Multi-scale algorithm for improved scintillation detection in a CCD-based gamma camera

Korevaar, Marc; Heemskerk, Jan W T; Goorden, Marlies C; Beekman, Freek J.

doi:10.1088/0031-9155/54/4/001

Cited by 25 publications

(48 citation statements)

References 26 publications

(28 reference statements)

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“…It shows that the effects of DOI are adequately suppressed with OCC. Table 1 shows the measured and intrinsic resolution (corrected for the projected spot size) of OPC versus OCC for the multi-scale algorithm (Korevaar et al 2009) that takes into account the varying light spread as a function of depth. As could be expected for gamma rays incident at a normal angle, the differences between OPC and OCC are very small.…”

Section: Resultsmentioning

confidence: 99%

A pinhole gamma camera with optical depth-of-interaction elimination

2009

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The performance of pinhole single photon emission computed tomography (SPECT) depends on the spatial resolution of the gamma-ray detectors used. Pinhole cameras suffer from strong resolution loss due to the varying depth-ofinteraction (DOI) of gamma quanta that enter the detector material at an angle. We eliminate DOI effects in a scintillation gamma camera via a dedicated optic fiber bundle that acts as a focusing collimator for light generated in a scintillation crystal. A curved crystal is connected to a concavely shaped fiberoptic bundle such that the fibers connect perpendicularly to the crystal's convex surface and point straight at the pinhole opening. Limiting the fiber numerical apertures can be used to suppress resolution losses due to light spread. Here we demonstrate experimentally that this prototype position-sensitive gamma sensor successfully eliminates DOI effects, and has an intrinsic resolution of better than 280 μm full width at half maximum with an interaction probability of 67% for 140 keV photons. Therefore, the detector has great potential for increasing the resolution of pinhole SPECT.

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Section: Resultsmentioning

confidence: 99%

A pinhole gamma camera with optical depth-of-interaction elimination

2009

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“…The alternative of saving unprocessed frames quickly exhausts storage media. The algorithms may involve dark-current subtraction, median filtering, thresholding, cross-correlation scanning of the 2-D raster with a template to locate event centers , and a means for determining how large a region of the image to associate with each center (Miller et al ., 2008; Miller et al ., 2009a; Korevaar et al ., 2009b). In the past, this kind of digital processing was the domain of dedicated Digital Signal Processors (DSPs), but in the new systems GPUs tend to be employed, with recent hardware providing enough computing power to handle several megapixel cameras at once each running at > 100 hundred frames per second.…”

Section: Advances In Signal Processing and Estimationmentioning

confidence: 99%

SPECT detectors: the Anger Camera and beyond

2011

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The development of radiation detectors capable of delivering spatial information about gamma-ray interactions was one of the key enabling technologies for nuclear medicine imaging and, eventually, single-photon emission computed tomography (SPECT). The continuous NaI(Tl) scintillator crystal coupled to an array of photomultiplier tubes, almost universally referred to as the Anger Camera after its inventor, has long been the dominant SPECT detector system. Nevertheless, many alternative materials and configurations have been investigated over the years. Technological advances as well as the emerging importance of specialized applications, such as cardiac and preclinical imaging, have spurred innovation such that alternatives to the Anger Camera are now part of commercial imaging systems. Increased computing power has made it practical to apply advanced signal processing and estimation schemes to make better use of the information contained in the detector signals. In this review we discuss the key performance properties of SPECT detectors and survey developments in both scintillator and semiconductor detectors and their readouts with an eye toward some of the practical issues at least in part responsible for the continuing prevalence of the Anger Camera in the clinic.

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“…The parallax errors arise from the variable depth of interaction (DOI) of gamma-ray/scintillator events, especially when gamma rays enter a scintillator at steep angles. There have been several efforts to address parallax errors in pinhole SPECT, including algorithm-based DOI modeling and correction, and the use of a curved fiber bundle to collimate light from a curved scintillator [5, 6]. In PET, various methods are used to correct DOI-related errors, including use of an avalanche photodiode at the front surface of a scintillator crystal to detect the entry point an annihilation photon [7], measuring the ratio of the signals of detectors placed at opposite ends of a scintillator crystal [8], and the use of a 3D scintillator crystal array [9].…”

Section: Introductionmentioning

confidence: 99%

Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera

Alhassen

Kudrolli

Singh

et al. 2011

IEEE Trans. Nucl. Sci.

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Preclinical SPECT offers a powerful means to understand the molecular pathways of drug interactions in animal models by discovering and testing new pharmaceuticals and therapies for potential clinical applications. A combination of high spatial resolution and sensitivity are required in order to map radiotracer uptake within small animals. Pinhole collimators have been investigated, as they offer high resolution by means of image magnification. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the detection scintillator at steep angles, introducing parallax errors due to variable depth-of-interaction in scintillator material, especially towards the edges of the detector field of view. These parallax errors ultimately limit the resolution of pinhole preclinical SPECT systems, especially for higher energy isotopes that can easily penetrate through millimeters of scintillator material. A pixellated, focused-cut (FC) scintillator, with its pixels laser-cut so that they are collinear with incoming rays, can potentially compensate for these parallax errors and thus improve the system resolution. We performed the first experimental evaluation of a newly developed focused-cut scintillator. We scanned a Tc-99m source across the field of view of pinhole gamma camera with a continuous scintillator, a conventional “straight-cut” (SC) pixellated scintillator, and a focused-cut scintillator, each coupled to an electron-multiplying charge coupled device (EMCCD) detector by a fiber-optic taper, and compared the measured full-width half-maximum (FWHM) values. We show that the FWHMs of the focused-cut scintillator projections are comparable to the FWHMs of the thinner SC scintillator, indicating the effectiveness of the focused-cut scintillator in compensating parallax errors.

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Multi-scale algorithm for improved scintillation detection in a CCD-based gamma camera

Cited by 25 publications

References 26 publications

A pinhole gamma camera with optical depth-of-interaction elimination

A pinhole gamma camera with optical depth-of-interaction elimination

SPECT detectors: the Anger Camera and beyond

Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera

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