FDA clears new system to perform simultaneous PET, MRI scans


The US Food and Drug Administration (FDA) cleared the Siemens Biograph mMR system, the first device to simultaneously perform a positron emission tomography (PET) scan and a magnetic resonance imaging (MRI) scan. 

PET scans allow physicians to see how the organs and tissues inside the body are actually functioning by injecting a radioactive chemical tracer into the patient’s bloodstream. MRI uses magnetic fields and radiowaves to produce detailed images of organs, soft tissues, bone and other internal body structures.

Previously, physicians could use a PET and computer tomography scanner to image the body. Advantages of the Biograph mMR system over current systems include simultaneous imaging, reduced radiation dose, and increased soft tissue contrast.

“The Siemens PET/MRI system allows two tests to run simultaneously without having to move the patient to a different scanning system,” said Alberto Gutierrez, director of the Office of In Vitro Diagnostic Device Evaluation and Safety in the FDA’s Center for Devices and Radiological Health. “Minimising changes in a patient’s position between tests allows physicians to compare images more easily and helps them get the most accurate information possible.”

The Biograph uses MRI rather than CT to produce detailed images of the internal structures of the body. Because MRI makes images based mainly on the concentration of water in the body, it can produce greater detail of nearly all the internal structures of the body as compared with CT, which uses X-rays to make images. This could provide the physician with additional information about a patient’s condition.

Additionally, the Biograph mMR system allows physicians to acquire images at a significantly lower radiation dose compared to a PET/CT system. Although the radiation dose from the PET exam remains unchanged, MRI does not use ionising radiation, so the entire ionising radiation dose from the CT scan is eliminated. The decreased radiation dose is especially significant for sensitive populations, such as children or patients who are receiving multiple scans.

The FDA cleared the Siemens system based on bench tests that compared the device with a predicate PET/CT device. The Biograph mMR system is indicated for anyone who needs diagnostic PET or MRI imaging. However, people with pacemakers, defibrillators or other implanted electronic devices should not be scanned with this system unless those devices are specifically indicated for use in the MRI environment.

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