8 Feb, 2022

MRI scans: what is the difference between a 3 Tesla and 1.5 Tesla scanner?

The key difference between the two types of scanners is simply the strength of the magnet. MRI stands for magnetic resonance imaging, meaning the scanners use powerful magnets of various strengths to enable the generation of images. 

A 3T scanner's magnets are twice as strong as a 1.5T scanner's, but how should you choose which scan to go for? 

💡 The 'T' in 1.5T or 3T stands for 'Tesla,' which is a unit of measurement for the strength of the magnets within MRI scanners. One Tesla is 30,000 times stronger than the gravitational pull on the surface of the earth. 

Image Clarity
In most clinical settings, a 1.5T MRI scanner is more than adequate to generate clear images and provide evidence for diagnosis and prognosis.
Initially, 3T scanners were mainly used in research settings, but now they are well suited to brain, vascular, musculoskeletal and small bone system imaging in clinics. This is due to the stronger magnetic field allowing clearer image quality for more intricate body parts.

However, a limitation of 3T scanners when it comes to image quality is that the movement of blood and fluid in the body is picked up so clearly by the scanner, it can often cause features to appear in the images that are not actually present in the imaged body part. These are also known as artifacts.

3.0T scanners also generate more heat and noise than their 1.5T counterparts.
As a 3T scanner has double the strength in terms of magnetism, it takes less time to accurately collect images as you can be passed through the scanner more quickly. This can be beneficial for people who struggle with anxiety around medical procedures, and can help hospitals reduce waiting times for scans.

If you wanted to increase the quality of an MRI scan with a 1.5T scanner, the patient would need to be in the scanner for a longer period of time.

However, 3T systems are more expensive to buy, so hospitals usually don't purchase them solely for the reduced scanning time as this doesn't offer much return on investment.
If you have any medical devices or metal implanted in your body, such as a pacemaker, artificial heart valve, replacement joints or even bullets and shrapnel, you would be better suited to a 1.5T MRI scan.
Before you have an MRI scan, any implants or foreign bodies are categorized as either safe, unsafe, or conditional. Safe means any magnetic strength can be used, while unsafe means no magnetic imaging is suitable for the patient.

In conditional cases, a 3.0T scanner's magnetism might be too strong and could damage the patient's implant/device. It could also risk the patient's safety if the magnets were to attract their metallic devices. Furthermore, artifacts, or errors in the MRI images, can be caused by foreign bodies being affected by the magnets.
This means that in some specific cases, a 1.5T scanner is recommended, due to reduced risk and better image quality.
Overall, the main deciding factor between a 1.5 T and 3.0T MRI scan is the body part being imaged. If you need a brain MRI scan, or more information about your musculoskeletal system, a 3.0T MRI can provide clearer images with more intricate details.
However, if you are having an MRI scan for any other reason, a 1.5 T scanner will provide your radiologist with all the information and accurate imagery they need to reach a diagnosis.
Furthermore, if you have any medical devices or implants, a 1.5 T scanner is a safer option as it still provides excellent images with fewer risks.
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