MR images are detailed pictures of the body’s internal structures, created using Magnetic Resonance Imaging (MRI). This non-invasive technique allows healthcare professionals to look inside the body without X-rays or other ionizing radiation. MR images provide significant information to help diagnose various medical conditions and guide treatment plans.
How MRI Creates Images
Magnetic Resonance Imaging uses strong magnetic fields and radio waves to generate signals from water molecules. The body is mostly water, and its hydrogen atoms possess tiny magnetic properties. When a patient lies in the MRI scanner, the magnetic field aligns hydrogen protons.
Brief radiofrequency pulses then knock these aligned protons out of equilibrium. As the pulse turns off, protons rapidly realign with the main magnetic field, releasing energy. MRI sensors detect this energy, and a computer processes signals to construct detailed cross-sectional images. Different tissues respond uniquely, allowing differentiation between organs, soft tissues, and bone.
What MR Images Reveal
MR images are particularly effective at visualizing soft tissues, making them invaluable for examining structures like the brain, spinal cord, nerves, muscles, ligaments, and tendons. The high level of detail and contrast in these images allows healthcare providers to identify a wide range of conditions that might not be visible with other imaging methods.
In the brain and spinal cord, MRI can help diagnose conditions such as aneurysms, tumors, strokes, multiple sclerosis, and injuries from trauma. It is also used to evaluate spinal cord compression, nerve inflammation, and disc problems. For bones and joints, MRI scans can reveal issues like torn ligaments or cartilage, bone infections, bone tumors, and joint inflammation from arthritis.
MRI is also beneficial for examining internal organs, detecting tumors or irregularities in the liver, kidneys, spleen, pancreas, uterus, ovaries, and prostate. Additionally, it can assess the heart and blood vessels for conditions like heart chamber function, damage from heart attacks, and blockages in vessels.
Preparing for an MRI Scan
Patients preparing for an MRI scan receive specific instructions to ensure image quality and safety. It is generally advised to remove all metal objects before entering the MRI room, including jewelry, watches, credit cards, hearing aids, hair accessories, and any clothing with metal zippers or fasteners. These items can interfere with the magnetic field of the MRI unit, potentially causing image distortion or becoming harmful projectiles.
Patients typically change into a hospital gown for the procedure. During the scan, it is important to remain very still, as any movement can blur the images. The MRI machine produces loud knocking and thumping noises, so earplugs or headphones are provided to reduce discomfort. Some scans may involve the injection of a contrast agent, often gadolinium, into a vein to enhance the visibility of certain structures or abnormalities.
The MRI machine is often a large, tube-shaped magnet, and the patient lies on a movable table that slides into the opening. While the procedure is generally painless, some individuals might experience anxiety due to the enclosed space. Communication with the technologist is maintained through an intercom system, and a call button is available for any concerns during the scan.
Safety and Important Considerations
The lack of ionizing radiation makes MRI a suitable option for individuals who require frequent imaging or for pregnant patients, though contrast agents are typically avoided during pregnancy unless absolutely necessary. Despite its general safety, certain contraindications exist due to the powerful magnetic field.
Patients must inform staff about any implanted medical devices or metal in their bodies. Devices such as pacemakers, certain types of brain aneurysm clips, cochlear implants, and some older implanted drug infusion pumps can be affected by the magnetic field and may pose a safety risk or malfunction.
Most modern implants are designed to be MRI-safe or MRI-conditional, meaning they can safely undergo an MRI under specific conditions. However, a thorough screening process is always conducted to identify any potential hazards. While reactions to contrast agents are rare, patients should inform the technologist of any allergies or kidney issues before the scan.