Medical Scans Explained

Have you ever undergone an X-ray, MRI, or another type of medical imaging? Are you familiar with what these procedures entail and their purposes?

Medical imaging plays a crucial role in assisting healthcare professionals in diagnosing a wide range of conditions, from head injuries to foot ailments. There are various imaging technologies available, each operating on distinct principles.

Certain imaging tests utilize radiation, while others rely on sound waves, radio waves, or magnetic fields. Understanding how these medical scans function can alleviate any anxiety you or a loved one may have when facing such tests. It also equips you with the knowledge to ask pertinent questions prior to undergoing an imaging procedure.

X-Rays

The introduction of X-rays marked a significant advancement in the ability to visualize the internal structures of the body, with over 120 years of clinical use.

“X-rays remain a daily tool because of their versatility,” states Dr. Kris Kandarpa, an imaging specialist at NIH. They are particularly effective for examining bones and identifying issues in specific tissues, such as detecting pneumonia in the lungs.

X-ray imaging operates by directing an energy beam through a specific area of the body. Some of the X-ray beams are obstructed by bones or other tissues, resulting in their shapes being captured on detectors. These detectors convert the X-rays into a digital image for analysis by a radiologist.

X-ray beams emit radiation, which is energy released in the form of invisible particles or waves. Prolonged exposure to high levels of radiation can harm cells and tissues and may elevate the risk of cancer.

However, contemporary X-ray examinations utilize minimal doses of radiation. Individuals are naturally exposed to radiation from various sources, including the atmosphere, rocks, and soil.

“A chest X-ray exposes you to a radiation level comparable to that experienced during a transatlantic flight,” Kandarpa clarifies.

CT Scans

CT scans also employ X-ray beams, but these beams rotate around the entire body to generate a three-dimensional image. These images provide more detailed information than standard X-rays and can be completed in under a minute, making them particularly valuable in emergency settings.

CT scans utilize a greater number of X-ray beams compared to standard X-rays, resulting in a higher radiation dose. However, medical professionals have methods to determine the minimum necessary radiation dose, as noted by Dr. Cynthia McCollough, a CT imaging researcher at the Mayo Clinic.

“We customize the radiation dose based on the patient’s size and the purpose of the examination,” McCollough states. For instance, a CT scan of the chest requires less radiation than one of the abdominal region.

Dr. McCollough’s laboratory, in collaboration with four other NIH-funded teams, is exploring further reductions in radiation exposure from these scans. Her team has analyzed hundreds of CT scans to identify the lowest radiation dose sufficient for radiologists to make accurate diagnoses.

“We have discovered that while significantly reducing the dose may result in less visually appealing images, they frequently still provide the correct diagnosis for physicians,” McCollough clarifies.

Although lower radiation doses could potentially decrease risk further, McCollough emphasizes that the standard doses are already quite minimal. This is crucial information for patients, as “some individuals who genuinely require a CT scan may hesitate to undergo the procedure,” she remarks.

Such apprehension can prevent individuals from receiving scans that could enhance their health or even save their lives. “Current CT radiation doses are so low that it is virtually impossible to demonstrate any associated risk,” she adds.

If you have concerns regarding tests that involve radiation, refer to the “Ask Your Doctor” section for relevant questions.

MRI operates on a fundamentally different principle. It does not employ X-rays; instead, it utilizes powerful magnets and radio waves to influence the atoms in the water molecules present in your body’s tissues. When the radio waves cease, the atoms emit energy that the MRI machine detects.

Atoms in various types of tissues return to their normal state at different rates and release varying amounts of energy. MRI software processes this data to generate three-dimensional images of the distinct tissue types.