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In this paper, we propose a combined Compton camera/magnetic resonance imaging (MRI) scanner. For this, the table-top Compton camera currently under development in our laboratory is suitable, considering that it is not very large (i.e., a table-top size) and that it uses semiconductor detectors (for both the scatterer and absorber detectors), which in principle are not very sensitive to a magnetic field. The Compton camera takes three-dimensional images from a fixed position and, therefore, does not require a large ring-type structure, making it possible to fit it into an existing MRI system, without requiring major modifications to the system. In the present study, the potential of combining the table-top Compton camera and an MRI scanner for real simultaneous imaging was demonstrated by fusing a Compton camera image of an instance of multi-tracing, generated by using Geant4 Monte Carlo simulations, with an MR image.

For a table-top Compton camera, which is currently under development in our group, the interaction position resolution of the absorber detector is a critical or limiting detector parameter that most seriously affects the imaging resolution of the Compton camera. Currently, it is assumed that all the interactions occur at the centers of the detector segments of the absorber detector, which is simple, but obviously not the best choice considering that the interaction depths of the photons in the absorber detector is not distributed uniformly, especially for the low-energy photons. To this end, the present study develops a novel method, called "average interaction depth (AID) method" to improve the imaging resolution of Compton camera by additionally considering the interaction depth of the incident photon in the absorber detector. Our simulation studies with Geant4 show that the imaging resolution of Compton camera can be significantly improved by using the AID method. The imaging resolution of the table-top Compton camera was improved from 9.9 mm to 7.6 mm in full width at half maximum (FWHM) for a 511 keV gamma point source. For a 364 keV gamma point source, the imaging resolution was improved more significantly, i.e., from 11.4 mm to 7.2 mm.

The imaging resolution in a Compton camera depends mainly on the position uncertainty, which is affected by the size of electrodes in a detector. Therefore, if any other method is not used for the reduction of the position uncertainty, the imaging resolution is limited by the size of electrodes. Recently, we have developed a Compton camera consisting of a double-sided silicon strip detector (DSSD) and a 25-segmented germanium detector (25-SEGD). The 25-SEGD has an active volume of 5 x 5 x 2 cm3. We have performed measurement for determination of the interaction depth in the 25-SEGD using the pulse shape analysis. After getting a rise-time correlation between the anode and the segment, we obtained a relation formula between the rise-time of the detector signal and the depth derived from the decay equation of gamma-ray in the detector. This decay formula has been used for the determination of interaction depth. As a result of applying the relation function to image reconstruction, we could improve the imaging resolution.

In the present study, a Compton camera, including detailed timing characteristics of the component detectors and related data acquisition (DAQ) electronics, was modeled very accurately with Geant4. The results are very convincing—the inclusion of the timing characteristics in the simulation reduced the imaging sensitivity discrepancy between the simulated and measured data to a negligible level (1–2%) for a 22 Na point source; this is a significant accuracy improvement compared with the results obtained previously without modeling the timing characteristics, for which the discrepancies were 30% and 6% for 511 and 1275 keV, respectively. The imaging resolution accuracy was also significantly improved.

TPD and infrared spectroscopy were used to study CO 2 hydrogenation over Cu/ZnO/SiO 2 catalyst. Adsorbed CO 2 was believed to form copper formate via the hydrogenation and the formate subsequently. The role of zinc oxide seemed to store more hydrogen during reaction, which promoted the hydrogenation of copper formate to methanol.

The Pt-Rh/Al 2 O 3 catalysts were prepared in an attempt to overcome the limitation of the narrow temperature window for NO reduction with C 3 H 6 in the presence of excess oxygen. The impregnated Pt-Rh/Al 2 O 3 catalyst by incipient wetness method did not show high NO conversion as well as high N 2 selectivity owing to the rapid oxidation of C 3 H 6 to CO 2 . But the mechanically attrited Pt-Rh/Al 2 O 3 catalyst could be an effective catalyst for NO reduction in a quite wide temperature window by preventing the spillover of the adsorbed C 3 H 6 from Rh to Pt surface.

The high-spin states of 93 Nb are studied by the 82 Se( 16 O, p4n) 93 Nb reaction at a beam energy of 100 MeV. The in-beam γ-ray spectroscopic techniques are used. The γt-, γγt-coincidence, γ-ray a...

High-spin states of odd-odd 168Lu were observed up to 18ħ for the first time using the 159Tb(13C, 4nγ)168Lu reaction at E 13C= 58.5 MeV. γ-γ coincidence, E γ singles, excitation function, and the DCO ratios were measured. Two rotational bands with signature splitting were populated, among which the lower-energy band is identified as π 7/2+[404] ⊗ν 5/2+[642] in view of alignment and energy systematics.

In the present study, a Compton camera simulator based on the GEANT4 detector simulation tool kit and MATLAB ™ , and designated the Compton Imaging Simulator (CIS), was developed. The software system encompasses a simulator, an image-reconstruction algorithm, and a data analysis tool. The computational time to obtain a sufficient number of Compton scattered data was dramatically reduced using the source-biasing and exponential transform techniques. Also, afour-dimensional Monte Carlo simulation capability was incorporated. A comparison of the simulation results with the experimental results shows that the CIS accurately simulates the Compton camera.