MR imaging of thoracic lymph nodes. A comparison of computed tomography and positron emission tomography

CT scanning has traditionally been the preferred imaging modality for the assessment of patients with non-small-cell lung cancer. The low sensitivity and specificity of CT scanning, however, has limited its usefulness in assessing nodal status. Despite this limitation, CT scanning still plays an important role by aiding the selection of the most appropriate procedure for staging purposes, guiding biopsy procedures, and providing anatomic information for visual correlation with FDG-PET images. Anatomic imaging with MR imaging has been shown to have accuracy comparable with CT scanning in assessing mediastinal lymph nodes. MR imaging, however, is more accurate than CT in the assessment of hilar lymph nodes. At present, anatomic imaging of lymph nodes with MR imaging should be considered a secondary, problem-solving tool for cases in which CT scanning is inconclusive. Advances in physiologic imaging of mediastinal lymph nodes with FDG-PET imaging have resulted in better diagnostic accuracy than obtained with anatomic imaging with CT scans or MR imaging. At present, an imaging strategy that employs both FDG-PET imaging and CT scanning appears to be the most accurate, noninvasive, and cost-effective means available for assessing nodal status in patients with non-small-cell lung cancer. Physiologic MR imaging with iron oxide is currently being assessed in clinical trials. Future studies are necessary to determine the clinical efficacy, accuracy, and cost effectiveness of this technique.