MRI examination is, generally speaking, used to confirm or disprove suspicion of having a disease, based on the clinical state of patient, symptoms and previous detection by other modalities. However, it is good to ask a couple of questions to consider whether MRI is or is not an appropriate imaging method for detection of cancer.
Methods used for early and primary detection of diseases are called screening methods. These are characterized as a strategy used in a population to identify the possible presence of an as-yet-undiagnosed disease in individuals without signs or symptoms. This can include individuals with pre-symptomatic or unrecognized symptomatic disease. As such, screening tests are somewhat unusual in that they are performed on persons apparently in good health. In many countries there are population-based screening programs, here are some examples:
- Cancer screening
- Pap smear or liquid-based cytology to detect potentially precancerous lesions and prevent cervical cancer
- Mammography to detect breast cancer
- Colonoscopy and fecal occult blood test to detect colorectal cancer
- Dermatological check-up to detect melanoma
- PPD test to screen for exposure to tuberculosis
- Bitewing radiographs to screen for interproximal dental caries
- Ophthalmoscopy or digital photography and image grading for diabetic retinopathy
- Ultrasound scan for abdominal aortic aneurysm
These methods should be non-invasive, sensitive and specific to the diagnosis as much as possible to be able to confirm or disprove the disease. An advantage of screening methods moreover includes their safety. They are also cheap, reachable, easy to perform and you get positive or negative results very quickly.
In comparison, MRI is more specific and sophisticated examination.
MRI scanner uses strong magnetic fields, electric field gradients, and radio waves to generate images of the organs in the body. The examination requires special room, the whole team of specialists and medical technicians. Moreover, MRI examination is not preferred as it takes more time and in general is more expensive. That makes MRI not the first choice for primary detection of cancer. Medical societies issue guidelines for when physicians should use MRI on patients and recommend against overuse.
MRI can effectively detect health problems or confirm a diagnosis. However, medical societies often recommend that MRI not be the first procedure for creating a plan to diagnose or manage a patient’s complaint. For example, for certain women at high risk for breast cancer, a screening MRI is recommended along with a yearly mammogram. But, MRI is not recommended as a screening test by itself because it can miss some cancers that a mammogram, as a good screening method, would find.