Radiation therapist Emilia Kiias and Chief Physician Antti Loimaala. @HUS/Ville Männikkö

Health & wellbeing

Helsinki University Hospital's (HUS) Isotope Unit has unveiled a cutting-edge PET-MRI scanner that simultaneously performs PET imaging and magnetic resonance imaging (MRI). This dual-functionality is particularly advantageous for pediatric patients who require sedation during the procedure. Moreover, the new technology reduces the amount of radiation exposure patients receive.

Installed in May, this state-of-the-art PET-MRI scanner showcases the latest in PET technology. It not only meets the demanding patient imaging requirements of a university hospital but also supports advanced scientific research.

The PET-MRI scanner captures both metabolic information from PET imaging and structural details from MRI in a single fused image. This groundbreaking fusion enhances diagnostics by directly aligning the metabolic changes captured in the PET scan with the structural features revealed in the MRI scan. Ylilääkäri (chief physician) Antti Loimaala explains, "This is achieved by combining the two images, wherein the metabolic changes seen in the PET image are directly matched with the structural image from the MRI, such as lymph nodes or abnormal lesions in the pancreas. This is a significant difference from the situation where PET and MRI scans are conducted separately."

The integrated PET-MRI technology expedites diagnosis by allowing two critical examinations to occur in a single session, enhancing patient convenience. Loimaala highlights the importance of this for pediatric patients who undergo sedation for imaging. Additionally, the structural imaging provided by MRI eliminates the need for the radiation exposure associated with computed tomography.

The PET component of the new scanner boasts high sensitivity, which enables a reduction in the amount of injected radiotracer while maintaining imaging quality. This, in turn, reduces patient radiation exposure. Loimaala emphasizes that this is advantageous not only for pediatric patients but also for those requiring multiple PET scans for disease monitoring.

HUS had previously used a PET-CT scanner, with approximately 80-85 percent of its scans dedicated to cancer cases. These scans help assess the extent of cancer spread and, for conditions like head and neck cancers, combine both MRI and PET-CT scans to evaluate treatment responses.

The simultaneous performance of PET and MRI, Loimaala explains, synergizes their strengths and minimizes their respective weaknesses in terms of sensitivity and precision. This results in a more precise diagnosis that reduces the need for further examinations and often leads to adjustments in treatment plans.

The outstanding tissue differentiation capacity of MRI combined with the sensitivity of PET significantly enhances the diagnosis and treatment monitoring of both pediatric and adult cancers. This heightened accuracy is pivotal in the monitoring of costly cancer treatments and radiation therapy planning, ensuring treatments are targeted correctly and avoiding ineffective therapies.

Furthermore, PET-MRI imaging is superior to CT scans, particularly for tumors primarily involving soft tissues. This is the case for gynecological cancers, prostate cancer, liver or intestinal cancers, and brain tumors.

Beyond cancer imaging, PET-MRI technology is also valuable in cardiac imaging, especially for categorizing heart muscle diseases and inflammations. The scanner can also pinpoint the area in the brain responsible for epileptic seizures before epilepsy surgery.

HUS's PET capacity receives a boost with the introduction of the PET-MRI scanner. While PET-MRI scans are slightly more expensive than PET-CT scans, the time and cost savings gained by eliminating the need for separate lengthy scans make it a cost-effective solution. "The new PET-MRI scanner significantly enhances the PET capacity of Meilahti Isotope Unit, with the PET-CT examinations gradually transitioning to PET-MRI. Hopefully, this device will also contribute to maintaining the treatment guarantee timeframes," notes Loimaala.

The PET-MRI scanner was put into patient use in August, and it is projected to serve around 700-1,000 patients annually in its initial years. In 2022, HUS performed approximately 4,000 PET-CT examinations, with an annual growth rate of about 10 percent. While the PET-MRI scanner is primarily used for patient imaging, it also supports HUS's research and development activities.