Posted on Wed Mar 20, 2019
‘Tesla’ is the unit that measures magnetic strength; one Tesla is equal to 10,000 gauss, which is approximately 30,000 times more than average gravity on the surface of the Earth. We are often asked what the difference is between a 1.5T scanner and a 3T. The answer is that a 3T scanner is twice the strength of a 1.5T scanner.
The strength of the MRI magnet is directly proportional to the amount of signal that is received from the human body during an MRI scan. Because the signal from the body is then used to create the images, the higher the magnetic strength, the more detailed the images, right?
Well, not necessarily. When comparing 1.5T to 3T MRI scanners, there are two important factors to consider: safety and image artefacts.
Some implants that are safe to go into a 1.5T scanner may not be safe in a 3T scanner. This is because the stronger magnet in the 3T scanner can possibly cause issues with implants that the weaker 1.5T magnet would not.
When implants and foreign bodies are present in the body, they can cause an error in the image quality because they interfere with the magnetic signal. As the strength of the magnet increases, the amount of distortion these foreign bodies can cause grows, which can decrease image quality.
The type of material the object is made from as well as its size and location, should always be discussed in advance with the Clinical team.
This is the estimated rate of energy that is being absorbed by the body during an MRI scan. The more absorption of energy, the more heat is produced. This can potentially be harmful for the patient, as the heating of implants and surrounding tissue may result in burns.
This isn’t really an issue in 1.5T scanner, but becomes more of a consideration on a 3T scanner simply because it’s more powerful. This means that sometimes the radiographer might have to pause the scan between sequences to allow the SAR to decrease.
Overweight patients might also be affected as the radiographers need to turn up the magnet strength to obtain quality images.
Just remember that there are no known long-term effects when it comes to SAR, and it is always closely monitored throughout the scan.
In a perfect world, the stronger magnet in a 3T scanner would give the best images and every MRI scanner would be 3T. However, when taking the previous considerations in mind, a 1.5T scanner is often a better choice.
The best scanner for the patient really depends on the exam needed and the body composition, (if there are any foreign artefacts, body weight etc.).
If you’re unsure about which scanner is best, contact our Clinical team on 020 7042 1888.
At Oryon Imaging we have a 1.5T scanner which allows us to produce high-quality MRI scan images at our centre in London. Our MRI prices start at only £190.
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