Understanding Medical Imaging Scans
Medical imaging allows doctors to look inside the human body without surgery. While “mm scans” is not a formal medical term, it commonly refers to diagnostic imaging techniques that provide detailed views of internal structures. These technologies are used to diagnose diseases, monitor treatments, and guide medical procedures.
Many people using the term “mm scans” are likely thinking of two widely used and powerful diagnostic tools: Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scans. These imaging modalities offer distinct advantages depending on the specific medical need. Both MRI and CT scans provide detailed images, but they achieve this through fundamentally different scientific principles.
MRI scans utilize strong magnetic fields and radio waves to generate images of organs, soft tissues, bone, and virtually all other internal body structures. Conversely, CT scans employ X-rays to create cross-sectional images, which are like slices, of bones, blood vessels, and soft tissues inside your body. The choice between an MRI and a CT scan depends largely on what the doctor needs to visualize and the patient’s specific medical situation.
How Medical Scans Work
Magnetic Resonance Imaging (MRI) places the patient in a powerful magnetic field, aligning water molecules within the body’s tissues. Radio waves are pulsed into the body, knocking these aligned protons out of alignment. When the radio waves are turned off, the protons relax back into alignment, releasing energy signals detected by the MRI scanner. Different tissues release energy at different rates, allowing a computer to translate these signals into cross-sectional images of soft tissues, such as the brain, muscles, and ligaments.
Computed Tomography (CT) scans rely on X-ray technology. A CT scanner rotates an X-ray beam around the patient, taking numerous images from various angles. As the X-rays pass through the body, different tissues absorb the radiation to varying degrees. Detectors measure the amount of X-rays that pass through, and a computer processes this information. This process creates cross-sectional images, which can be combined to form three-dimensional representations of bones, internal organs, and blood vessels.
Common Diagnostic Uses
MRI scans examine soft tissues and organs, making them particularly useful for evaluating the brain and spinal cord. They can help diagnose conditions such as strokes, tumors, multiple sclerosis, and aneurysms. MRI also assesses joint injuries, including tears in ligaments and tendons, and for detecting issues in organs like the liver, kidneys, and heart. The detailed soft tissue contrast provided by MRI makes it a common choice for these examinations.
CT scans assess injuries and conditions affecting bones and blood vessels. They are effective in detecting bone fractures, internal bleeding, and organ damage following trauma. CT is also used for cancer detection and staging, as it can identify tumors and assess their size and spread within various organs. These scans can guide biopsies and other minimally invasive procedures.
Preparing for Your Scan
Preparing for an MRI or CT scan involves specific instructions. For some scans, you may be asked to fast for a few hours beforehand, especially if a contrast agent will be used. It is important to inform the medical staff about any medications you are taking or any allergies you might have. You will typically be asked to remove all metal objects, such as jewelry, eyeglasses, and hearing aids, before entering the scanning room.
During an MRI scan, you will lie on a movable table that slides into a large, tube-shaped machine. The machine can be noisy, so earplugs or headphones are provided to help dampen the sound. It is important to remain still throughout the procedure, which can last anywhere from 15 minutes to over an hour, depending on the area being scanned. Some patients may experience a feeling of claustrophobia due to the enclosed space.
A CT scan involves lying on a table that slides into a doughnut-shaped machine. The scan itself is usually much quicker, often taking only a few minutes to complete. You may hear buzzing or clicking noises as the scanner rotates around you. For both types of scans, a contrast agent might be administered intravenously or orally to enhance the visibility of specific tissues or blood vessels.
Safety and Important Considerations
Both MRI and CT scans are generally safe procedures, but there are important considerations for patients to discuss with their healthcare providers. For MRI scans, the strong magnetic field means that individuals with certain medical implants, such as pacemakers, cochlear implants, or some types of metal clips, may not be able to undergo the procedure. Disclose all metallic implants and medical devices to the imaging staff before the scan. Patients who experience severe claustrophobia may require sedation to complete an MRI.
CT scans involve exposure to a small amount of ionizing radiation. While the risk from a single diagnostic CT scan is generally considered low, medical professionals carefully weigh the benefits against this minimal risk, especially for pregnant women or children. Inform your doctor if you are pregnant or suspect you might be. Additionally, some individuals may experience an allergic reaction to the contrast agents used in both MRI and CT scans, though these reactions are typically mild and rare.