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Positron Emission Tomography (PET)
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"Design of a Small Animal PET Imaging System with 1 Microliter Volume Resolution",
Ned C. Rouze, Matthias Schmand, Stefan Siegel, Gary D. Hutchins, IEEE Transactions on Nuclear Science,
Vol. 51, No. 3, June 2004
Copyright ©2004 IEEE
The design of a new scanner for use in small animal PET imaging is described. The goal is to achieve 1mm FWHM resolution
in each of three orthogonal directions throughout a volume suitable for whole body mouse imaging, roughly 40 mm diameter x 80 mm long. Simultaneously, the design should achieve a sensitivity of greater than 5% of all decays from a point source located
at the center of the scanner. The scanner uses 12, plane detector banks mounted in a 160 mm diameter ring on a rotating gantry. Each detector bank consists of
a 48 x 108 array of 20 mm long LSO scintillator crystals with an array pitch of 0.87 mm. Each bank uses two Hamamatsu H8500 large-area,
multi-anode photomultiplier tubes for fluorescence detection. The detector banks are divided into two sets with the respective lines of
response offset by one quarter of the array pitch to give increased sampling density.
"Optimization and Performance Evaluation of the
MicroPET II Scanner for in vivo Small-Animal Imaging",
Yongfeng Yang, Yuan-Chuan Tai, Stefan Siegel, Danny F Newport,
Bing Bai, Quanzheng Li, Richard M Leahy, Simon R Cherry, Physics of Medicine and Biology, 49 (2004) 2527–2545
Copyright ©2004 IOP Publishing Ltd
MicroPET II is a newly developed PET (positron emission tomography)
scanner designed for high-resolution imaging of small animals. It consists of
17 640 LSO crystals each measuring 0.975 x 0.975 x 12.5 mm3, which are
arranged in 42 contiguous rings, with 420 crystals per ring. The scanner has an
axial field of view (FOV) of 4.9 cm and a transaxial FOV of 8.5 cm. The purpose
of this study was to carefully evaluate the performance of the system and to
optimize settings for in vivo mouse and rat imaging studies. The volumetric
image resolution was found to depend strongly on the reconstruction algorithm
employed and averaged 1.1mm (1.4 ul) across the central 3 cm of the transaxial
FOV when using a statistical reconstruction algorithm with accurate system
modelling. The sensitivity, scatter fraction and noise-equivalent count (NEC)
rate for mouse- and rat-sized phantoms were measured for different energy
and timing windows. Mouse imaging was optimized with a wide open energy
window (150 to 750 keV) and a 10 ns timing window, leading to a sensitivity
of 3.3% at the centre of the FOV and a peak NEC rate of 235,000 cps for a
total activity of 80 MBq (2.2 mCi) in the phantom. Rat imaging, due to the
higher scatter fraction, and the activity that lies outside of the field of view,
achieved a maximum NEC rate of 24,600 cps for a total activity of 80 MBq
(2.2 mCi) in the phantom, with an energy window of 250 to 750 keV and a 6 ns
timing window. The sensitivity at the centre of the FOV for these settings is
2.1%. This work demonstrates that different scanner settings are necessary to
optimize the NEC count rate for different-sized animals and different injected
doses. Finally, phantom and in vivo animal studies are presented to demonstrate
the capabilities of microPET II for small-animal imaging studies.
"Novel Design of a Parallax Free Compton Enhanced PET
Scanner",
A. Braem, M. Chamizo, E. Chesi, N. Colonna, F. Cusanno, R. De Leo, F. Garibaldi, C. Joram, S. Marrone, S. Mathot, E. Nappi, F. Schoenahl,
J. Seguinot, P. Weilhammer, H. Zaidi, Nuclear Instruments and Methods in Physics Research A 525 (2004) 268–274
Copyright ©2004 Elsevier B.V.
Molecular imaging by PET is a powerful tool in modern clinical practice for cancer diagnosis. Nevertheless,
improvements are needed with respect to the spatial resolution and sensitivity of the technique for its application to
specific human organs (breast, prostate, brain, etc.), and to small animals. Presently, commercial PET scanners do not
detect the depth of interaction of photons in scintillators, which results in a not negligible parallax error. Described
here is a novel concept of PET scanner design that provides full three-dimensional (3D) gamma reconstruction with high
spatial resolution over the total detector volume, free of parallax errors. It uses matrices of long scintillators read at
both ends by hybrid photon detectors. This so-called 3D axial concept also enhances the gamma detection efficiency
since it allows one to reconstruct a significant fraction of Compton scattered events. This paper describes the
concept, a possible design and the expected performance of this new PET device. Also reported is first
characterization measurements of 10 cm long YAP:Ce scintillation crystals.
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