MRI is the way to go. There is still a lot of work to be done before MRI is offered as a mainstream test.

Recent years have seen tremendous advances in the development and application of magnetic resonance imaging (MRI), allowing imaging of structures and even processes in the human body that would have been unimaginable 30 years ago, when the first generation of commercial MRI scanners was introduced.

MRI systems are becoming increasingly affordable, with both large- bore 1.5T and higher-resolution 3T platforms being a common sight in medical imaging suites around the world. Remarkable improvements in image quality and speed have evolved directly from technological advances in design and construction of superconducting magnets, radio-frequency (RF) and digital technologies, and the engineering of coils and amplifiers to control magnetic-field gradients. These developments have been accompanied by inventive conceptual advances such as parallel imaging, compressed sensing, and new acquisition and reconstruction techniques.

The MRI systems market represents the fastest growing segment as hospitals and clinics upgrade old equipment with state-of-the-art systems. The market is witnessing increasing use of proper systems meant for specific applications including heart, brain, and orthopedics. The expansion of new techniques for imaging-specific portions of smart formidable structures is driving the market.

Technology Update

New scanning technology which will give a much clearer picture of lung disease has taken a major step forward, thanks to scientists at The University of Nottingham.

The experts at the Sir Peter Mansfield Imaging Centre have developed a process using specially treated krypton gas as an inhalable contrast agent to make the spaces inside the lungs show up on an MRI scan. It is hoped the new process will eventually allow doctors to virtually see inside the lungs of patients.

Traditional MRI uses hydrogen protons in the body as molecular targets to give a picture of tissue, but this does not give a detailed picture of the lungs because they are full of air. Recent technological developments have led to a novel imaging methodology called inhaled hyperpolarized gas MRI that uses lasers to hyperpolarize a noble (inert) gas which aligns (polarizes) the nuclei of the gas so it shows up on an MRI scan. The work will make 3-D imaging using atomic spies like helium, xenon, or krypton possible in a single breath-hold by the patient. Nottingham has pioneered hyperpolarized krypton MRI and is currently advancing this technology toward the clinical approval processes.

Hyperpolarized MRI research has been trying to overcome a problem with these noble gases retaining their hyperpolarized state for long enough for the gas to be inhaled, held in the lungs, and scanned. Now in a paper published in the Proceedings of the National Academy of Sciences, the Nottingham team has developed a new technique to generate hyperpolarized krypton gas at high purity, a step that will significantly facilitate the use of this new contrast agent for pulmonary MRI.

Chair in Translational Imaging at the Sir Peter Mansfield Imaging Centre, Prof. Thomas Meersmann, said, "It is particularly demanding to retain the hyperpolarized state of krypton during preparation of this contrast agent. We have solved a problem by using a process that is usually associated with clean energy-related sciences. It is called catalytic hydrogen combustion. To hyperpolarize the krypton-83 gas, we diluted it in molecular hydrogen gas for the laser pumping process. After successful laser treatment, the hydrogen gas is mixed with molecular oxygen and literally exploded away in a safe and controlled fashion through a catalyzed combustion reaction.

This new technique can also be used to hyperpolarize another useful noble gas, xenon-129, and may lead to a cheaper and easier production of this contrast agent. As part of a recent Medical Research Council funding award, hyperpolarized krypton-83 is currently being developed for whole-body MRI at a high magnetic field strength in the Sir Peter Mansfield Imaging Centre's large 7T scanner. Studies will be carried out first on healthy volunteers before progressing to patient trials at a later phase.

MRI is the way to go. There is still a lot of work to be done before MRI could be offered as a mainstream test. It is also availability of time in an MRI machine magnet. There are only a limited number of machines around the country. But it is a very exciting thing to be looking at.

Future Outlook

The future lies in MR systems, which are patient-friendly and targeted to specific body parts and diseases. Public-private partnership may also play a huge role in providing accessibility to patients residing in remote parts of the country. There is a constant increase in the number of hospitals, day centers, and private clinics all over India, and to cater to this growing need there will be immense demand for diagnostics in the country.

Dr Mona Bhatia, HOD Radiodiagnosis and Imaging, Fortis Escorts Heart Institute, New Delhi
Second Opinion
Cardiac MRI - The Game Changer

The role of cardiovascular magnetic resonance (CMR) is now firmly established in the diagnosis and management of cardiac conditions and this accounts for the recent exponential growth in demand for cardiac MRI.

Growth in the field of CMR brings with it new demands for novel CMR techniques and contrast agents with improved software and hardware. Novel MR signal-acquisition architectures that digitize the MR signal at the source have now made it possible to run MRI scans faster at high-field with increased SNR. The new 4D-multitransmit technology is now capable of addressing challenges in real-time cardiac MRI at the high field, while advanced parallel imaging can contribute to acquiring even faster images without compromising the image quality. Multitransmit technology with RF shimming provides a homogeneous field with uniform signal, better image contrast, homogeneous local SAR distribution, and shorter TR and TE with excellent cine and black-blood images.

Other advancements in MRI algorithms have enabled reduction in scan times in applications like TSE-based two-point mDIXON, for fat-suppressed imaging of challenging body parts, and mDIXON-FFE for estimating liver-fat fraction among other applications. Advanced techniques like T1-permeability, pseudo-continuous ASL for non-contrast perfusion, and susceptibility-weighted imaging with phase information for micro-bleed and calcium-deposition detections are excellent. Latest MR pulse sequences and applications for advanced cartilage assessments, high-resolution MR neurography, and advanced motion correction are demonstrating potential in different research studies. The future holds great promise for new expansions in non-traditional applications including intraoperative MRI suites, real-time MR guided biopsy, MR-guided interventions, and MR-guided radio-therapy using hybrid systems like MR-Linac.

Indications for CMR Imaging in heart failure have widened to include cardiac morphology and function, evaluation of native and prosthetic valves, cardiac masses, great vessels, pulmonary veins, localization and quantification of acute and chronic myocardial necrosis, assessment of viability, area at risk, salvageable myocardium, and inducible ischemia. In pediatric and other structural heart diseases, the pulmonary-to-systemic flow ratio (Qp/Qs) can be determined most often by measuring flow in the main pulmonary artery and the ascending aorta.

CMR today is thus emerging as the preferred problem solver where discordant results are received from other modalities. The harmonious integration of demand, improving technology, and clinical benefit will most definitely pave the way for unprecedented growth of MRI. It is anticipated that cardiac MRI in the future will play a key role in patient assessment, work up, prognostication, management, and risk stratification of cardiac conditions including heart failure, ischemic, non-ischemic cardiomyopathies, and congenital heart diseases.

Dr Mona Bhatia
HOD Radiodiagnosis and Imaging,
Fortis Escorts Heart Institute, New Delhi

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