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Understanding How MRI, CT and X-ray Medical Imaging are Different

Today’s medical imaging utilizes three important technologies that provide the foundation of radiology. X-rays, CT scans and MRI scans each provide a unique spectrum of capabilities and benefits to the medical community. They are all valuable and useful, and they have their own individual characteristics.
Patient Getting an MRI Scan


X-rays involve exposing the patient to a small dose of radiation to produce an image of internal structures. X-rays are used in situations when a quick, preliminary view is required. The procedure can also be used as a second check to verify another type of imaging or examination. X-rays are advantageous because they are not time consuming and are less expensive than other forms of imaging. They also may be preferred by patients who are claustrophobic or who may be too large to fit into a CT or MRI machine. Due to its portability, x-rays are often employed in emergency situations or for injuries when imaging results are needed rapidly to move forward with patient care. X-rays are most often used on the chest, extremities and spine.

X-rays do pose disadvantages that may cause physicians to opt for other medical imaging procedures in certain situations. X-ray images cannot capture the detail or volume of images that other imaging methods can. X-ray images display superimposed anatomy, unlike CT and MRI which give a cross-sectional view of internal structures. They also expose the patient to radiation, unlike some other types of procedures such as ultrasound or MRI. The potential radiation risk must be carefully weighed against the value of the proposed exam to the diagnosis and treatment process. However, the cost-effectiveness and speed achievable with X-rays make them valuable for certain situations. On balance, X-rays remain an important member of the medical imaging family.

CT Scans

Computed Tomography (CT) scans also utilize ionizing radiation combined with sophisticated computerized capabilities and software. This makes it possible to collect a large volume of information with a single scan. CT scans usually take between five to twenty minutes to perform, making them faster than MRI scans and thus more suitable for emergency or urgent injury situations. CT facilitates the ability to scan a patient “head-to-toe” in a matter of minutes, providing physicians with a lot of information on trauma patients who have sustained multiple injuries. CT scans can depict not just skeletal structures but soft tissues and other internal elements including blood vessels, organs and muscle mass. CT scans are widely used to collect images of the head and brain, heart, and other organs and internal processes as well as extremities and injuries.

For all their advantages however, CT scans may not always be the best choice in certain situations. For example, CT scans cannot display subtle differences or abnormalities in soft tissues as effectively as MRI scans. Also, CT scans may not be a viable option for large or claustrophobic patients who are unable to enter a CT machine. Patients who are allergic to the contrast media used in some CT scans may have to undergo alternative imaging with another modality. In spite of their few shortcomings, CT scans offer many advantages that make them a valuable asset in a variety of circumstances. CT scans allow for quick imaging, a high level of imaging detail, and are able to ‘see’ many more angles and views than X-rays.

MRI Scans

Magnetic Resonance Imaging, or MRI scans, provide the third leg of the medical imaging technology trio. Unlike CT scans and X-rays, MRI scans do not utilize radiation when scanning patients. They instead create a powerful magnetic field and use radio waves along with highly developed software to digitally collect images. MRI’s offer advantages over other types of imaging. First, MRI scans better differentiate subtle changes or irregularities in soft tissues. This makes MRI scanning the imaging method of choice for many types of muscle or tendon injuries. MRI’s also remove the risk of radiation exposure because they utilize different technology. As a result, MRI scans can be useful for pregnant patients or children who may be more susceptible to the potential risks of radiation exposure.

As in all imaging methods, MRI scans do have some weaknesses. The MRI process takes longer than other types of imaging, often lasting half an hour or more. They also do not display certain types of soft tissue as well as CT scans do. Additionally, like a CT scan, MRI imaging demands that the patient lie horizontally inside a small chamber. This may not be possible or it may be uncomfortable for large or claustrophobic patients. MRI scans also require the patient to remain still for the duration of the procedure. Movement risks compromising the quality and readability of the images. Remaining still enough to ensure a successful scan can be difficult for some patients and small children. Sedation can sometimes be used to assist a patient, but sedation poses its own risks and must be weighed against the value of the scan. Even though MRI’s may not be optimal for every patient situation, they represent a versatile and powerful imaging technique that can be applied to a plethora of medical situations and needs.

Each of the three major forms of medical imaging technology offers physicians and medical professionals its own set of advantages. Together, they can serve a vast spectrum of medical and patient needs. As each type of imaging undergoes further development, the future of radiology is looking brighter and brighter. Imaging technologies are likely to offer an even broader spectrum of possibilities that promise to benefit the medical community and those for whom it cares.

Recommended Readings:

Career Outlook for Diagnostic Medical Sonography
Medical Sonography: A Job for the Future of Healthcare