Original Research Dynamic Contrast-Enhanced MRI of Primary Rectal Cancer: Quantitative Correlation With Positron Emission Tomography/Computed Tomography Jing Gu, MD, 1 Pek-Lan Khong, MD, 1 Silun Wang, MD, PhD, 1 Queenie Chan, PhD, 2 Ed X. Wu, PhD, 3 Wailun Law, MD, 4 Rico Kingyin Liu, MD, 5 and Jingbo Zhang, MD 1 * Purpose: To assess the correlations between parameters measured on dynamic contrast-enhanced magnetic reso- nance imaging and 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in rectal cancer. Materials and Methods: To assess the correlations between parameters measured on dynamic contrast- enhanced MRI and FDG-PET in rectal cancer. Results: Significant correlations were only demonstrated between k ep and SUVmax (r ¼ 0.587, P ¼ 0.001), and k ep and SUVmean (r ¼ 0.562, P ¼ 0.002). No significant differ- ences were found in imaging parameters between well, mod- erately and poorly differentiated adenocarcinoma groups. However, there was a trend that higher imaging values were found in poorly differentiated adenocarcinomas. Conclusion: Positive correlations were found between k ep and SUV values in primary rectal adenocarcinomas sug- gesting an association between angiogenesis and meta- bolic activity and further reflecting that angiogenic activ- ity in washout phase is better associated with tumor metabolism than the uptake phase. Key Words: DCE-MRI; PET/CT; rectal adenocarcinoma J. Magn. Reson. Imaging 2011;33:340–347. V C 2011 Wiley-Liss, Inc. ANGIOGENESIS, THE PHYSIOLOGICAL process of new blood vessel formation, is essential in human de- velopment, reproduction, and repair (1). However, pathological angiogenesis, triggered by activation of certain cellular signal pathways, is considered a key factor for solid tumor to develop, grow, and metasta- size (2). Colorectal carcinoma has been found highly associated with angiogenesis and malignant rectal tu- mor tissue generally has greater angiogenic activity than normal rectal tissue (3–6). Activity of tumor angiogenesis may be assessed by several methods. In human tumors, angiogenesis can be assessed by the expression levels of microvessel density and vascular endothelial growth factor (VEGF) using histopathological methods (4,7–11). However, these techniques require tumor tissues and need to be performed on either preoperative biopsy samples or postoperative surgical specimens. Dynamic contrast- enhanced MRI (DCE-MRI) is a noninvasive imaging technique assessing angiogenesis activity by meas- uring signal intensity change in tumor tissue over time, which is related with the concentration change of diluted low molecular weight paramagnetic contrast agent in the extravascular-extracellular space (EES) in vivo (12–14). Quantitative data analysis was based on commonly used two-compartment pharmachoki- netic modeling (blood plasma and EES) by which a set of standardized quantity terms have been generated, such as K trans (transfer constant between the blood plasma and the EES), k ep (rate constant between the EES and the blood plasma) and the EES fractional vol- ume (y e , interstitial space; 15). Some studies have dem- onstrated the relationship between VEGF or microves- sel density and K trans or k ep (16–18), suggesting that DCE-MRI may be a potential tool to characterize the angiogenic activity of a tumor other than invasive histo- morphological approaches. On the other hand, increased glucose metabolism is another feature commonly seen in many tumors (19). Malignant cells often show increased glucose uptake in vitro and in vivo, which is believed to be facilitated by glucose transporters (20,21). It has been reported that the levels of glucose transporter expression are associ- ated with tumor aggressiveness and patient survival (20). In addition, glucose levels in the primary rectal adenocarcinoma are significantly higher than normal tissues (22). Positron emission tomography (PET) is 1 Department of Diagnostic Radiology, The University of Hong Kong, Queen Mary Hospital, Hong Kong. 2 Philips Healthcare, Philips Electronics Hong Kong Limited, Wanchai, Hong Kong. 3 Laboratory of Biomedical Imaging and Signal Processing and the Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong. 4 Division of Colorectal Surgery, Queen Mary Hospital, The University of Hong Kong, Hong Kong . . 5 Department of Clinical Oncology, Queen Mary Hospital, The University of Hong Kong, Hong Kong. *Address reprint requests to: J.Z., Department of Diagnostic Radiol- ogy, Memorial Sloan-Kettering Cancer Center, C278, 1275 York Ave- nue, New York, NY 10073. E-mail: zhangj12@mskcc.org Received April 24, 2010; Accepted September 15, 2010. DOI 10.1002/jmri.22405 View this article online at wileyonlinelibrary.com. JOURNAL OF MAGNETIC RESONANCE IMAGING 33:340–347 (2011) V C 2011 Wiley-Liss, Inc. 340