MRI Scans: A Comprehensive Introduction to Magnetic Resonance Imaging

Magnetic Resonance Imaging (MRI) is a state-of-the-art diagnostic method that captures detailed images of internal body structures using magnetic fields and radiofrequency waves. Unlike traditional imaging tools such as CT scans or X-rays that utilize radiation, MRI is completely radiation-free, making it a safer alternative for many patients.

This technique provides incredibly sharp visuals of soft tissues, organs, and other structures, which helps healthcare professionals diagnose a wide variety of medical conditions - ranging from infections and tumors to inflammation and structural abnormalities.

Try Viewing MRI Results Online with Medivue

Interested in seeing how an MRI scan appears? The Medivue viewer makes it easy to access and interact with your imaging studies online. Whether you're using a mobile device or desktop browser, your DICOM files are safely hosted in a secure, cloud-based PACS system through Medivue.

How MRI Technology Works

The MRI machine works by utilizing the natural magnetic characteristics of hydrogen atoms, which are abundant in the human body due to its high water content (approximately two-thirds of body mass).

Each type of tissue in the body contains different amounts of water, and disease or injury can change these levels. These variations are picked up during scanning to distinguish between healthy and abnormal areas.

The MRI procedure involves several steps:

• A powerful magnet aligns hydrogen atoms in the body temporarily.
• Short bursts of radio waves then disrupt this alignment.
• As atoms return to their original state, they emit signals.
• These signals are detected by the scanner and transformed into high-resolution, multi-dimensional images using advanced software.

This process allows doctors to get a clearer picture of internal abnormalities and assess tissue differences that may not be visible using other imaging methods.

Contrast Agents in MRI Scans

In certain MRI procedures, a contrast agent, typically gadolinium, is administered to enhance the visibility of specific tissues. This enhancement is particularly beneficial in detecting tumors, visualizing blood vessels, and identifying infections or inflammation.

For breastfeeding mothers, it's important to note that multiple national recommendations indicate that it's not necessary to interrupt breastfeeding following the use of a gadolinium contrast during an MRI scan, due to the low bioavailability of the injected medium [1].

Preparing for an MRI Scan

Before an MRI scan, patients should wear loose-fitting, metal-free clothing and inform the medical team about any implants, claustrophobia, or pregnancy. The MRI machine consists of a large tunnel, a movable table, and a computer that processes the images.

During the scan, the patient lies on the table, which slides into the tunnel where the imaging takes place. The procedure can last between 15 to 60 minutes, depending on the area being examined and the number of images required. Remaining still is crucial to ensure clear and accurate images [2].

To protect against the loud noises produced by the MRI machine, patients are provided with headphones that also allow communication with the medical team during the scan.

Applications of MRI Scans

MRI is a versatile imaging technique used to diagnose a wide range of conditions across various parts of the body:

• Brain MRI:
  Provides detailed images of the brain, aiding in the detection of strokes, trauma, degenerative diseases, and tumors.
• Spinal MRI:
  Evaluates the spine for abnormalities such as disc degeneration, herniations, fractures, and nerve compression.
• Abdominal MRI:
  Assesses abdominal organs like the liver, kidneys, pancreas, and spleen for tumors, internal bleeding, or inflammatory diseases.
• Cardiac and Vascular MRI:
  Visualizes the heart and blood vessels to assess conditions like coronary artery disease, congenital heart defects, and valve disorders.
• Chest MRI: Examines the chest area, including the heart and lungs, to detect tumors, pericardial disease, and other abnormalities.
• Pelvic MRI: Investigates the pelvic region for disorders affecting muscles and organs.
• Gynecological MRI: Evaluates the female reproductive system and can be used during pregnancy to monitor fetal development.
• Breast MRI: Used alongside mammography and ultrasound to detect breast cancer or investigate unusual findings.
• Urological MRI: Provides detailed images of the prostate and urinary system to assess potential issues.
• Magnetic Resonance Angiography (MRA): Specializes in imaging blood vessels to identify aneurysms, clots, and arterial blockages.
• Oncological MRI: Crucial for detecting and monitoring tumors in sensitive areas like the brain and bones, aiding in the diagnosis and treatment of various cancers.

Patient Safety and MRI

Magnetic Resonance Imaging (MRI) is considered one of the safest medical imaging techniques available today, primarily because it does not use harmful ionizing radiation like X-rays or CT scans. However, to ensure the safety and comfort of patients and healthcare staff, certain precautions must be followed.

• Medical History
  Patients should inform their doctor or technician about any existing medical conditions or implanted devices, such as pacemakers, stents, or neurostimulation devices. Other important considerations include cochlear implants, artificial heart valves, and any metallic implants. These may interact with the magnetic field and pose safety risks or affect image quality.
• Pregnancy
  Pregnant women should inform the medical team before undergoing an MRI. Although current research shows no evidence that MRI harms a developing fetus, it's standard practice to take precautions.
• Tattoos
  Some tattoo inks contain metallic pigments, which may cause a slight warming sensation during the MRI scan. This effect is usually harmless, but patients should still notify the technician about any tattoos.
• Claustrophobia
  Patients with claustrophobia may feel anxious in the enclosed MRI scanner. A mild sedative may be administered to help them relax. Communication is maintained throughout the scan via headphones equipped with a microphone, allowing the patient to speak with the medical team.
• Metal Objects
  All metal items - including jewelry, watches, piercings, hearing aids, and clothing with metallic components - must be removed before the scan. This not only ensures safety but also helps produce clear, accurate images.
• Implants and Devices
  Most non-ferrous dental implants are safe for MRI scans. However, implants made from stainless steel or chromium-cobalt may cause image distortion or discomfort and must be evaluated beforehand.

Benefits of MRI

• Non-Invasive: MRI is a non-invasive diagnostic tool that does not involve surgical procedures or incisions.
• No Ionizing Radiation: Unlike X-rays and CT scans, MRI does not expose the patient to ionizing radiation, making it a safer option for repeated use.
• Highly Detailed Images: MRI provides high-resolution images, ideal for detecting a wide range of conditions, including tumors, heart problems, and joint or spinal issues.
• Safe for All Ages: MRI can be safely performed on individuals of all ages, from newborns to the elderly.

Advantages of MRI Over Other Imaging Methods

• Soft Tissue Imaging: MRI offers superior visualization of soft tissues, such as the brain, spinal cord, muscles, and ligaments. It is especially effective for neurological and musculoskeletal imaging.
• No Radiation: MRI is safer for frequent imaging since it does not use ionizing radiation, unlike CT scans and X-rays.
• Multi-Planar Imaging: MRI allows imaging from multiple angles (axial, sagittal, and coronal planes), providing a more comprehensive view of the area being examined.
• Functional MRI (fMRI): A specialized type of MRI, fMRI measures brain activity by detecting changes in blood flow, and is widely used in neuroscience and clinical assessments.

MRI vs. CT Scan

• Imaging Technique: MRI uses magnetic fields and radio waves, making it ideal for soft tissue imaging. CT scans, on the other hand, use X-rays to capture detailed cross-sectional images, especially useful for bone and hard tissue imaging.
• Contrast Agents: Both MRI and CT scans use contrast agents to enhance visibility. MRI typically uses gadolinium, while CT scans use iodine-based contrast agents.
• Applications: MRI is preferred for imaging the brain, spine, and soft tissues, whereas CT scans are commonly used in emergency situations to quickly assess conditions in the chest, abdomen, and pelvis.
• Safety and Risks: MRI does not involve ionizing radiation, making it safer for repeated use, but it is unsuitable for patients with certain metal implants due to the magnetic field. CT scans, while faster and excellent for certain applications, do expose patients to ionizing radiation.

Considerations and Limitations of MRI

• Cost: MRI scans are generally more expensive than other imaging methods, which can be a barrier for some patients depending on healthcare coverage and access.
• Claustrophobia: The enclosed design of traditional MRI machines may trigger anxiety in some patients. Open MRI systems are available in some facilities but may have lower image resolution.
• Time: MRI procedures typically take longer (15 to 60 minutes) compared to other imaging methods, which may not be ideal for emergencies requiring rapid diagnosis.
• Metal Implants: Patients with certain types of metal implants or fragments (especially ferromagnetic materials) may not be eligible for MRI due to potential risks associated with the strong magnetic field.

Despite these considerations, MRI remains an incredibly valuable diagnostic tool. Its unmatched ability to image soft tissues in detail, combined with the absence of ionizing radiation, makes it a preferred method for many clinical scenarios. When used appropriately and with attention to safety protocols, MRI is both effective and safe for patients across a wide range of medical needs.

References:

• https://www.nhs.uk/conditions/mri-scan/
• https://www.osc-ortho.com/services/open-mri/mri-frequently-asked-questions/what-is-an-mri-with-contrast-why-do-i-need-contrast-is-it-safe/
• https://www.webmd.com/a-to-z-guides/what-is-a-mri#2-5
• https://www.ismrm.org/resources/information-for-patients/#What%20is%20MRI%20used%20for
• https://www.nibib.nih.gov/science-education/science-topics/magnetic-resonance-imaging-mri#pid-961
• https://stanfordhealthcare.org/medical-tests/m/mri/risk-factors.html
• https://www.fda.gov/radiation-emitting-products/mri-magnetic-resonance-imaging/benefits-and-risks