Positron emission tomography imaging for guiding therapies
In this project, a prototype simultaneous MRI-PET system was designed and built by integrating thin PET detectors into a commercial 1.5T MRI system. To solve the associated technological challenges, a strong consortium was needed combining clinical, PET, MRI, system and RF coil design expertise from the University Medical Centre Utrecht (UMCU), Philips Healthcare and MRCoils.
MRI-PET can significantly increase the precision of new image-guided cancer therapies such as MR-guided radiotherapy (MR-LINAC), reducing the required number of therapy sessions (fractions) from 30 to only 3, which significantly reduces side effects for the patient. Unfortunately, current PET-MRI scanners have a much smaller patient bore diameter than the radiotherapy systems. Therefore, treatment precision is often compromised because the patient cannot be positioned in the same posture as during therapy.
To increase the patient bore diameter, thin PET detectors and radiofrequent (RF) shielding were redesigned specifically to be integrated into a newly designed MRI-PET body coil. The design was based on the innovative concept of positioning the PET detectors between the RF shield and the conductors of the body coil. The body coil compromised only 3 cm of bore diameter compared to the commercial wide-bore MRI system on which the design is based, whereas other simultaneous MRI-PET systems typically compromise 10 cm or more. This will greatly facilitate the application of the MRI-PET system in (radio)therapy planning and increase the number of patients eligible for MR-guided therapy.
Tests with 2 newly designed PET detectors inside a commercial MRI system using the prototype body coil showed that the PET performance was not degraded by the simultaneously operating MRI, and that similar MRI performance can be achieved as with the commercial MRI body coil. Having successfully set this first step, a full MRI-PET system (with a full ring of PET detectors) can now be realised quickly.
