Molecular Imaging Instrumentation Laboratory  

Advanced Time-of-Flight (ToF) PET Photon Detectors

For the last three decades, a significant amount research has focused on improving the scintillation crystal of the detector to go beyond simple coincidence detection capability to time-of-flight (ToF) capability. A scintillation crystal creates a tiny cascade of thousands of visible light photons in response to absorbing a 511 keV annihilation photon interaction. The process is characterized by the crystal’s light output (number of light photons created per keV of absorbed energy) and decay constant t (ns). LYSO MPPC DetectorIn a PET detector, the scintillation crystal’s properties determine how precisely one can say whether two photons are detected simultaneously. The resulting uncertainty in the arrival time difference for the two photons over many events is known as the coincidence time resolution. The scintillation crystal properties are the dominant factor that determines the time resolution: the brighter and faster the light pulse, the better the results. In ToF-PET, in addition to being able to determine to which LOR the event belongs, the detector coincidence time resolution is so good that by measuring the arrival time difference between the two photons one can constrain the two-photon emission point to a particular segment along that line. The coincidence time resolution directly maps into ToF position uncertainty along the LOR, Δx, by the formula Δx= c* Δt/2, where c is the speed of light, and Δt is the full-width-at-half-maximum (FWHM) time resolution of two detectors in coincidence. We are working on scintillation crystal, photodetector, and electronics features to enable <300 ps coincidence time resolution to advance ToF performance.

Time-of-Flight

Advantages of DoI combined with ToF:

Time-of-Flight and Depth-of-Interaction

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Related Publications

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    Author Title Year Jour./Proc./Book
    Olcott, P.D.; Labruyere, A.F.; Habte, F.; Warburton, W.K. & Levin, C.S. High Speed Fully Digital Data Acquisition System for Positron Emission Tomography 2006 2006 IEEE Nuclear Science Symposium and Medical Imaging Conference Record, pp. 1909-1911  
    BibTeX:
    @conference{Olcott2006b,
      author = {P. D. Olcott and A. F. Labruyere and F. Habte and W. K. Warburton and C. S. Levin},
      title = {High Speed Fully Digital Data Acquisition System for Positron Emission Tomography},
      booktitle = {2006 IEEE Nuclear Science Symposium and Medical Imaging Conference Record},
      year = {2006},
      pages = {1909-1911}
    }
    					
    Olcott, P.D. & Levin, C.S. Pulse Width Modulation: A Novel Readout Scheme For High Energy Photon Detection 2008 Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 4530-4535  
    BibTeX:
    @conference{Olcott2008,
      author = {P. D. Olcott and C. S. Levin},
      title = {Pulse Width Modulation: A Novel Readout Scheme For High Energy Photon Detection},
      booktitle = {Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2008},
      pages = {4530-4535}
    }
    					
    Olcott, P.D.; Peng, H. & Levin, C.S. Novel Electro-Optically Coupled MR Compatible PET Detectors 2008 Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 4640-4645  
    BibTeX:
    @conference{Olcott2008a,
      author = {P. D. Olcott and H. Peng and C. S. Levin},
      title = {Novel Electro-Optically Coupled MR Compatible PET Detectors},
      booktitle = {Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2008},
      pages = {4640-4645}
    }
    					
    Peng, H.; Olcott, P.D.; Foudray, A.M.K. & Levin, C.S. Evaluation of Free-Running ADCs for High Resolution PET Data Acquisition 2007 Conference Record of the 2007 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 3328-3331  
    BibTeX:
    @conference{Peng2007,
      author = {H. Peng and P. D. Olcott and A. M. K. Foudray and C. S. Levin},
      title = {Evaluation of Free-Running ADCs for High Resolution PET Data Acquisition},
      booktitle = {Conference Record of the 2007 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2007},
      pages = {3328-3331}
    }
    					
    Spanoudaki, V.C. & Levin, C.S. Photo-Detectors for Time of Flight Positron Emission Tomography (ToF-PET) 2010 SENSORS
    Vol. 10, pp. 10484-10505  
    Abstract: We present the most recent advances in photo-detector design employed in time of flight positron emission tomography (ToF-PET). PET is a molecular imaging modality that collects pairs of coincident (temporally correlated) annihilation photons emitted from the patient body. The annihilation photon detector typically comprises a scintillation crystal coupled to a fast photo-detector. ToF information provides better localization of the annihilation event along the line formed by each detector pair, resulting in an overall improvement in signal to noise ratio (SNR) of the reconstructed image. Apart from the demand for high luminosity and fast decay time of the scintillation crystal, proper design and selection of the photo-detector and methods for arrival time pick-off are a prerequisite for achieving excellent time resolution required for ToF-PET. We review the two types of photo-detectors used in ToF-PET: photomultiplier tubes (PMTs) and silicon photo-multipliers (SiPMs) with a special focus on SiPMs.
    BibTeX:
    @article{Spanoudaki2010a,
      author = {V. C. Spanoudaki and C. S. Levin},
      title = {Photo-Detectors for Time of Flight Positron Emission Tomography (ToF-PET)},
      journal = {SENSORS},
      year = {2010},
      volume = {10},
      number = {11},
      pages = {10484-10505},
      doi = {http://dx.doi.org/10.3390/s101110484}
    }
    					

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