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Characterization of a SPECT pinhole collimator for optimal detector usage (the lofthole)

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Abstract
In single-photon emission computed tomography (SPECT), multi-pinhole collimation is often employed nowadays. Most multi-pinhole collimators avoid overlap (multiplexing) of the projections on the detector. This can be done by using additional shielding or by spacing the pinholes far enough apart. Using additional shielding has the drawback that it increases weight, design complexity and cost. Spacing the pinholes far enough apart results in suboptimal detector usage, the valuable detector area is not entirely used. This is due to the circular projections of pinholes on the detector; these ellipses can not be tiled with high detector coverage. To overcome this we designed a new pinhole geometry, the lofthole, that has a rectangular projection on the detector. The lofthole has a circular aperture and a rectangular entrance/exit opening. Sensitivity formulae have been derived for pinholes and loftholes. These formulae take the penumbra effect into account; the proposed formulae do not take penetration into account. The derived formulae are valid for geometries where the field-of-view and the sensitivity of the aperture are solely limited by the exit window. A flood map measurement was performed to compare the rectangular projection of a lofthole with the circular projection of a pinhole. Finally, measurements were done to compare the amount of penetration of pinholes with the amount of penetration of a lofthole. A square lofthole collimator has less penetration than a knife-edge pinhole collimator that irradiates the same rectangular detector area with full coverage. A multilofthole collimator allows high detector coverage without using additional shielding. An additional advantage is the lower amount of penetration.
Keywords
HIGH-RESOLUTION SPECT, SMALL-ANIMAL SPECT, ANALYTIC DETERMINATION, MULTIPINHOLE SPECT, SPATIAL-RESOLUTION, GAMMA-CAMERA, BRAIN SPECT, SYSTEM, DESIGN, SENSITIVITY

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Chicago
Deprez, Karel, Lara da Rocha Vaz Pato, Stefaan Vandenberghe, and Roel Van Holen. 2013. “Characterization of a SPECT Pinhole Collimator for Optimal Detector Usage (the Lofthole).” Physics in Medicine and Biology 58 (4): 859–885.
APA
Deprez, K., da Rocha Vaz Pato, L., Vandenberghe, S., & Van Holen, R. (2013). Characterization of a SPECT pinhole collimator for optimal detector usage (the lofthole). PHYSICS IN MEDICINE AND BIOLOGY, 58(4), 859–885.
Vancouver
1.
Deprez K, da Rocha Vaz Pato L, Vandenberghe S, Van Holen R. Characterization of a SPECT pinhole collimator for optimal detector usage (the lofthole). PHYSICS IN MEDICINE AND BIOLOGY. 2013;58(4):859–85.
MLA
Deprez, Karel, Lara da Rocha Vaz Pato, Stefaan Vandenberghe, et al. “Characterization of a SPECT Pinhole Collimator for Optimal Detector Usage (the Lofthole).” PHYSICS IN MEDICINE AND BIOLOGY 58.4 (2013): 859–885. Print.
@article{3144493,
  abstract     = {In single-photon emission computed tomography (SPECT), multi-pinhole collimation is often employed nowadays. Most multi-pinhole collimators avoid overlap (multiplexing) of the projections on the detector. This can be done by using additional shielding or by spacing the pinholes far enough apart. Using additional shielding has the drawback that it increases weight, design complexity and cost. Spacing the pinholes far enough apart results in suboptimal detector usage, the valuable detector area is not entirely used. This is due to the circular projections of pinholes on the detector; these ellipses can not be tiled with high detector coverage. To overcome this we designed a new pinhole geometry, the lofthole, that has a rectangular projection on the detector. The lofthole has a circular aperture and a rectangular entrance/exit opening. Sensitivity formulae have been derived for pinholes and loftholes. These formulae take the penumbra effect into account; the proposed formulae do not take penetration into account. The derived formulae are valid for geometries where the field-of-view and the sensitivity of the aperture are solely limited by the exit window. A flood map measurement was performed to compare the rectangular projection of a lofthole with the circular projection of a pinhole. Finally, measurements were done to compare the amount of penetration of pinholes with the amount of penetration of a lofthole. A square lofthole collimator has less penetration than a knife-edge pinhole collimator that irradiates the same rectangular detector area with full coverage. A multilofthole collimator allows high detector coverage without using additional shielding. An additional advantage is the lower amount of penetration.},
  author       = {Deprez, Karel and da Rocha Vaz Pato, Lara and Vandenberghe, Stefaan and Van Holen, Roel},
  issn         = {0031-9155},
  journal      = {PHYSICS IN MEDICINE AND BIOLOGY},
  keyword      = {HIGH-RESOLUTION SPECT,SMALL-ANIMAL SPECT,ANALYTIC DETERMINATION,MULTIPINHOLE SPECT,SPATIAL-RESOLUTION,GAMMA-CAMERA,BRAIN SPECT,SYSTEM,DESIGN,SENSITIVITY},
  language     = {eng},
  number       = {4},
  pages        = {859--885},
  title        = {Characterization of a SPECT pinhole collimator for optimal detector usage (the lofthole)},
  url          = {http://dx.doi.org/10.1088/0031-9155/58/4/859},
  volume       = {58},
  year         = {2013},
}

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