TY - JOUR

T1 - Calibration method for ML estimation of 3D interaction position in a thick gamma-ray detector

AU - Hunter, William C.J.

AU - Barrett, Harrison H.

AU - Furenlid, Lars R.

N1 - Funding Information:
Manuscript received February 18, 2008; revised August 26, 2008. Current version published February 11, 2009. This work was supported in part by the U.S. National Institutes of Health NIBIB under Grant P41-EB002035.

PY - 2009/2

Y1 - 2009/2

N2 - High-energy (< 100 keV) photon detectors are often made thick relative to their lateral resolution in order to improve their photon-detection efficiency. To avoid issues of parallax and increased signal variance that result from random interaction depth, we must determine the 3D interaction position in the imaging detector. With this goal in mind, we examine a method of calibrating response statistics of a thick-detector gamma camera to produce a maximum-likelihood estimate of 3D interaction position. We parameterize the mean detector response as a function of 3D position, and we estimate these parameters by maximizing their likelihood given prior knowledge of the pathlength distribution and a complete list of camera signals for an ensemble of gamma-ray interactions. Furthermore, we describe an iterative method for removing multiple-interaction events from our calibration data and for refining our calibration of the mean detector response to single interactions. We demonstrate this calibration method with simulated gamma-camera data. We then show that the resulting calibration is accurate and can be used to produce unbiased estimates of 3D interaction position.

AB - High-energy (< 100 keV) photon detectors are often made thick relative to their lateral resolution in order to improve their photon-detection efficiency. To avoid issues of parallax and increased signal variance that result from random interaction depth, we must determine the 3D interaction position in the imaging detector. With this goal in mind, we examine a method of calibrating response statistics of a thick-detector gamma camera to produce a maximum-likelihood estimate of 3D interaction position. We parameterize the mean detector response as a function of 3D position, and we estimate these parameters by maximizing their likelihood given prior knowledge of the pathlength distribution and a complete list of camera signals for an ensemble of gamma-ray interactions. Furthermore, we describe an iterative method for removing multiple-interaction events from our calibration data and for refining our calibration of the mean detector response to single interactions. We demonstrate this calibration method with simulated gamma-camera data. We then show that the resulting calibration is accurate and can be used to produce unbiased estimates of 3D interaction position.

KW - 3D interaction position

KW - Depth of interaction

KW - Gamma-ray imaging

KW - Maximum likelihood estimation

KW - Mean detector response calibration

KW - Multiple-hit event filtering

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U2 - 10.1109/TNS.2008.2010704

DO - 10.1109/TNS.2008.2010704

M3 - Article

AN - SCOPUS:60449113413

SN - 0018-9499

VL - 56

SP - 189

EP - 196

JO - IEEE Transactions on Nuclear Science

JF - IEEE Transactions on Nuclear Science

IS - 1

M1 - 4782175

ER -