This study proposes a 10-bit low-power high-color-depth LCD column driver IC with two-stage multi-channel RDACs and switch resistance compensation. The design removes intermediate buffers from two-stage RDACs and uses global reference buffers to isolate the global resistor string and output channels. Because the global resistor string is isolated from output channels, the global resistor string can use a larger resistance value to achieve lower power consumption. This study proposes a class-AB buffer for the global reference buffers to compensate for the errors caused by the voltage drop on switches connected in series with the channel resistor string. The channel resistor strings also reuse the output stage current of the global buffer to reduce power consumption. A prototype of a 200-channel column driver was fabricated using 0.18-m/0.35-m CMOS technology with the worst DNL/INL being 1.2/1.1 LSB. The proposed 10-bit DAC occupies only 66 % of the area of a conventional 8-bit RDAC using the same technology. The 200-channel column driver consumes a total static current of only 0.38 mA.
In this research, characteristics of combination of PSPMTs (position sensitive photo-multiplier tube) to form a larger detection area is studied. A home-made linear divider circuit was built for merging signals and readout. Borosilicate glasses were chosen for the scintillation light sharing in the crossover region. Deterioration effect caused by the light guide was understood. The influences of light guide and crossover region on the separable crystal size were evaluated. According to the test results, a gamma camera with a crystal block of 90 × 90 mm2 covered area, composed of 2 mm LYSO crystal pixels, was designed and fabricated. Measured performances showed that this camera worked fine in both 511 keV and lower energy gammas. The light loss behaviour within the crossover region was analyzed and realized. Through count rate measurements, the 176Lu nature background didn't show severe influence on the single photon imaging and exhibited an amount of less than 1/3 of all the events acquired. These results show that with using light sharing techniques, combination of multiple PSPMTs in both X and Y directions to build a large area imaging detector is capable to be achieved. Also this camera design is feasible to keep both the abilities for positron and single photon breast imaging applications. Separable crystal size is 2 mm with 2 mm thick glass applied for the light sharing in current status.
Chemical exchange saturation transfer magnetic resonance imaging (CEST-MRI) is capable of both microenvironment and molecular imaging. The optimization of scanning parameters is important since the CEST effect is sensitive to factors such as saturation power and field homogeneity. The aim of this study was to determine if the CEST effect would be altered by changing the length of readout RF pulses. Both theoretical computer simulation and phantom experiments were performed to examine the influence of readout RF pulses. Our results showed that the length of readout RF pulses has unremarkable impact on the Z-spectrum and CEST effect in both computer simulation and phantom experiment. Moreover, we demonstrated that multiple refocusing RF pulses used in rapid acquisition with relaxation enhancement (RARE) sequence induced no obvious saturation transfer contrast. Therefore, readout RF pulse has negligible effect on CEST Z-spectrum and the optimization of readout RF pulse length can be disregarded in CEST imaging protocol.
In this research, Characteristics of combination of H8500 PSPMTs to form a larger detection area is studied. A home-made linear divider circuit was built for the merged signals readout. Borosilicate glasses with several thicknesses (0-5 mm) were chosen for scintillation light sharing in crossover region. The effects of light guide and crossover region on separable crystal size were evaluated. According to the test results, an imaging gamma head with larger crystal block with 89 x 89 mm2 covered area, composed of 2 mm LYSO pixels, was fabricated and tested. Measured performances showed that this imaging head worked fine in both 511 keV and lower energy gamma rays.Through count rate measurements, the influence of 176Lu nature background for single photon imaging was also presented. These results showed that using light sharing and linear resistor chain techniques, combination of PMTs in X,Y directions to build a large area imaging detector is still able to keep the ability of positron and single photons detections. Separable crystal size was 2 mm with 2 mm glass applied for light sharing in current status.
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