4 Types of MRI’s and Their Purpose
Magnetic Resonance Imaging is a medical imaging technique that utilizes a strong magnetic field to form pictures of the anatomy and other physiological processes of the body. The difference between MRI and CT scans is that an MRI does not utilize any x-rays or ionizing radiation. It is a technique that utilizes a nuclear magnetic field, radio waves, and a computer to produce an image by manipulating the properties of water molecules (mostly H+ ions) in our bodies.
MRI Scans and Their Types
MRI scans may differ in their type based on its construction, properties, and applications. Here we will go through a few of them:
Based on construction MRI scanners are classified into
Wide bore MRI
Truly open MRI
Open upright MRI
⦁ Closed MRI
Closed MRI, Image credits: pixabay
A closed MRI machine is a narrow cylindrical tube with a bore diameter of 60 cm. It takes high-quality images and has up to 3T strength which is the highest strength available among all commercial MRIs. 3 tesla MRI can easily capture blood vessels as tiny as 200-300 microns. 3 Tesla MRI machine price can range anywhere between 15 – 20 crore Indian Rupees. However, the MRI cost can vary if you are buying an already used one.
⦁ Wide bore MRI
Wide bore MRI, Image credits: pixabay
As the name suggests Wide bore MRIs are partly open scanners with wider openings and more headspace than the closed MRI scanners. The bore diameter is 70 cm and a person with a broader build can easily pass into it. However, the field or magnetic strength is just 1.5 T and the image clarity is not as good as closed MRI scanners.
⦁ Truly open MRI scanners
Truly open MRI, Image credits: pixabay
These scanners are the open type which allows more ventilation during the scan. However, the magnetic field strength is too low (1.2T) to capture images that are high in clarity.
⦁ Open upright MRI
This type is a completely open front where the patients are allowed to sit upright during the entire examination. It has the lowest magnetic strength of all types.
MRI types based on Properties and Applications
Magnetic Resonance Angiography
Functional MRI– Functional MRI is used to check brain activity that occurs due to the changes in the blood. It gives a clear picture of how blood flows within the nervous system. fMRI can be applied to diagnose the effects of neurological disorders like stroke and Alzheimer’s disease on the brain. Along with this, fMRI also helps study the effects of blood flow in the brain during brain surgery guiding the brain surgeon where to exercise utmost care and caution.
Interventional MRI– It helps surgeons perform minimally invasive surgeries, whereby they can assess the safety and correctness of the procedure being performed. The technique is widely used to remove tissues non invasively, for biopsies of suspected lesions and in various heart procedures. It provides great access and detailed images of the tissues and organs.
Cardiac MRI – MRI which is specially customized to study the heart is cardiac MRI. Cardiac MRI helps study the Anatomy of the heart, pericardial diseases, thrombus, coronary artery disease, cardiomyopathies, and ventricular disorders all can be easily diagnosed using this technique.
Magnetic resonance angiography – Angiography is an MRI technique used to study abnormalities related to the blood vessels of the body, arteries of the brain, abdomen, legs, chest, neck, pelvis, and arms. It is of two types: flow-dependent and flow independent.
Diffusion MRI – Water molecules in the body follow the diffusion law and travel from a region of higher concentration to lower concentration. Similarly, diffusion MRI works on the principle of diffusion and is applied to study different regions of the brain.
MRI screening vs diagnostic MRI
A screening MRI is designed to screen for conditions like aneurysms and cancer in which the symptoms usually do not appear in the early stages. Whereas, A diagnostic MRI is designed to look at a specific body part or area for a detailed view.
Some other types of MRI’s which can be customized based on the requirements and physiology of different body systems include Magnetic resonance venography, magnetic resonance spectroscopy, real-time MRI, molecular imaging MRI, and magnetic resonance-guided focussed ultrasound.