Since its invention in 1977, MRI has become a staple of clinical radiology, used across the world to identify health problems in millions of patients worldwide. But despite its prominence, MRI suffers from low sensitivity, which can be improved by injecting patients with potentially toxic agents. Publishing in PNAS, researchers from the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have found a way to achieve high spatial and temporal resolution MRI using a safe compound that is naturally produced in the body. The well-known low sensitivity weakness of MRI can be addressed with the use of hyperpolarization techniques, which involve injecting patients with substrates that contain a stable carbon isotope that is almost perfectly aligned with the system’s magnetic field. However, the preparation of these contrast agents requires the use of highly reactive chemicals called persistent radicals, which can be potentially toxic. Consequently, they have to also be filtered out prior to injecting the substrates and require additional pharmacological tests, all of which considerably reduce the MRI contrast, while posing a risk to the patient. A research team led by Arnaud Comment at EFPL developed a breakthrough solution to this problem. They found that high resolution in contrast-enhanced MRI can still be achieved with pyruvic acid, the organic chemical that occurs naturally in the body as a result of glucose breakdown, without the need of persistent radicals. The scientists exposed frozen, pure pyruvic acid to ultraviolet light for an hour, which resulted in the generation of non-persistent radicals at a high concentration. The radicals automatically recombine to produce a solution only containing compounds that are naturally present in the body but in much lower concentrations. It was used to perform high-resolution MRI on a mouse brain. The resulting images showed detailed spatial and temporal resolution to the point of tracking the metabolism of pyruvic acid in the animal’s brain. The new hyperpolarization method opens a way to perform MRI with compounds that are not toxic, thus reducing or altogether eliminating associated health risks. In addition, because it does not require filtering or additional tests, the method will cut down on the time and cost of contrast-enhanced MRI protocols, thus improving the quality of the scans and diagnosis. The authors believe that the technique will be rapidly incorporated into the clinical setting and call it “a substantial step forward toward clinical radiology free of side effects”.
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