What is PET/MR?

In the world of medical imaging, PET/MR is a relatively new technology. While we have been studying the human body with positron emission tomography (PET) and magnetic resonance (MR) separately for over 40 years, the integration of the two modalities began only 9 years ago in response to the success of the more mature PET/CT. The combination of the functional information from PET, the soft-tissue contrast from MR, and the extremely low level of radiation offers exciting results.1

PET scans use a radioactive compound (called a tracer) that is injected into the patient and then measured to reveal areas with high levels of metabolic activity, often corresponding to disease.2

MR scanners create images by using a strong magnetic field to measure the alignment of hydrogen atoms in the patient. This is especially effective in studying soft-tissues of the human body including the brain, heart, abdomen, breasts and prostate.3

While PET/CT can provide shorter exam times and similar results for certain cases, patients are exposed to significantly more radiation when compared to PET/MR since MR does not include potentially harmful X-rays. This is especially important when treating pediatric patients as they are more sensitive to ionizing radiation.

Situations in which soft tissue contrast or motion correction are important can also benefit from PET/MR over PET/CT, since PET/MR is simultaneous while PET/CT is not. Unfortunately, PET/MR is not as widely available due to the higher cost of the scanner.4

While further uses for PET/MR are still being researched, this imaging technology has already proven successful in various disease areas, including detection the origin of epileptic seizures,5 prostate cancer,1 and even pain generators.6 If the major challenges of cost, and reimbursement can be overcome, PET/MR will be even more widely used.

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  1. PET/MR - Technical Review. Semin Roentgenol Last accessed July 22, 2019.
  2. Positron emission tomography scan. MayoClinic.org Last accessed July 9, 2019.
  3. MRI. MayoClinic.org Last accessed July 9, 2019.
  4. PET/MRI: Where Might It Replace PET/CT? J Magn Reson Imaging Last accessed July 8, 2019.
  5. Thirty-minute PET/MR exam for pediatric cancer patients. SIGNA Pulse of MR Last accessed July 8, 2019.
  6. SNMMI: FDG-PET/MRI improves pain diagnosis, management. AuntMinnie.com Last accessed July 22, 2019.