TAG: GS 3: SCIENCE AND TECHNOLOGY
THE CONTEXT: Magnetic Resonance Imaging (MRI) is a pivotal diagnostic tool used in modern medicine to visualize soft tissues within the body without invasive procedures.
EXPLANATION:
- It was developed in the 1970s.
- MRI techniques were refined by Paul Lauterbur and Peter Mansfield, earning them the Nobel Prize in Medicine in 2003.
Magnetic resonance imaging (MRI):
- MRI is a non-invasive diagnostic procedure used to obtain images of soft tissues within the body, including the brain, cardiovascular system, spinal cord, joints, muscles, liver, and arteries.
- It is crucial for detecting cancers like prostate and rectal cancer, as well as tracking neurological conditions such as Alzheimer’s, dementia, epilepsy, and stroke.
- MRI scans can also reveal changes in blood flow, aiding in the assessment of brain activity through functional MRI.
- However, individuals with embedded metallic objects or implants, such as pacemakers, may not be suitable candidates for MRI scans due to the strong magnetic fields involved.
- Even items like credit cards can be affected by these magnetic fields.
- MRI scanners create images of the body using a large magnet and radio waves.
- No ionizing radiation is produced during an MRI exam, unlike X-rays.
- Images produced by an MRI scan can show organs, bones, muscles and blood vessels.
Working of the MRI:
- An MRI procedure relies on hydrogen atoms found in the body, particularly abundant in fat and water.
- The MRI machine comprises four essential components: a donut-shaped structure with a central hole (the bore), a powerful superconducting magnet housed inside, a device emitting radiofrequency pulses, and a detector.
- The superconducting magnet generates a robust and stable magnetic field around the body.
- This magnetic field causes the spins of hydrogen atoms to align, with roughly half pointing in one direction and the other half in the opposite direction.
- The machine emits a radiofrequency pulse directed at the specific body part being scanned.
- During this pulse, only a small population of “excess” atoms absorbs the radiation and becomes excited.
- Once the pulse ceases, these excited atoms release the absorbed energy and return to their original lower energy states.
- The frequency of the pulse corresponds to the Larmor frequency, dependent on the magnetic field strength and tissue type.
- Lastly, a detector captures the emissions from the excited atoms and converts them into signals.
- These signals are then transmitted to a computer, which utilizes them to reconstruct two- or three-dimensional images of the scanned body part.
MRI offers several advantages:
- Precise Imaging: MRI utilizes powerful magnetic fields and gradient magnets to highlight specific portions of the body with high precision, allowing for scans as narrow as a few millimeters without the need for the patient to move.
- Versatile Imaging: The design of the MRI machine allows for imaging from various angles and in small increments, providing comprehensive views of the body.
- Tissue Differentiation: By exploiting the different T1 relaxation times of hydrogen atoms in water, MRI can distinguish between different types of tissues, showing them in varying shades of grey.
- Contrast Enhancement: Contrast agents, like gadolinium-based compounds, can be injected to further improve visibility of specific tissues by lowering their T1 relaxation times.
- Safety: Extensive research has demonstrated that MRI scans do not pose long-term harm to the body, as the effects of the magnetic fields are temporary and reversible. However, the impact on pregnant women is not as well-studied, leading many facilities to avoid scanning pregnant patients.
Cons of MRI:
- Cost: MRI machines are expensive to purchase and maintain, with prices ranging from tens of lakhs to crores of rupees depending on specifications. These costs are passed on to patients, making MRI scans expensive, especially for those without insurance or requiring multiple scans.
- Discomfort and Immobility: Patients undergoing MRI scans must remain still for extended periods, often tens of minutes, to avoid distorting the images. This immobility can be challenging for patients, particularly claustrophobic individuals, although some open-bore MRI designs aim to mitigate this issue.
- Energy Intensive: Generating a magnetic field of 1 tesla or more, as required for MRI, requires passing a heavy current through superconducting coils cooled with liquid helium. While superconducting materials eliminate energy loss as heat, maintaining this setup is energy-intensive and costly.
- Noise: MRI machines produce loud noises due to the switching of heavy currents in the gradient coils during operation. This noise can cause discomfort or anxiety for patients undergoing scans.