IMAGING

Prostate cancer: apparent diffusion coefficient map with T2-weighted images for detection - a multireader study
Lim HK, Kim JK, Kim KA, Cho KS
Department of Radiology, Asan Medical Center, University of Ulsan, Songpa-gu, Seoul, South Korea
Radiology. 2009; 250: 145-51

• Purpose: To retrospectively assess the incremental value of an apparent diffusion coefficient (ADC) map combined with T2-weighted magnetic resonance (MR) images compared with T2-weighted images alone for prostate cancer detection by using a pathologic map as the reference standard.
• Materials and Methods: This retrospective study was approved by the institutional review board; informed consent was waived. The study included 52 patients (mean age, 65 years +/- 5 [standard deviation]; range, 48-76 years) who underwent endorectal MR imaging and step-section histologic examination. Three readers with varying experience levels reviewed T2-weighted images alone, the ADC map alone, and T2-weighted images and ADC maps. The prostate was divided into 12 segments. The probability of prostate cancer in each segment on MR images was recorded with a five-point scale. Areas under the receiver operating characteristic curve (AUCs) were compared by using the Z test; sensitivity and specificity were determined with the Z test after adjusting for data clustering.
• Results: AUC of T2-weighted and ADC data (reader 1, 0.90; reader 2, 0.88; reader 3, 0.76) was greater than that of T2-weighted images (reader 1, 0.79; reader 2, 0.75; reader 3, 0.66) for all readers (P < .0001 in all comparisons). AUC of T2-weighted and ADC data was greater for readers 1 and 2 than for reader 3 (P < .001). Sensitivity of T2-weighted and ADC data (reader 1, 88%; reader 2, 81%; and reader 3, 78%) was greater than that of T2-weighted images (reader 1, 74%; reader 2, 67%; reader 3, 67%) for all readers (P = .01 for reader 1; P = .02 for readers 2 and 3). Specificity of T2-weighted and ADC data was greater than that of T2-weighted images for reader 1 (88% vs. 79%, P = .03) and reader 2 (89% vs. 77%, P < .001).
• Conclusion: The addition of an ADC map to T2-weighted images can improve the diagnostic performance of MR imaging in prostate cancer detection. (c) RSNA, 2008.
  
  
• Editorial Comment
  Nowadays there is a worldwide tendency to perform a multiparametric endorectal magnetic resonance imaging evaluation of patients suspected or having prostate cancer. On multiparametric MRI evaluation, prostate cancer appears as an area with reduced T2 signal intensity on conventional T2-weighted images, increased choline and decreased citrate and polyamines on magnetic resonance spectroscopic imaging, decreased diffusivity on diffusion weighted-imaging (DWI), and increased uptake on dynamic contrast enhanced (DCE) imaging. All techniques are accomplished in a complete, one-stop shop examination that takes place in about 60-min. Each complementary method has inherent advantages and disadvantages; therefore, they should be combined. The best way to combine these techniques however still needs to be determined. The authors found that the addition of DWI (which is quantified by the apparent diffusion coefficient map-ADC) to the conventional T2-weighted images further improves the performance of MRI in prostate cancer detection.
  The results of this work support that the best characterization of prostate cancer in individual patients will most like result from a multiparametric examination that combines conventional MRI, spectroscopy, diffusion-weighted images and dynamic contrast enhanced technique.

Dr. Adilson Prando
Chief, Department of Radiology and
Diagnostic Imaging, Vera Cruz Hospital
Campinas, São Paulo, Brazil
E-mail: adilson.prando@gmail.com