Scans are helpful tools in helping your doctors see what is happening inside your body’s organs. The imaging tests you need will depend on the stage of your cancer and your lab results.

The CT scan is the most common scan you’ll be requested to get. A CT of the chest, abdomen, and pelvis can show where colorectal cancer is in your body. Doctors use this scan to see if cancer has spread beyond the colon and if so, where and how far.

Sometimes tumors are too small to be seen on scans, and tests may need to be repeated at intervals to find small masses. Or sometimes, liquid biopsy blood tests are performed to confirm or compare the CT imaging to.

CT scans can be done with and without contrast. Contrast refers to a drug or substance that can be taken by IV and/or orally, and its dye that highlights tissues differently and can make abnormal findings easier to see. When you are going to receive oral or IV contrast, you are usually required to fast before the procedure, and it’s typically a solution that you are asked to drink and/or it is injected into your veins.

You and your doctor should discuss and agree upon when to do your next scan. Typically, patients on active treatment are re-scanned every three or six months and follow-up care involves yearly scans for up to five or more years.

MRI (magnetic resonance imaging) uses extremely strong magnetic fields to visualize soft tissues in the body. Unlike a CT scan or Xray, an MRI does not use ionizing radiation to view the body. MRI imaging takes longer to produce than a CT, and as such you will be required to lay motionless in the MRI machine while the image is produced. MRIs can be performed with or without contrast, at the ordering physician’s discretion.

And endorectal MRI is similar to a regular MRI, except that a small coil will be placed in the rectum to help get more detailed images of that area.

An ultrasound, as the name suggests, uses sound waves to visualize tissues and organs within the body. An ultrasound is performed by a technologist using a machine with varying types of “wands” that deliver sound energy to the body and record the images that sound produces. Ultrasounds do not use ionizing radiation, and do not require you to be placed into a narrow machine, so claustrophobia shouldn’t be an issue.

An endorectal ultrasound is simply and ultrasound that uses a wand placed within the rectum to visualize the structures of that organ more completely.

A PET (positron emission tomography) scan is a special test that uses an injectable radioactive substance called a radiotracer and a PET scanner to view how organs and tissues are working in real time. Cancer cells are highly metabolic (use a lot of energy), and because of this they will absorb more of the injected radiotracer than normal, healthy cells. This cancer cell activity can then be viewed using the PET scanner to give your care providers more information about your cancer.

Angiography is a scan that looks specifically at the blood vessels in your body using X-rays. Normally, soft tissues (like blood vessels) don’t show up well on X-rays, so before an angiography begins you will be injected with a special dye to help your blood vessels stand out. Angiography is typically used to view the arteries within the heart but can be used to help visualize the blood vessels that are feeding cancerous tumors within the body.