Molecular Imaging Instrumentation Laboratory  

Frances Lau

Frances Lau

Phone: 650-498-4325 Fax: 650-736-0234 E-mail »

Frances is interested in biomedical circuits and system design. She is developing the front-end circuits and hardware for a breast cancer imaging PET (positron emission tomography) system. She is also designing a mixed-signal front-end integrated circuit (IC) with fast timing capabilities.

Publications




Education

  • M.S. in Electrical Engineering, Stanford University, 2007
  • B.A.Sc. in Electrical Engineering, University of Toronto, 2005

Honors and Awards

  • California Breast Cancer Research Program Dissertation Award
  • IEEE Travel Grant 2007 and 2008
  • McCormick Travel Grant 2007
  • Bio-X Graduate Student Fellowship, Stanford University
  • Edward S. Rogers Sr. Scholarship, University of Toronto

Projects

Publications

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    Author Title Year Jour./Proc./Book
    Gu, Y.; Pratx, G.; Lau, F.W.Y. & Levin, C.S. Effects of multiple-interaction photon events in a high-resolution PET system that uses 3-D positioning detectors 2010 MEDICAL PHYSICS
    Vol. 37, pp. 5494-5508  
    Abstract: Purpose: The authors' laboratory is developing a dual-panel, breast-dedicated PET system. The detector panels are built from dual-LSO-position-sensitive avalanche photodiode (PSAPD) modules-units holding two 8 X 8 arrays of 1 mm(3) LSO crystals, where each array is coupled to a PSAPD. When stacked to form an imaging volume, these modules are capable of recording the 3-D coordinates of individual interactions of a multiple-interaction photon event (MIPE). The small size of the scintillation crystal elements used increases the likelihood of photon scattering between crystal arrays. In this article, the authors investigate how MIPEs impact the system photon sensitivity, the data acquisition scheme, and the quality and quantitative accuracy of reconstructed PET images. Methods: A Monte Carlo simulated PET scan using the dual-panel system was performed on a uniformly radioactive phantom for the photon sensitivity study. To establish the impact of MIPEs on a proposed PSAPD multiplexing scheme, experimental data were collected from a dual-LSO-PSAPD module edge-irradiated with a Na-22 point source, the data were compared against simulation data based on an identical setup. To assess the impact of MIPEs on the dual-panel PET images, a simulated PET of a phantom comprising a matrix of hot spherical radiation sources of varying diameters immersed in a warm background was performed. The list-mode output data were used for image reconstruction, where various methods were used for estimating the location of the first photon interaction in MIPEs for more accurate line of response positioning. The contrast recovery coefficient (CRC), contrast to noise ratio (CNR), and the full width at half maximum spatial resolution of the spheres in the reconstructed images were used as figures of merit to facilitate comparison. Results: Compared to image reconstruction employing only events with interactions confined to one LSO array, a potential single photon sensitivity gain of >46.9% (>115.7% for coincidence) was noted for a uniform phantom when MIPEs with summed-energy falling within a +/- 12% window around the photopeak were also included. Both experimental and simulation data demonstrate that <0.4% of the events whose summed-energy deposition falling within that energy window interacted with both crystal arrays within the same dual-LSO-PSAPD module. This result establishes the feasibility of a proposed multiplexed readout of analog output signals of the two PSAPDs within each module. Using MIPEs with summed-energy deposition within the 511 keV +/- 12% photopeak window and a new method for estimating the location of the first photon interaction in MIPEs, the corresponding reconstructed image exhibited a peak CNR of 7.23 for the 8 mm diameter phantom spheres versus a CNR of 6.69 from images based solely on single LSO array interaction events. The improved system photon sensitivity could be exploited to reduce the scan time by up to approximately 10 while still maintaining image quality comparable to that achieved if MIPEs were excluded. Conclusions: MIPE distribution in the detectors allows the proposed photodetector multiplexing arrangement without significant information loss. Furthermore, acquiring MIPEs can enhance system photon sensitivity and improve PET image CNR and CRC. The system under development can therefore competently acquire and analyze MIPEs and produce high-resolution PET images. (C) 2010 American Association of Physicists in Medicine. [DOI: 10.1118/1.3483262]
    BibTeX:
    @article{Gu2010,
      author = {Y. Gu and G. Pratx and F. W. Y. Lau and C. S. Levin},
      title = {Effects of multiple-interaction photon events in a high-resolution PET system that uses 3-D positioning detectors},
      journal = {MEDICAL PHYSICS},
      year = {2010},
      volume = {37},
      number = {10},
      pages = {5494-5508},
      doi = {http://dx.doi.org/10.1118/1.3483262}
    }
    					
    Lau, F.W.Y.; Fang, C.; Reynolds, P.D.; Olcott, P.D.; Vandenbroucke, A.; Olutade, F.; Horowitz, M.A. & Levin, C.S. 1 mm^3 Resolution Breast-Dedicated PET System 2008 Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 5619-5622  
    BibTeX:
    @conference{Lau2008a,
      author = {F. W. Y. Lau and C. Fang and P. D. Reynolds and P. D. Olcott and A. Vandenbroucke and F. Olutade and M. A. Horowitz and C. S. Levin},
      title = {1 mm^3 Resolution Breast-Dedicated PET System},
      booktitle = {Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2008},
      pages = {5619-5622}
    }
    					
    Lau, F.W.Y.; Olcott, P.D.; Horowitz, M.A.; Peng, H. & Levin, C.S. Noise analysis of LSO-PSAPD PET detector front-end multiplexing circuits 2007 Conference Record of the 2007 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 3212-3219  
    BibTeX:
    @conference{Lau2007,
      author = {F. W. Y. Lau and P. D. Olcott and M. A. Horowitz and H. Peng and C. S. Levin},
      title = {Noise analysis of LSO-PSAPD PET detector front-end multiplexing circuits},
      booktitle = {Conference Record of the 2007 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2007},
      pages = {3212-3219}
    }
    					
    Lau, F.W.Y.; Vandenbroucke, A.; Reynolds, P.D.; Ho, H.; Innes, D. & Levin, C.S. Signal Conditioning Technique for Position Sensitive Photodetectors to Manipulate Pixelated Crystal Identification Capabilities 2012 Nuclear Science, IEEE Transactions on
    Vol. 59, pp. 1815 -1822  
    BibTeX:
    @article{Lau2012,
      author = {F. W. Y. Lau and A. Vandenbroucke and P. D. Reynolds and H. Ho and D. Innes and C. S. Levin},
      title = {Signal Conditioning Technique for Position Sensitive Photodetectors to Manipulate Pixelated Crystal Identification Capabilities},
      journal = {Nuclear Science, IEEE Transactions on},
      year = {2012},
      volume = {59},
      number = {5},
      pages = {1815 -1822}
    }
    					
    Lau, F.W.Y.; Vandenbroucke, A.; Reynolds, P.D.; Olcott, P.D.; Horowitz, M.A. & Levin, C.S. Analog Signal Multiplexing for PSAPD-Based PET Detectors: Simulation and Experimental Validation 2010 Physics in Medicine and Biology
    Vol. 55, pp. 7149-7174  
    BibTeX:
    @article{Lau2009,
      author = {F. W. Y. Lau and A. Vandenbroucke and P. D. Reynolds and P. D. Olcott and M. A. Horowitz and C. S. Levin},
      title = {Analog Signal Multiplexing for PSAPD-Based PET Detectors: Simulation and Experimental Validation},
      journal = {Physics in Medicine and Biology},
      year = {2010},
      volume = {55},
      number = {23},
      pages = {7149-7174}
    }
    					
    Lau, F.W.Y.; Vandenbroucke, A.; Reynolds, P.D.; Olcott, P.D.; Horowitz, M.A. & Levin, C.S. Front-end electronics for a 1mm3 resolution avalanche photodiode-based PET System with analog signal multiplexing-end Electronics for a 1mm3 Resolution LSO-PSAPD-based PET System with Multiplexing 2008 Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 3871-3874  
    BibTeX:
    @conference{Lau2008,
      author = {F. W. Y. Lau and A. Vandenbroucke and P. D. Reynolds and P. D. Olcott and M. A. Horowitz and C. S. Levin},
      title = {Front-end electronics for a 1mm3 resolution avalanche photodiode-based PET System with analog signal multiplexing-end Electronics for a 1mm3 Resolution LSO-PSAPD-based PET System with Multiplexing},
      booktitle = {Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2008},
      pages = {3871-3874}
    }
    					
    Olcott, P.D.; Lau, F.W.Y. & Levin, C.S. Data Acquisition System Design for a 1 mm^3 Resolution PSAPD-Based PET System 2007 Conference Record of the 2007 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 3206-3211  
    BibTeX:
    @conference{Olcott2007a,
      author = {P. D. Olcott and F. W. Y. Lau and C. S. Levin},
      title = {Data Acquisition System Design for a 1 mm^3 Resolution PSAPD-Based PET System},
      booktitle = {Conference Record of the 2007 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2007},
      pages = {3206-3211}
    }
    					
    Reynolds, P.D.; Lau, F.W.Y.; Vandenbroucke, A. & Levin, C.S. Readout design and validation for a 1 mm3 resolution clinical PET system 2010 Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE, pp. 3097 -3099  
    BibTeX:
    @inproceedings{Reynolds2010,
      author = {P. D. Reynolds and F. W. Y. Lau and A. Vandenbroucke and C. S. Levin},
      title = {Readout design and validation for a 1 mm3 resolution clinical PET system},
      booktitle = {Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE},
      year = {2010},
      pages = {3097 -3099},
      doi = {http://dx.doi.org/10.1109/NSSMIC.2010.5874370}
    }
    					
    Reynolds, P.D.; Olcott, P.D.; Lau, F.W.Y. & Levin, C.S. Convex Optimization of Coincidence Time Resolution for High Resolution PET Systems 2008 Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 4068-4073  
    BibTeX:
    @conference{Reynolds2008,
      author = {P. D. Reynolds and P. D. Olcott and F. W. Y. Lau and C. S. Levin},
      title = {Convex Optimization of Coincidence Time Resolution for High Resolution PET Systems},
      booktitle = {Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2008},
      pages = {4068-4073}
    }
    					
    Reynolds, P.D.; Olcott, P.D.; Pratx, G.; Lau, F.W.Y. & Levin, C.S. Convex Optimization of Coincidence Time Resolution for a High-Resolution PET System 2011 Medical Imaging, IEEE Transactions on
    Vol. 30, pp. 391 -400  
    BibTeX:
    @article{Reynolds2011,
      author = {P. D. Reynolds and P. D. Olcott and G. Pratx and F. W. Y. Lau and C. S. Levin},
      title = {Convex Optimization of Coincidence Time Resolution for a High-Resolution PET System},
      journal = {Medical Imaging, IEEE Transactions on},
      year = {2011},
      volume = {30},
      number = {2},
      pages = {391 -400},
      doi = {http://dx.doi.org/10.1109/TMI.2010.2080282}
    }
    					
    Spanoudaki, V.C.; Lau, F.W.Y.; Vandenbroucke, A. & Levin, C.S. Physical effects of mechanical design parameters on photon sensitivity and spatial resolution performance of a breast-dedicated PET system 2010 MEDICAL PHYSICS
    Vol. 37, pp. 5838-5849  
    Abstract: Purpose: This study aims to address design considerations of a high resolution, high sensitivity positron emission tomography scanner dedicated to breast imaging. Methods: The methodology uses a detailed Monte Carlo model of the system structures to obtain a quantitative evaluation of several performance parameters. Special focus was given to the effect of dense mechanical structures designed to provide mechanical robustness and thermal regulation to the minuscule and temperature sensitive detectors. Results: For the energies of interest around the photopeak (450-700 keV energy window), the simulation results predict a 6.5% reduction in the single photon detection efficiency and a 12.5% reduction in the coincidence photon detection efficiency in the case that the mechanical structures are interspersed between the detectors. However for lower energies, a substantial increase in the number of detected events (approximately 14% and 7% for singles at a 100-200 keV energy window and coincidences at a lower energy threshold of 100 keV, respectively) was observed with the presence of these structures due to backscatter. The number of photon events that involve multiple interactions in various crystal elements is also affected by the presence of the structures. For photon events involving multiple interactions among various crystal elements, the coincidence photon sensitivity is reduced by as much as 20% for a point source at the center of the field of view. There is no observable effect on the intrinsic and the reconstructed spatial resolution and spatial resolution uniformity. Conclusions: Mechanical structures can have a considerable effect on system sensitivity, especially for systems processing multi-interaction photon events. This effect, however, does not impact the spatial resolution. Various mechanical structure designs are currently under evaluation in order to achieve optimum trade-off between temperature stability, accurate detector positioning, and minimum influence on system performance. (C) 2010 American Association of Physicists in Medicine. [DOI: 10.1118/1.3484059]
    BibTeX:
    @article{Spanoudaki2010b,
      author = {V. C. Spanoudaki and F. W. Y. Lau and A. Vandenbroucke and C. S. Levin},
      title = {Physical effects of mechanical design parameters on photon sensitivity and spatial resolution performance of a breast-dedicated PET system},
      journal = {MEDICAL PHYSICS},
      year = {2010},
      volume = {37},
      number = {11},
      pages = {5838-5849},
      doi = {http://dx.doi.org/10.1118/1.3484059}
    }
    					
    Spanoudaki, V.C.; Lau, F.W.Y.; Vandenbroucke, A. & Levin, C.S. Monte Carlo assessment of a dense mechanical design for a 1 mm3 resolution breast-dedicated PET system: effects on photon sensitivity, spatial resolution and multi-interaction photon events 2009 Medical Physics  
    BibTeX:
    @article{Spanoudaki2009,
      author = {V. C. Spanoudaki and F. W. Y. Lau and A. Vandenbroucke and C. S. Levin},
      title = {Monte Carlo assessment of a dense mechanical design for a 1 mm3 resolution breast-dedicated PET system: effects on photon sensitivity, spatial resolution and multi-interaction photon events},
      journal = {Medical Physics},
      year = {2009},
      note = {Submitted}
    }
    					
    Spanoudaki, V.C.; Vandenbroucke, A.; Lau, F.W.Y.; Fang, C. & Levin, C.S. Effects of Thermal Regulation Structures on the Photon Sensitivity and Spatial Resolution of a 1 mm^3 Resolution Breast-Dedicated PET System 2008 Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 5657-5661  
    BibTeX:
    @conference{Spanoudaki2008,
      author = {V. C. Spanoudaki and A. Vandenbroucke and F. W. Y. Lau and C. Fang and C. S. Levin},
      title = {Effects of Thermal Regulation Structures on the Photon Sensitivity and Spatial Resolution of a 1 mm^3 Resolution Breast-Dedicated PET System},
      booktitle = {Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2008},
      pages = {5657-5661}
    }
    					
    Vandenbroucke, A.; Foudray, A.M.K.; Lau, F.W.Y.; Olcott, P.D.; Reynolds, P.D. & Levin, C.S. Performance characterization of a new high resolution, 3-D positioning PET scintillation detector 2008 Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 3604-3608  
    BibTeX:
    @conference{Vandenbroucke2008,
      author = {A. Vandenbroucke and A. M. K. Foudray and F. W. Y. Lau and P. D. Olcott and P. D. Reynolds and C. S. Levin},
      title = {Performance characterization of a new high resolution, 3-D positioning PET scintillation detector},
      booktitle = {Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2008},
      pages = {3604-3608}
    }
    					
    Vandenbroucke, A.; Lee, J.; Spanoudaki, V.C.; Lau, F.W.Y.; Reynolds, P.D. & Levin, C.S. Temperature and bias voltage studies of a large area position sensitive avalanche photodiode 2009 Conference Record of the 2009 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 3664-3669  
    BibTeX:
    @conference{Vandenbroucke2009a,
      author = {A. Vandenbroucke and J. Lee and V. C. Spanoudaki and F. W. Y. Lau and P. D. Reynolds and C. S. Levin},
      title = {Temperature and bias voltage studies of a large area position sensitive avalanche photodiode},
      booktitle = {Conference Record of the 2009 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2009},
      pages = {3664-3669}
    }
    					

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