RESUMO
PURPOSE: Conventional gamma-ray detector, PET and SPECT, have the limitation of energy and field of view. These limitations are major problems of studying for a new medical imaging. Therefore, we have developed the new imaging detector which is an electron-tracking Compton camera (ETCC). METHODS: A reconstruction method of Compton camera (CC) is using the physics principle. Because of using physics principle, CC can have a wide energy dynamic range and wide field of view. Conventional CC, however, cannot catch Compton recoil electron tracks, and this is one of the reasons of low imaging power. We have developed a time projection chamber (TPC) using micro pixel chamber (µPIC) as the new detector for ETCC. The µPIC is 2-dimensional gaseous detector and this position resolution is less than 400 µm. Using this detector, ETCC can get electron tracks which are generated from Compton scattering. In this paper, we show the prototype ETCC performance and imaging results. RESULTS: ETCC achieved a wide energy dynamic range (200-1300keV) and wide field of view (3 steradian). Also we succeeded in imaging new imaging reagents using mice as follows; (1) F-18-FDG (511 keV) and I-131-MIBG (364 keV) simultaneous imaging for double clinical tracer imaging, (2) Zn-65- porphyrin (1116 keV) imaging for high energy gamma-ray imaging and, (3) imaging of some minerals (Mn-54, Zn-65) in mice and so on. And we succeeded in 3-D imaging which has imaged only one direction using one head camera. CONCLUSIONS: We have developed the ETCC for new medical imaging device and succeeded in imaging the some imaging reagents. We started to develop the new ETCC which can image the mouse within 30 min. Thus, this detector has the possibility of new medical imaging.
RESUMO
Protons with energies up to approximately 10(15) eV are the main component of cosmic rays, but evidence for the specific locations where they could have been accelerated to these energies has been lacking. Electrons are known to be accelerated to cosmic-ray energies in supernova remnants, and the shock waves associated with such remnants, when they hit the surrounding interstellar medium, could also provide the energy to accelerate protons. The signature of such a process would be the decay of pions (pi(0)), which are generated when the protons collide with atoms and molecules in an interstellar cloud: pion decay results in gamma-rays with a particular spectral-energy distribution. Here we report the observation of cascade showers of optical photons resulting from gamma-rays at energies of approximately 10(12) eV hitting Earth's upper atmosphere, in the direction of the supernova remnant RX J1713.7-3946. The spectrum is a good match to that predicted by pion decay, and cannot be explained by other mechanisms.
RESUMO
A two-dimensional microstrip gas chamber (MSGC) has been developed with a 10 cm-square detection area and an ultrafast read-out system. The MSGC was made using multi-chip module (MCM) technology, and has a very thin substrate of 17 micro m and many anodes and back strips, both with 200 micro m pitches. The new read-out system, in which the hit addresses of the electrodes were sequentially encoded to the hit positions by a synchronous clock, handles data rates of up to 10(7) events s(-1) from MSGCs. This enables the acquisition of fast and sequential digital images. Furthermore, since the MSGC is a real photon-counting detector, the timing of the photons, to an accuracy of a few tens of nanoseconds, and energy can be recorded. Here, the performance of the MSGC system as a real-time area detector is reported, and the abilities of this system are discussed.
RESUMO
A two-dimensional microstrip gas chamber (MSGC) with a 5 cm x 5 cm detection area has been developed. It has 254 anodes and 255 back strips, both with 200 micro m pitches. Using this MSGC, linear polarization of X-rays was successfully measured in the energy range 6-14 keV. In addition, the performance of the MSGC as an X-ray imaging polarimeter has been simulated using the EGS4 program (Electron Gamma Shower, Version 4) modified for this purpose. In this article, the results of both the polarization measurement and the simulation are reported.
RESUMO
A high-performance data-acquisition system has been developed in order to obtain time-resolved sequential images from a two-dimensional microstrip gas chamber (MSGC). This was achieved using fully digital processing with a synchronized pipeline method. Complex logical circuits for processing large numbers of signals are mounted on a small number of complex programmable logic devices. The system is operated with a 10 MHz synchronous clock, and has the capability of handling more than 3 x 10(6) counts s(-1) for asynchronous events. The system was examined using a 5 x 5 cm MSGC and the recently developed 10 x 10 cm MSGC (1024 outputs); the anticipated performances were achieved.
