3,183 research outputs found
Tomographic image quality of rotating slat versus parallel hole-collimated SPECT
Parallel and converging hole collimators are most frequently used in nuclear medicine. Less common is the use of rotating slat collimators for single photon emission computed tomography (SPECT). The higher photon collection efficiency, inherent to the geometry of rotating slat collimators, results in much lower noise in the data. However, plane integrals contain spatial information in only one direction, whereas line integrals provide two-dimensional information. It is not a trivial question whether the initial gain in efficiency will compensate for the lower information content in the plane integrals. Therefore, a comparison of the performance of parallel hole and rotating slat collimation is needed. This study compares SPECT with rotating slat and parallel hole collimation in combination with MLEM reconstruction with accurate system modeling and correction for scatter and attenuation. A contrast-to-noise study revealed an improvement of a factor 2-3 for hot lesions and more than a factor of 4 for cold lesion. Furthermore, a clinically relevant case of heart lesion detection is simulated for rotating slat and parallel hole collimators. In this case, rotating slat collimators outperform the traditional parallel hole collimators. We conclude that rotating slat collimators are a valuable alternative for parallel hole collimators
An Electron-Tracking Compton Telescope for a Survey of the Deep Universe by MeV gamma-rays
Photon imaging for MeV gammas has serious difficulties due to huge
backgrounds and unclearness in images, which are originated from incompleteness
in determining the physical parameters of Compton scattering in detection,
e.g., lack of the directional information of the recoil electrons. The recent
major mission/instrument in the MeV band, Compton Gamma Ray
Observatory/COMPTEL, which was Compton Camera (CC), detected mere
persistent sources. It is in stark contrast with 2000 sources in the GeV
band. Here we report the performance of an Electron-Tracking Compton Camera
(ETCC), and prove that it has a good potential to break through this stagnation
in MeV gamma-ray astronomy. The ETCC provides all the parameters of
Compton-scattering by measuring 3-D recoil electron tracks; then the Scatter
Plane Deviation (SPD) lost in CCs is recovered. The energy loss rate (dE/dx),
which CCs cannot measure, is also obtained, and is found to be indeed helpful
to reduce the background under conditions similar to space. Accordingly the
significance in gamma detection is improved severalfold. On the other hand, SPD
is essential to determine the point-spread function (PSF) quantitatively. The
SPD resolution is improved close to the theoretical limit for multiple
scattering of recoil electrons. With such a well-determined PSF, we demonstrate
for the first time that it is possible to provide reliable sensitivity in
Compton imaging without utilizing an optimization algorithm. As such, this
study highlights the fundamental weak-points of CCs. In contrast we demonstrate
the possibility of ETCC reaching the sensitivity below erg
cm s at 1 MeV.Comment: 19 pages, 12 figures, Accepted to the Astrophysical Journa
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