July 15, 2015

5 Common Diagnostic Tests

Radiology terms can seem like an alphabet soup of confusion to the average person. Some common questions people may ask about diagnostic testing are what’s the difference between a CT scan and a PET scan? Why would you need an MRI instead of an X-ray? Bryon Dickerson, MD, president and CEO of Asheville Radiology Associates explains the technological and diagnostic differences between the different Radiology tests:


One of the earliest forms of radiology testing, X-ray machines have been in use for over 100 years. They work by beaming X-rays (a type of electromagnetic radiation) through the body, causing certain portions of the internal anatomy—particularly the skeletal frame and body cavities—to be visible on film.

What it’s used for: X-rays are ideal for examining bones, lungs, gas and foreign objects. They are less helpful at investigating soft tissue.


An ultrasound machine uses the echoes of high frequency sound waves to capture images inside internal organs. The images created by these sound waves are known as sonograms (sound images). An ultrasound is often used in conjunction with other imaging tests.

What it’s used for: An ultrasound is ideal for viewing organs with fluid in them, like the kidneys and gallbladder. It’s not useful for examining solid structures, like bones.


Magnetic resonance imaging (MRI) is a diagnostic scan that uses strong magnetic fields and sound waves, rather than radiation, to create a frequency within the body that can be transmitted into images.

What it’s used for: An MRI can reveal a lot about soft tissues, bone marrow and solid organs. It’s not as helpful in examining air or solid bone.

CT Scan

Computed tomography (CT) uses a combination of X-rays and advanced computer technology to process images. As a result, a CT scan can offer a look at body tissues that aren’t visible through traditional X-rays. A CT is an advanced, faster version of computerized axel tomography (CAT). In the early days of CAT scans, it would take several minutes to capture an image of just a small portion of the brain. Now, with a multi-detector CT, a radiologist can scan the entire body in a matter of seconds.

What it’s used for: A CT can look at bones, as well as solid and hollow organs throughout the body. It’s useful for interpreting the progression of diseases, cancers and inflammatory processes.

PET Scan

Instead of sending beams or waves through the body, positron emission tomography (PET)—which is a type of nuclear medicine—uses radiopharmaceuticals. Once these drugs are injected into the body, the radiologist can use a CT scanner to view a three-dimensional image of where they accumulate.

What it’s used for: A PET scan can be used for viewing multiple organs and the stage of a disease. It’s frequently used in cancer imaging. Often, a radiologist will use a combination of the above imaging tests to get to the root of a problem. Dr. Dickerson explained, “It’s kind of like we’re putting together pieces of a puzzle to see the complete picture.”

Interventional Radiology

Radiology services aren’t just for diagnosing diseases; they can also be used during certain medical procedures. Imaging guidance can assist a physician in performing a precise treatment using needles or catheters that is less invasive.

Radiology Services Near You

Asheville Radiology Associates is Mission Health’s exclusive provider of radiology services. They provide diagnostic imaging at 22 locations throughout our community. To learn more, visit AshevilleRadiology.com.

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