In the world of medical imaging, magnetic resonance imaging (MRI) stands at the forefront of pursuing technological advances and creating high-quality images. MRI scanners are used in clinical settings around the world, to provide physicians with valuable diagnostic and prognostic information about a patient’s health.

To simplify a highly complex machine, an MRI scanner uses radio frequency waves and a magnetic field generated by a very large magnet to create a highly detailed 3-D image of the body.

MRI scanners are created with varying magnetic field strength, measured in a unit called teslas (T). Today, the most common magnet strengths in MRI machines used in clinical settings are 1.5T and 3.0T. As the numbers imply, a 3.0T magnet is twice as strong as a 1.5T magnet. To put this into perspective, the strength of the magnet that picks up cars in a junk yard is about the same as a 1.5T magnet in an MRI.¹

1.5T has long been the standard strength magnet used in clinical settings, whereas 3.0T machines have typically been used in research settings. However, advances in technology have made 3T machines safer to use and more widely available. 1.5 and 3.0T scanners have some differences in their capabilities, but both machines offer a great deal of value in patient care.

1.5T compared to 3.0T

Even though 3.0T magnets have become more common and accessible outside of research settings, 1.5T is still more than adequate for most routine scans. In fact, many people consider 1.5T to be state-of-the-art in medical imaging. In most situations using a 1.5T scanner will provide the desired diagnostic benefits. However, the value in increasing the scanner’s magnetic field to 3.0T is that it provides even better image quality and faster scan speeds.

The improvement in 3.0T image quality is largely due to improvements in the machine’s signal-to-noise ratio (SNR). This is the ratio between the intensity of the image’s signal and the background noise, appearing as graininess in the image.² SNR in a 3.0T scanner is twice as sensitive compared to 1.5T, creating a clearer image.

Improved SNR allows for higher spatial resolution and higher temporal resolution. Higher spatial resolution is essential for detecting lesions in small, complex anatomical structures. This is critical in many instances, such as labrum pathology in the shoulder or hip, and triangular fibrocartilage complex pathology in the wrist. Also, when imaging the spine, the capabilities of high spatial resolution help detect nerve root, spinal cord, and neuroforaminal pathologies.²

Higher temporal resolution is advantageous because it improves the efficiency of the MRI scanner. A 3.0T scanner with these abilities can scan more patients in the same amount of time, while retaining image quality similar to that of a 1.5T machine. Faster scan times without loss of image quality is a huge benefit to clinicians.

In addition, studies show that 3.0T scans provide significant diagnostic advantages for certain exams:

Prostate MRI: Because of the small size of the prostate gland, imaging the prostate with a 1.5T scanner requires the use of a endorectal coil. The increased signal of a 3.0T system makes it possible to image the prostate with an external surface coil instead.
Spectroscopy: This exam evaluates the amount of certain chemicals in tissues, most often utilized when imaging the brain. The increased static field strength of a 3.0T MR system improves the quality of these studies, helping to characterize lesions and assess response to therapy.
Functional MRI (fMRI): fMRI is a technique utilized to evaluate areas of the brain responsible for various functions; speech hearing sight motor, etc. 3.0T MR is more sensitive to changes in blood flow in these areas.
Arterial Spin Labeling (ASL): A technique used to assess blood flow perfusion, primarily to the brain. This test is much more effective at higher magnetic fields such as 3.0T. 3

Furthermore, the increased spatial resolution of 3.0T scanners allows for high-quality vascular imaging. Therefore, 3.0T MR studies may replace the need for invasive interventional catheter studies.

How to Choose between 1.5T and 3.0T MRI

As a medical professional looking to purchase an MRI machine, you can’t go wrong when choosing between 1.5T and 3.0T scanners. Both machines offer the best image quality that modern MRI technology can offer. However, determining which MRI equipment is the best choice for your hospital or imaging center can be a complex undertaking. Four key contributing factors should be used to determine which type of MRI scanner is right for you: image quality, speed, cost, and safety.⁵

Image Quality

Imaging quality is critical for ensuring the most accurate patient diagnosis

Advantages
- 1.5T
  - 1.5T is the standard for producing high quality images.
  - Longer sequences with 1.5T can greatly improve image quality.
- 3.0T
  - 3.0T is proven to be ideal for imaging the brain, vascular, musculoskeletal, and small bone systems.
  - 3.0T provides higher clarity and better detail because it’s magnetic field is twice as strong as 1.5T.⁵
Limitations
- 1.5T
  - The level of clarity at 1.5T is less effective for studies requiring extremely detailed images, such as brain scans.
- 3.0T
  - Images from 3.0T scans are more likely to have artifacts present. An artifact is any feature that appears in the image that is not present in the original imaged object. These are sometimes called “flow” artifacts, as they appear due to movement of blood or fluid in the body.⁴

Speed/Throughput

When there is high patient volume, speed takes on great importance. A shorter scan time can be beneficial to an imaging facility, as well as the patient.

Advantages
- 1.5T
  - It is possible to shorten scan times with a 1.5T system with minor sacrifice in image quality.
  - Low volume facilities where speed is not a concern can maintain high quality images.
- 3.0T
  - Scan time is decreased because a 3.0T machine has double the signal strength
Limitations
- 1.5T
  - While it is possible to improve image quality with longer sequence scans, this can cause delays and bottlenecks, affecting wait times, patient satisfaction and revenue.
- 3.0t
  - If speed is not a concern for your clinic, then using a 3.0T system specifically for its speed is cost-prohibitive

Cost

Cost can be the main driver when purchasing expensive medical equipment.

Advantages
- 1.5T
  - A 1.5T system and its replacement parts are more readily available than 3.0T.
- 3.0T
  - The imaging speed of the 3.0T system can have a great impact on operational efficiency.
Limitations
- 1.5T
  - Medicare, Medicaid, and private insurance payers reimburse the same amount for an MRI exam regardless of magnet strength.
- 3.0T
  - The cost for 3.0T system is sometimes twice as much as a 1.5T.
  - Generally, maintenance and repair cost more on the 3.0T machine.

Safety

Advantages
- MRI safety is highly regulated, and under strict safety guidelines, patients can be scanned equally as safe in both 1.5T and 3.0T systems.
Limitations
- Patients who have implants or medical devices are safest in a 1.5T magnet.

Both the 1.5T and 3.0T MRI systems produce exceptional images, making either magnet a valuable option. 1.5T systems remain the standard and are the most commonly used MRI equipment today. They provide safe, secure, and dependable imaging environments and quality images. However, if your imaging facility is concerned with a high volume of patients or focuses on highly detailed imaging work, investing in a 3.0T system may be worthwhile. Regardless of your decision, you can be sure that your imaging professionals are working today’s most valued MRI systems.

References:

Campisi, Lisa. "What patients want to know about their MRI machines- 1.2T, 1.5T, 3.T, what's the difference?". Shields Healthcare Group Blog. Web. July 23 2018. <http://info.shields.com/bid/85107/what-patients-want-to-know-about-mri-machines-1-2t-1-5t-3t-whats-the-difference>.
Del Grande, Filippo, Chhabra, Avneesh, Carrino, John A. "Getting the most out of 3 Tesla MRI of the spine". Rheumatology Network. ModernMedicine Network. May 03 2012. Web. July 23 2018. <http://www.rheumatologynetwork.com/articles/getting-most-out-3-tesla-mri-spine>.
Faulkner, William A. "1.5 T Versus 3 T". Web. July 23 2018. <http://www.medtronic.com/mrisurescan-us/pdf/UC201405147a_EN_1_5T_Versus_3T_MRI.pdf>.
Harmonay, Vikki. "3T MRI vs 1.5T MRI- Do You Know the Difference?" Atlantis Worldwide. October 18 2016. Web. July 23 2018. <https://info.atlantisworldwide.com/blog/3t-mri-vs-1.5t-mri>
Evans, Eric. "The Pros and Cons of 1.5T V. 3T MRI: One Size Does Not Fit All." Linkedin.February 14 2018. Web. July 23 2018. <https://www.linkedin.com/pulse/pros-cons-15t-v-3t-mri-one-size-does-fit-all-eric-evans/>.