Because the symptoms of mesothelioma match those of other diseases, mesothelioma can be difficult to diagnose and locate. The tumors may show up in any part of the thin layer that surrounds the organs. They can even be found between organs. For this reason, it is important to use advanced imaging technology to assist with proper diagnosis.
A cancer doctor begins a patient examination with a thorough review of the patient’s medical history. As the diagnosis process continues, there may be several tools used simultaneously to get the most accurate results. Along with blood tests and other examinations, a medical professional may use one or more noninvasive body scans to detect any abnormalities.
The most basic imaging scan is an X-ray. This scan is limited, but may be able to detect damage or abnormalities in the body. One of the biggest drawbacks of an X-ray is that it can only produce a flat, two-dimensional image. When an X-ray is taken, electromagnetic radiation is sent through the body with a photographic film on the other side. The way the waves, or rays, behave will change as they pass through the body, creating a representative image.
On standard X-rays, healthy lungs appear black. When a tumor is present on the pleura, doctors will see a wispy white area that indicates tumor growth. Tumors can also distort the normal shape of the lungs, which can be detected on the radiograph. A tumor-encased lung appears compressed and can show an elevated diaphragm.
One single chest X-ray exposes patients to the same amount of radiation they would naturally encounter over a period of 10 days. This exposure generally does not cause any serious side effects. However, patients are encouraged to hold on to copies of their results to avoid the need for unnecessary duplicate tests over their lifetime.
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Computed axial tomography scans, referred to as either CT scans or CAT scans, utilize X-rays to capture images from inside the body. Radiologists consider the CT scan an optimal tool for detecting cancers, mainly because of the great detail in which the images can portray tumors.
Before the procedure, some patients are given a contrast agent that improves the visibility of specific body parts during the scan. This dye, usually barium or iodine, is either swallowed or injected into the patient’s vein in a 30-second process.
The X-ray machine and the film rotate around the body on one axis and take a large number of images. Scanning takes 30 minutes to an hour. The images are then collated and combined to give doctors an idea of which kinds of tissues are present in the areas of concern. The data can even be manipulated to show different slices of the tissue and rendered into 3-D representations. Although it’s an incredibly valuable tool for the medical industry, a CT scan only represents data in shades of black and white.
Many doctors hail this as the best imaging technology for scans of the chest and abdomen — the two locations where mesothelioma tumors most commonly form. CT scans can help doctors determine the stage of a tumor by revealing whether or not it has spread to nearby tissues, the lymph nodes or to distant organs. A relatively new technique known as CT perfusion is especially effective at determining whether cancer cells have spread throughout the bloodstream.
Magnetic resonance imaging (MRI) scans use electromagnetic radiation to develop images of the body. Hydrogen atoms in the body respond to the magnetic signals by putting out a very weak radio wave, which a computer can analyze. With a few exceptions, MRI scans are not harmful to the human body, while excessive exposure to X-rays can be.
The scanning process is noisy. Patients can hear repetitive knocking sounds as the magnetic field gradients turn on and off, but the test itself is painless. However, some patients experience dizziness, nausea, a metallic taste and brief flashes of light.
The biggest bonus to MRI scans is the ability of the computer to differentiate between tissues in the body and assign them various colors. Doctors get a very clear picture of the interior of the body, which can help locate tumors much earlier than with X-rays and CT scans. They also are generally superior at detecting the extent of a tumor’s invasion of other local structures — one of the key steps in staging a mesothelioma tumor. The earlier mesothelioma is discovered and operated on, the better odds a patient has for survival.
According to a 2019 study published in Cancer Imaging, researchers are investigating the use of dynamic contrast-enhanced MRIs in mesothelioma to better stage the cancer and to better predict a patient’s response to chemotherapy.
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One of the best and most widely used scans for detecting and diagnosing mesothelioma and other kinds of cancer is the positron emission tomography scan, known as a PET scan.
Patients are injected with a radioactive tracer isotope combined with some form of glucose. After a short time, the scanners are able to detect gamma radiation produced by the tissues in the body that are interacting with the tracer isotope. PET scans create detailed images of the body. They can even detect changes in biological processes, allowing doctors to find the smallest tumors.
The most powerful scanning technique combines at least two types of imaging tools. Many scanning machines include PET and CT scanners in the same casing, and some are combined with an MRI. The advantage: Biochemical processes, which show up in a PET scan, can be compared with the anatomy that appears in the CT scan. Both scans can happen almost simultaneously, so the patient does not have to be moved during the scan. This ensures that the images are accurate and aligned.
Some studies suggest that PET scans are more useful than CT and MRI scans for mesothelioma staging. PET scans are highly effective at revealing cancerous activity in the lymph nodes, which implies a later stage of cancer in the traditional TNM staging system. They are also effective for highlighting a spread of cancer that may not appear on other conventional imaging scans.
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Last Modified June 7, 2019