MRIs vs. X-Rays: What Is the Difference?

By Ibtisam AbbasiReviewed by Lexie CornerNov 4 2024

Medical imaging techniques provide structural visuals of organs and tissues and are foundational to medical diagnosis and biomedical research. X-ray and Magnetic Resonance Imaging (MRI) are among the most widely used methods in healthcare for diagnosing medical conditions and detecting abnormalities.¹

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How Do MRI and X-Ray Technologies Work?

MRI

MRI scanners use strong magnets and radio waves to produce detailed images of body organs. The cylindrical MRI scanner creates a powerful magnetic field around the patient, directing radio waves at the specific area or soft tissue being studied.²

The magnetic field in MRI aligns body molecules uniformly, while the radio waves disturb this alignment, displacing atoms from their organized positions. When the radio waves stop, the atoms return to their original positions, emitting radio signals from each targeted area. Each part emits radio signals of varying intensities, which a computer connected to the MRI machine processes to create a detailed image of the body part under examination.³

X-Ray

X-ray technology and other traditional imaging methods use ionizing radiation that can penetrate body structures, allowing images of tissues and organs to be generated.⁴ During an X-ray procedure, the area of the body to be examined is placed between the source of ionizing radiation and an X-ray detector. The X-rays create an image on specialized film or, when connected to a computer, display the image digitally, aiding doctors in diagnosis.

Different body tissues absorb X-rays at varying levels based on their density. Bones, which absorb X-rays strongly, appear bright white on an X-ray image, while softer tissues and organs, like the lungs, display as shades of dull grey. This contrast enables doctors to examine bone structures closely and diagnose potential issues.⁵

Applications of MRI and X-Ray Imaging

MRI

MRI is a non-invasive imaging technique. It enables detailed visualization of critical organs such as the brain and heart and is instrumental in detecting cancer and tumors.

Cardiac MRI effectively highlights contrasts between soft tissues in the heart, making it essential for cardiac tissue characterization and facilitating the rapid detection of myocardial changes.⁶ MRI is also considered the most accurate technology for locating and measuring lesions in the brain.⁷

Beyond the heart and brain, MRI is also effective in diagnosing traumatic cervical spinal cord injuries (TSCI), such as those resulting from high-speed car accidents that cause vertebrae damage. These severe injuries are often undetectable with other imaging methods, but studies indicate that MRI offers a sensitivity of approximately 94-97 % for identifying traumatic disc ruptures.⁸

Consequently, MRI is widely considered the most effective method for imaging soft tissues and detecting spinal cord injuries, providing significantly greater sensitivity than other imaging techniques.

X-Ray

X-ray is regarded as the method for detecting fractures and bone damage. It enables the diagnosis of various fracture types, including simple fractures, compound fractures where the bone pierces the skin, comminuted fractures involving bone fragmentation, and stress fractures.⁹ X-ray imaging has also proven essential in diagnosing and managing COVID-19, with researchers integrating computer vision and machine learning algorithms to enhance its diagnostic capabilities.

X-ray technology is also a key tool for the dental industry, where it is used for diagnostics, detecting bone loss, and teeth enumeration.¹⁰ As a fast and effective method, X-ray imaging is one of the most highly utilized imaging technologies across various industries.

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Advantages and Limitations

MRI

MRI is unique in that it is entirely noninvasive and does not expose patients to harmful ionizing radiation. It is highly effective for soft-tissue imaging and can detect abnormalities that may not be visible with other methods.

However, certain limitations accompany MRI technology. Although the strong magnetic field is safe for patients, it can interfere with some implanted medical devices, potentially causing malfunctions or image distortions. Consequently, special precautions are needed for patients with implants.¹¹

The procedure requires patients to remain very still to produce high-quality images, which can be challenging for infants, young children, or those unable to stay still; sedation or anesthesia may be needed in these cases, introducing risks such as slowed breathing or low blood pressure.¹¹

MRI systems are costly, have high operating expenses, and are less accessible in developing countries. Imaging neonatal brains presents additional challenges, as obtaining precise images and effective tissue characterization can be difficult. Specialized post-processing tools are often required for imaging infants, further adding to the costs associated with MRI.¹²

X-Ray

X-ray medical imaging, which is non-invasive and painless, is highly effective for diagnosing bone fractures and monitoring recovery during therapy. X-rays are cost-effective and play a critical role in guiding the placement of stents and other devices within the body.

However, radiation exposure remains a key concern with this technology. Ionizing radiation has been linked to cancer and other serious health risks, prompting ongoing efforts to develop new methods that reduce radiation exposure. Additionally, while the preferred method for visualizing bone structure, X-rays are limited in characterizing soft tissue.

Furthermore, studies have found that producing and disposing X-ray equipment and materials can negatively impact the environment. Manufacturing these systems and using chemicals in analog film-based radiography can contribute to environmental pollution.¹³

Conclusion: MRI vs. X-Ray

Both MRI and X-ray technologies are essential tools in medical diagnostics. MRI excels in soft tissue imaging, while X-rays remain the preferred method for visualizing bone structures. Advances in imaging algorithms have further accelerated diagnostic capabilities with these methods. Ongoing research continues to improve their safety, sustainability, and cost-effectiveness.

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References and Further Reading

1. Hussain, S., et al. (2022). Modern diagnostic imaging technique applications and risk factors in the medical field: a review. BioMed research international. Available at: https://doi.org/10.1155/2022/5164970
2. National Health Service. (2022). MRI Scan Overview. [Online] National Health Service. Available at: https://www.nhs.uk/conditions/mri-scan/ (Accessed on: October 22, 2024)
3. Johns Hopkins Medicine (2024). Magnetic Resonance Imaging (MRI). Health: Treatments, Tests and Therapies. [Online] Johns Hopkins Medicine. Available at: https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/magnetic-resonance-imaging-mri#:~:text=What%20is%20MRI%3F,large%20magnet%20and%20radio%20waves (Accessed on: October 22, 2024)
4. National Institute of Biomedical Imaging and Bioengineering. (2023). X-rays. [Online] National Institute of Biomedical Imaging and Bioengineering. Available at: https://www.nibib.nih.gov/science-education/science-topics/x-rays#pid-1121 (Accessed on: October 23, 2024).
5. United States Environmental Protection Agency. (2024). Radiation and Medical X-rays. (Online). Available at: https://www.epa.gov/radtown/radiation-and-medical-x-rays (Accessed on: October 23, 2024)
6. Thomas, K., et. al. (2023). Imaging methods: magnetic resonance imaging. Circulation: Cardiovascular Imaging. https://doi.org/10.1161/CIRCIMAGING.122.014068
7. Martucci, M., et al. (2023). Magnetic Resonance Imaging of Primary Adult Brain Tumors: State of the Art and Future Perspectives. Biomedicines. https://doi.org/10.3390/biomedicines11020364
8. Liao, W., et al. (2023). Role of magnetic resonance imaging features in diagnosing and localization of disc rupture related to cervical spinal cord injury without radiographic abnormalities. Spinal Cord. https://doi.org/10.1038/s41393-023-00886-2
9. Luke Zurich Open MRI. (2024). X-Rays in Diagnosing Bone Fractures. [Online]. Available at: https://lakezurichopenmri.com/x-rays-in-diagnosing-bone-fractures/
   (Accessed on: October 24, 2024)
10. Abdulhaleem, S. (2023). X-Ray and its application in dentistry. International Journal of Dental Research. https://www.dentaljournal.net/assets/archives/2023/vol5issue1/5003-441.pdf
11. FDA. (2017). MRI: Benefits and Risks. [Online] FDA. Available at: https://www.fda.gov/radiation-emitting-products/mri-magnetic-resonance-imaging/benefits-and-risks#:~:text=The%20magnetic%20fields%20that%20change,to%20heating%20of%20the%20body.
12. Dubois, J., et al. (2021). MRI of the neonatal brain: a review of methodological challenges and neuroscientific advances. Journal of Magnetic Resonance Imaging.  https://doi.org/10.1002/jmri.27192
13. Hutchison, C. (2024). X-Ray Advantages and Disadvantages. Maven Imaging. [Online] Maven Imaging. Available at: https://www.mavenimaging.com/blog/x-ray-advantages-disadvantages (Accessed on: October 24, 2024).

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