considered positive, the combined use of MR spectroscopy and diffusion-weighted MRI increases the specificity for prostate cancer detection while retaining the sensitivity compared with MR spectroscopy alone or diffusion-weighted MRI alone.
Reinsberg
Stefan A
SA
Clinical Magnetic Resonance Group, Royal Marsden NHS Foundation Trust, Royal Marsden Hospital, Downs Rd., Sutton, Surrey SM2 5PT, United Kingdom.
Payne
Geoffrey S
GS
Riches
Sophie F
SF
Ashley
Sue
S
Brewster
Jonathan M
JM
Morgan
Veronica A
VA
deSouza
Nandita M
NM
D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000378:metabolism*; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D014408:Biomarkers, Tumor; D011522:Protons