By: Joseph Maslak, M.D., F.A.C.P.
Board Certified in Internal Medicine
Fellow of the American College of Physicians
834 N. Seminary Street, Suite 301
Galesburg, IL 61401
309-342-9183
You've seen the doctor for a routine wellness exam – or perhaps you've had a recent injury. During your visit, your doctor recommends additional tests: a confusing mix of alphabet soup such as MRI, CT, or other such language. It can be intimidating: what do they all mean?
Advanced imaging tests help your doctor examine the inside of your body, in a noninvasive way, to provide more detailed information about your health. Most imaging tests are simple, painless procedures that help with an accurate diagnosis and treatment of illnesses, injuries and chronic diseases.
Common imaging tests include x-ray, ultrasound, computed tomography (CT) scans, magnetic resonance imaging (MRI), and nuclear medicine exams.
X-ray
An x-ray uses radiation to produce pictures of the body that can help to diagnose conditions ranging from broken bones to pneumonia, heart conditions, intestinal blockages, kidney stones, and digestive tract problems. X-rays can also detect fractures and infections, arthritis, osteoporosis, and bone cancer, as well as diagnose lung infections and detect breast tissue abnormalities (i.e. mammogram).
Ultrasound
An ultrasound does not use radiation, but rather high-frequency sound waves to produce "echoes" which, in turn, create pictures that show the size, shape and distance between organs and tissues. Ultrasound waves easily pass through fluids and soft tissues, and are good for examining fluid-filled spaces in the body (the joints, gallbladder, blood vessels or the uterus during pregnancy), as well as soft organs like the heart and liver. An ultrasound is painless – conducted with gel wiped onto the skin's surface and a probe rubbed across the skin to project and receive sound waves.
Computed tomography (CT) scan
A CT scan combines x-ray and computer technology to produce very detailed cross-sectional pictures of the body. Unlike the single beam of radiation as used in an X-ray, a CT scan uses multiple x-ray beams to produce multiple pictures of the body from different angles. A computer reassembles the image "slices," or cross sections, which are displayed on a monitor. CT scans are valuable because they can produce pictures of bone, soft tissue and blood vessels. A CT scan can quickly identify injury to vital organs in trauma situations, as well as diagnose cancers, cardiovascular disease, abdominal problems such as appendicitis, and musculoskeletal disorders. It can also measure bone mineral density to help detect osteoporosis. Because it provides real-time images, it is also frequently used to guide minimally invasive surgeries and biopsies.
Magnetic resonance imaging (MRI)
If you've ever had a sports injury – or a fall – chances are, you've had an MRI. This exam uses a magnetic field, radio frequency pulse and a computer to create pictures of soft tissue, bone, joints, tendons and ligaments. An MRI can yield more detailed information about body parts than other imaging methods, such as the flow of blood in blood vessels, bleeding in the brain or stroke-related damage. An MRI is also used to examine the chest and abdominal organs (the heart, liver, or kidneys); diagnose pelvic pain by detecting cysts or other abnormalities in reproductive organs; pinpoint blood vessel blockages; and locate internal bleeding, infection and tumors.
An MRI is a valuable diagnostic tool for bone and joint issues: arthritis, torn ligaments or tendons, cartilage damage. It can detect nerve problems, from disc bulges in the spine (herniated disc) to nervous system disorders.
Nuclear medicine
Nuclear medicine uses small bits of radioactive material – swallowed, inhaled, or injected – to create images. The technique is used to diagnose, determine the severity of, and treat various diseases and conditions, including cancer, heart disease, and gastrointestinal, endocrine, or neurological disorders. Nuclear medicine exams are safe and painless, and the amount of radiation used is comparable to – and often less than – that of a typical x-ray.
A nuclear medicine exam is sometimes referred to as an "inside-out" x-ray, because it records radiation emitting from the patient's body rather than radiation directed through the patient's body. The exam is unique because it not only shows the structure, but also the function, of the organ or area being studied. It is typically used for bone and lung scans, cardiac stress tests, and liver and gallbladder procedures. Primarily a diagnostic tool, nuclear medicine can also treat disease, and provide pain relief from certain cancers.
The advantages of diagnostic imaging tests are rapid diagnosis and more detailed health information, without the need for invasive procedures such as exploratory surgery. Most tests can be conducted on an outpatient basis and take less than a half hour to perform, depending on the exam.
For more information on how diagnostic imaging tests are used for your health, click here to take the Coronary Artery Disease and Angioplasty Quiz, or the Mammogram Quiz.
Preparing for Your Test
Is a diagnostic exam in your near future? Each exam – and the instructions you will receive from your doctor in order to prepare – are a bit different, but these preparation tips will help ensure your exam goes smoothly.
Follow your doctor's instructions for eating and drinking, before your exam. You may be asked not to eat or drink anything for several hours beforehand, especially if a contrast material – dye injected into a vein to help structures being examined to show up more clearly – will be used in your exam.
Wear comfortable, loose-fitting clothing. You may be provided a medical gown to wear during your exam. If not, two-piece clothing that is easy to remove is preferable.
Bring a copy of your medical history, including a medication list. You will be asked to fill out a screening form before your exam to provide information about conditions that may create a health risk (heart disease, asthma, diabetes, kidney disease or thyroid problems), as well as any implanted medical devices that may interfere with the imaging process (cardiac pacemaker, defibrillator, medication pump, or inner ear implant).
Leave metal objects at home or in a safe place. Certain metal objects may affect CT or MRI images and should be left at home or removed before your test. These include: eyeglasses, jewelry, hairpins, money clips, credit cards with magnetic strips, beepers or cell phones, hearing aids, watches, paper clips, keys, coins, and clothing with metal zippers, belt buckles, buttons, or hooks.
Inform your doctor of any allergies or medications you are taking. If you have a known allergy to contrast material, or dye, your doctor may prescribe medications to reduce the risk of an allergic reaction.