MR imaging of hepatic metastases.

MR imaging is an excellent diagnostic tool for the detection and characterization of liver metastases. The most characteristic finding is peripheral ring enhancement on immediate postgadolinium images.

Post-treatment malignant liver lesions. MR imaging.

MR imaging is very accurate in the diagnosis and staging of tumors and in surgical planning. MR imaging is also an excellent method for evaluation of the liver after surgical resection, systemic or local tumor therapies, and liver transplantation. It permits early recognition of complications and the presence of recurrent tumor, providing an opportunity to repeat treatment or use alternative treatment. Surgical resection remains the standard therapy for treating liver metastases. The relatively small number of patients who are candidates for curative resection have provided impetus for the implementation and improvement of other techniques. The variety of techniques and the sensitivity for contrast enhancement have made MR imaging an ideal method to follow the response of tumors to various treatment approaches. The appearance of tumor recurrence and the response to treatment are relatively consistently shown on MR images; however, the time course of change in lesion appearance has not been fully elucidated, particularly in the setting of chemotherapy. Evaluating the response to chemotherapy is rendered complex because of the longer duration of the therapy, the types of response that various chemotherapeutic agents engender, the method of action of this therapy and the time of imaging in relation to therapy. The various local therapies share some general principles of action, and many have similar MR imaging findings. Some local therapies are effective only with certain malignancies (e.g., alcohol therapy and HCC), whereas other therapies are more limited because of the size of the tumor kill zone (e.g., interstitial laser therapy). We are in the early stages of using MR imaging to guide local therapies and to monitor response during treatment in real time. This appears to be an important future direction for MR imaging. The role of MR imaging in liver transplantation involves pre- and postoperative investigation of both donors (in the case of living-related transplantation) and recipients. These issues are described further in the section on MR imaging of liver transplantation.

Magnetic resonance imaging of pulmonary parenchymal disease using a modified breath-hold 3D gradient-echo technique: initial observations.

PURPOSE: To determine the potential of a modified breath-hold 3D gradient-echo technique for visualizing pulmonary parenchymal diseases. MATERIALS AND METHODS: Twenty-one magnetic resonance imaging (MRI) studies of the lungs were performed in 20 patients (15 male and 5 female; age range, 7.7-86.1 years) with pulmonary diseases comprising non-small-cell, small-cell, and bronchioalveolar carcinomas, endobronchial mucoepidermoid carcinoma, metastases, pneumonia, Wegener's granulomatosis, chronic obstructive pulmonary disease, arterio-venous malformation, and bronchogenic cyst. Confirmation of diagnoses was obtained via histopathology (14 patients) and follow-up (6 patients). MRI studies were performed at 1.5 T before and after administration of gadolinium using a modified volumetric interpolated breath-hold examination (VIBE) sequence. All images were evaluated prospectively regarding lesion detection and characterization. MR findings were correlated with final diagnoses. Retrospective grading (scores, 1-4) was performed for general image quality (rated "poor" to "excellent"); presence of artifacts ("negligible" to "severe"); and imaging quality of pulmonary lesions (conspicuity and contrast on pre- and postgadolinium images). RESULTS: Twenty-three solid pulmonary lesions, 25 infiltrates and segmental atelectases, and 1 cyst were detected and prospectively correctly diagnosed. Sizes ranged from 0.3-10 cm. The mean scores for image quality and presence of artifacts were 3.3 (SD, 0.7) and 1.8 (SD, 0.7), respectively. Conspicuity and contrast of pulmonary lesions received mean scores between 3.0 and 3.8 (SD, 0.4-0.7). CONCLUSION: This MRI technique allows imaging of a wide spectrum of solid and nonsolid pulmonary parenchymal diseases with reproducible high image quality, effective suppression of artifacts, high resolution, and visualization of gadolinium enhancement.