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There are many ways doctors use imaging to diagnose or monitor a medical condition. Different types of scans are used for different conditions, and the kind of scan your doctor orders will depend on your symptoms. Imaging scans are relatively safe and carry minimal risks, but you'll feel more prepared if you know what to expect. Here's what you should know.
One of the most common types of scans is a magnetic resonance imaging (MRI) scan. An MRI can detect nerve injuries, tumors, brain injuries, stroke, or even the cause of a headache. There is no radiation involved in an MRI since it uses radio waves and magnetic fields to scan the body.
"MRIs are very commonly used for brain imaging, spine imaging, and the imaging of the joints," said Daniel Herron, MD, the director of women's imaging at Mercy Imaging Centers, a service of Dignity Health Medical Foundation. They can detect liver abnormalities, as well as appendicitis in pregnant women, he said.
Before your MRI, make sure you fill out the screening questionnaire fully and honestly. Tell the radiologist or technician if you have any medical device implants, pacemakers, or knee or hip replacements. Mention any tattoos as well; these can cause burns or skin irritation during the exam, according to the Food and Drug Administration.
An MRI can be loud, and nearly all technicians will offer earplugs when you arrive for your appointment. Side effects are minimal and may include headache or nausea. An MRI can take between 10 minutes to an hour to complete.
X-rays are one of the most common types of scans. According to the National Institute of Biomedical Imaging and Bioengineering, X-rays are a form of ionizing radiation that can pass through most objects, including the human body. As X-rays travel through the body, different tissues absorb them in different amounts.
Dr. Herron explained that an X-ray can typically be completed in 15 minutes or less, and use less radiation than a CT scan. X-rays are used in mammography to detect and diagnose breast cancer, and Dr. Herron said they are also useful for finding pneumonia, certain tumors or abnormal masses, and bone fractures.
Computerized tomography (CT) and computerized axial tomography (CAT) are two names for the same type of scan. This scan combines several X-ray images taken from multiple angles to create cross-sectional "slices" of bones, blood vessels, and soft tissues. A CT/CAT scan can be performed on every area of the body and provides greater clarity than traditional X-rays.
"A CT scan is sort of our workhorse of radiology," Dr. Herron said. It is used in the emergency room to evaluate headaches or trauma, such as a broken rib. CT/CAT scans are also being used to screen for lung cancer, he explained.
A CT/CAT scan is painless and noninvasive; no instruments are introduced into the body, other than contrast dye to increase visibility. A CT/CAT scan can be performed if you have an implanted medical device and takes about half an hour to complete. They do, however, involve some radiation risk, which accumulates over time.
An ultrasound uses high-frequency sound waves to take images of the inside of the body. The scan is performed by applying a water-based gel and then gliding a transducer over the area to be scanned. The transducer sends sound waves into the body and then receives the echoing waves to form an image. An ultrasound is typically used during pregnancy, but it can also detect and diagnose conditions that affect the body's organs and soft tissues.
"The images from ultrasound are getting better each year, and the technology is getting better, so we're using it more and more for things because of concerns over contrast reactions and radiation," Dr. Herron said. Ultrasounds can evaluate the thyroid gland and find breast cancer, Dr. Herron said. They can also guide procedures, such as biopsies.
Your doctor may either instruct you to fast (not eat or drink for a number of hours) before the test or to drink a certain number of glasses of water to make sure your bladder is full. An ultrasound takes between a half an hour to an hour, and does not require anesthesia or medication.
Medical imaging is a useful tool for diagnosing and detecting certain conditions and illnesses, and the benefits outweigh the minimal risks. If you have concerns, be sure to talk to your doctor before undergoing any testing.