Medical Physics X-rays in radiography and CT

Characteristics of X-rays:

The combination of (1) the ability to penetrate opaque materials, (2) the atomic-scale wavelength, and (3) the high energy of individual X-ray photons has led to a wide range of industrial, medical, and scientific applications.

How do medical X-rays work?

X-ray images are an indispensable diagnostic tool in modern medicine, such as the detection of diseases such as tooth decay, fractures, foreign bodies and cancer. X-rays can easily distinguish between bone and soft tissue. X-rays pass through the body and are absorbed by different tissues in different amounts, depending on the density of the tissue they pass through. For example, structures such as bones contain calcium, which has an atomic number higher than most tissues and contains relatively more electrons, which have a greater chance of interacting with X-rays and therefore penetrate less. Due to this property, bones absorb X-rays easily. Therefore, against the black background of the X-ray film, bone structures appear whiter than other tissues. Conversely, X-rays can more easily pass through less radiodense tissues such as fat and muscle, as well as air-filled cavities such as the lungs.

The term "white lung" is often heard in the diagnosis of COVID-19. When the lungs are inflamed, the density of this area becomes relatively higher than that of blood vessels and air in the lungs, and an abnormally large white area may appear in the X-ray image of the lungs, so it is called "white lung", which means that the patient's symptoms may be quite serious.

Examples of Common Medical X-Ray Uses

(1) X-ray imaging: Detect fractures, certain tumors and other abnormal masses, pneumonia, certain types of injuries, calcifications, foreign bodies, dental problems, etc.; such as what is often called taking an X-ray.

(2) CT (Computed Tomography): refers to a computerized X-ray imaging procedure in which X-rays are aimed at the patient and rotated rapidly around the body, producing signals that are processed by a computer to generate cross-sectional images or "slices" of the body. These slices are called tomograms and contain more detailed information than conventional X-rays. Once the computer collects multiple consecutive slices, they can be digitally "stacked" together to form a 3D image of the patient, making it easier to obtain richer medical information.

Are there any risks?

If used properly, the diagnostic benefits of X-ray scans certainly far outweigh the risks. However, X-rays produce ionizing radiation - a form of radiation that can harm living tissue. This risk increases with the number of exposures. Therefore, it is necessary to take adequate radiation protection measures.