M.K. Limkeman's scientific contributions

Publications (1)

  • D. Luo · J.J. Williams · M.K. Limkeman · M.J. Cook · D.L. McDaniel
    Abstract: A crystal-based timing calibration method is implemented and investigated on a GE PET scanner. This method first calculates block-level adjustments using a commercially available algorithm, and then, based on the calculated block-level adjustments, derives the crystal-level adjustments needed within each block. Concurrently with the time difference acquisition for block-pair adjustment, the time differences are also accumulated for all the crystals within each block. The crystal averages are... Show More
    Conference Paper · Dec 2002

Publications citing this author (13)

    • The authors in [21] show a similar problem formation, and are, in effect, using a single-coordinate descent method, iteratively optimizing a parameter for each coordinate, the per crystal delay time.
    [Show abstract] [Hide abstract] ABSTRACT: We are developing a dual panel breast-dedicated positron emission tomography (PET) system using LSO scintillators coupled to position sensitive avalanche photodiodes (PSAPD). The charge output is amplified and read using NOVA RENA-3 ASICs. This paper shows that the coincidence timing resolution of the RENA-3 ASIC can be improved using certain list-mode calibrations. We treat the calibration problem as a convex optimization problem and use the RENA-3's analog-based timing system to correct the measured data for time dispersion effects from correlated noise, PSAPD signal delays and varying signal amplitudes. The direct solution to the optimization problem involves a matrix inversion that grows order (n(3)) with the number of parameters. An iterative method using single-coordinate descent to approximate the inversion grows order (n). The inversion does not need to run to convergence, since any gains at high iteration number will be low compared to noise amplification. The system calibration method is demonstrated with measured pulser data as well as with two LSO-PSAPD detectors in electronic coincidence. After applying the algorithm, the 511 keV photopeak paired coincidence time resolution from the LSO-PSAPD detectors under study improved by 57%, from the raw value of 16.3 ±0.07 ns full-width at half-maximum (FWHM) to 6.92 ±0.02 ns FWHM ( 11.52 ±0.05 ns to 4.89 ±0.02 ns for unpaired photons).
    Full-text · Article · Sep 2010

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