Original Research Role of the Apparent Diffusion Coefficient in the Differential Diagnosis of Gastric Wall Thickening Mehmet Ruhi Onur, MD, 1 * Fatma Ozturk, MD, 1 Cem Aygun, MD, 2 Ahmet Kursad Poyraz, MD, 1 and Erkin Ogur, MD 1 Purpose: To evaluate the role of the apparent diffusion coef- ficient (ADC) measurement made using diffusion-weighted magnetic resonance imaging (DWMRI) in the differential diagnosis of benign and malignant gastric wall thickening. Materials and Methods: Axial T2-weighted and DWMRI at b 600 and b 1000 s/mm 2 gradients were performed in 94 patients (44 patients with gastric malignancy and 50 patients with benign gastric diseases) with gastric wall thickening which was detected by multidetector computed tomography (MDCT). The ADC values of the gastric lesions and healthy gastric walls in patients with gastric malignancies and in patients with benign gastric diseases were used in the differential diagnosis of benign and ma- lignant lesions of the stomach. Results: The mean ADC values were lower in patients with gastric malignancies (1.62 6 0.57 and 1.40 6 0.33 at b 600 and b 1000, respectively) compared to those with healthy gastric walls (2.95 6 0.59 and 2.18 6 0.48) and benign gastric diseases (3.08 6 0.52 and 2.34 6 0.42) at b 600 and b 1000 gradients (P < 0.0001). Conclusion: The ADC measurement on DWMRI may be used to differentiate between benign and malignant gastric diseases. Key Words: stomach; gastric cancer; DWI; ADC; MRI J. Magn. Reson. Imaging 2012;36:672–677. V C 2012 Wiley Periodicals, Inc. GASTRIC CANCER is one of the most aggressive neo- plasms of the gastrointestinal tract (1). Endoscopic examination, barium studies, and multidetector com- puted tomography (MDCT) have been used for the di- agnosis of gastric cancer. MDCT can also be used for determining the presence of recurrent tumors and their response to chemotherapy. However, this modal- ity carries the risk of radiation and CT-detected gas- tric wall thickening of 1 cm or greater has limited specificity for gastric malignancy, which is as low as 42% in some studies (2–4). Although gastric cancers can present as large solid masses or wall thickening on CT or magnetic resonance imaging (MRI), the wall thickening may also be caused by benign gastric dis- eases such as gastritis or portal hypertensive gastro- pathy. Thus, CT and MRI are not the gold standard diagnostic tools for the differential diagnosis of benign and malignant gastric wall thickenings. Recently, diffusion-weighted (DW) MRI has been introduced as a tool for the differential diagnosis of benign and malignant lesions of various organs. The idea to use this technique emerged from the concept that malignant lesions in different tissues show increased signal intensity on DW images due to re- stricted diffusion of water molecules in regions of hypercellularity (5,6). The apparent diffusion coeffi- cient (ADC) value is a quantitative parameter that reflects the thermal diffusion of water molecules in bi- ological tissues. ADC values have been shown to be decreased in various malignancies of different organs due to hypercellularity, as well as gastric malignan- cies (3,5,6). Given the past literature, it may be expected that ADC measurements made using DWMRI would help a radiologist differentiate between benign and malignant gastric lesions. The goal of the present study was to investigate the utility of the ADC measurement as a quantitative parameter for the dif- ferential diagnosis of benign and malignant gastric lesions that present with gastric wall thickening. MATERIALS AND METHODS Participants Between July 2010 and March 2011, a total of 94 patients (57 male, 37 female; age range 27 to 81 years, mean age 57 6 6.3) who were suspected to have abdominal or gastric malignancy and/or gastric wall thickening (>5 mm) detected on CT were pro- spectively evaluated by MRI. The local ethics commit- tee approved the study protocol and written informed consent was obtained from all patients. Forty-four (47%) patients (30 men and 14 women) with a mean age of 62 6 5.3 years (range: 27–72 years) were diagnosed with gastric cancer using endoscopic 1 Department of Radiology, University of Firat Faculty of Medicine, Elazig, Turkey. 2 Department of Gastroenterology, University of Firat Faculty of Medicine, Elazig, Turkey. *Address reprint requests to: M.R.O., Firat Universitesi Hastanesi Rektorluk Kampusu 23119 Elazig, Turkey. E-mail: ruhionur@yahoo. com Received August 11, 2011; Accepted April 11, 2012. DOI 10.1002/jmri.23698 View this article online at wileyonlinelibrary.com. JOURNAL OF MAGNETIC RESONANCE IMAGING 36:672–677 (2012) CME V C 2012 Wiley Periodicals, Inc. 672