MRI’s unmatched richness of contrast has made it an essential modality in many settings, such as abdominal, brain, cardiac and MSK imaging. Equipment that provides exceptional spatial resolution is constantly improving and 7T has shown results in a number of clinical applications, including early diagnosis of MSK and central nervous system disorders. The discussion around gadolinium has also triggered interest in novel contrast products and a need for new guidelines. Experts will review the latest advances in MR and ponder where its future lies, in a New Horizons session today.
“MRI allows us to image pathology in ways that are not possible with any other modality. MRI enables us to look at anatomy, physiology, metabolism and molecular information all in one examination,” said Ferdia A. Gallagher, a Senior Cancer Research Fellow (funded by Cancer Research UK) at the department of radiology, University of Cambridge, and an honorary consultant radiologist at Addenbrooke’s Hospital Cambridge, UK.
MR is rapidly expanding, and researchers are finding new ways to evaluate normal and diseased tissue, such as in stroke or cancer. Today’s session will tackle many techniques that are starting to find their way into clinical practice, as well as very novel techniques in research, which may follow, such as hyperpolarisation and fingerprinting.
Research in 7T has taken leaps recently, and Siegfried Trattnig, a professor of radiology at Vienna Medical University, Austria, will present some of the latest developments. “With a higher field, you can achieve a higher signal-to-noise ratio. The higher the signal, the more you can play around with different applications in MR and the more you can benefit from it,” he said.
A high signal-to-noise ratio improves the spatial resolution of small structures in the human body by a mean factor of two in the same scan time compared to 3T.
“With a high spatial resolution, you can see more details in morphological MR imaging and most importantly improve your diagnostic confidence,” Trattnig said.
Higher spatial resolution with 7T can also help in brain examinations in patients who suffer from epileptic seizures. Subtle findings like focal cortical dysplasias can cause the seizures but are not easy to detect.
“Every lesion counts. When you detect this lesion, you can operate, and the patient will not suffer from seizures anymore. Using 7T helps to spot those lesions that were not spotted with 3T. We have shown that 7T is positive in about 25% of 3T MR-negative patients. So, when patients with epileptic seizures show no abnormality on 3T, we should refer them to a 7T examination,” he recommended.
In patients suffering from the chronic progressive type of multiple sclerosis, one of the hallmarks is the presence of iron rims around 40% of the MS plaques.
Iron is contained in inflammatory cells and the increased presence of iron rims indicates a chronic inflammatory process in MS. Typically, MS lesions with the iron rims increase in size over years, whereas lesions without iron rims do not get larger but shrink over time. The only way to detect these iron rims around MS lesions is with 7T, while only about one third of these iron rims can be detected with 3T.
“These patients with iron rims around MS plaques therefore have a poorer prognosis in the longer run because of progressive disease, so it is very important to look out for these rims,” he said.
MSK is an excellent field for 7T. Combined with sodium imaging, 7T not only offers high-resolution morphological imaging, but also enables the quantification of glycosaminoglycans (GAGs), which are an important part of the cartilage microstructure related to the biomechanical properties. Healthy cartilage has a high concentration of GAGs. Loss of GAGs is the earliest stage of cartilage degeneration while cartilage is still intact on morphological imaging. Viewing that process as early as possible can help in osteoarthritis to treat patients before irreversible osteoarthritis develops, to monitor the efficacy of newly developed disease-modifying drugs, and to follow up after cartilage transplantation surgery.
Using 7T combined with sodium imaging can also help assess treatment response in breast cancer adjuvant chemotherapy much earlier than with conventional MR methods.
High resolution spectroscopic imaging is possible with 7T and can help to create metabolic maps of the brain with higher quality and shorter scan times compared to 3T. “For brain tumour evaluation, 7T is better for grading and defining the extent of tumours, and detecting recurrent tumours,” Trattnig concluded.
The session will also tackle the discussion on gadolinium-based contrast agents that has shaken radiology ever since nephrogenic fibrosis was first described in renal patients in 2007. “This was an atomic bomb in radiology. For the first time, we questioned gadolinium, which we always assumed was totally safe,” said Olivier Clément, a professor of radiology at the Hôpital Européen Georges-Pompidou, Paris Descartes University, France.
A second alert was raised in 2014, after a study revealed the presence of gadolinium deposition in the brain. The doubts raised by this new information and following studies eventually led to the complete withdrawal of linear gadolinium-based contrast products in 2018.
Radiologists are now debating applications for macrocyclic gadolinium-based contrast agents, which are still on the market. “We do not fully understand the implications of potential gadolinium accumulation in the brains of patients undergoing contrast-enhanced MRI and further research is required to investigate this in the future,” Gallagher said.
“We have to think twice before we inject patients now. We need to completely rethink our use of gadolinium,” Clément added.
New guidelines are necessary as well as alternative techniques to gadolinium, which remains indispensable in most brain, cardiac and abdominal examinations. “We can use sequences without contrast, and the industry is actively working on new agents. But we need scientific societies to help us define which applications specifically require gadolinium and which do not,” Clément said.
The session will look at alternatives to gadolinium, including perfusion imaging and experimental contrast agents, such as manganese and iron, which enable non-invasive depiction of molecules.
New Horizons Session, Friday, July 17, 17:00–18:00
NH 17 MRI of the future
- Chairperson’s introduction
Ferdia A. Gallagher; Cambridge/UK
- Is there a future for gadolinium-based contrast agents?
Olivier Clément; Paris/FR
- High field MRI: is higher better and is there a limit?
Siegfried Trattnig; Vienna/AT
- Novel MRI contrast methods: CEST, hyperpolarisation
Silvio Aime; Turin/IT
- Quantitative MRI: fingerprinting and beyond
Vikas Gulani; Ann Arbor, MI/US
- Live Q&A: What are the promising emerging areas in MRI?
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