MRI is an imaging technique used to get cross-sectional images using strong magnetic field and radio waves (radio frequency pulses) instead of X-rays. In MRI scanning, patients are placed inside a very large and strong magnet, so that all the protons in the atoms of the patient's body can be aligned to a magnetic field. Then, radio waves (called radio frequency pulses) are directed at the protons (the nuclei of hydrogen atoms) to excite the protons.
Knee MRI
MR image of the knee - articular cartilage is shown particularly well.
Once the radio waves are stopped, excited atoms emit radio signals received by an antenna (a surface coil in the MRI machine), which are then measured and processed to form an image using a computer. In the human body, protons are most abundant in the hydrogen atoms of water. Thus, MRI images represent the water content in the area of the exam. The more water present, the more radio signals emitted, and the whiter the image. All intra-articular structures, including menisci, ligaments and articulating surfaces, can be visualised in great detail. The indications for MRI of the knee are difficult to define and depend on the specific clinical situation and the particular information needed. Routine MR knee imaging is usually very accurate and helpful diagnostically. MRI is also safe. There are no known side effects to having an MRI scan performed but you should be aware of the following:
The strong magnetic field can cause metal implants to dislodge, burn,and causeadditional injuries. When you have any metal implant in your body, such as a pacemaker, prosthetic valves, or clips, you should let your radiologist or MR technician know. If it is not confirmed to be compatible with the magnet, you should not take the MRI. If you have had bullet injuries or possible metal fragments in your body, X-rays can be taken instead for detection of metal objects.
Metallic implants or fragments that might be affected by magnet: Cardiac pacemakers, Artificial cardiac valves, Cerebral aneurysm clips, vascular clips, Epidural electrodes, Prosthetic (implanted) hip, knee or ankle joint, Chemotherapy or insulin pumps, Intrauterine device (IUD), Metallic bone plates, pins, screws, surgical staples, especially within 4-6 weeks after surgery, Bullets, shrapnel, metal fragments, especially in and around eyes, Metallic ear implants, etc.
Women in the first 12 weeks of pregnancy should avoid MRI and the contrast medium. There are no known harmful effects to pregnant women and unborn babies. However, because it is a recently-developed technology, the long term effects of MRI are not known.
Allergic reactions to the contrast medium are possible, but very rare.
Claustrophobia: lying alone inside the tunnel of huge magnet may provoke intense fear of confinement. If you hav any history of claustrophobia, you should inform your radiologist or technologist. Sedatives can be given before scanning.
Knee MRI
MR image of the knee - articular cartilage is shown particularly well.
Once the radio waves are stopped, excited atoms emit radio signals received by an antenna (a surface coil in the MRI machine), which are then measured and processed to form an image using a computer. In the human body, protons are most abundant in the hydrogen atoms of water. Thus, MRI images represent the water content in the area of the exam. The more water present, the more radio signals emitted, and the whiter the image. All intra-articular structures, including menisci, ligaments and articulating surfaces, can be visualised in great detail. The indications for MRI of the knee are difficult to define and depend on the specific clinical situation and the particular information needed. Routine MR knee imaging is usually very accurate and helpful diagnostically. MRI is also safe. There are no known side effects to having an MRI scan performed but you should be aware of the following:
The strong magnetic field can cause metal implants to dislodge, burn,and causeadditional injuries. When you have any metal implant in your body, such as a pacemaker, prosthetic valves, or clips, you should let your radiologist or MR technician know. If it is not confirmed to be compatible with the magnet, you should not take the MRI. If you have had bullet injuries or possible metal fragments in your body, X-rays can be taken instead for detection of metal objects.
Metallic implants or fragments that might be affected by magnet: Cardiac pacemakers, Artificial cardiac valves, Cerebral aneurysm clips, vascular clips, Epidural electrodes, Prosthetic (implanted) hip, knee or ankle joint, Chemotherapy or insulin pumps, Intrauterine device (IUD), Metallic bone plates, pins, screws, surgical staples, especially within 4-6 weeks after surgery, Bullets, shrapnel, metal fragments, especially in and around eyes, Metallic ear implants, etc.
Women in the first 12 weeks of pregnancy should avoid MRI and the contrast medium. There are no known harmful effects to pregnant women and unborn babies. However, because it is a recently-developed technology, the long term effects of MRI are not known.
Allergic reactions to the contrast medium are possible, but very rare.
Claustrophobia: lying alone inside the tunnel of huge magnet may provoke intense fear of confinement. If you hav any history of claustrophobia, you should inform your radiologist or technologist. Sedatives can be given before scanning.
1 comment:
Very impressive article! The blog is highly informative and has answered all my questions.
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