Diagnostic X-Rays

Diagnostic X-Rays

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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). There are four main mechanisms of X-ray attenuation: two, which absorb photons, and two, which scatter photons. X-ray technology is used to examine many parts of the body, such as bones and teeth fractures and infections, arthritis, and other medical conditions. X-rays taken over the years can help doctors determine if a condition is worsening.

Diagnostic X-ray definition

Diagnostic X-rays, also known as radiography, is a test used by medical professionals to diagnose medical conditions. This type of examination uses electromagnetic radiation beams to produce high-resolution images. X-rays are a fast and reliable way for doctors to examine a patient's internal organs and bones without the need for an incision. In fact, X-rays are one of the most frequently used and widely-available methods for diagnosis. X-rays can help diagnose a variety of medical conditions, such as bone fractures, infections, and arthritis. They can also help doctors monitor a condition over time by comparing X-rays taken at different times.

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 [^2]. X-rays are high-energy electromagnetic waves that are transmitted through body tissues with relatively little absorption, making them ideal for producing images of internal structures.

For more information on X-ray technology and its use in medical imaging, please see the explanation on Absorption of X-Rays.

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 hand X-ray
A hand X-ray

Computed tomography (CT)

Computed tomography (CT) is a powerful medical imaging technique that combines traditional X-rays with computer processing to create higher resolution images. Unlike traditional X-rays, which produce two-dimensional 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.

A CT scan 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 a wide variety of medical conditions, including tumours, diseases, injuries, blood clots, fractures, and more.

One advantage of CT scans is that they can provide much more detailed images than traditional X-rays, making them a valuable tool for diagnosing complex medical conditions. However, CT scans also expose patients to higher levels of radiation than traditional X-rays, so they should only be used when necessary.

A CT scanner
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.


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.

A retinal angiogram


Mammography is a powerful diagnostic tool used to detect early of breast cancer. It works by using low-energy X-rays to create high-resolution images of the breast tissue. The mammogram machine compresses the breast between two plates, while an X-ray source on the top of the breast emits the X-ray beam.

The X-ray beam moves 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, which can be indicative of breast cancer. In recent years, 3D mammography has become increasingly popular. This more advanced mammogram takes three-dimensional images of the entire breast, using thin slice images (similar to a CT scan) as it moves in an arc over the breast. These images are processed by a computer to create a 3D image with even greater detail and accuracy.

Mammography is a vital tool in the early detection and treatment of breast cancer. Regular mammograms are recommended for women over the age of 50, as well as for women with a family history of breast cancer or other risk factors.


Fluoroscopy is a powerful medical imaging technique used to produce real-time images of movement within the body. This procedure is commonly used to diagnose diseases and injuries, as medical professionals can visually assess the condition of a patient's internal organs.

During a fluoroscopy procedure, a continuous X-ray beam is transmitted through the patient's body and onto a monitor. The X-ray beam is located underneath the patient's bed, and it emits the X-rays vertically upwards. The X-rays 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, which is displayed on the monitor in real-time.

The advantage of fluoroscopy is that it allows medical professionals to visualize the movement of internal organs, such as the digestive system or the heart, as they function in real-time. This makes it easier to diagnose diseases and injuries that may not be visible with other imaging techniques. Fluoroscopy is commonly used for procedures such as barium enemas, cardiac catheterizations, and joint injections.

While fluoroscopy is a valuable tool for medical professionals, it does expose patients to radiation. As with any medical procedure, the risks and benefits should be carefully considered before undergoing a fluoroscopy procedure.

A fluoroscopy room

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?

X-rays are a valuable tool in medical diagnosis, but it is important to consider their safety. X-rays use ionising radiation, which has the potential to damage living cells. However, X-rays are safe when they use the minimum amount of radiation needed to conduct the required tests. All types of X-ray machines emit a certain amount of ionising radiation, but the risk of developing cancer from this radiation is relatively small.

In addition to the risk of radiation exposure, there is also a risk of developing an allergic reaction when contrasting agents are used. It is important to inform medical professionals of any allergies or previous reactions to contrasting agents before undergoing any X-ray procedures.

Despite these risks, the benefits of X-rays outweigh the risks for most patients. X-rays can capture high-resolution images of bones, organs, tissues, arteries, and vessels, making them a valuable tool for diagnosing a wide range of conditions. Some common abnormalities detected with X-rays include tumours, infections, and fractures. X-rays can be used to view any part of the body, including the chest, abdomen, arms, and legs.

Overall, X-rays are a safe and effective tool for medical diagnosis when used appropriately. Patients should discuss any concerns about radiation exposure with their medical professionals before undergoing any X-ray procedures.

Diagnostic X-Rays

What is the diagnostic range of X-rays?

The X-ray tubes have a diagnostic range of around 20 to 150 kiloelectronvolts (keV). 

Why are X-rays used for medical diagnosis?

X-rays are used in medical diagnosis because they can capture high-resolution images of the internal structure of the body without the need for an incision.

What are X-rays used to diagnose?

X-rays are used to diagnose fractures of bones, tumours, injuries, blockages, state of organs, etc.

What makes an X-ray image suitable for diagnostic radiology?

High energy waves, such as X-rays, are transmitted through body tissues with little absorption, which makes them suitable for diagnostic radiology. 

Is an X-ray a diagnostic test?

Yes, X-rays are used for diagnostic tests in medical physics.

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