Over the past decade positron emission tomography (PET) has changed the way disease is managed by providing a molecular imaging technique accessible to clinicians. Through PET FDG studies, tumors throughout the body can be located and characterized. PET, however, does not provide high resolution anatomical information. As a result, almost all clinical PET scans are now performed in conjunction with X-ray computed tomography (CT) scans. Recently, there have been great efforts to combine MRI with PET to produce complementary molecular and anatomical data sets. MRI provides better soft tissue contrast and the potential for a wide variety of functional and spectroscopic information not available from CT. CT also typically accounts for over 50% of the radiation dose of a PET/CT scan. The approximately 28 mSv delivered by a PET/CT study can be a significant dose, especially for pediatric patients or cancer patients who require annual PET scans to check for recurrence. Producing PET detectors and electronics capable of operating in the presence of the MRI's strong magnetic and radio frequency (RF) fields has proven challenging. The strong MRI magnets can cause PET system to malfunction and the presence of PET electronics and conductive materials produces artifacts in MRI images. My project aims to take a novel approach to create an RF-transmissive PET ring. By adopting advanced technology from the field of optical telecommunications and also newly available silicon-based light-sensing technology, we hypothesize that we can transmit MRI radiofrequency (RF) signals through the PET system into the patient and PET signals out of the MRI bore while still preserving the image quality and accuracy of both MRI and PET. Optical fibers allow fast data transmission, are compact, insensitive to interference from MRI's static and RF fields, and do not require electrical grounding. The fibers can be driven inside the MRI bore by compact non-magnetic VCSEL lasers designed for high speed telecommunications. This approach enables the PET to be inserted into any existing MRI system without requiring modifications to the latter. If successful, this would greatly reduce the cost of achieving an integrated PET/MRI system, thereby making it more widely available. My goal is to build a ring of 16 PET detector modules with a custom RF receiver coil as a prototype system. If successful, my work could be the basis for a new powerful imaging tool.
Positron emission tomography (PET) and magnetic resonance imaging (MRI) are medical imaging technologies that have revolutionized the detection and management of patient disease. Combining these scanners will yield a powerful tool for characterizing patient's diseases while significantly reducing the radiation dose compared to a PET/CT scan, and improve the accuracy of registering the two data sets. The proposed research will enable state-of-the-art PET performance to be combined with uncompromised MRI, dramatically improving the signal-to-noise ratio of PET/MRI systems for substantially enhanced visualization, characterization, and quantification of molecular, anatomical, and physiological signatures of diseases; furthermore, we study the concept of an 'RF-transmissive PET insert' to enable simultaneous PET/MRI without requiring modifications on the MR system hardware, a critical factor to reduce the cost of this dual-modality, thereby making it more widely available.