Imaging Tests

Imaging tests are the next step in figuring out whether a person has lung cancer. Imaging tests create pictures of the inside of the body by using X-rays, magnetic fields, sound waves, or radioactive particles.

Imaging tests cannot confirm that a person has lung cancer. However, they provide a lot of information to help put the whole picture together for the doctor. Imaging tests may be done before a diagnosis of lung cancer, during treatment for lung cancer, and after treatment. They are done for a number of reasons, including:

  • To get more specific information about a suspicious area that might be cancerous
  • To determine how far cancer may have spread
  • To find out if treatment has been effective
  • To monitor for possible signs of cancer coming back after treatment1

Different imaging tests a person might undergo include chest X-ray, CT (computed tomography or CAT) scan, MRI (magnetic resonance imaging) scan, PET (positron emission tomography) scan, and bone scan. These are explained below.

Chest X-ray

An X-ray is a type of energy beam that goes through the body and onto film to produce a picture. A chest X-ray takes pictures of the bones and organs in the chest.2

Chest x-ray

A chest X-ray is often the first test a doctor uses to look for a mass when symptoms are more general. However, chest X-rays often miss small lung cancers when the disease is in its early stage. If you believe you may have lung cancer, ask your doctor for a CT scan instead of, or in addition to, a chest X-ray.

Chest x-ray

Computed tomography (CT or CAT scan)

Computed tomography uses a computer linked to an X-ray machine to make detailed pictures of the inside of the body. Unlike a conventional X-ray, which takes one picture, a CT scanner takes multiple pictures as it rotates around the patient, in order to get images from different angles. Three-dimensional (3D) views of the organs and tissues can be created.

CT scannerA CT scan can provide specific information about the size, shape, and position of masses or nodules in the lung. It also can help find enlarged lymph nodes or masses in other organs that might be caused by the spread of lung cancer. It is important to note that, while a CT scan is very good at showing that something is there, it cannot tell what it is. For that, other tests are needed.

Sometimes a patient will be asked to drink a contrast solution, or a dye will be injected intravenously before a CT scan, so that some organs and blood vessels show up more clearly. A patient must not move while the pictures are being taken. Sometimes a patient may be asked to hold his or her breath for a few seconds. CT scans usually only take a few minutes to complete.1

Today, a low-dose CT scan (LDCT) is most commonly used to look for lung cancer and follow up on changes in lung nodules. This uses less than half the radiation of a regular chest CT scan.3

Chest CT scan

Magnetic resonance imaging (MRI)

Magnetic resonance imaging (MRI) is used in lung cancer to find out whether the cancer has spread to the brain or spinal cord.

MRI scans provide detailed pictures of areas inside the body by using radio waves and strong magnets. The energy from the radio waves is absorbed and then released in a pattern that a computer translates into images. A contrast dye is usually injected intravenously prior to the MRI to make clearer images.

MRI scanner

The scanner is typically a narrow tube in which a patient lies. There are special “open” MRI machines, for people who are not comfortable in a closed MRI machine, but the images are not always as clear. An MRI scan takes longer to perform than a CT scan, sometimes up to an hour. Patients are usually given earplugs because the MRI machines make loud buzzing and clicking noises.1,2

MRI scan

Positron emission tomography (PET)

For a positron emission tomography (PET) scan, a form of radioactive sugar is given intravenously to the patient. Because cancer cells grow rapidly, they absorb more of the radioactive sugar than most healthy cells. About an hour after the injection, the patient is placed on a table in the PET scanner. The patient lies on the table for approximately 30 minutes while a special camera creates a picture of the areas in the body that absorbed the radioactive sugar.

PET scanner

PET scan

A PET scan is used to help determine whether an abnormal area on a chest X-ray or CT scan may be cancer. lt is also used to check whether cancer has spread to lymph nodes, bones, or other organs in the body. PET scans are not as useful in checking for cancer that has spread to the brain because brain cells also absorb a lot of sugar. PET scans cannot differentiate between cells that are rapidly dividing due to infection and those due to cancer; therefore, activity on a PET scan in an abnormal mass is suggestive of cancer, and biopsies are still required to be sure.

Some hospitals and radiology centers have a special scan called a PET-CT scan that is able to do a PET and a CT scan at the same time. This allows the doctor to compare areas of radioactivity on the PET scan with the more detailed appearance of that area on the CT scan.1

Combined PET-CT scan

Bone scan

A bone scan is similar to a PET scan in that a small amount of a radioactive tracer is injected into a vein. Over a couple of hours, the radioactive tracer settles in areas of the bone that have suffered injury, such as injury caused by cancer. The patient then lies on a table for 30 minutes while a camera detects the radioactivity and creates a picture of the skeleton.

Since PET scans also pick up cancer in the bones, they are usually used in place of a bone scan in lung cancer.1,2

Updated February 26, 2016


References

  1. Uses of Imaging. National Cancer Institute website. http://imaging.cancer.gov/patientsandproviders/cancerimaging/usesofimaging. Accessed February 26, 2016.
  2. Lung Cancer – Non-Small Cell: Diagnosis. American Society of Clinical Oncology website. http://www.cancer.net/cancer-types/lung-cancer-non-small-cell/diagnosis. Approved August 2015. Accessed February 26, 2016.
  3. Computed Tomography (CT)—Chest. Radiological Society of North America, Inc. (RSNA) website. http://www.radiologyinfo.org/en/info.cfm?pg=chestct. Reviewed August 13, 2014. Accessed February 26, 2016.

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