Arthritis includes more than 100 different rheumatic diseases and conditions, and it is one of the most common causes of disability in the country. According to the Centers for Disease Control and Prevention, approximately 50 million U.S. adults report having doctor-diagnosed arthritis.
Many types of arthritis are difficult to diagnose without the aid of diagnostic imaging. In addition to complete physical exams and blood tests, diagnostic services like X-rays, CT scans, MRIs and ultrasounds are often used to evaluate internal tissues for signs of arthritis.
An X-ray shows how bones move together at the joints, such as the wrists, elbows, ankles and toes. They can provide an indication of whether there is any damage from arthritis or if there is sufficient cartilage at the end of each bone. They can also show whether there are any bone deformities or underlying conditions that can lead to arthritis down the road.
An X-ray may be taken at a doctor’s office, hospital, or at a specialized diagnostic services center. The technician will position the body at different angles in order to obtain the necessary images. Safe levels of radiation are passed through the body, and images are recorded onto a specialized plate. Bones appear white, and soft tissues appear in shades of gray. The X-ray itself is painless, although the patient may be asked to hold uncomfortable positions while the image is taken.
A CT scan – or body computed tomography – is particularly useful when arthritis is suspected in joints that are deeper in the body. In these cases, X-rays can have a difficult time capturing the quality images that a CT scan can obtain. A CT scan also shows soft tissues (like ligaments and tendons) more clearly than X-rays, which can also be useful in diagnosing arthritis.
A CT machine looks like a large box with a short tunnel in the center. The patient is positioned on a narrow table that slides into the tunnel. A technician operates the machine from a different room but will always maintain visual contact with patients and communicate with them via a speaker and microphone.
Once inside the tunnel, patients hold perfectly still while X-ray beams and electronic X-ray detectors rotate around them. Depending on the type of CT scan that has been ordered, the machine may make several passes around the body. A computer then processes this data to create images of the body’s interior. Today’s modern CT scanners are quite fast and can scan large parts of the body in seconds.
Similar to CT scans, musculoskeletal magnetic resonance imaging (MRI) depicts both bones and the surrounding soft tissues like cartilage and the inner linings the joints. These are read by a computer and turned into detailed pictures. MRIs can show abnormalities in a joint’s soft tissue, which can indicate if there are complications of arthritis. In addition, recent studies have found that contrast-enhanced MRI can speed up the diagnosis of rheumatoid arthritis. The earliest sign of rheumatoid arthritis is the presence of synovitis, which contrast-enhanced MRI can detect as early as two months after symptoms appear.
Unlike X-rays and CT scans which use ionizing radiation, MRI machines use a magnetic field and radio frequencies to create images. Due to the magnet, any diagnostic services using MRI may not be suitable for patients with pacemakers, medical implants, prosthetic devices, or other internal metal objects. If the procedure requires contrast dye, there is a risk that the patient could experience an allergic reaction to the dye. The contrast dye can also have a negative impact on pre-existing asthma, anemia, hypotension, kidney disease and sickle cell disease. It’s important for patients to discuss these and other health issues with their doctors before undergoing any MRI procedure.
Before the MRI, patients will be given a gown and asked to remove other clothing, jewelry, glasses, hearing aids, and other items that can interfere with the imaging process. If contrast dye is needed, it is administered through an IV line in the hand or arm. The rest of the procedure is similar to a CT scan in that the patient lies very still on a table that slides into the MRI machine. The technologist runs the test from a different room, communicating with the patient via a speaker and microphone and maintaining direct visual contact. Patients hear a loud clicking noise as the magnetic field is created and pulses of radio waves are sent from the scanner. The procedure itself is painless, although patients may experience some discomfort in lying still for the required period of time.
Ultrasounds may be ordered to diagnose arthritis, particularly if rheumatoid arthritis is suspected. Ultrasounds can detect small amounts of fluid in joints and tendon sheaths, and they aid in the confirmation of synovitis. In some cases, physical therapists may use ultrasound as part of arthritis treatment. It provides heat to joints deep within the body and is believed to speed up the healing process by improving cellular function.
Ultrasounds are noninvasive, completely painless, and considered so safe that they are regularly used on pregnant women. A warm gel is applied to the outside of the body, and the ultrasound probe is then moved over the area to create the necessary images. The probe emits high-frequency sound waves that are read by a computer to create the images.
X-rays, CT scans, MRIs and ultrasounds are all useful diagnostic services for doctors in evaluating and treating arthritis. The best test, or combination of tests, is selected depending on factors such as the severity of the condition and the joint’s location within the body. Patients are encouraged to always ask questions and make sure they fully understand the procedure, its benefits and its risks.