Knee pain, X-ray, CT and MRI can all help diagnose knee problems, but their indications are different and the focus is also different.
X-ray and NMR are essentially both electromagnetic wave . The difference is that X-ray and CT use the rays of electromagnetic waves, while NMR utilize the magnetic field of electromagnetic waves. X-rays penetrate the human body to produce black and white photos. The white part absorbs the most rays (bones), the gray part absorbs less (fat and soft tissue), and the pure black part shows that there is only air, so it is most valuable for diagnosing bone lesions. Whether it is trauma or degenerative changes, doctors usually recommend X-rays to determine whether there are fractures, joint dislocations or other problems that affect bones.
CT scanning is a technology that combines X-ray and computers. It can generate a 360-degree cross-sectional view, cut a part into many layers through X-rays, and then perform computer secondary imaging and reconstruct it into a 3-dimensional model. It is more detailed than X-rays. In addition to bones, it is also suitable for the examination of physiological and motor functional organs and blood vessels.
NMR and the above are different. It is to place the patient in an cylinder magnetic field. uses radio frequency excitation to observe the different activities of water molecules in the human body, observe the differences between normal and abnormal , and then generates images. Therefore, magnetic resonance imaging can be understood as water molecules imaging in the human body, and soft tissue contains the most water in the human body.
So the problem is, my knee is very painful, should I do MRI?
Generally speaking, doctors usually recommend X-rays first, which are short and cheap. X-rays can show abnormal bone structure, whether the joint gap is narrow, and the formation of bone spurs. It is speculated that the bone density of is . If doubtful points are found but cannot be concluded, further CT examination of may be performed. If X-rays are basically OK, but knee pain still exists, an MRI may be required. NMR is more suitable for viewing soft tissues, such as tendons and ligaments around the knee joint, which are not visible on X-rays.
Usually, for older patients, X-rays and CT scans will be arranged. For younger patients, X-ray and MRI are more commonly used. NMR is highly sensitive to meniscus tear in the knee joint, knee effusion, synovial lesions, anterior cruciate ligament injury , as well as sprains and strains. Especially for young people with high activity or love to exercise, it is recommended to undergo MRI examinations to avoid further damage when the following situations occur:
- Take painkillers and physical therapy are ineffective.
- The knee joint continues to swell and pain.
- Knee pain accompanied by sounds.
- Suddenly or intermittently, the knees cannot be fully extended
- feel that the knees are unstable or the legs are weak.
There is another situation. If an older patient has been diagnosed with osteoarthritis, cartilage wear, and degenerative meniscus tear, but after physical therapy, anti-inflammatory drugs, and steroid injections, it is also necessary to undergo a nuclear magnetic resonance examination. The advantage of
NMR is that it can avoid radiation, multi-parameter, multi-sequence, and multi-directional imaging, which can provide richer diagnostic information. But it also has disadvantages. The examination time is much longer than X-ray and CT, and the results will be slower and the cost will be more expensive. In addition, the examination is carried out in a closed space in , and the noise of the machine will also make some patients feel uncomfortable.
Medical science popularization, for reference only.
