So You Need Medical Imaging

How does an MRI Work?

MRI, or magnetic resonance imaging, is a non-invasive medical diagnostic test that produces detailed 3D images of the inside of the body. It is used to detect, diagnose, and monitor a wide range of diseases and conditions and is particularly useful for imaging soft tissues such as the brain, muscles, and ligaments.

So, how does an MRI work? At the heart of the MRI process is a strong magnetic field, which forces the protons found in the water molecules of the body’s tissues to align with it. When a radiofrequency current is pulsed through the patient, the protons are stimulated and spin out of equilibrium. When the radiofrequency field is turned off, the MRI sensors detect the energy released as the protons realign with the magnetic field.

The time it takes for the protons to realign, as well as the amount of energy released, varies depending on the environment and chemical nature of the molecules. This allows doctors to distinguish between different types of tissue based on their magnetic properties. To create an MRI image, a patient is placed inside a large magnet and must remain very still to avoid blurring the image.

Contrast agents, which often contain the element gadolinium, may be injected into the patient’s bloodstream to help improve the speed at which protons realign with the magnetic field. The faster the protons realign, the brighter the image will appear on the MRI scan.

MRI is particularly effective at imaging soft tissues such as the brain, nerves, and muscles, and is often used to diagnose injuries to the knee and shoulder. It can also be used to identify aneurysms and tumors in the brain, and is the preferred imaging modality for frequent scans, especially in the brain, as it does not use ionizing radiation like X-rays or CT scans. However, MRI is generally more expensive than X-ray or CT scans.

Functional MRI (fMRI) is a specialized type of MRI that can be used to observe brain structures and determine which areas of the brain “activate” or consume more oxygen during different cognitive tasks. This can help researchers better understand brain organization and offers a potential new standard for evaluating the neurological status and neurosurgical risk.

While MRI is generally considered safe, it is not suitable for everyone. It should not be used on patients with certain medical implants such as pacemakers or aneurysm clips, and is not recommended for women who are pregnant as the effects of the magnetic field on the developing baby are not fully understood. Before undergoing an MRI scan, it is important to inform your doctor of any medical implants or conditions.

In conclusion, MRI is a valuable diagnostic tool that combines a strong magnetic field, radio waves, and a computer to create detailed 3D images of the inside of the body. It is beneficial for imaging soft tissues and can be used to diagnose a wide range of medical conditions. While it has some limitations and contraindications, it is generally considered safe and can provide valuable information for doctors in diagnosing and treating various diseases and conditions.

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  • 1. Imaging referral / prescription

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