WCMS: CT, MRI, ultrasound or X-ray? Which one is the right choice?

From the Western Carolina Medical Society:


Patients often ask, “Why do I need an MRI instead of a CT?” or “Why can’t I just get an x-ray?” looking inside the body. There are a lot of choices including x-ray, computerized tomography (CT), ultrasound, magnetic resonance imaging (MRI), nuclear medicine, and positron emission tomography (PET). Choosing the right type of imaging is important in making the right diagnosis. Some factors a radiologist may consider include visualization of area, patient tolerance, cost of exam, radiation exposure and availability of equipment.
The most common exam in radiology is x-ray. X-ray is performed by passing high energy radiation through the body to create an image of that body part. X-ray’s are good at looking at bone.
Computerized Tomography (CT) is performed by rotating the x-ray detector and the recording device around the patient. The recording device sends data to a computer that compiles it into an image. Like a loaf of bread, the image is made up of many slices. The data is then constructed so the radiologist can look at just one slice at a time or the whole loaf. CT is good at looking at bone and organs.
Magnetic Resonance Imaging (MRI) utilizes magnetic field and high frequency radio waves and is typically used when more detail of the tissue is needed. MRI does not use radiation therefore there is no risk of exposure. The magnetic field and radio waves cause the body’s protons to release energy which differ by tissue. An image is then produced from these signals. MRI is also a good choice when looking at soft tissues (ligaments, bone marrow, muscle and solid organs), when the person is allergic to iodinated contrast used in CT scans and when additional information is needed.
Ultrasound passes sound waves through tissues and converts the data into electrical signals. A computer then converts the signals into an image. Since the sound waves can easily pass through a structure or be blocked by a structure, ultrasound serves as a useful tool for detecting abnormalities in soft tissues. It can also be used to diagnose clots in veins in the legs and arms. Ultrasound is good at looking at organs (kidney, gallbladder, liver) and vascular anatomy (arteries, and veins). It is not good at looking at bone.
Nuclear Medicine uses injected radionuclides (atoms that release energy as radiation) to discover problem areas. Once in the system, a camera can detect areas where radionuclides have accumulated. Nuclear Medicine exams are good at assessing the patient’s physiology and biochemical interactions in the body.

Positron Emission Tomography (PET) scanning also uses radionuclides and can be fused with CT images. This exam is frequently used to look for cancer growth.
Whichever modality is recommended, all imaging exams are geared to give the radiologist a good look at the physiology and anatomy of the patient. Once the correct diagnostic procedure is performed and final diagnosis made, patients and physicians can make informed decisions. Often different types of radiology procedures will complement each other and are separate pieces of the puzzle and help to form a complete picture of the patient.


Dr. Bryon Dickerson is the President of Asheville Radiology Associates (ARA). He attended medical school at Albany Medical College, completed his Diagnostic Radiology Residency at Wake Forest University Baptist Medical Center, and was a Musculoskeletal Radiology Fellow at WFUBMC. Dr. Dickerson was a faculty member at Wake Forest University Medical prior to being recruited to Asheville Radiology Associates in 2002. He is a member of the Western Carolina Medical Society. ARA is a physician group consisting of 40 multispecialty radiologists and 5 vascular surgeons. The group has provided services for Western North Carolina for more than 40 years with solid expertise and knowledge.

About Lea McLellan
Lea McLellan is a freelance writer who likes to write stories about music, art, food, wellness and interesting locals doing interesting things.

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