The chest radiograph remains the primary imaging technique in the evaluation of lung cancer. Further evaluation of the extent of bronchogenic carcinoma in the thorax for the extent of the tumor (T) or the involvement of lymph nodes (N) can be performed with approximately equal efficacy with either computerized tomography (CT) or magnetic resonance imaging (MR). CT is performed more frequently because of lower cost and greater availability.

Prediction of the presence or absence of mediastinal lymph node involvement is poor. Sensitivity and specificity are both in the 50% to 60% range because these judgments are based entirely on nodal size. Larger lymph nodes are more likely to be involved with metastatic disease. Identification of metastatic disease in normal sized nodes cannot be performed with either CT or MR.

Identification of obvious chest wall or mediastinal invasion can be obtained with equal accuracy using either CT or MR. However, MR, because of its multiplanar imaging ability, is the examination of choice for evaluating superior sulcus tumors and may be helpful in resolving specific questions regarding the chest wall and mediastinum.

Identification of metastatic disease (M) beyond the thorax is usually a contraindication to surgery. CT evaluation for lung cancer should include the liver and adrenal glands to rule out metastasis at these sites. As a general rule of thumb, approximately 5% of all patients will have silent metastasis beyond the thorax. This estimate will vary with the stage of the disease--less than 5% in low stage and above it in high stage disease.

Investigation of the brain is more effective with MR than CT. MR is more sensitive. CT and MR are of approximately equal effectiveness in evaluating the liver and adrenal glands. As in the thorax, MR may be used to resolve specific problems in the liver and adrenal glands. Radionuclide scanning remains the preferred technique in seeking bony metastases. It is quite sensitive, but not specific. Positive findings must be confirmed with other imaging.

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose is an exciting new area in the staging of bronchogenic carcinoma and other malignancies. Early reports are encouraging, but further experience with PET scanning is needed. Also, PET scanning currently is not available in many institutions.