Difference between CT Scanner vs MRI Scanner vs Ultrasound Scanner machine

This page describes CT Scan, MRI scan and Ultrasound Scan. It mentions difference between CT Scanner machine, MRI scanner machine and Ultrasound Scanner machine used for CT scan, MRI scan and ultrasound scan respectively. It mentions advantages and disadvantages of each of these scanner types.

What is CT Scan?

CT scan

CT stands for Computerized Tomography. This technology is based on X-ray principle. CT scan machine takes many X-rays from different angles and uses a computer to create 3D picture of the inside of the body.

CT scanner or CT Scan Machine

CT scanner machine

CT scanner consists of moving cache on which patients are kept in sleeping position. The cache is slowly moved during scanning. Patients are required to be scanned twice, during first time general image is captured and during second time detailed scan is performed. It takes about 5 minutes to complete the CT scan using CT scanner machine. The figure-1 and Figure mentions images of CT scan and CT scanner respectively.

Advantages of CT scan

• It is better for bony lesions.
• Faster than MRI scan, takes 5-10 minutes.
• Medium cost
• small risk of irradiation.

Disadvantages of CT scan

• Poor resolution of demyelinating lesions.
• This method has risk due to ionizing radiation.
• Sensitive to acute hemorrhae

What is MRI Scan?

MRI scan

MRI stands for Magnetic Resonance Imaging. This technology is based on magnetism principle. It is latest scan technology available after CT scan. It uses magnetism to build up 3D image of the inside of the body. It consists of moving cache. Patients are kept in sleeping position on this cache and is supposed to be moved in the narrow cyclinder. This cylinder is fixed with magnets which generates magnetic field surrounding to the patient body. Cylinder of MRI scan machine is slightly narrower compare to CT scanner.

During the MRI scanning, all the metallic objects from the body should be removed. It takes about 30 minutes to complete the MRI scanning. The figure-3 depicts image taken during MRI scan.

MRI scanner or MRI scan machine

MRI Scanner or MRI Scan Machine

There are four key components of MRI scanner machine are shown in the figure-4.
• A powerful permanent magnet.
• Gradient coils which produce a variable magnetic field.
• Radio frequency (RF) coils which produce radio waves.
• Scanner: It detects energy emitted from the body.

Advantages of MRI scan

• No radiation used and hence it is safe.
• Provides better images compare to CT scan and hence used to distinguish different tissue types.

Disadvantages of MRI scan

• It is very expensive among all the scan techniques.
• Care should be taken during scanning with metal objects.
• Electronic equipments should not be kept in the room as strong magnetic fields used in this technique can damage them.

What is Ultrasound Scan?

Ultrasound scan

• It works on the principle of ultrasound imaging and piezoelectric effect.
• It is used to help diagnose causes of pain, swelling and infection in the body's internal parts and organs. It helps in biopsies. It helps to diagnose heart conditions and to assess the damage after heart attack. It is used to examine baby in the pregnant women. • Here sound waves are produced in order to take pictures of the inside of the body.
• During this type of scan patients are asked to lie down and small brobe is used to move around manually over the body parts by radiologist to capture the images in realtime.

Ultrasound scanner machine

Ultrasound scanner machine

• During the scanning ultrasound waves are bombarded to the body which gets reflected by the human body tissues. The reflected waves are varying in time and intensities (amplitudes) which are used by piezoelectric crystal in the probe to convert mechanical vibration into varying electric current. This varying current helps in producing image on the screen of Ultrasound scanner machine.
• As Ultrasound scan does not use any radiation exposure, it is considered to be very safe and painless for the patient. The figure-5 and figure-6 depicts Ultrasound scan and ultrasound scanner machine respectively.

Advantages of Ultrasound scan

Following are the advantages of ultrasound scanner machine:
• Ultrasound is safe, noninvasive and does not use ionizing radiation.
• Images are captured and displayed on screen in real time and hence proper image can be captured as required after looking at movement of body's internal parts.
• Shows clear picture of soft tissues which does not show up well during CT scan.
• Ideal to examine unborn babies during pregnancies.

Disadvantages of Ultrasound Scan

• Not suitable for deep body scan as ultrasound can not penetrate bone and larger amount of tissues.
• Not suitable for organs obscured by bowel as ultrasound waves are disrupted by gas or air.

Difference between CT Scan, MRI scan and Ultrasound scan

Following table summarizes difference between CT scan, MRI scan and Ultrasound scan types.

Feature CT scan MRI scan Ultrasound scan
Waves/method used for scan X-Rays Magnetic Waves Ultrasound waves
Injection Yes Yes No
Time to conduct tests Within 5 minutes Approx. 30 minutes Immediate, will take about 5 minutes to analyze on the screen in real time and capture appropriate image
Cost of test Medium High Medium
Bony structure More detail about bony structure Less detailed compare to CT scan Not suitable for deep bone tests, upper swallowing can be tested.
Soft tissue Less detailed in soft tissue. Much higher detailed in soft tissue. Ideal for this test

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