Know what Magnetic Resonance Imaging is all about

By Dr. Modala Mallesh Subject Expert Palem, Nakrekal, Nalgonda 9989535675 This article is in continuation of previous articles that help you understand what constitutes the biological sciences and its varied branches/ concepts. Today, we would be discussing the second part of the Biomedical technology with a focus on Magnetic Resonance Imaging (MRI). Magnetic Resonance Imaging […]

By Dr. Modala Mallesh
Subject Expert
Palem, Nakrekal, Nalgonda
9989535675

This article is in continuation of previous articles that help you understand what constitutes the biological sciences and its varied branches/ concepts. Today, we would be discussing the second part of the Biomedical technology with a focus on Magnetic Resonance Imaging (MRI).

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Magnetic Resonance Imaging (MRI scan)

•  An MRI (Magnetic Resonance Imaging) scan is a diagnostic radiology technique that uses magnetism, radio waves and a computer to produce images of body components.
• It is important to note that MRI does not use ionising radiation, as involved in X-rays, and is generally a safe procedure.
• MRI is a non-invasive medical imaging technique that helps physicians diagnose certain anatomical abnormalities/ pathological conditions.
• This technique uses nuclear magnetic resonance of protons to generate proton density images of body parts.
• MRI uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, bones and virtually all other internal body structures.

Note:  BMRI provides good contrast between the different soft tissues of the body, which makes it especially useful in imaging the brain, muscles, heart, and cancerous tissues compared to other medical imaging techniques such a computed tomography (CT)/ X-rays.

MRI scanner and procedure:

• MRI scanner is a giant circular magnetic tube.
• A patient is placed on a movable bed that is inserted into the magnet.
• Human body is mainly composed of water molecules which contain two hydrogen nuclei/protons each.
• The magnet creates a strong magnetic field that makes protons align with the direction of the magnetic field (protons are not aligned under normal conditions).
• A second radio frequency electromagnetic field is then turned on for a brief period. The protons absorb some energy from these radio waves.
• When this second radio frequency emitting field is turned off, the protons release energy at a radio frequency which can be detected by the MRI scanner. (The protons return to their equilibrium state from the energised state at different relaxation rates).
• Different types of tissues emit different ‘quanta’ of energy (in the form different wave lengths and at different rates)
• Abnormal tissues, such as tumours, can be detected because the protons in different types of tissues return to their equilibrium state at different rates.
• Tissues such as bones with less water content (hence, less number of protons) look different in an MRI Image.
• Accordingly, there is a contrast between the images of different tissues based on their water content.
• Even in the case of the same tissue, normal healthy cells and pathological cells emit different energy waves – hence the difference in the images of the different types of cells.
• The information received is processed by a computer, and an image is generated.
• The image and resolution produced by MRI is quite detailed and can detect tiny changes of structures within the body.
• For some procedures, radio contrast agents, such as gadolinium, are used to increase the accuracy/resolution of the images.
• After scanning is completed, the computer generated images (tomographs – images of thin slices of body parts) can be transferred to a film (hard copy).
• A radiologist interprets the images of the body parts and gives his/her diagnostic opinion.

Note:

• MRI is used to distinguish pathologic tissue (such as brain tumours) from normal tissue.
• MRI can show even hairline fractures of the pelvis and hip that may not be detected by the traditional X-ray / CT scan.
• Ballooning of blood vessels called aneurysms can be detected using MRI (aneurysms may occur when a tear begins in the layers of the walls of aorta, arteries, veins / part of heart).
• Moreover, MRI is preferred to CT scans, as CT scan involves effects of ionising radiation whereas MRI does not have ionizing radiation.