Magnetic Resonance Imaging (MRI) 3T and 1.5T Applications- A Comparison

MRI stands for magnetic resonance imaging. It is a diagnostic imaging technique that uses a magnetic field and radio waves to produce detailed images of your body's internal organs and tissues. An MRI machine can also produce three-dimensional images that may be viewed from several different angles.

The unit of measurement used to quantify the strength of a magnetic field in an MRI machine is called a Tesla (T). Most MRI scanners operate at a strength of 1.5 Tesla. A 3 Tesla MRI, however, operates at twice the normal strength, providing a greater signal-to-noise ratio, which is a major determinant in generating the highest quality image. The strength of a 3 Tesla MRI yields many benefits for radiologists and their patients.

Advantages of Using a 3 Tesla MRI Scanner Over 1.5T

It is extremely efficient, leading to shorter examination times.

It provides a more pleasant patient experience, since the shorter size of the magnet bore relieves the sense of confinement patients associate with most MRI scanners.

The higher resolution of the 3 Tesla MRI produces more detailed images, which are beneficial when diagnosing pathological conditions involving the brain, spine, and musculoskeletal system. The resolution and clarity also allow radiologists to identify smaller lesions and anatomical structures that cannot be seen with less powerful machines.

It allows for more sophisticated imaging procedures with more accurate diagnosis.

It lowers the risk of distorted images, thus eliminating the need for repeated scans.

Image quality

One of the most important aspects of an accurate diagnosis is image quality, and 3T MRI scanners show superior imaging abilities. Since the technology includes powerful magnetic field strength, results are obtained with high clarity, without any bargain.6

This machinery is especially practical in evaluating the health of the brain, blood vessels, muscles, and bones.5 In fact, studies conducted in the past have proven an increased sensitivity while tracking cerebral lesions with 3T devices.

The 3T systems are also known to possess ergonomic and user-friendly interfaces for easy handling by technicians.

Patient experience

In recent years, there has been an increased focus on improving the patient experience across all fields of medicine, and this certainly applies to MR as well. 3T machines are much gentler on the body as the tables are designed to alleviate pressure points. This could provide for a more relaxing and comfortable exam.6

In addition, 3T MRI could replace traditional, more uncomfortable means of biopsy. The need for invasive needles for biopsies and use in delicate areas could eventually subside, replaced by higher powered scans. For individuals with conditions that are not life-threatening, for instance, some stages of prostate cancer, the high-Tesla MRI can help in avoiding over treatment or the risks of exposure to radiation after surgery.

Speed

Providers, especially at major health centers, often have to contend with high patient volumes, and 3T MRI can be of great assistance here. While 1.5T MRIs are capable of reducing scan times, this can come at the cost of decreased image quality. However, 3T MRI can shorten scans without a compromise on the accuracy of images, enabling providers to manage high patient volume without any reduction in scan quality.

That said, it's important to note that studies have not found any difference in patient outcomes to date, so clearly 1.5T MRIs are still quite capable. However, as MRI continues to be a high growth area within healthcare, it's certainly worth considering 3Ts capabilities when it comes to managing have patient volumes. but the technology itself shows promise in delivering quality diagnoses to patients, keeping in line with the fasted-pace growth rate.

Although it is mandatory that safety guidelines should be adhered to and extreme care must be maintained by healthcare professionals while handling a 3T MRI system, this advancement is surely a welcome addition to the world of health and medicine.

1. Cardiology Magnetic Resonance Imaging

3T CMR imaging improved the performance of several CMR sequences, particularly dynamic first-pass perfusion and delayed enhancement. Signal-to-Noise Ratio (SNR) and Contrast-to-Noise Ratio (CNR) were better at 3T with an improved diagnostic value, especially in perfusion studies, to evaluate the decreased cardiac reserve.

Ref: Lights and shadows of Cardiac MR Imaging at 3T: quality assessment and comparison with 1.5T .

Authors: S. Torlone, A. Corridore, C. De Cataldo, P. Palumbo, E. cannizzaro, M. C. De Donato, E. Di Cesare, C. Masciocchi; L'Aquila/IT, L'Aquila, ITALY/IT

2. Prostate Imaging

 The best accuracy of local prostate cancer staging was obtained in patients examined in 3T MR scanner in the MR protocol including DCE. No signicant difference in tumor localization assessment between 3T and 1.5T MR scanners was found. 

Reference: Comparison of 1.5T and 3T Prostate MR Examination using Surface Array Coils in Routine Clinical Practice

Authors: Ryznarova Z , Dezortova M , Jiru F , Vik V , Zachoval R and Hajek M

3. MR neuroimaging

MRI of the Central Nerve System (CNS) at 3T is associated with the potential for significant clinical benefit. However, an understanding of the impact of the physics of higher field strength imaging is critical to leveraging the maximum gain from this technique. Protocols at 3T should be optimized to take advantage of the high SNR provided by these systems while minimizing SAR and artifact. Regardless of magnet strength, the use of a higher-relaxivity contrast agent provides the ability to achieve adequate contrast enhancement at lower doses compared with standard gadolinium agents, potentially improving patient tolerability.

Reference: MR neuroimaging protocols at 1.5T and 3T: What you need to know.

Authors: L. N. Tanenbaum1, H. A. Rowley2, M. J. Kuhn3, D. S. Enterline4; 1New York, NY/US, 2Madison, WI/US, 3Peoria, IL/US, 4Durham, NC/US

4. MR Imaging of the Abdomen

There are both advantages and disadvantages to imaging the abdomen at 3.0 T rather than at 1.5 T. The increase in SNR and CNR may be used to improve image resolution, shorten imaging time, or both. Because of increases in SNR and CNR, changes in T1 and T2 relaxation times, an increase in magnetic susceptibility, and an increase in chemical shift, many abdominal applications stand to benefit from 3.0-T imaging. The increase in CNR obtained with the use of a gadolinium-based contrast agent at 3.0 T improves lesion conspicuity and allows the use of a lower dose of intravenous contrast material. Increased CNR, as well as the potential for faster temporal and spatial resolution, allows improved MR angiographic image quality. Increased SNR results in improved fluid conspicuity and resolution for heavily T2-weighted imaging applications such as MR cholangiopancreatography. Increased SNR also may prove beneficial for abdominal diffusion-weighted imaging, although issues related to magnetic susceptibility artifacts and field inhomogeneity are paramount. Increased chemical shift effect leads to improved spectral resolution for MR spectroscopy. There are several potential problems with 3.0-T imaging, especially as it applies to abdominal imaging. Doubling the field strength results in a quadrupling of the SAR. Compromising pulse sequence timing and flip angles to decrease energy deposition may result in a longer imaging time and altered image contrast. Magnetic susceptibility and chemical shift artifacts are worsened at 3.0 T, but they may be counteracted by shortening TE, performing parallel imaging, and increasing bandwidth. RF field inhomogeneity is also a major concern when imaging larger portions of the body, such as the abdomen. Standing wave effects especially become a concern when imaging larger fields of view at field strengths of 3.0 T or higher and often result in substantial local variations in signal intensity. Many issues related to MR device compatibility and safety still need to be addressed at 3.0 T. Installation and upkeep of a 3.0-T MR system entail a higher initial cost and a higher cost of upkeep. At higher field strengths, additional factors need to be addressed in terms of room design and shielding. Although there are many potential benefits to imaging the abdomen at 3.0 T, these benefits must be weighed against the disadvantages. Ultra-high-field abdominal imaging holds much promise, but imaging protocols and scanner hardware require further optimization before 3.0-T imaging can become as robust and as widely accepted as 1.5-T imaging is.

Reference: 3.0-T MR Imaging of the Abdomen: Comparison with 1.5 T

Authors: Kevin J. Chang, MD • Ihab R. Kamel, MD, PhD • Katarzyna J. Macura, MD, PhD • David A. Bluemke, MD, PhD

5. MR Fetal Imaging

There is an overall advantage to performing fetal MRI with a magnetic field strength of 3 T. Improvements in imaging software and protocols allow optimal visualization and examination of fetal pathologic abnormalities, thus better identifying fetal and maternal needs both prenatally and postnatally.

Reference: Comparison Between 1.5-T and 3-T MRI for Fetal Imaging: Is There an Advantage to Imaging With a Higher Field Strength?

Source: Radiology Department, The Children's Hospital of Philadelphia, 34th St and Civic Center Blvd, Philadelphia, PA 10104. 

6. MR Acute bone stress in the foot Imaging

The study shows that 3T images are generally at least equal to 1.5T images for the diagnosis of bone stress changes. Based on our results, 1.5T images can be considered adequate in routine stress fracture diagnosis, as even low-field MRI has been proven sufficient in the diagnosis of lower extremity pain . However, in future 3T images may also contribute to the evaluation of other conditions affecting bone such as infection and malignancy.

References: Comparison of 1.5T and 3T MRI scanners in evaluation of acute bone stress in the foot

Authors: Markus J Sormaala,corresponding author Juha-Petri Ruohola, Ville M Mattila, Seppo K Koskinen, and Harri K Pihlajamäki

7. MR Knee Imaging

The study shows that 3.0 T MRI was superior for detecting and grading cartilage lesions compared to 1.5 T. Though a higher diagnostic confidence was found at 3.0 T, the false-positive rate was not decreased. Overall image quality at 3.0 T was rated superior to 1.5 T consistently by all four radiologists.

Reference: Comparative study of imaging at 3.0 T versus 1.5 T of the knee

Authors: Scott Wong, Lynne Steinbach, Jian Zhao, Christoph Stehling, C. Benjamin Ma, and Thomas M.

8. MR Detecting Significant Coronary Artery Disease

The 3T CMR perfusion imaging has similar diagnostic performance to 1.5T in detecting significant CAD, except for higher performance in patients with MVD and without old MI. From this point of view, additional research such as a multicenter prospective study is needed to confirm the diagnostic value of 3T CMR compared with that of 1.5T CMR

Reference: Comparison of the Diagnostic Accuracies of 1.5T and 3T Stress Myocardial Perfusion Cardiovascular Magnetic Resonance for Detecting Significant Coronary Artery Disease

Authors: Jee Young Min, MD, Sung Min Ko, MD,corresponding author In Young Song, MD, Jung Geun Yi, MD, Hweung Kon Hwang, MD, and Je Kyoun Shin, MD

9. MR Peripheral arterial occlusive disease

Standardized single-injection 3-station moving-table 3T CE-MRA is reliable for stenosis detection and classification in POAD with equivalent diagnostic performance as 1.5T CE-MRA, while CNR significantly Standardized single-injection 3-station moving-table 3T CE-MRA is reliable for stenosis detection and classification in POAD with equivalent diagnostic performance as 1.5T CE-MRA, while CNR significantly increased at 3T for identical contrast dosage.

Reference: 3T versus 1.5T MR angiography in peripheral arterial occlusive disease: an equivalence trial in comparison with digital subtraction angiography

Authors: Harrie van den Bosch, Jos J Westenberg, Lucien E Duijm, Alette Daniels-Gooszen, Erik Kersten, Philippe W Cuypers & Albert de Roos 

Conclusion

Most hospitals have 1.5T and are going to 3T because of its speed and better being prepared for the future. For example, for prostate imaging, it will increase the signal and potential for better image clarity or better speed, or a hybrid of the two. It all goes back to the efficiency. Facilities may make the move to 3T because of the intrinsic higher resolution that can be achieved, expanding the system's value in some imaging scenarios, but the decision may also be driven by marketing needs in competitive environments. The decision of when to purchase or upgrade an MR system is very dynamic. Health systems today must evaluate their patient population and demographics to determine what type of MR system can help best serve their patients' care . For the clinical areas [neuroradiology] and musculoskeletal, 3T gives a higher resolution and more possibilities to do advanced work like looking at degenerative diseases, brain connectivity, or sports medicine. The initial challenges of 3T for other areas of the body have been overcome with technologies such as MultiTransmit, which make 3T also suitable for robust body and cardiac exam.