HANFORD — Many patients ask about the differences between a CT (Computed Tomography) scan and an MRI (Magnetic Resonance Imaging) scan: “Which is better?” or “Should I have one over the other?”

While the machines look similar, what occurs inside these “donut holes” is quite different. A CT scanner sends X-ray beams through the body as it moves through an arc taking many pictures. A CT scan sees different levels of density and tissues inside a solid organ, and can provide detailed information about the body, including the head (brain and its vessels, eyes, inner ear, and sinuses), chest (heart and lungs), skeletal system (neck, shoulders and spine), pelvis and hips, reproductive systems, bladder and gastrointestinal tract.

Advances in CT scanning include increased patient comfort, faster scanning times and higher resolution images. As scans become quicker, X-ray exposure has decreased, providing better images at lower doses. The average CT scan today exposes patients to less radiation than what airline passengers receive on long flights. That said, anyone having a CT scan should talk to their doctor about the risks from radiation exposure versus the benefits of early diagnosis.

Unlike CT scans, which use X-rays, MRI scans use powerful magnetic fields and radio frequency pulses to produce detailed pictures of organs, soft tissues, bone and other internal body structures. Differences between normal and abnormal tissue is often clearer on an MRI image than a CT. And while there is no radiation involved in an MRI scan, it can be a noisy exam and take longer than a CT.

They sound similar — so which one is better?

It depends on what part of your body your doctor is interested in and the reason for the exam. Radiologists are the doctors who specialize in reading these images and collaborate with your doctor to determine what issue they want to diagnose.

For example, doctors will ask for a CT scan when they want to diagnose a muscle or bone disorder or look for tumors, a fracture or a blood clot. Bleeding in the brain, especially from an injury, can be seen better on a CT scan than an MRI. If you are in an accident, where damage to internal organs is not clear from a physical examination, a CT scan shows organ tear and injury, broken bones and spinal damage more efficiently. This is usually why ER doctors order CT scans. Normally for any abdomen and pelvis scan, a CT is the benchmark over an MRI.

However, if your doctor is interested in seeing your tendons and ligaments, then an MRI is the best choice. The spinal cord also can be seen better on an MRI image, since the density of these structures and tissues are more defined.

Adventist Health has partnered with Radisphere National Radiology Group to provide comprehensive radiology coverage through a combination of local onsite radiologists and a remote network of subspecialists who work together to deliver final reports around the clock.

Undergoing any medical exam — CT, MRI or otherwise — can be a trying time for anyone. You should feel empowered to talk with your doctor or anyone in our Medical Imaging Department if you are uncomfortable or have questions. We are here to help and make your experience as positive as possible.

For either exam, be sure to:

* Ask if you should fast before the exam.

* Find out how long the exam will take.

* Have someone accompany you to take you home.

* Find out if you will receive a contrast agent (if so, alert the Radiology Department to any kidney function issues or allergic reaction you may have had in the past).

* Bring a list of your current medications:  prescriptions, over the counter medications and vitamins.

* For women, inform your physician or the radiology technologist if there is any possibility you are pregnant.

Athale is the medical director of radiology at Adventist Medical Center - Hanford. He is part of Radisphere National Radiology Group (www.radispheregroup.com), which provides radiology services to the Adventist Health/Central Valley Network and more than 35 hospitals in the U.S.

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