What Imaging (Radiology) Tests Are Used in Cancer?

We use imaging tests to take pictures of the body, detect problems and understand what they are. Imaging tests are our most important tool for looking for cancer, determining how far it has spread and seeing whether cancer treatment is working.

What Are Imaging Tests?

An imaging test is a method that allows doctors to see what is happening inside your body. These tests send forms of energy, such as X-rays, sound waves, radioactive particles or magnetic fields, into the body. Different tissues respond differently to these energies, creating anatomical images in which tissue boundaries can be distinguished or an abnormal formation within a tissue, such as a tumor, becomes visible.

What Are Imaging Tests Used for in Oncology?

Imaging tests are used in cancer for many reasons:

• To look for cancer in its early stages before it causes symptoms. This can be called early detection or cancer screening tests .
• To look for a tumor in someone with symptoms or signs of cancer. We call this searching for the primary tumor. They can also help determine whether symptoms result from cancer or another disease.
• Sometimes, they help predict whether a tumor may be cancerous. This can help healthcare professionals decide whether a biopsyis necessary. In a biopsy, a small sample of suspicious tissue is taken and examined under a microscope. A biopsy is almost always necessary to confirm that a change is cancer.
• They can show a tumor’s location, even deep inside the body. This helps if a biopsy is needed.
• They can help determine cancer stage: whether and/or how far it has spread.
• For radiotherapy planning, to show where the beam should be focused.
• They can show whether a tumor shrinks with treatment, stays the same or grows after treatment. This gives the oncology team an idea of how well treatment is working.
• They can help determine whether cancer has returned after treatment (recurrence).

-Related topic: What is a biopsy, what are its types, and who needs one and how is it performed?

Imaging tests are only one part of cancer diagnosis and treatment. A complete cancer evaluation also includes your medical history, symptoms and risk factors, physical examination, blood tests and other laboratory tests.

Detailed imaging is requested before cancer treatment, at diagnosis, for later use. These images are subsequently used to monitor changes during treatment.

Imaging Tests Are Not Perfect

Imaging tests are among our most important aids in cancer treatment, but they have limitations. For example, these tests alone often cannot definitively establish whether a change is caused by cancer.

Imaging tests can show cancer only after a tumor reaches a certain size. Tumors need to reach approximately 5 millimeters to be detected radiologically, and a 5-millimeter tumor contains nearly a million cancer cells. No imaging method yet shows a single cancer cell; this is one of the most important areas of cancer research. Nuclear scans such asPSMA-PET and liquid biopsies are being tested for this purpose. These invisible cancer cells are why cancer treatment continues even when no tumor is seen on imaging (adjuvant treatment).

Who Performs Imaging Tests and Who Interprets Them?

A doctor, radiology technologist or another certified healthcare professional may perform an imaging test. It can take place in a hospital, private clinic, imaging center or doctor’s office. In large medical centers, imaging tests are generally performed in radiology or nuclear medicine departments.

Radiologists and nuclear medicine specialists are doctors specializing in imaging techniques; they both oversee the imaging process and interpret the images produced. The radiologist or nuclear medicine specialist writes a report on the findings and sends it to your doctor. A copy becomes part of your medical records. Your other doctors, such as oncologists and surgeons, may also review the images.

Types of Imaging Tests

Different imaging tests show different organs well. Doctors choose the radiological method suited to the organ in which they suspect a tumor.

• Computed tomography (CT): Uses X-rays. Shows the lungs and abdominal organs well.
• Magnetic resonance imaging (MRI): Uses electromagnetic fields and radiofrequency waves. Preferred for tumors of the brain, liver, breast, bones, head and neck, and lower abdomen.
• Mammography: Uses X-rays. Breast cancer screening.
• Nuclear medicine scans (for example, PET-CT, PET-MRI): Use radioactive particles, and the resulting nuclear scan image may be combined with computed tomography or magnetic resonance imaging. Used to image tumors in organs throughout the body (PET-CT is less effective in the brain and liver).
• Ultrasound (USG): Uses sound waves. For superficial tumors of the breast, liver, abdominal organs and head-neck region. Also, biopsies are often performed under ultrasound guidance.

Below, you can find information about PET-CT, the imaging tool we use most frequently for cancer diagnosis, staging and assessment of treatment response.

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