The incidence of hepatocellular carcinoma (HCC) is expected to increase in the next 2 decades, largely due to hepatitis C infection and secondary cirrhosis. HCC is being detected at an earlier stage owing to the implementation of screening programs. Biopsy is no longer required prior to treatment, and diagnosis of HCC is heavily dependent on imaging characteristics. The most recent recommendations by the American Association for the Study of Liver Diseases (AASLD) state that a diagnosis of HCC can be made if a mass larger than 2 cm shows typical features of HCC (hypervascularity in the arterial phase and washout in the venous phase) at contrast material-enhanced computed tomography or magnetic resonance (MR) imaging or if a mass measuring 1-2 cm shows these features at both modalities. There is an ever-increasing demand on radiologists to detect smaller tumors, when curative therapies are most effective. However, the major difficulty in imaging cirrhosis is the characterization of hypervascular nodules smaller than 2 cm, which often have nonspecific imaging characteristics. The authors present a review of the MR imaging and pathologic features of regenerative nodules and dysplastic nodules and focus on HCC in the cirrhotic liver, with particular reference to small tumors and lesions that may mimic HCC. The authors also review the sensitivity of MR imaging for the detection of these tumors and discuss the staging of HCC and the treatment options in the context of the guidelines of the AASLD and the imaging criteria required by the United Network for Organ Sharing for transplantation. MR findings following ablation and chemoembolization are also reviewed.

radiology.rsnajnls.org/cgi/content/full/2373041639/DC1

Extravasation of nonionic iodinated contrast medium results only rarely in moderate or severe adverse effects, and these usually occur only when large volumes of contrast medium are involved.

Purpose/Objective Our current understanding of intra-fraction pancreatic tumor motion due to respiration is quite limited. In this study, we characterized pancreatic tumor motion and evaluated the application of several radiotherapy motion management strategies. Materials/Methods 17 patients with unresectable pancreatic cancer were enrolled in a prospective IRB-approved study and imaged during shallow free-breathing using cine MRI on a 3T scanner. Tumors borders were agreed upon by a radiation oncologist and an abdominal MRI radiologist. Tumor motion and correlation with the potential surrogates of the diaphragm and abdominal wall were assessed. This data was also used to evaluate PTV margin construction, respiratory gating, and 4-dimensional treatment planning for pancreatic tumors. Results Tumor borders moved much more than expected. To provide 99% geometric coverage, margins of 20mm inferiorly, 10mm anteriorly, 7 mm superiorly, and 4 mm posteriorly are required. Tumor position correlated poorly with diaphragm and abdominal wall position, with patient-level Pearson correlation coefficients of −0.18 to 0.43. Sensitivity and specificity of gating with these surrogates was also poor, at 53–68%, with overall error of 35–38%, suggesting that the tumor may be underdosed and normal tissues overdosed. Conclusions Motion of pancreatic tumor borders is highly variable between patients and larger than expected. There is substantial deformation with breathing, and tumor border position does not correlate well with abdominal wall or diaphragmatic position. Current motion management strategies may not account fully for tumor motion and should be used with caution.

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