Over the past decade positron emission tomography (PET) has changed the way cancer 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 PET scans are now performed in conjunction with X-ray computed tomography (CT) scans. Recently, MRI has also been combined with PET to produce complimentary 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 in a PET/CT scan. The approximately 25mSv delivered by a PET/CT study can be a significant dose, especially for pediatric, or cancer patients who require annual PET scans to check for recurrence. Producing PET electronics that can operate in the presence of the MRI's strong magnetic and radio frequency fields has been challenging. In addition, the PET technology should be capable of measuring photon """"""""time- of-flight"""""""" (ToF), but to date ToF capable PET/MRI scanners have not been produced. ToF significantly increases the signal to noise ratio (SNR) of PET, which can be used to decrease radiation dose, decrease scan time, or increase PET resolution. My project aims to develop PET detector modules that are both time-of-flight capable and MRI compatible. By replacing electrical connections with optical fibers, we hypothesize that we can send PET signals out of the MRI bore while still preserving the timing information necessary for photon time-of-flight measurements. The optical fibers are fast, 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. Timing information will be picked off by an asynchronous comparator, minimizing interference of the MRI signal. My goal is to build two PET detector modules from which an MRI-compatible, ToF-PET system can be built.. If successful, our work could be the basis for a powerful new cancer imaging tool.

Public Health Relevance

Positron emission tomography (PET) and magnetic resonance imaging (MRI) are medical imaging technologies that have revolutionized the detection and management of cancer;the majority of cancer patients undergo both studies. Combining these scanners will yield a powerful tool for characterizing patient's cancers while significantly reducing the radiation dose given during a PET scan, and improving the accuracy of registering the two data sets. The proposed research will enable state-of- the art time-of-fligh PET performance to be combined with MRI, dramatically improving the signal to noise ratio of PET/MRI systems for significantly enhanced visualization, characterization, and quantification of molecular, anatomical, and physiological signatures of cancer.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Predoctoral Individual National Research Service Award (F31)
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Special Emphasis Panel (ZRG1-F15-P (20))
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Korczak, Jeannette F
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Stanford University
Schools of Medicine
United States
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Cates, Joshua W; Bieniosek, Matthew F; Levin, Craig S (2017) Highly multiplexed signal readout for a time-of-flight positron emission tomography detector based on silicon photomultipliers. J Med Imaging (Bellingham) 4:011012
Bieniosek, M F; Cates, J W; Levin, C S (2016) A multiplexed TOF and DOI capable PET detector using a binary position sensitive network. Phys Med Biol 61:7639-7651
Bieniosek, M F; Cates, J W; Grant, A M et al. (2016) Analog filtering methods improve leading edge timing performance of multiplexed SiPMs. Phys Med Biol 61:N427-40
Bieniosek, M F; Cates, J W; Levin, C S (2016) Achieving fast timing performance with multiplexed SiPMs. Phys Med Biol 61:2879-92
Bieniosek, M F; Levin, C S (2015) Analog electro-optical readout of SiPMs achieves fast timing required for time-of-flight PET/MR. Phys Med Biol 60:3795-806
Bieniosek, Matthew F; Lee, Brian J; Levin, Craig S (2015) Technical Note: Characterization of custom 3D printed multimodality imaging phantoms. Med Phys 42:5913-8
Bieniosek, M F; Olcott, P D; Levin, C S (2013) Readout strategy of an electro-optical coupled PET detector for time-of-flight PET/MRI. Phys Med Biol 58:7227-38