A Geant4 tool for edge-illumination X-ray phase-contrast imaging

The PEPI project is developing a new experimental facility integrating a chromatic photon-counting detector within an edge-illumination (EI) phase-contrast setup. In this context, a novel Geant4-based simulation tool has been introduced with the aim of defining the optimal design of the experimental setup. The code includes a custom X-ray refraction process and allows simulating the whole EI system, comprising a polychromatic and extended source, absorbing masks, substrates, their movement during acquisition, and X-ray detection. In this paper, a realistic spectral detector model is introduced and its energy response validated against experimental data acquired with synchrotron radiation at energies between 26 and 50 keV. Moreover, refraction and transmission images of a plastic phantom are reconstructed from simulation data and successfully compared with theoretical predictions. Finally, an optimization study aiming at finding the effect of the X-ray focal spot size (i.e. spatial coherence) on image quality is presented; the results suggest that, in the considered configuration, the system can tolerate source sizes up to 30 μm, while, for a fixed exposure time, the best signal-to-noise ratio in refraction images is found for source sizes in the order of 10 to 15 μm.

Planar EPID-Based Dosimetry for SRS and SRT Patient-Specific QA

The study’s purpose was to develop and validate Electronic Portal Imaging Device (EPID)-based dosimetry for Stereotactic Radiosurgery (SRS) and Stereotactic Radiation Therapy (SRT) patient-specific Quality Assurance (QA). The co-operation between extended Source-to-Imager Distance (SID) to reduce the saturation effect and simplify the EPID-based dosimetry model was used to perform patient-specific QA in SRS and SRT plans. The four parameters were included for converting the image to dose at depth 10 cm; dose-response linearity with MU, beam profile correction, collimator scatter and water kernel. The model accuracy was validated with 10 SRS/SRT plans. The traditional diode arrays with MapCHECK were also used to perform patient-specific QA for assuring model accuracy. The 150 cm-SID was found a possibility to reduce the saturation effect. The result of model accuracy was found good agreement between our EPID-based dosimetry and TPS calculation with GPR more than 98% for gamma criteria of 3%/3 mm, more than 95% for gamma criteria of 2%/2 mm, and the results related to the measurement with MapCHECK. This study demonstrated the method to perform SRT and SRT patient-specific QA using EPID-based dosimetry in the FFF beam by co-operating between the extended SID that can reduce the saturation effect and estimate the planar dose distribution with the in-house model.

Study And Investigation of Silicon Extended Source Vertical Double Gate Tunnel Transistor For Analog/RF Performance

In this paper, a Silicon Double Gate tunnel field effect transistor with Extended Source (ESVDG-TFET) is disclosed while addressing the need for dc/switching and analog/RF applications using Silvaco-Atlas simulator which is used to examine and explore the performance of the proposed device. The mechanics of band-to-band tunnelling and accompanying carrier injection are used to illustrate the operation of the proposed silicon ESVDG-TFET device. The gate is designed to overlap with extended source region along with N+ pockets and channel in order to facilitate both the lateral and vertical tunnelling . The silicon ESVDG-TFET provide lower subthreshold swing of 10.1 mV/decade that allow higher ratio of ION / IOFF of 1013 for optimized device structural parameters with threshold voltage of 0.35 V. Moreover, peak transconductance of 800 uS/ um, cutoff frequency of 82 GHz, gain bandwidth product of 16.8 GHz and transit time of 1p sec is obtained by proposed device.