In this animal model, unenhanced CT was an effective way to monitor RF ablation compared with sonography because of increased lesion discrimination, reproducible decreased attenuation during ablation, and improved correlation to pathologic size.

Purpose: To evaluate the feasibility and added value of single breathhold diffusion-weighted (DW) imaging (DWI) in oncology patients undergoing abdominal MRI. Materials and Methods:A total of 169 patients with malignancy underwent abdominal MRI at 1.5T, including T1-weighted (T1W), T2-weighted (T2W), and dynamic gadolinium-enhanced imaging. Axial DWI was performed with a single-shot spin-echo (SE) echo-planar imaging (EPI) sequence using a b-value of 500 seconds/mm 2 . A total of 24 slices were obtained during a 20-second breathhold. Two observers reviewed the conventional MR images for tumor. Next, the DW images were reviewed for additional tumor not depicted on conventional MR images Results: For the 169 patients, additional tumors were noted on the DW images in 77 (0.46) for observer 1 and 67 (0.40) for observer 2. For observer 1 the additional tumor included lymphadenopathy (47), peritoneal metastases (15), renal (1), liver (12), and osseous (2), while for observer 2 the corresponding values were lymphadenopathy (40), peritoneal (12), renal (1), liver (6), osseous (4), and gastrointestinal (1). The DW images resolved as benign findings noted on the conventional MR images in three patients for observer 1 and four patients for observer 2. The conventional MR exam was entirely normal while the DW images showed tumor in 12 (0.07) patients for observer 1 and 10 (0.06) patients for observer 2.Conclusion: DWI is feasible in a single breathhold and provides additional clinically important information in oncology patients when added to routine abdominal MR sequences. DIFFUSION IS A PHYSICAL PROPERTY that describes the microscopic random movement of molecules in response to thermal energy. Also known as Brownian motion, diffusion may be affected by the biophysical properties of tissues such as cell organization and density, microstructure, and microcirculation. Diffusionweighted (DW) imaging (DWI) utilizes pulse sequences and techniques that are sensitive to very small-scale motion of water protons at the microscopic level. Singleshot echo-planar imaging (EPI) DWI is utilized to provide very rapid imaging sensitive to subtle small-scale alternations in diffusion. Areas of restricted water diffusion are displayed as areas of high signal intensity (1-4).The application of DWI for the evaluation of acute cerebral infarcts is well established. However, the challenges posed by DWI of the abdomen and pelvis have limited its application for body MRI. On DWI, artifacts related to physiologic motion, susceptibility, and chemical shift are compounded by inherent limitations in signal-to-noise ratio and image resolution. The larger fields of view used for abdominal imaging accentuate many of the artifacts inherent in DWI and single-shot EPI (1-4).Hardware and technical advances in MRI have overcome many of these limitations, making DWI feasible for abdominal and pelvic MRI. Recent works have described the use of single-shot EPI DWI for evaluation of lymphadenopathy (5), liver tumors (6 -8), renal masses (9 -15), prostate cancer ...

Of the MR techniques evaluated, delayed gadolinium-enhanced MRI was the most accurate for the staging and classification of mucinous appendiceal neoplasms and provided prognostic information useful for patient selection.