Doctor, should I have an MRI or a simple CT scan?
I first became aware of Magnetic Resonance imaging (MRI) as a medical technology in 1981 while on a fellowship in Royal Melbourne Hospital, Australia. I attended a very well attended grand round on this subject and this facility was not available anywhere in Australian Hospitals. It came there only in 1985.
The first clinically useful image of a patient's internal tissues using MRI was obtained in August 1980 at the University of Aberdeen in Scotland. The machine was a full-body MRI scanner built by a team led by John Mallard. This machine was later used at St Bartholomew's Hospital in London, starting in 1983, which marked another significant step in the clinical adoption of MRI.
The 1980s saw the commercialization and wider availability of MRI scanners, making them a staple in medical diagnostics worldwide. The U.S. Food and Drug Administration (FDA) approved the first MRI systems for clinical use in 1983. Several companies received approval that year for systems with various magnetic field strengths, including Diasonics, Technicare, and Philips Medical Systems. At present almost all major companies are into this business. This marked a crucial step in the widespread adoption of MRI technology for medical diagnosis in the United States.
The first MRI machine in India was installed in 1987 at the Institute of Nuclear Medicine and Allied Sciences (INMAS) in Delhi.
How MRI Became a Clinical Tool
MRI is a powerful medical tool that gives doctors incredibly detailed pictures of the inside of the human body. Unlike X-rays or CT scans, it doesn't use radiation. This technology was born from the discovery of nuclear magnetic resonance (NMR) in the 1940s, a physics principle that found that certain atoms, when placed in a magnetic field, can absorb and emit radio waves.
For decades, this was mainly a tool for chemists to study the structure of molecules. The big breakthrough came in the 1970s, when scientists realized they could use this principle to create images of living things. Dr. Paul Lauterbur and Sir Peter Mansfield, who won the Nobel Prize for their work, figured out how to use magnetic gradients to turn the signals from atoms in the body into detailed, two-dimensional images. This innovation paved the way for the first full-body MRI scans in the late 1970s, and by the 1980s, MRI machines began to appear in hospitals, forever changing medical diagnostics.
Tesla is the unit of measurement for magnetic field strength named after Nikola Tesla. Low field Tesla (0.2 T to 0.5T) machines have lower image quality while High field MRI (3.0 T) have much higher resolution and Ultra-high field MRI (4.0 to 7.0 T) have extremely high-resolution images.
MRI vs. CT scans: What's the Difference?
MRI and CT (Computed Tomography) scans are both used to see inside the body, but they work in very different ways and are best for different things. MRI has the advantage of no radiation. It uses powerful magnets and radio waves, not ionizing radiation like CT scans. This makes it a much safer option for people who need frequent scans, like those with chronic conditions, or for sensitive populations like children and pregnant women. MRI gives a superior soft tissue images and is excellent at showing the difference between various types of soft tissues. This makes it the top choice for examining the brain, spinal cord, nerves, muscles, ligaments, and organs. For example, an MRI can clearly show, a brain tumour its details and evaluation of a chronic stroke, a herniated spinal disc or a torn ligament, which might not be visible on a CT scan. Over the years MRI of the heart has become a very valuable tool to assess the viability of the heart muscle before deciding regarding angioplasty or bypass surgery in patients following a heart attack. It however needs a dedicated cardiac MRI machine.
With all its advantages MRI has several limitations also. MRI scans take much longer than CT scans, sometimes 30 to 60 minutes or more and is generally more expensive. The machines make loud banging and knocking noises, and the patient has to lie still inside a narrow, tube-like space. This can be a challenge for people with claustrophobia or those who can't remain still for long periods, such as young children.
The strong magnetic field means that people with certain metal implants, like some pacemakers, defibrillators, or metal clips from previous surgeries, cannot have an MRI. The magnetic field can damage these devices or even cause them to move, which can be dangerous. Recent years with advanced technology MRI safe cardiac devices are available and can be programmed into an MRI mode during the examination.
While MRI is great for soft tissues, CT scans are often faster and better at visualizing bone fractures and internal bleeding, making them the preferred choice in emergency situations.
Take home message:
A medical MRI is an indispensable diagnostic tool that provides unparalleled, detailed images of the body's soft tissues without the use of ionizing radiation. Its non-invasive nature and ability to differentiate between various tissue types make it a cornerstone of modern medicine. From diagnosing neurological disorders and musculoskeletal injuries to staging cancers, MRI has revolutionized patient care by enabling accurate, early detection and guiding effective treatment strategies. The ongoing advancements in technology, such as higher field strengths and faster scanning techniques, promise to further expand its diagnostic capabilities and accessibility, solidifying its role as a vital component of the future of healthcare. However it has not replaced CT in areas of trauma including bone fractures, internal bleeding, identifying a bleed in acute stroke, acute pulmonary conditions like pulmonary embolism.
This article is for general awareness, not a substitute for medical advice.
Author is Founder Director Gauri Kaul Foundation
