We report a new time-resolved optical measurement method which combines single photon counting and the spread spectrum time-resolved optical measurement method. A laser diode modulated with pseudo-random bit sequences replaces the short pulse laser used in conventional time-resolved optical systems, while a single photon detector records the pulse sequence in response to the modulated excitatio...

During last two decades, several photon counting detectors have been developed in our laboratory. One of the most promising detector coming from our group silicon K14 Single Photon Avalanche Diode (SPAD) is presented with its valuable features and space applications. Based on the control electronics, it can be operated in both gated and non-gated mode. Although it was designed for photon counti...

background: monte carlo method (mc) has played an important role in design and optimization of medical linacs head and beam modeling. the purpose of this study was to compare photon beam features of two commercial linacs, varian 21ex and elekta sl-25 using mcnp4c mc code. materials and methods: the 6mv photon beams of varian 21ex and elekta sl-25 linacs were simulated based on manufacturers pro...

Measuring fluorescence lifetimes of fast-moving cells or particles have broad applications in biomedical sciences. This paper presents a dynamic lifetime sensing (DFLS) system based on the time-correlated single-photon counting (TCSPC) principle. It integrates CMOS 192 × 128 avalanche diode (SPAD) array, offering an enormous photon-counting throughput without pile-up effects. We also proposed q...

Background: In conventional radiation therapy, regarding normal tissue tolerance, the treatment of bulk tumors is one of the remaining challenges. Grid Radiation Therapy (GRT) is a technique to deliver high doses, approximately 15 – 20 Gy per fraction, to several small volumes located in a large radiation field. This can be performed using a grid block. The current work has concentrate...

A beam spoiler is often used to increase the build-up dose near the surface for treatment of superficial treatment areas. Photon-beam spoilers produce a large amount of contaminant electrons, conditions for which standard, commercial treatment-planning system dose-calculation algorithms are inadequate for producing accurate dose calculations. In this study, we implemented a Monte Carlo (MC) dos...

In this report we study the dynamics of passive quenching in a single-photon avalanche diode. Our discussion is based on microscopic description electron-hole coupled to equivalent circuit device, consisting quench resistor and junction capacitance. Analytic expressions for resulting signal shape are derived from model simple electric field configurations, efficient numerical prescriptions give...