MRI: What Is It Used For And Why?

  • Sarvesh Puranik M.Sc. in Translational Neuroscience, University of Sheffield
  • Regina Lopes Senior Nursing Assistant, Health and Social Care, The Open University

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Magnetic Resonance Imaging (MRI) is a non-invasive imaging technology that produces three-dimensional detailed anatomical images. It is often used for disease detection, diagnosis, and treatment monitoring. It is based on sophisticated technology that excites and detects the change in the direction of the rotational axis of protons found in the water that makes up living tissues.

What is MRI used for?

MRI scanners excel in imaging the soft tissues of the body, such as muscles, ligaments, and organs, without relying on harmful ionising radiation like x-rays, which are used in CT scans. This makes MRI a superior choice for detailed views of the brain, spinal cord, nerves, as well as injuries in the knees and shoulders.

Definition of MRI:

MRI is a non-invasive imaging technology that produces three-dimensional detailed anatomical images. It is often used for disease detection, diagnosis, and treatment monitoring. MRI utilises powerful magnets which produce a strong magnetic field that forces protons in the body to align with that field. When a radiofrequency current is then pulsed through the patient, the protons are stimulated, and spin out of equilibrium, straining against the pull of the magnetic field. When the radiofrequency field is turned off, the MRI sensors are able to detect the energy released as the protons realign with the magnetic field, and an image is created using this information.

Basic principle: how MRI works:

The basic principle of MRI involves the interaction of nuclei in the body with pulses of radio waves in the presence of a powerful magnetic field. This interaction results in a variety of signals that can be used to construct images of organs and tissues. The technique exploits the magnetic properties of certain atomic nuclei. An MRI scan can differentiate tissues based on their physical and chemical properties, allowing it to reveal structures that other imaging techniques cannot.

What is MRI used for?

MRI scanners excel in imaging the soft tissues of the body, such as muscles, ligaments, and organs, without relying on harmful ionising radiation like X-rays, which are used in CT scans. This makes MRI a superior choice for detailed views of the brain, spinal cord, and nerves, as well as injuries in the knees and shoulders.

In neurological applications, MRI is invaluable for distinguishing between different types of brain tissue, such as white matter and grey matter, and it is instrumental in diagnosing conditions like aneurysms and tumours. Its ability to operate without radiation makes MRI the preferred method for repeated imaging, crucial for ongoing diagnosis or treatment, particularly in sensitive areas like the brain. Despite its advantages, MRI is generally more costly than X-ray and CT imaging.

Types of MRI scans: exploring functional MRI and open MRI

MRI is a powerful diagnostic tool used across the medical field for detailed internal body structures imaging. Among the various types of MRI scans available, functional MRI (fMRI) and open MRI stand out due to their unique capabilities and applications.

Functional MRI (FMRI)

Functional MRI is particularly distinguished by its ability to measure and map brain activity. This capability is crucial for neuroscientific research and clinical practices. fMRI operates by detecting changes in blood flow to various brain regions, assuming that blood flow and neuronal activation are correlated. When a brain area is more active, it consumes more oxygen, and fMRI detects these changes as a cue to neuronal activity. This type of MRI is indispensable in brain mapping for surgical planning and understanding vital neural pathways affected by disorders such as Alzheimer's or schizophrenia. Recent studies utilise fMRI for predictive analysis and treatment efficacy, showcasing its application beyond basic imaging.

Open MRI

Unlike the conventional enclosed MRI machines, open MRIs do not surround the entire body of a patient. This structure is a significant advantage for patients who suffer from claustrophobia or who are of larger size, making it difficult to fit comfortably in traditional MRI units. Open MRI is also advantageous for procedures that require some degree of patient movement or access, such as those involving young children or certain types of physical assessments. Studies have highlighted the use of open MRI for a better understanding of joint behaviours under different physical conditions, which can be crucial for orthopaedic and sports-related injuries.

Understanding the versatile uses of MRI in medical diagnostics

MRI is a non-invasive imaging technology that has revolutionised the way diseases are diagnosed and managed. Its ability to produce high-resolution images of organs and structures inside the body makes it an indispensable tool in modern medicine.

Common areas examined

Brain: MRI of the brain can detect brain tumours, traumatic brain injury, developmental anomalies, multiple sclerosis, stroke, dementia, infection, and causes of headache.

Detecting Tumours: MRI is highly sensitive in detecting and pinpointing the location of tumours within the body, including the brain, liver, and breast.

Spinal Cord: It is critical for diagnosing disorders such as spinal cord injuries, herniated discs, spinal tumours, and other abnormalities affecting the spinal column.

Heart: Cardiac MRI helps in assessing several conditions affecting the heart including congenital heart disease, cardiomyopathies, and complications from a heart attack. It provides a detailed image of the heart and its blood vessels.

Joints: MRI is invaluable in diagnosing joint abnormalities, including tears of ligaments and tendons, joint infections, and even subtle bone fractures that may not be visible on other imaging modalities.

Abdomen: It helps in identifying liver diseases, kidney stones, and other abdominal pathologies.

MRI's broad range of applications not only helps in accurate disease diagnosis but also in the assessment of treatment response, making it a cornerstone of modern diagnostic medicine.

Advantages of MRI over other imaging techniques

Medical imaging is a crucial tool in modern healthcare as discussed above, offering insights that lead to accurate diagnosis and effective treatment. Among the various imaging technologies available, MRI stands out due to its unique benefits. Here’s a closer look at why MRI is often the preferred choice over other methods like X-rays and CT scans.

Non-invasive nature: no radiation exposure

One of the most significant advantages of MRI is its non-invasive nature. Unlike X-rays and computed tomography (CT) scans, which use ionising radiation, MRI employs powerful magnetic fields and radio waves to produce detailed images. This absence of radiation means there is no risk of radiation exposure, making MRI safer for patients, particularly those who require frequent imaging such as individuals with chronic conditions or ongoing treatment monitoring. This aspect is especially important in paediatric care, where minimising radiation exposure is crucial.

Superiority in providing high-contrast images of soft tissues

MRI is renowned for its exceptional ability to provide high-contrast images of soft tissues. The technology excels at visualising the structure of soft tissues, including the brain, muscles, heart, and ligaments, which are often not as clearly seen with other imaging techniques. This capability makes MRI indispensable in diagnosing a wide range of conditions from joint and tendon injuries to brain disorders. The detailed images produced help physicians to assess the severity of a condition and plan the most effective treatment.

Ability to produce 3D images that can be viewed from different angles

Another technological marvel of MRI is its ability to create three-dimensional images that can be viewed from multiple angles. This feature provides a comprehensive view of the body’s internal structures, allowing for a more thorough examination. Surgeons, in particular, find this feature invaluable for planning surgical procedures, ensuring precision and improving outcomes. The 3D imaging capability also enhances the effectiveness of treatments by allowing more accurate targeting of areas affected by disease or injury.

Limitations and considerations of MRI technology

MRI is renowned for its ability to provide detailed images of the body's internal structures without the use of damaging radiation. However, despite its many advantages, MRI is not without its limitations and considerations. Understanding these challenges is crucial for both patients and healthcare providers when choosing the most appropriate imaging technique for a particular situation.

Contraindications: patients with certain implants or devices

One of the primary limitations of MRI technology concerns patients who have certain metal implants or devices. The powerful magnetic fields generated by an MRI scanner can interfere with or be affected by metal objects such as pacemakers, cochlear implants, certain artificial joints, and drug infusion pumps. Exposure to MRI in these cases can lead to malfunctions of the devices or cause harm to the patient. Therefore, thorough screening for metallic implants is essential before an MRI scan is performed.

High cost and availability of MRI machines

Another significant consideration is the high cost associated with MRI scans. MRI technology involves complex machinery and highly detailed imaging technology, which are costly to purchase and maintain. This high cost is often passed on to patients and can make MRI less accessible, especially in less affluent or rural areas where medical facilities may not be able to afford to house, maintain, and staff MRI equipment. The availability of MRI machines can therefore be limited, leading to long wait times for patients needing scans.

What’s the final verdict on MRI?

Overall, while MRI is a cornerstone of modern diagnostic medicine, its use must be tailored to individual patient needs and circumstances. The choice between different types of MRI scans, such as functional MRI and open MRI, further allows customization of care, enhancing patient comfort and the diagnostic accuracy of medical evaluations. As we continue to advance in medical technology, the role of MRI remains crucial, consistently offering detailed insights that drive better patient outcomes. Understanding both its power and its limitations allows healthcare providers to utilise MRI most effectively, ensuring the best care for patients in diverse medical scenarios.

Summary

Magnetic Resonance Imaging (MRI) is a non-invasive imaging technique vital in disease detection, diagnosis, and treatment monitoring, particularly excelling in visualizing soft tissues without ionizing radiation. It operates by aligning protons in the body with a magnetic field and detecting their realignment using radio waves. MRI's applications range from neurological to orthopaedic diagnostics, including brain, spinal cord, joint, and abdominal imaging.

Notable variants include Functional MRI (fMRI), crucial for brain activity mapping, and Open MRI, offering accessibility benefits. Advantages include its non-invasiveness, high soft tissue contrast, and ability to produce 3D images. However, limitations include contraindications due to metallic implants and the high cost and limited availability of machines. Overall, MRI remains a cornerstone of modern diagnostics, offering detailed insights for better patient outcomes while requiring tailored usage and consideration of its limitations.

References:

  1. National Institute of Biomedical Imaging and Bioengineering [Internet]. Magnetic Resonance Imaging (MRI). Available from: https://www.nibib.nih.gov/science-education/science-topics/magnetic-resonance-imaging-mri
  2. Goldman M. Basic Principles of NMR and MRI. In: EPJ Web of Conferences [Internet]. 2012. p. 01001. Available from: http://www.epj-conferences.org/10.1051/epjconf/20123001001
  3. Fujiwara Y. 19. Basic Principle and Clinical Application of Synthetic MRI. Nippon Hoshasen Gijutsu Gakkai Zasshi. 2023 Aug 20;79(8):851–6.
  4. Radiology (ACR) RS of NA (RSNA) and AC of. Radiologyinfo.org. Functional MRI (fMRI). Available from: https://www.radiologyinfo.org/en/info/fmribrain
  5. Developer. Health Images. 2019. Open MRI vs. Closed MRI. Available from: https://www.healthimages.com/open-mri-vs-closed-mri/
  6. on behalf of the European Society of Cardiovascular Radiology (ESCR), the European Association of Nuclear Medicine (EANM) Cardiovascular Committee, Nensa F, Bamberg F, Rischpler C, Menezes L, et al. Hybrid cardiac imaging using PET/MRI: a joint position statement by the European Society of Cardiovascular Radiology (ESCR) and the European Association of Nuclear Medicine (EANM). European J Hybrid Imaging. 2018 Dec;2(1):14.

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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sarvesh puranik

M.Sc. in Translational Neuroscience, University of Sheffield

Sarvesh Puranik is currently completing his Master's thesis, which centers on Alzheimer's disease research. Prior to this, he earned his Bachelor's degree in Homoeopathic Medicine and worked as a junior doctor, where he managed and treated patients with neurological conditions such as Alzheimer's, Parkinson's disease, stroke, and epilepsy and various other neurological disorders.

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