Dr. James Stevenson, M.D.
Imaging Scans and Diagnosing Mesothelioma
Imaging tests are used to detect and aid in the diagnosis of malignant mesothelioma. After presenting symptoms, a patient’s physician will likely look over their medical history and conduct a physical exam, blood tests and image testing. An X-ray, MRI or other scan is designed to show any abnormalities that may be causing the patient’s symptoms.
Imaging scans can aid in the following:
- Diagnosis: Can show the presence of malignant tissues, along with location and sizing of existing tumors
- Staging: Shows if the cancer is localized or has spread to nearby or distant organs and lymph nodes
- Progression: Repeated imaging scans can benchmark tumor growth or reduction before, throughout and after treatment
Types of Mesothelioma Imaging Tests
There are five primary types of imaging tests used during a mesothelioma diagnosis, including X-rays, MRI scans, CT scans, PET scans and ultrasounds. Imaging scans are non-invasive and act as a stepping stone in the diagnostic process for mesothelioma patients.
An X-ray provides a flat, 2D image of bones and soft tissue. This is often used by doctors as a first-level diagnostic tool to look at a particular area of the body and determine if additional testing is needed. X-rays can also help rule out other potential misdiagnoses. For example, mesothelioma symptoms like difficulty breathing and chest pain typically lead to a chest X-ray, which can help rule out more common conditions like pneumonia or bronchitis and aid in early detection of the cancer.
X-rays of the chest and abdomen are common for pleural, pericardial and peritoneal mesothelioma and can reveal metastasis and potential indicators of a tumor, such as blockages or effusion (fluid buildup). During the diagnosis of malignant pleural mesothelioma, for instance, chest X-rays may show pleural effusion, pleural thickening, pleural plaques and tumors within the pleura.
An MRI (magnetic resonance imaging) scan uses magnetic fields, radio waves and computer imaging to provide detailed, 3D images of bones and soft tissues. Patients enter a closed or open MRI machine and must lay completely still while scanners circle around the body during a lengthy 30 – 90-minute procedure.
MRI images have been proven to detect tumors sooner than X-rays and CT scans, while also offering more clarity with high contrast between cancerous and healthy tissues. This helps physicians identify the presence of mesothelioma tumors and the extent of the cancer, such as invasion into the chest wall or diaphragm, which are key indicators of stage 3 or stage 4 pleural mesothelioma.
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A CT scan (also referred to as a CAT scan, “computer-assisted tomography” or computed tomography) uses a donut-shaped device that is positioned over the affected area to take a series of X-ray images, composing a 3D model of the scanned area. CT scans are most commonly used to look at organs, tissues and tumors.
These scans can show differences between healthy and cancerous tissues, helping to identify mesothelioma tumors while also displaying symptoms of the disease like pleural and peritoneal effusion. CT scans are not as clear as MRI scans or X-rays and typically are only used for pleural or peritoneal mesothelioma, due to the risks radiation may pose when testing over the heart to diagnose pericardial mesothelioma.
PET (positron emission tomography) scans use nuclear imaging technology and require patients to ingest a radioactive, glucose-based tracer like FDG (fluorodeoxyglucose) that can be detected by a scanning machine. Fast-growing cancer cells have higher metabolic activity and absorb more glucose, allowing the PET scanner to distinguish between healthy and cancerous tissues.
PET scans can help stage mesothelioma cancer by detecting metastasis and can also help determine the viability of certain cancer treatments. Chemotherapy patients may undergo PET scans for physicians to identify damaged tissue after treatment.
Similar to a PET scan, a PET-CT scan combines features of both PET and CT scans to provide
enhanced images of the disease. For late-stage mesothelioma, this hybrid may be a critical tool to view and evaluate the advancing cancer.
Ultrasounds are less common in diagnosing mesothelioma, but are used in some cases, particularly those with testicular mesothelioma. An ultrasound uses high-frequency sound waves to take live images of the body, a process known as sonography, showing organs, vessels and tissues.
Ultrasounds have been performed on mesothelioma patients to help identify tumors after symptoms like dyspnea and chest pain have emerged. They may be preferred for high-risk patients, such as those in poor health or older patients, since they produce no radiation.
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Diagnosis After Imaging Scans
After conducting imaging scans, physicians will likely recommend a biopsy. The biopsy will definitively classify tissues as malignant or benign, and will also determine mesothelioma type, cell type and staging. Imaging scans in combination with a biopsy will help establish an effective treatment plan for the patient, as well as prognosis.
Even after diagnosis, imaging scans are often used to monitor potential metastasis or tumor reduction throughout cancer treatment. Patients who enter remission also undergo frequent followups with image testing to monitor potential recurrence.