Poly[bis(phenethyl­ammonium) [di­bromido­plumbate(II)]-di-μ-bromido]]

Crystals of the title compound, {(C6H5C2H4NH3)2[PbBr4]}n, were grown at room temperature from a solution in N,N-dimethyl­formamide (DMF) using nitro­methane as the poor solvent. This perovskite-type organic–inorganic hybrid compound consists of well ordered sheets of corner-sharing disordered PbBr6 octa­hedra separated by bilayers of phenethyl­ammonium cations. The octa­hedra are rotated and tilted due to N—H⋯Br hydrogen bonds with the ammonium groups, generating a superstructure in the unit cell similar to that of the tetra­chloridoplumbate (C6H5C2H4NH3)2[PbCl4]

Performance evaluation of an OpenPET Detector for Heavy Ion Therapy under Actual In-beam Condition

OpenPET which consists of two detector rings separated axially is suitable for in-beam PET in heavy ion therapy due to the open space between the separated detector rings. Although the primary ion beam do not enter into the PET detector in the OpenPET, light fragment ions from a target can enter into the detectors and affect the detector performance under the actual in-beam condition. Previously, we demonstrate that the OpenPET detector can be sufficiently operated in off-beam experiments after carbon beam irradiation. In this presentation, we report the results of in-beam measurements with a prototype OpenPET detector optimized for the in-beam measurement.Experiments were performed in the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National institute of Radiological Sciences (NIRS). The OpenPET detector consisted of a 8 x 8 x 4 LGSO crystal array and a 64-channel PS-PMT. The size of the crystals was 2.9mmx2.9mmx5.0mm. The energy and intensity of the 12C beam were 290MeV/u and 108 -109 particle per second (pps). This beam condition is similar to the actual treatment condition in HIMAC. Carbon ions entered to a water phantom and all of the primary carbon ions were stopped in the water. The OpenPET detector was positioned 30cm apart from the backside of the water phantom at an angle of 30 degree. A coincidence detector was positioned at the opposite side of the water phantom. As a result, the sufficient crystal identification performance was achieved with slight deterioration of the position histograms.2010 Nuclear Science Symposium and Medical Imaging Conferenc

X-Ray Detector Made of Plastic Scintillators and WLS Fiber for Real-Time Dose Distribution Monitoring in Interventional Radiology

Interventional radiology (IVR) is a medical subspecialty of radiology to realize image-guided surgical procedures using imaging modalities, such as x-ray fluoroscopy. Recently, IVR is increasingly used in treatment of vascular lesions due to its low invasiveness. On the other hand, skin injuries due to prolonged x-ray exposure during the procedure have been reported. Therefore, monitoring of skin dose is desired in clinical sites for reduction of excessive x-ray exposure. We propose a real time dose distribution monitor for IVR. Some scintillation detectors which consist of low stopping power materials, such as plastic scintillators, are placed on a stretchable cap which can be worn by the patient. Scintillation light is fed to photo detectors outside the FOV through plastic optical fibers. This arrangement means that there are only radiolucent materials in the FOV and the proposed dose monitor does not interfere with the IVR procedure. As a result, the proposed monitor realizes real-time monitoring of the dose distribution on the patients skin. As the first step, we are developing a prototype x-ray detector element which consists of plastic scintillators and a wavelength shifting (WLS) fiber connected to the optical fiber. The square shaped WLS fiber is sandwiched by two plastic scintillators with a plate shape and dimensions of 10.0 mm x 4.5 mm x 1.0 mm. Scintillation light generated in the plastic scintillators is captured and converted to different wavelength light in the WLS fiber. The converted photons are transported to a MPPC through the 1 m length optical fiber which has the same diametrical size as the WLS fiber. We conducted evaluation experiments of detector performance with synchrotron-generated X-rays in the beamline BL-14A at the Photon Factor and micro CT (R_mCT2, RIGAKU) operating in the projection mode. The experimental results indicated that the proposed detector can measure X-ray doses in real-time with at least a 30 s interval.2012IEEE NSS&MI

Performance evaluation of four-layer DOI detectors

Multi pixel photon counters (MPPC) have many advantages to be used in PET detector, such as high internal gain, high photon detection efficiency, lower power supply and insensitivity to magnetic fields. However, the saturation effect is unavoidable phenomenon for PET detectors using MPPCs which need to collect large number of scintillation photons to achieve high resolutions. In a lot of cases, pulse height of PET detectors using MPPCs are saturated in high energy region. On the other hand, since our DOI encoding method previously presented is sharing scintillation photons to multiple pixels, the saturation effect can be suppressed. We constructed prototype four-layer detectors using two MPPC arrays and evaluated their detector performances. We constructed the prototype detector consisting of four layers of a 6 x 6 array with Lu2(1-x)Y2x SiO5 (LYSO) (Lu: 98 %, Y: 2 %) (Proteus Inc., U. S. A.) crystals, and a MPPC array with a 4 x 4 pixels array (S11064 series, Hamamatsu Photonics K.K. ). The size of each crystal element is 1.46 mm x 1.46 mm x 4.5 mm and all surfaces of crystal elements were chemically etched. For comparison, the two types of MPPC, S11064-050P (3600 cells) and S11064-025P (14400 cells), were used in the experiment. As a result, the all of the crystals of the detector using 050P were clearly identified while the crystal identification performance of the detector using 025P was degraded due to lower photon detection efficiency. The energy resolution of 11.0-13.6% (050P) and 12.7-15.2% (025P) were achieved for each detector. No saturations were observed for both detectors under the 511keV energy region.2010 Nuclear Science Symposium and Medical Imaging Conferenc

A staggered 3-layer DOI PET detector using BaSO4 reflector for enhanced crystal identification and inter-crystal scattering event discrimination capability

The spatial resolution of small animal positron emission tomography (PET)scanners can be improved by the use of crystals with fine pitch and rejection of inter-crystal scattering (ICS) events, which leads to a better quantification of radiopharmaceuticals. On the other hand, depth-of-interaction (DOI) information is essential to preserve the spatial resolution at the PET field-of-view(FOV) periphery while keeping the sensitivity. In this study we proposed a novel staggered 3-layer DOI detector using BaSO4 reflector material for an enhanced crystal identification performance as well as ICS event rejection capability over those of ESR reflector based DOI detectors. The proposed staggered 3-layerDOI detector had 3-layer staggered LYSO crystal arrays(crystal pitch = 1 mm), an acrylic light guide, and a 4 × 4 SiPM array. The 16 SiPM anode signals were read out by using a resistive network to encode the crystal position and energy information while the timing signal was extracted from the common cathode. The crystal map quality was substantially enhanced by using the BaSO4 reflector material as compared to that of the ESR reflector due to the low optical crosstalk between the LYSO crystals. The ICS events can be rejected with BaSO4 by using simple pulse height discrimination thanks to the light collection efficiency difference that depends on the crystal layers. As a result, the totalnumber of events was decreased around 26% with BaSO4 as compared to that of ESR. The overall energy resolution and coincidence timing resolution with BaSO4were 19.7 ± 5.6% and 591 ± 160 ps, respectively which were significantly worse than 10.9 ± 2.2% and 308 ± 23 ps values of ESR because of the relatively low light collection efficiency with BaSO4 (1057 ± 308 ADC) compared to that of ESR (1808 ± 118 ADC). In conclusion, we found the proposed staggered 3-layer DOI detector using the BaSO4 reflector material with ICS event rejection capability can be a costeffective solution for realizing high resolution and highly sensitive small animal PET scanners while minimizing the complexity of the SiPM readout circuit

Optimization of a Staggered 3-Layer DOI PET Detector with a 1 mm LYSO Pitch for High-Resolution Small Animal PET Imaging

Small animal positron emission tomography (PET) requires a submillimeter resolution for better quantification of radiopharmaceuticals. The aim of this study was to develop a staggered 3-layer depth-of-interaction (DOI) PET detector with a 1 mm crystal pitch for realizing a 0.5 mm small animal PET scanner of 52 mm ring diameter. The proposed small animal DOI PET detector had 3-layer staggered LYSO crystal arrays, an acrylic light guide with a 1 mm thickness, and a 4×4 SiPM (Hamamatsu, S13361-3050NE-04, Japan) array with a pixel pitch of 3.2 mm. The LYSO crystal had dimensions of 0.9 × 0.9 × 5.0 mm3 with a pitch of 1 mm. The 1st (10 × 9), 2nd (10 × 10), and 3rd (11 × 11) LYSO layers were stacked with a staggered configuration to encode DOI information in the 2D crystal map. In order to investigate the optimal reflector material and light guide thickness, the performance of the PET detector module was evaluated with different reflectors (ESR and BaSO4), and different light guide thicknesses (0.5, 1.0, and 2.0 mm). Sixteen SiPM anode signals were multiplexed into four positional signals by using a resistive network. The SiPM analog signals were digitized by CAMAC DAQ. The BaSO4 reflector resulted in better crystal identification than the ESR did. However, the energy resolution with the BaSO4 reflector (15.8±2.0%) was worse than that of the ESR reflector (11.1±1.0%). The acrylic light guide thickness of 1 mm resulted in the best crystal identification for both BaSO4 and ESR reflectors. In conclusion, a staggered 3-layer DOI PET detector with a 1 mm crystal pitch was developed by using a 1 mm thick light guide and BaSO4 reflector. In the near future, a prototype high-resolution small animal DOI PET scanner will be developed.2019 IEEE Nuclear Science Symposium and Medical Imaging Conferenc

A prototype real-time dose distribution monitoring system using plastic scintillators connected to optical fiber for interventional radiology

Interventional radiology (IVR) is a medical subspecialty of radiology to realize image-guided surgical procedures using imaging modalities, such as X-ray fluoroscopy. Recently, monitoring of skin dose is desired at clinical sites to reduce skin injuries by excessive X-ray exposure during the IVR procedures.We proposed a real-time dose distribution monitoring system for IVR. Some scintillation detectors which consist of low stopping power materials, such as plastic scintillators, are placed on a stretchable cap which can be worn by the patient. Scintillation light is fed to photo detectors outside the FOV through plastic optical fibers. This arrangement means that there are only radiolucent materials in the FOV and the proposed dose monitor does not interfere with the IVR procedure. As a result, the proposed monitor realizes real-time monitoring of the dose distribution on the patient\u27s skin.We are developing a prototype of the proposed system which consists of three X-ray detectors. Each X-ray detector consists of a square-shaped plastic scintillator (BC400), optical fiber and photodiode. Dimensions of the plastic scintillator are 10.0 mm x 10.0 mm x 1.0 mm. A corner of the plastic scintillator is cut and connected to the plastic optical fiber (Eska GH4001) which has a 1.0 mm diameter and 1.5 m length. The scintillation photons are transported to a silicon photodiode (S1337-66BQ, Hamamatsu Photonics K. K.) through the optical fiber Each photodiode output is independently fed to a current-to-voltage conversion amplifier and measured with a 16ch multi function DAQ (NI USB-6351, National instruments) and displayed in real-time by LabView-based software.We conducted evaluation experiments of detector performance with the micro CT apparatus operating in the projection mode. The experimental results indicated that the proposed dose monitoring system could measure real-time dose distribution with at least a 1 s interval.The 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference, and Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors worksho