Few discoveries have changed modern medicine as much as imaging modalities, beginning with the discovery of “X-rays” in 1895 by Conrad Röntgen, followed by a computerized combination of X-rays, the computed tomography (CT) scan. , which created cross-sectional images as virtual “slices” of the body and enabled us to visualize the internal structures without cutting – to open them, ie non-invasively, to imagine them almost like a fantasy!
CT scan was a notable discovery that led to the award of the prestigious Nobel Prize in Physiology or Medicine to South Africa-born American physicist Dr. Allan Cormack and British electrical engineer Dr. Godfrey Hounsefield led.
MRI (Magnetic Resonance Imaging) went even further and completely changed the imaging process as it is extremely safe and just as versatile in image acquisition as the CT scanner uses safe magnetic field gradients and radio waves instead of ionizing radiation to gather the information needed to do this effectively converted to 2D and 3D images in any plane you want.
HISTORY OF MAGNETIC RESONANCE IMAGING is very fascinating and includes thirteen Nobel Prize winners, including nine from physics, two each from chemistry and medicine with a fair share of controversy! This was one such discovery that the scientist who owns the patent for MRI, Dr. Raymond Damidian, who was not found good enough to be awarded the coveted Nobel Prize, and who published a full-page advertisement in protest, justifying his claim in the world-famous newspaper. ‘New York Times’ shortly before the Nobel Prize Ceremony.
Dr. Paul C. Lauterbur and Sir Peter Mansfield received the 2003 Nobel Prize in Physiology or Medicine for their groundbreaking discovery of delivering the ultimate concept and approximate design of modern MRI.
Dr. Lauterbur, a trained chemist, postulated that the nuclear magnetic resonance (NMR) property, first introduced by Nobel Prize winners Dr. Bloch and Dr. Purcell was enlightened that imaging could be used by introducing gradients into the magnetic field. For the first time he was able to take pictures of a pipe cross-section with ordinary water (H2O) surrounded by heavy water (D2O), which contains the isotope of hydrogen, deuterium, the nucleus of which contains an extra neutron, making it heavier and more clearly magnetic resonance property. Overall, this ushered in a new era of transformation in imaging.
Sir Peter Mansfield, son of a poor gas fitter, was a renowned physicist from Great Britain who was able to come up with a remarkable mathematical formula for quickly identifying and analyzing the humorous data obtained through various gradients. This makes the MRI a versatile and faster imaging tool. that it is today!
Nottingham Professor of Physics Peter Mansfield went to India to attend an NMR conference where he first heard Paul Lauterbur and got much-needed insight into the problem that eventually led him to share the Nobel Prize by solving Dr. Lauterbur.
PRINCIPLE BEHIND THE MAGNETIC RESONANCE IMAGE
Water is the most abundant molecule in all living things, including humans. This consists of hydrogen and oxygen atoms. The nuclei of the hydrogen atoms act like microscopic compass needles. Under a very strong magnetic field such as 0.5 to 20 Tesla (one Tesla corresponds to twenty thousand times the earth’s magnetic field), hydrogen atoms in the tissue water orient themselves to the magnetic field. These hydrogen atoms are exposed to radio waves that take them to another high energy level and create resonance. When these atoms return to their relaxation states, they emit energy that is trapped by the system. These differ for different tissues in terms of health and disease states. Such emitted vibrations due to the relaxation of resonant hydrogen atoms are converted into two- or three-dimensional image shapes using a complex mathematical calculation known as a “Fourier transform”.
Often the injectable contrast of a paramagnetic molecule such as “gadolinium” is used to change the local magnetic field in the tissue, which further differentiates the normal from the diseased.
MRI imaging not only helps in diagnosis, but also in tracking the progression of the disease during the course of treatment without exposure to radiation or possible damage to the body’s cells. This is a very useful imaging method, especially in pregnant women and in fast-growing infants and children, where radiation is particularly harmful. In contrast to the CT scan, which does not provide good soft tissue details (tissues other than bone), MRI is very accurate at detailing soft tissues where the CT scan gives poor results, e.g. B. in crowded areas of hindbrain and head-neck junctions.
It’s a very useful tool for distinguishing white and gray matter in the brain and spinal cord, making it an overwhelming choice of imaging for neuroscientists. In addition to the head, neck, spine and CNS (central nervous system) parts, it is a very useful tool for viewing abdominal structures such as pancreas, liver, kidney, etc. in both health and disease states. It has now almost replaced many routine surgical procedures such as diagnostic laparotomy to examine the diseased abdomen and arthroscopy (examining the joints by creating a hole) for injured or diseased joints.
Many MRI offshoots such as mammography (breast cancer imaging), elastography (fatty liver and cirrhosis of the liver), MRCP (obstruction of the pancreas and biliary system), etc. are very useful techniques that are performed using the magnetic resonance protocol.
Diffusion MRI and functional MRI (f-MRT) are further additional examination instruments that record the neural pathways or blood flow in real time and reveal many other hidden features of the mysteriously functioning dynamic operations of the brain and nervous system.
Recently, MRI has been increasingly used in forensic and veterinary studies and occasionally in paleontological studies (fossil) in certain complex situations.
RESTRICTIONS OF MRI
Unlike the modern CT scan, MRI stays right due to the high maintenance costs due to the need to keep the superconducting magnet functional in an artificially created extremely cold environment created by liquid helium and a layer of liquid nitrogen around the magnet expensive.
MRI takes a long time to complete the study and is easily prone to movement-related artifacts. These continue to give cause for concern. Restless people and children have difficulty taking the test. Also, people who are claustrophobic (fear of confined spaces) and dislike loud noises generated by radio pulse generators or who have metallic implants in their body are not advised to perform this test. Lately, many welcome changes have been made to its design to address the above issues, but it has only significantly increased costs and limited its use in resource-poor countries.
The author is a former professor and head of the Department of Medicine, RIMS, Ranchi, Jharkhand.