Molecular Imaging Instrumentation Laboratory  

Strategies for Practical, High Quality and Accurate List Mode Iterative Image Reconstruction for PET

The 1 mm resolution clinical PET system under development utilizes 1x1x1 mm3 crystal elements integrated into two panels, each measuring roughly 10x16 cm2, that form several billion possible annihilation photon response lines (LORs) between pairs of individual elements from each panel. To avoid a potentially enormous memory burden we chose to perform the required line projection operations, the critical and most computational steps of iterative tomographic image reconstruction, using on-the-fly calculations, on a per event basis. To address this problem we drew from advances in the computer graphics field. It turns out that these line projection operations can be reformulated as geometric calculations that can run much more efficiently on graphics hardware known as the graphics processing unit (GPU) rather than running software on a cluster of CPUs. As a result of this novel reformulation of the problem, the iterative image reconstruction algorithm, known as 3-D list-mode ordered subsets expectation maximization (3D-OSEM), runs a factor of 50 to 100 times faster on a GPU than an equivalent-cost state-of-the-art CPU, thus replacing the need for a large CPU cluster, and reducing associated costs and physical footprint, in order to make the system more available and practical for use in the tight confines of the breast imaging clinic, while maintaining equivalent or better image quality/quantitative accuracy.

In addition to high resolution PET, the techniques are being developed to handle list-mode 3D-OSEM image reconstruction for time-of-flight (ToF) PET.

Gaussian Kernel       Graphics Card

People Involved

Related Publications

Global QuickSearch:   Number of matching entries: 0

Search Settings

    Author Title Year Jour./Proc./Book
    Gu, Y. & Levin, C.S. Effects of Photon Multiple Interactions in a High Resolution PET System that Uses 3-D Positioning Detectors 2008 Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 3814-3819  
    BibTeX:
    @conference{Gu2008a,
      author = {Y. Gu and C. S. Levin},
      title = {Effects of Photon Multiple Interactions in a High Resolution PET System that Uses 3-D Positioning Detectors},
      booktitle = {Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2008},
      pages = {3814-3819}
    }
    					
    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}
    }
    					
    Habte, F.; Pratx, G.; Olcott, P.D. & Levin, C.S. New Geometry for a Whole Body PET System 2009 IEEE Transactions on Nuclear Science  
    BibTeX:
    @article{Habte2009a,
      author = {F. Habte and G. Pratx and P. D. Olcott and C. S. Levin},
      title = {New Geometry for a Whole Body PET System},
      journal = {IEEE Transactions on Nuclear Science},
      year = {2009},
      note = {Submitted}
    }
    					
    Levin, C.S. New Imaging Technologies to Enhance the Molecular Sensitivity of Positron Emission Tomography 2008 Proceedings of the IEEE, pp. 439-467  
    BibTeX:
    @article{Levin2008,
      author = {C. S. Levin},
      title = {New Imaging Technologies to Enhance the Molecular Sensitivity of Positron Emission Tomography},
      booktitle = {Proceedings of the IEEE},
      year = {2008},
      pages = {439-467}
    }
    					
    Pratx, G.; Chinn, G.; Habte, F.; Olcott, P.D. & Levin, C.S. Fully 3D List-mode OSEM Accelerated with Graphics Processing Units 2006 2006 IEEE Nuclear Science Symposium and Medical Imaging Conference Record, pp. 2196-2202  
    BibTeX:
    @conference{Pratx2006,
      author = {G. Pratx and G. Chinn and F. Habte and P. D. Olcott and C. S. Levin},
      title = {Fully 3D List-mode OSEM Accelerated with Graphics Processing Units},
      booktitle = {2006 IEEE Nuclear Science Symposium and Medical Imaging Conference Record},
      year = {2006},
      pages = {2196-2202}
    }
    					
    Pratx, G.; Chinn, G.; Olcott, P.D. & Levin, C.S. Fast, Accurate and Shift-Varying Line Projections for Iterative Reconstruction Using the GPU 2008 Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference  
    BibTeX:
    @conference{Pratx2008,
      author = {G. Pratx and G. Chinn and P. D. Olcott and C. S. Levin},
      title = {Fast, Accurate and Shift-Varying Line Projections for Iterative Reconstruction Using the GPU},
      booktitle = {Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2008}
    }
    					
    Pratx, G. & Levin, C.S. Online detector response calculations for high-resolution PET image reconstruction 2011 Physics in Medicine and Biology
    Vol. 56, pp. 4023-4040  
    BibTeX:
    @article{Pratx2011d,
      author = {G. Pratx and C. S. Levin},
      title = {Online detector response calculations for high-resolution PET image reconstruction},
      journal = {Physics in Medicine and Biology},
      year = {2011},
      volume = {56},
      number = {13},
      pages = {4023-4040}
    }
    					
    Pratx, G. & Levin, C.S. Bayesian reconstruction of photon interaction sequences for high-resolution PET detectors, (Selected as Feature Article of the Month, American Institute of Physics, August 2009) 2009 Physics in Medicine and Biology
    Vol. 54, pp. 5073-5094  
    BibTeX:
    @article{Pratx2009a,
      author = {G. Pratx and C. S. Levin},
      title = {Bayesian reconstruction of photon interaction sequences for high-resolution PET detectors, (Selected as Feature Article of the Month, American Institute of Physics, August 2009)},
      journal = {Physics in Medicine and Biology},
      year = {2009},
      volume = {54},
      number = {17},
      pages = {5073-5094}
    }
    					
    Pratx, G. & Levin, C.S. Online calculation of the detector response for high-resolution PET iterative image reconstruction 2009 IEEE Transactions on Medical Imaging  
    BibTeX:
    @article{Pratx2009b,
      author = {G. Pratx and C. S. Levin},
      title = {Online calculation of the detector response for high-resolution PET iterative image reconstruction},
      journal = {IEEE Transactions on Medical Imaging},
      year = {2009},
      note = {Submitted}
    }
    					
    Pratx, G. & Levin, C.S. Accurately Positioning Events in a High-Resolution PET System that uses 3D CZT Detectors 2007 Conference Record of the 2007 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 2660-2664  
    BibTeX:
    @conference{Pratx2007,
      author = {G. Pratx and C. S. Levin},
      title = {Accurately Positioning Events in a High-Resolution PET System that uses 3D CZT Detectors},
      booktitle = {Conference Record of the 2007 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2007},
      pages = {2660-2664}
    }
    					
    Pratx, G.; Olcott, P.D.; Chinn, G. & Levin, C.S. Fast, Accurate and Shift-Varying Line Projections for Iterative Reconstruction Using the GPU 2009 IEEE Transactions in Medical Imaging
    Vol. 28, pp. 435-445  
    BibTeX:
    @article{Pratx2009,
      author = {G. Pratx and P. D. Olcott and G. Chinn and C. S. Levin},
      title = {Fast, Accurate and Shift-Varying Line Projections for Iterative Reconstruction Using the GPU},
      journal = {IEEE Transactions in Medical Imaging},
      year = {2009},
      volume = {28},
      number = {3},
      pages = {435-445}
    }
    					
    Pratx, G.; Reader, A.J. & Levin, C.S. Faster Maximum-Likelihood Reconstruction via Explicit Conjugation of Search Directions 2008 Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference, pp. 5070-5075  
    BibTeX:
    @conference{Pratx2008a,
      author = {G. Pratx and A. J. Reader and C. S. Levin},
      title = {Faster Maximum-Likelihood Reconstruction via Explicit Conjugation of Search Directions},
      booktitle = {Conference Record of the 2008 IEEE Nuclear Science Symposium and Medical Imaging Conference},
      year = {2008},
      pages = {5070-5075}
    }
    					
    Pratx, G.; Surti, S. & Levin, C.S. Fast List-Mode Reconstruction for Time-of-Flight PET Using Graphics Hardware 2011 Nuclear Science, IEEE Transactions on
    Vol. 58, pp. 105 -109  
    BibTeX:
    @article{Pratx2011,
      author = {G. Pratx and S. Surti and C. S. Levin},
      title = {Fast List-Mode Reconstruction for Time-of-Flight PET Using Graphics Hardware},
      journal = {Nuclear Science, IEEE Transactions on},
      year = {2011},
      volume = {58},
      number = {1},
      pages = {105 -109},
      doi = {http://dx.doi.org/10.1109/TNS.2010.2081376}
    }
    					

    Footer Links: