W192 AJR:189, October 2007 AJR 2007; 189:W192–W201 0361–803X/07/1894–W192 © American Roentgen Ray Society 10_06_1329_Ocak.fm — 9/27/07 Ocak et al. MRI Diagnosis of Prostate Cancer Based on Pharmacokinetic Parameters Genitourinary Imaging • Original Research Dynamic Contrast-Enhanced MRI of Prostate Cancer at 3 T: A Study of Pharmacokinetic Parameters Iclal Ocak 1,2 Marcelino Bernardo 3 Greg Metzger 4 Tristan Barrett 1 Peter Pinto 5 Paul S. Albert 6 Peter L. Choyke 1 Ocak I, Bernardo M, Metzger G, et al. Keywords: dynamic contrast-enhanced MRI, genitourinary imaging, MRI, pharmacokinetics, prostate cancer DOI:10.2214/AJR.06.1329 Received October 18, 2006; accepted after revision April 23, 2007. Funded in part with federal funds from the National Cancer Institute, National Institutes of Health, under contract N01- CO-12400; and by the Intramural Research Program of the National Institutes of Health, National Cancer Institute, Center for Cancer Research. The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement of the U.S. government. 1 Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892. 2 Present address: Department of Radiology, University of Pittsburgh Medical Center, 200 Lothrop St., Pittsburgh, PA 15213-2582. Address correspondence to I. Ocak (ocaki@upmc.edu). 3 NCI Molecular Imaging Program and Research Technology Program, SAIC-Frederick, Inc., Frederick, MD. 4 Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN. 5 Urologic Oncology Branch, National Cancer Institute, Bethesda, MD. 6 Biometric Research Branch, Division of Cancer Treatment and Diagnosis, National Cancer Institute, Bethesda, MD. WEB This is a Web exclusive article. OBJECTIVE. The objectives of our study were to determine whether dynamic contrast-en- hanced MRI performed at 3 T and analyzed using a pharmacokinetic model improves the di- agnostic performance of MRI for the detection of prostate cancer compared with conventional T2-weighted imaging, and to determine which pharmacokinetic parameters are useful in diag- nosing prostate cancer. SUBJECTS AND METHODS. This prospective study included 50 consecutive patients with biopsy-proven prostate cancer who underwent imaging of the prostate on a 3-T scanner with a combination of a sensitivity-encoding (SENSE) cardiac coil and an endorectal coil. Scans were obtained at least 5 weeks after biopsy. T2-weighted turbo spin-echo images were obtained in three planes, and dynamic contrast-enhanced images were acquired during a single-dose bolus injec- tion of gadopentetate dimeglumine (0.1 mmol/kg). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were estimated for T2-weighted and dynamic contrast-enhanced MRI. The following pharmacokinetic modeling parameters were determined and compared for cancer, inflammation, and healthy peripheral zone: K trans (forward volume transfer constant), k ep (reverse reflux rate constant between extracellular space and plasma), v e (the fractional volume of extracellular space per unit volume of tissue), and the area under the ga- dolinium concentration curve (AUGC) in the first 90 seconds after injection. RESULTS. Pathologically confirmed cancers in the peripheral zone of the prostate were characterized by their low signal intensity on T2-weighted scans and by their early enhance- ment, early washout, or both on dynamic contrast-enhanced MR images. The overall sensitiv- ity, specificity, PPV, and NPV of T2-weighted imaging were 94%, 37%, 50%, and 89%, re- spectively. The sensitivity, specificity, PPV, and NPV of dynamic contrast-enhanced MRI were 73%, 88%, 75%, and 75%, respectively. K trans , k ep , and AUGC were significantly higher (p < 0.001) in cancer than in normal peripheral zone. The v e parameter was not significantly associated with prostate cancer. CONCLUSION. MRI of the prostate performed at 3 T using an endorectal coil produces high-quality T2-weighted images; however, specificity for prostate cancer is improved by also performing dynamic contrast-enhanced MRI and using pharmacokinetic parameters, particu- larly K trans and k ep , for analysis. These results are comparable to published results at 1.5 T. rostate cancer is the most preva- lent noncutaneous cancer in men and is the second leading cause of cancer-related deaths in American men. In 2006, the American Cancer Society estimated that 234,460 American men would be diagnosed with prostate cancer and that 27,350 men would die from the disease [1]. The incidence of prostate cancer has been in- creasing because of improved diagnosis, higher prevalence in an aging population, and increases in potential environmental carcino- gens [2]. Most of these newly detected tumors are confined to the prostate gland; however, existing imaging methods fail to localize the site of prostate cancer in 25–30% of the cases [1, 3]. Moreover, endorectal sonography and MRI using a conventional endorectal coil lack specificity for prostate cancer [4]. The ability of MRI to localize and stage prostate cancer could assist in the management of newly di- agnosed prostate cancer. There are several methods that can improve the localization of prostate cancer using T2- weighted MRI. One method is to perform MRI at higher field strengths, thus improving the signal-to-noise ratio (SNR). Another method is to use additional imaging tech- P Downloaded from www.ajronline.org by 52.73.204.196 on 05/16/22 from IP address 52.73.204.196. Copyright ARRS. 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