Mesothelioma Diagnosis Through CT, MRI, and PET Scans

Mesothelioma Diagnosis

Mesothelioma Diagnosis: Imaging Is a Crucial Step

Imaging is crucial in diagnosing mesothelioma as well as in discovering how far the cancer has spread (mesothelioma staging). Your doctor will usually take chest x–rays, and then decide if further tests such as CT, MRI, and PET scans are required. Tissue and fluid sampling may be used to confirm imaging results.

Chest X–Rays

The diagnosis of respiratory problems often begins with chest x–rays. An x–ray of a patient with mesothelioma may show irregular thickening of the pleura or the thin covering that protects and cushions the lungs. It may also show pleural calcifications (mineral deposits), lowering of the lung fissures (spaces between the lobes of the lungs) and accumulation of fluid in the lungs (pleural effusion) or in the abdomen (ascites) (American Cancer Society, Malignant Mesothelioma). These can be ominous signs leading to further testing and a mesothelioma diagnosis.

Computed Tomography or CT Scans

If your x–rays show pleura and lung abnormalities, your doctor may ask you to undergo a computed tomography or CT scan. A CT scan is a special radiographic technique that uses a computer to combine multiple x–ray images into a 2 dimensional cross–sectional x–ray image. A machine rotates 180 degrees around the patient’s body, sending out a thin x–ray beam at numerous points. Crystals at the opposite points of the beam pick up and record the absorption rates of the varying thickness levels of tissue and bone. The computer turns the information into a detailed picture. The CT scan allows a radiologist to see distinct areas of the lungs and pleura to better advantage than x–rays.

For most chest scans, you will lie on a machine couch while the scanning machine goes over you. The process is not painful, although you may be a bit uncomfortable because you will need to remain still. You may be given an injection of dye to help show structures near the area containing the cancer. The CT scan takes from 20 minutes to an hour to complete, depending upon the type of scanning equipment and the tests required.

A CT scan helps determine the location, size and extent of any mesothelioma tumors. Besides showing pleural effusions and pleural thickening, the CT scan may sometimes indicate disease beyond the pleura within the chest wall or lymph nodes (AJR Am J Roentgenol. 1990 Nov; 155(5): 965–9). It may also be useful in evaluating the condition of the lungs (Semin Oncol. 2002 Feb; 29(1):26–35).

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) scans use magnetic fields, radio waves, and a computer to create images of selected areas of the body. MRI images tend to be quite clear and are superior to routine x–ray images. Theoretically, an MRI scan may improve the contrast between tumor and normal tissues.

MRI scans have been used in mesothelioma patients who are candidates for surgery in order to obtain additional information about possible tumor spread. Some doctors feel that the difference in diagnostic accuracy between MRI and CT scans in staging pleural mesothelioma for purposes of surgery are not that great. Others point to significant improvement in the ability of MRI scans to show invasion of the diaphragm area by tumors (AJR Am J Roentgenol. 1999 Apr; 172(4):1039–47).

An MRI scan is painless, but noisy. You may want to wear ear plugs during an MRI scan. You will also have to take off any jewelry or metal, which may interfere with the test.

Positron Emission Tomography (PET)

Positron emission tomography (PET) scans use cameras and tracers to form images that indicate biological changes and detect extremely small cancerous tumors. PET scans often provide even more information than CT or MRI scans. See a detailed description of PET techniques in mesothelioma diagnosis.