The main consideration for doctors regarding which test to choose (CT, PET-CT, MRI, or Ultrasound) is the clinical question that needs to be answered. What are they looking for? What are they trying to diagnose?
CT (Computerized Tomography): This is a digital imaging test that uses X-rays that are sent together to create a cut-image using advanced computer programs. This test is intended for imaging of most of the internal organs, including the bones. The test time is short however, its main disadvantage is the high level of radiation necessary in order to create the image.
MRI (Magnetic Resonance Imaging): This is a test using advanced technology that receives an image as a result of a strong magnetic field created around the patient. This test is sensitive to processes in soft tissues, especially the nervous system, the muscles, the bone marrow etc. This imaging method is less suitable for imaging of bones, intestines, and other organs that contain air. Its disadvantages: longer test time than CT, and high cost due to the device maintenance.
PET-CT (Positron Emission Tomography – Computed Tomography): This test is mainly intended to map cancer cells in the body. Prior to the test, the patient is injected with radioactive glucose, which is absorbed by the cancer cells in an enhanced manner in comparison to regular cells, and the radiation is received by the special camera, and this creates an image of the cancer dispersion in the body. The test’s disadvantages, besides the radiation involved, is that also tissues with infection will have increased reception and make it difficult to accurately diagnose. For this reason, this is usually performed together with the CT test, and together a better picture of the situation is received.
US (Ultrasound): This test creates imaging of various organs in the body, using very high frequency radio waves (which the human ear cannot detect), and these are returned to the device, which translates it into an image. The test is usually performed in order to see the internal organs, their shape, size, how they are functioning, and whether they have some sort of injury. Its advantage is that it is not accompanied by radiation exposure, but its disadvantage is that it is not suitable for scanning organs that contain air, like the stomach, the intestines, or skeletal imaging.
It is important to mention that according to the State Comptroller Report on the topic, the number of mistakes in imaging interpretation can sometimes reach about 30%, and so if there is any doubt about the interpretation, it is recommended to receive a second opinion from another radiologist. If you have questions about your imaging tests, you are invited to ask them in the ”Ask the Imaging Expert” in the Belong – Beating Cancer Together app.