Anesthesia is currently required for positron emission tomography (PET) studies of the animal brain in order to eliminate motion artifacts. However, anesthesia profoundly affects the neurological ...state of the animal, complicating the interpretation of PET data. Furthermore, it precludes the use of PET to study the brain during normal behavior. The rat conscious animal PET tomograph (RatCAP) is designed to eliminate the need for anesthesia in rat brain studies. It is a miniaturized full-ring PET scanner that is attached directly to the head, imaging nearly the entire brain. RatCAP utilizes arrays of 2 mm /spl times/ 2 mm LSO crystals coupled to matching avalanche photodiode arrays, which are in turn read out by full custom integrated circuits. Principal challenges have been addressed considering the physical constraints on size, weight, and heat generation in addition to the usual requirements of small-animal PET, such as high spatial resolution in the presence of parallax error. A partial prototype has been constructed and preliminary measurements and optimization completed. Realistic Monte Carlo simulations have also been carried out to optimize system performance, which is predicted to be competitive with existing microPET systems.
A study on the properties of lead tungstate crystals Zhu, R.Y.; Ma, D.A.; Newman, H.B. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/1996, Volume:
376, Issue:
3
Journal Article
Peer reviewed
Open access
This report summarizes the results of a study on the properties of five large and five small size lead tungstate (PbWO
4) crystals. Data are presented on the longitudinal optical transmittance and ...light attenuation length, light yield and response uniformity, emission spectra and decay time. The radiation resistance of large crystals and possible curing with optical bleaching are discussed. The result of an in depth materials study, including trace impurities analysis, are also presented. The general conclusion from this investigation is that further research and development is needed to develop fast, radiation-hard PbWO
4 crystals for the CMS experiment at the CERN LHC.
One of the most promising high resolution positron emission tomography detector designs comprises an array of small, optically isolated scintillator crystals each coupled to an independent ...photosensor, such as an avalanche photodiode (APD). However, crosstalk between crystals (due to Compton scatter, photoelectron escape, or incomplete optical isolation) can significantly degrade performance and is expected to increase as crystals become narrower to improve spatial resolution. Various measures of crosstalk have been determined for different configurations of 4 /spl times/ 8 blocks of 2 mm /spl times/ 2 mm lutetium oxyorthosilicate (LSO) crystals coupled to matched Hamamatsu APD arrays. Results indicate that ignoring crosstalk signals could lead to a /spl sim/ 30% loss in coincidence sensitivity for a tomograph using these detectors and a decrease in energy resolution of /spl sim/ 2 percentage points. Spatial and time resolution would not be significantly affected with most practical front-end architectures.
The capability to create high quality images from data acquired by the Rat Conscious Animal PET tomograph (RatCAP) has been evaluated using modified versions of the PET Monte Carlo code Simulation ...System for Emission Tomography (SimSET). The proposed tomograph consists of lutetium oxyorthosilicate (LSO) crystals arranged in 12 4 /spl times/ 8 blocks. The effects of the RatCAPs small ring diameter (/spl sim/40 mm) and its block detector geometry on image quality for small animal studies have been investigated. Since the field of view will be almost as large as the ring diameter, radial elongation artifacts due to parallax error are expected to degrade the spatial resolution and thus the image quality at the edge of the field of view. In addition to Monte Carlo simulations, some preliminary results of experimentally acquired images in both two-dimensional (2-D) and 3-D modes are presented.
This report presents recent progress of a study on the radiation damage in lead tungstate (PbWO/sub 4/) crystals. The dose rate dependence of radiation damage in PbWO/sub 4/ has been observed. An ...optimization of the oxygen compensation through post-growth thermal annealing has led to PbWO/sub 4/ samples with significantly improved radiation hardness. Front irradiation is found to cause a factor of 2 to 6 times less severe damage than uniform irradiation. Lanthanum doping was found not to be a determining factor for PbWO/sub 4/ radiation hardness improvement. Finally, a TEM/EDS analysis revealed that the radiation damage in PbWO/sub 4/ crystals is caused by oxygen vacancies.
A study of scintillation beta microprobes Woody, C.L.; Stoll, S.P.; Schlyer, D.J. ...
IEEE transactions on nuclear science,
10/2002, Volume:
49, Issue:
5
Journal Article
Peer reviewed
Several types of scintillation microprobes have recently been developed to directly measure positron activity from radiotracers in live animals. These probes consist of either a small lutetium ...oxyorthosilicate (LSO) crystal or plastic scintillator coupled to an optical fiber that is read out with a photomultiplier tube operated in a single photon counting mode. In this paper, a comparison is made between the two types of probes in terms of their sensitivity to both positrons and gammas. It was found that LSO offers very high sensitivity to positrons due to its high density and light output, and allows the construction of very small probes for certain applications. The LSO probe can also provide effective discrimination between positrons and gammas, and provide better localization of positron decays, using pulse height discrimination. Results are also given on the use of the microprobe on live laboratory animals.
A study has been carried out to investigate the possibility of using a pair of LSO + APD detector arrays to obtain a noninvasive measurement of the arterial input function for use in PET. The main ...focus of this study was to determine the spatial resolution and sensitivity required to obtain a high quality image that would permit a precise determination of the region of interest around the wrist artery. From these data a quantitative arterial input function that has minimal interference from the tissue and vein background can be obtained. The detector arrays were operated in coincidence counting mode to obtain planar images of various phantoms to demonstrate the feasibility of the concept.
GEM detectors can serve as high precision tracking detectors in a variety of high energy and nuclear physics experiments. However, relativistic heavy ion experiments can potentially provide not only ...very high track multiplicities, but also severe background conditions for operating GEM detectors. To study their use under these conditions, a test was carried out of a three stage GEM detector in the PHENIX experiment at RHIC. The detector was placed in a region close to the collision point inside the PHENIX central spectrometer and operated during full luminosity gold-gold collisions. Results are given on the stability of operation and the sensitivity of the detector to beam related backgrounds using both argon/CO/sub 2/ and pure CF/sub 4/ gas mixtures.
The current method for measuring the input function of a PET tomograph is by withdrawing arterial blood from a patient's wrist In this study, the possibility of making a noninvasive measurement of ...the arterial blood is explored to determine the feasibility of using a planar set of detectors situated around the wrist. The arterial measurement was simulated using a peristaltic pump and an anatomically correct wrist phantom with attenuation. A step function was used to measure the activity flowing through arterial and venous tubing in the phantom. The detector was tested for spatial resolution and counting efficiency. The results showed the detector was able to discriminate the arterial and venous flows from noise when using planar coincidence images.
We describe a custom data acquisition system for the RatCAP tomograph. It is a small, head-mounted PET detector designed to image the brain of an awake rat. At its core, the tomograph consists of a ...number of LSO crystals read out with an array of APDs. The data will be collected through a custom-designed ASIC, along with a custom VME board. We describe the design, implementation, and performance of a versatile VME-based data acquisition system which will be used to read out the VME board, as well as other off-the-shelf data acquisition electronics.
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