Mesothelioma Diagnosis: Imaging Scans
If a patient has a history of exposure to asbestos, the first type of testing that will be used to determine if they have mesothelioma is an imaging scan. Different types of scans are used for diagnosis and staging of the tumor.
A Chest X-Ray is the First Diagnostic Tool
Although a chest x-ray is usually the first test that is ordered, its usefulness
is limited. The disease image produced by the x-ray is not specific enough
to make a diagnosis of mesothelioma. That’s because the findings
from this type of imaging scan are similar to the findings that would
be observed in a number of diseases such as lymphoma and benign asbestos-related disease.
In addition, if the patient has only a small buildup of fluid, it may not be visible on a chest x-ray. On the other hand, a large fluid buildup may hide that fact that the pleural layer is thickening and/or parts of the tumor, resulting in a misdiagnosis of the extent of the disease.
Computed Tomography Gives More Detail
The next type of imaging scan that is used is Computed Tomography or CT scan. This test allows the radiologist to see if the pleural lining is thickening, and any fluid buildup that is present regardless of its size. Also, the extent the tumor has invaded the pleura, the area between the lungs and the chest wall can also be evaluated on the basis of the image provided by a CT scan.
If peritoneal mesothelioma is suspected, a CT scan can help determine if the diaphragm has been invaded and if there is ascites (fluid buildup in the abdominal cavity).
Magnetic Resonance Imaging Shows Images in More than One Dimension
Magnetic Resonance Imaging, or MRI as it is more commonly known, collects
information about the various types of tissues, and it uses that information
to create images that have more than one dimension. That is why it is
superior to a one-dimension CT scan in demonstrating individual points
where the tumor has invaded the chest wall and diaphragm invasion.
Special dyes that can be injected into the patient called contrast change the magnetic field in the tissue being evaluated. Normal and abnormal tissue react differently to the change made by the contrast and they will send out different signals that appear as images. An MRI reads these signals and then translates them into images using various shades of gray. By analyzing the lightness or darkness of the shade, the radiologist can tell the difference between normal and abnormal tissue and how extensive the abnormality is.
It is important to note that neither CT scanning nor MRI provides enough information for the doctor to make a definite diagnosis of mesothelioma. Additional tests like tissue biopsy are also needed.
Ultrasound may be Required to Help Ensure the Accuracy of a Biopsy
Although an ultrasound is able to demonstrate the presence of pleural thickening and fluid buildup, it doesn’t give a very detailed evaluation. If an ultrasound is ordered, it is usually to guide the surgeon where to remove tissue/fluid samples for biopsy in order to make the most accurate diagnosis.