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What are the differences between X-rays and CT scans?

Many diagnostic imaging techniques are commonly used by doctors to assess patients with pain, illness, or other abnormalities and ultimately lead to a diagnosis. The most common diagnostic imaging tests include X-rays, ultrasound scans, CT scans and MRI. The type of imaging used mainly depends on the part of the body and the disease process that is suspected by the doctor.
X-rays and CT scans are discussed below as they are the most common type of imaging to utilize low dose ionizing radiation to detect abnormalities. The ultrasound and MRI scans do not use radiation and will be discussed later on.

What are X-Rays?

X-rays are the most commonly available diagnostic imaging technique.
X-rays normally use radiation to generate images of the body. As soon as the rays pass through the body, dense objects like bones, appear white on the film. X-rays are normally used to view and diagnose bone disease, degeneration, fractures, dislocations, infections, and tumors. Even though x-rays are mainly used to examine skeletal structures, an X-ray can be used to look at other internal structures, such as organs as well; however other modalities are more commonly used nowadays.

At the time of an X-ray in Perth, the part of the body that is being looked at needs to be placed between an X-ray machine and a digital x-ray detector. There is a much lower radiation dose to the patient with modern digital x-ray systems. The dose is usually negligible compared to background radiation which we are all exposed to daily.

What are CT Scans?

A computed tomography (CT) scan produces detailed, high-quality images of the body. The CT scan is a more advanced and powerful form of X-ray. It takes a 360-degree series of hundreds or thousands of images to evaluate the internal organs, the spine, joints, brain and vertebrae. Contrast dyes are usually injected into the blood to make structures standout better when having a CT scan. This scan produces detailed images of organs, bones, soft tissue, and blood vessels. It can be used to more easily diagnose cancer, heart disease, appendicitis, musculoskeletal disorders, trauma, and infectious diseases. The scans are performed for nearly every body part rather than having limited utility to certain regions.

A CT scanner appears like a large machine with a tunnel in the center. The patient needs to lie on a table that slides in and out of the tunnel. In the meanwhile, the scanner rotates around the patient, generating cross-section images of the body. The technologist performing the scan sits in a separate room with computers on which the images are displayed. The technologist is able to speak with the patient using speakers so the process is very easy, safe, and relaxing.

Differences between CT scan and X-ray:

X-ray was invented by Wilhelm Rontgen in 1895. CT scan was invented by Godfrey Hounsfield and Allan Cormack in 1972. A CT scanner is more expensive than an X-ray machine. The CT scan in Perth is a sophisticated x-ray that takes 360-degree pictures of the region of interest. Combining a series of rotating x-rays, a detector and a computer, the scanner generates cross-sectional views of the body part being scanned. In most of the cases, a contrast dye is injected into the blood to make the structures standout and highlight abnormalities.

Images produced by X-ray are in 2D, while 3D images are formed in CT scan. The amount of tissue analysis is much more accurate with CT scan, whilst x-rays are usually satisfactory for bone examinations but not soft-tissue examinations.

What are the other Imaging modalities used in radiology?

Other imaging modalities include ultrasound, MRI and bone scan. Read about ultrasound below.


An ultrasound uses high-frequency sound waves that echo off the body. It is painless and noninvasive. It does not require radiation. Ultrasound is used commonly in all body regions and can assess a very wide of diseases or injuries. The main limitation is poor visualization of bones and very deep internal organs that are protected by bones e.g. the lungs are not well seen, and the brain cannot be seen. The most common reasons we perform ultrasound include joint or muscle injuries, leg DVT, pregnancy, abdominal and pelvic examinations.