Original Research Prostate Cancer: Utility of Fusion of T2-Weighted and High b-Value Diffusion-Weighted Images for Peripheral Zone Tumor Detection and Localization Andrew B. Rosenkrantz, MD, 1 * Lorenzo Mannelli, MD, 1 Xiangtian Kong, MD, 2 Ben E. Niver, BA, 1 Douglas S. Berkman, MD, 3 James S. Babb, PhD, 1 Jonathan Melamed, MD, 2 and Samir S. Taneja, MD 3 Purpose: To retrospectively assess the utility of fusion of T2-weighted images (T2WI) and high b-value diffusion- weighted images (DWI) for prostate cancer detection and localization. Materials and Methods: In this IRB-approved HIPAA- compliant study, 42 patients with prostate cancer under- went MRI including multiplanar T2WI and axial DWI before prostatectomy. Two independent radiologists first assessed multiplanar T2WI and axial DWI b-1000 images and recorded whether tumor was present in each sextant. Axial T2WI was then fused with axial DWI b-1000 images, and the radiologists re-evaluated each sextant for tumor. Accuracy was compared using generalized estimating equations based on a binary logistic regression model. Results: The accuracy, sensitivity, specificity, PPV, and NPV for tumor detection on a sextant-basis using sepa- rate and fused image sets was 65.1%, 50.8%, 78.0%, 67.8%, and 63.6% and 71.0%, 60.8%, 80.3%, 73.7%, and 69.3%, respectively, for reader 1, and 54.0%, 42.5%, 64.4%, 52.0%, and 55.2%, and 61.1%, 56.7%, 65.2%, 59.6%, and 62.3%, respectively, for reader 2. The improvements in accuracy, sensitivity, and NPV using fused images were statistically significant for both read- ers, as was the improvement in PPV for reader 2 (P rang- ing from <0.0001 to 0.041). With either separate or fused images, there was greater sensitivity for tumors of higher grade or larger size (P ranging from <0.001 to 0.099). Conclusion: Fusion of T2WI and high b-value DWI resulted in significant improvements in sensitivity and ac- curacy for tumor detection on a sextant-basis, with simi- lar specificity. Key Words: prostate cancer; T2-weighted imaging; diffu- sion-weighted imaging; fusion J. Magn. Reson. Imaging 2011;34:95–100. V C 2011 Wiley-Liss, Inc. STANDARD T2-WEIGHTED imaging (T2WI) of the prostate has traditionally been used for staging the local extent of disease in patients with prostate can- cer, while being comparatively limited in the detection and localization of areas of tumor within the prostate (1,2). Functional MRI techniques, such as MR spec- troscopy, dynamic contrast-enhanced imaging, and diffusion-weighted imaging have shown added value in this regard (3). In particular, diffusion-weighted imaging (DWI) is a noncontrast technique that can be easily acquired and processed and that increases the accuracy for tumor localization compared with the use of T2WI alone (4,5). The use of DWI is supported by data showing differences in the apparent diffusion coefficient (ADC) between benign and malignant regions of the prostate (6–8). Past studies have shown the utility of performing DWI of the prostate using relatively strong diffusion weighting as reflected by a high b-value (often 1000 s/mm 2 ) (7,9,10). While this approach may increase the conspicuity of tumor foci, high b-value DWI generally suffers from poor anatomic localization due to reduced signal-to-noise ratio (SNR) and sus- ceptibility artifact that can lead to image distortion and artifactual areas of increased signal intensity (SI) (11,12). One possible technique to improve the anatomic localization of findings identified on high b- value DWI is to perform fusion of these images with T2WI. Indeed, higher accuracy has been shown for the detection of locally recurrent pelvic malignancy (13) and of abdominal malignancy (14) when using fusion of T2WI and DWI compared with the use of these two image sets in a separate manner. However, to our knowledge, no previous study has evaluated fusion of T2WI and high b-value DWI for prostate can- cer detection. Therefore, the purpose of our study was to assess the added value of performing fusion of 1 Department of Radiology, NYU Langone Medical Center, TCH-HW202, New York, New York, USA. 2 Department of Pathology, NYU Langone Medical Center, TCH-HW202, New York, New York. 3 Division of Urologic Oncology, Department of Urology, NYU Langone Medical Center, TCH-HW202, New York, New York. *Address reprint requests to: A.B.R., Department of Radiology, NYU Langone Medical Center, 560 First Avenue, TCH-HW202, New York, NY 10016. E-mail: rosena23@nyumc.org Received June 7, 2010; Accepted March 7, 2011. DOI 10.1002/jmri.22598 View this article online at wileyonlinelibrary.com. JOURNAL OF MAGNETIC RESONANCE IMAGING 34:95–100 (2011) CME V C 2011 Wiley-Liss, Inc. 95