CT Scan vs. Ultrasound

The difference between an ultrasound and CT Scan is the source of exposure. During CT scan the patient is passed through a scanning system and exposed to effective radiation dose ranges from 2 to 10 mSv while in ultrasound there is no radiation exposure and the process is based on echoes and sound waves. Ultrasound and CT scan both are very popular and widely used diagnostic tools but each has its own way of doing its job.

Comparison Chart

Basis CT Scan Ultrasound
Radiation Exposure Yes No radiation
 Advantages This technique is using greater definition and precision and is able to image bone, soft tissue, and blood vessels all at the same time Ultrasounds are usually not used to image bones so it is commonly used for visualizing the size, structure, or other abnormalities in muscles, tendons, and internal organs and often used in prenatal care
Cost Expensive Less expensive
Time Duration Usually completed within 5  minutes It will take around 15 minutes
Principle Uses X-rays for imaging High-frequency sound waves are used

What is CT Scan?

The term CT Scan stands for Computed Tomography Scan and sometimes also called X-ray computed tomography, computed axial tomography scan or CAT scan.

Principle of CT Scan

When a patient is passed through a CT scan it creates a 3D image of an organ or of the interior body structure.

It produces tomographic images or cross-sectional images by putting together multiple X-ray images created by low-powered rays passing several times over the same body area, from different angles. A computer merges all the images into a single high-definition image that enhances clarity and definition that allows the doctor to view the area slice by slice.

Procedure CT Scan

During the CT scan, the patient is passed through the scanning system that uses X-rays and allows doctors to see inside your body.

During the process, a narrow X-ray beam and an X-ray detector circles around one part of your body so that the X-rays that are passed through the region of interest can produce different image slices in axial or helical mode.

The multiple images are then computed to create a view of the organ. The high contrast CT image can be immediately viewed on a television monitor or can be recorded for storage and analysis later.

Applications of CT Scan

A CT scan has a number of diagnostic uses, but it’s particularly well-suited to quickly examine people who may have internal injuries from car accidents or other types of trauma.

It can be used to visualize nearly all parts of the body and is much better at screening for certain types of cancer tumors and used to diagnose disease or injury as well as to plan medical, surgical or radiation treatment depending upon the prognosis.

Doctors ask for CT scans for a long list of reasons:

  • It can detect complex bone and joint problems, and tumors.
  • It can detect a number of dangerous vascular diseases that can cause kidney, failure, stroke, and death
  • It can show internal injuries and bleed, such as those caused by a car accident.
  • It gives a better image and can easily reveal a tumor, blood clots in the vessels, and excess fluid in any organ.

Moreover, doctors use CT scans to find out if certain treatments are working or not. For example, scans of a tumor after some time helps in identifying the

What is Ultrasound?

The term ultrasound refers to sound waves with a frequency that humans cannot hear.

It is also called sonography or diagnostic medical sonography that uses high-frequency sound waves to produce images of fetuses development during pregnancy and can also diagnose kidney and gall stones to make available valuable information for diagnosing and treating a variety of diseases and conditions.

Principle of  Ultrasound

Ultrasound is a sound wave that can travel through soft tissue and fluids, for example, if it hits a heart valve, it will echo or bounces back.

The denser the object the sound-wave hits, the more of the waves bounce back.

These sound waves, when reflected back from the body, will be first received by a transducer and will pass through the ultrasonic scanner, where they are processed and transformed into a digital image.

This bouncing back, or echo, gives the ultrasound image its features depends on the time and strength of the echo and is displayed on the computer screen for analysis. Varying shades of gray reflect different densities.

Procedure of  Ultrasound

Before entering the ultrasound room, you will be asked to change into a hospital gown. Depending on the area being examined, a sonographer who is responsible to do your ultrasound will apply a special lubricating jelly to your skin to prevent friction so they can rub the ultrasound transducer on your skin.

Before your ultrasound begins, you may be asked to do the following:

  • You may be asked to fast for 8-12 hours when your abdomen is being examined as undigested food can block the sound waves
  • Remove any jewelry from the area being examined
  • You may be asked to drink plenty of water and hold your urine so that your bladder can be better visualized

In the end, the gel will be wiped off and the whole procedure usually lasts less than 30 minutes, depending on the area being examined.

Applications of Ultrasound

Your doctor may request an ultrasound if you are having pain, swelling, or other symptoms that require an internal view of your organs. An ultrasound can provide a view of the:

  • Uterus and ovaries during pregnancy to monitor the developing baby’s health
  • Identify abdominal problems in major organs such as the appendix, stomach, gall bladder, and liver
  • Examine a breast lump
  • Detect genital and prostate problems
  • Assess joint inflammation
  • Evaluate metabolic bone disease

Ultrasound is often used to image muscles, internal organs, and tendons as it is particularly good at determining the size of organs and tissues as well as finding lesions and other problems.

In terms of procedures, ultrasound is used in prenatal care, removal of gall stones, kidney stones, and many other types of medical applications.

It is also used to investigate a frozen shoulder, tennis elbow, carpal tunnel syndrome, and others.

Key Differences between CT Scan and Ultrasound

  1. A CT scan will usually cost more than an ultrasound procedure.
  2. The time duration of CT scan will be shorter usually it will take about 5 minutes however, ultrasound usually take more than 15 minutes.
  3. During CT scan patient is exposed to radiation for this reason CT scan is not recommended to children and pregnant women however, there is no radiation exposure with the use of ultrasounds.

Comparison Video


Both CT scan and ultrasound are often preferable over X-rays as CT scan shows a much better image from many different angles so the doctor can have a better view of the targeted area over a flat X-ray exposure.

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