Diagnostic X-Rays

X-rays are electromagnetic waves that lie in the range of 0.001 nanometres (nm) up to 10nm. X-rays used for diagnostic imaging are highly energetic and are partially absorbed when they pass through a material (this depends on the type of substance).

Diagnostic X-ray definition

X-ray imaging allows medical professionals to perform fast and reliable medical diagnoses on the condition of a patient's internal organs and bones without the need for an incision. X-rays are one of the most frequently used and widely-available methods for diagnosis.

Diagnostic imaging with X-rays: the different types of X-ray techniques

X-ray imaging is an essential tool for assessing skeletal trauma and capturing a comprehensive snapshot of the status of a person’s (or animal’s!) lungs, heart, and blood vessels. It is also commonly used to diagnose problems in the digestive tract, for high-resolution diagnostic imaging of the breasts, and to produce images of bones, organs (like the kidneys), teeth and jaws, and the structures of the ear, nose, and throat.

The X-ray tubes used have a range of around 20 to 150 kiloelectronvolts (keV). This means that the highest energy photons used for X-rays are around 20keV. X-rays are high-energy electromagnetic waves that are transmitted through body tissues with relatively little absorption.

Conventional radiology

This is the traditional X-ray type used to create two-dimensional images of bones (for bone fracture diagnosis) and the teeth (dental diagnosis). It is also typically used to scan the chest.

Traditional X-ray machines use a fixed tube to point X-rays at a single spot, and as X-rays move through the body, they are absorbed in different amounts depending on the tissue.

If the X-ray is viewed on conventional film, the image is produced later. This process includes covering a sheet of plastic with a radiation-sensitive chemical contained in an X-ray cassette, which is a light-resistant flat container that holds the X-ray film closely with the intensifying screen.

When X-rays enter the body:

• Soft tissue like organs and muscles cannot absorb the radiation, so the X-rays pass through the body, leaving the cassette behind. The patient is exposed to larger amounts of radiation, which turns the film black in those spots.
• Hard tissue like bones absorbs large amounts of radiation. This leaves the film exposed to much less radiation, and the film appears white or grey as a result.

A wrist X-Ray

Computed tomography (CT)

Computed tomography (also called computerised tomography) or CT is a combination of traditional X-rays with computer processing to create higher-resolution images. A CT scan creates a series of very thin cross-sectional images or slices of the body by using a rotating version of the X-ray machine. It captures details of muscles, blood vessels, organs, bones, and tissues to form a three-dimensional image with very high resolution and detail.

This type of image is used to diagnose tumours, diseases, injuries, blood clots, fractures, etc.

A CT scanner

Sometimes a contrast agent may be required to view specific features of the body in greater detail. A contrast agent is a liquid that is either prescribed orally or via injection, and it is used to increase the contrast of structures or fluids within the body during the CT procedure. Contrast agents absorb external electromagnetism, which affects the CT machine. The most frequently used contrasting agent is barium-sulphate.

Angiography

An angiogram is a machine similar to a conventional X-ray machine. It is used to take images of arteries, veins, vessels, and organs. This is done by injecting a contrasting agent into the bloodstream so that the blood-flowing structures of the body are more visible. Angiograms are very useful for blockage and narrowing diagnoses.

Mammography

Mammography is the process of using low-energy X-rays to examine the human breast for early diagnosis of breast cancer. This is done using a mammogram – a machine that creates high-resolution images of the breasts. It works by compressing the breasts between two plates with an X-ray source located on the top (see image below).

The X-ray beam is located on top of the breast. The beams move vertically to meet a film underneath the breast and a fibre optic sensor that detects X-rays and the amount of radiation that goes through the breast. The sensor is connected to a computer that can identify immediately the amount of radiation absorbed by the tissue in the breast, forming a digital X-ray image. This machine is able to show irregular-shaped tumours or masses.

A mammogram machine

Nowadays, an even more advanced mammogram exists, which can take three-dimensional images of the entire breast. This is known as a 3D mammogram, and it takes images of thin slices (similar to a CT scan) as it moves in an arc over the breast. A computer processes these thin slice images into a 3D image.

Fluoroscopy

Fluoroscopy is an imaging technique that produces real-time images of movement. Medical professionals use this to assess the condition of a patient’s internal organs. This type of procedure is beneficial to diagnose diseases and injuries.

The continuous X-ray beam is transmitted to a monitor so that the body motion can be seen in detail. The beam is located underneath the patient’s bed, and it emits the X-rays vertically upwards, which are then absorbed either partially or fully by the patient’s tissues. An image intensifier, which is connected to a TV monitor, intensifies the remaining radiation. This produces a digital image of the X-ray.

What kind of abnormalities can be visualised by diagnostic X-rays?

Several different abnormalities or medical conditions can be detected with X-ray imaging so that proper medical treatment can be given to a patient. These include cancers and tumours, blood vessel blockages, digestive problems, bone and joint fractures, and infections.

Different body parts are inspected using X-ray imaging, including internal body parts and external body parts, such as the head, abdomen, chest, arms, legs, hands, and feet.

Are diagnostic X-rays safe?

The safety of X-ray machines has been studied over the years. X-rays are safe when they use the minimum amount of radiation needed to conduct the required tests. X-rays are a form of ionising radiation, which is radiation capable of removing electrons from atoms. This then changes the composition of cells. Higher energy X-rays can damage living cells, so it’s crucial that X-rays must not emit high amounts of electromagnetic radiation in the body.

All types of X-ray machines emit a certain amount of ionising radiation, so there is always a very slight increase in the risk of developing cancer. However, this amount is relatively small, and because the benefits of X-rays outweigh the risks, they are deemed safe. There is also a risk of developing an allergic reaction when contrasting agents are used.