arXiv subjects

I-Chun Cho

Publications and source records attributed to I-Chun Cho.

3 recordsLinked to original sources

arXiv2026

Using Fast Reading Current Integrator for Advanced Ion Beam Diagnostics Across Continuous and Pulsed Modes

A fast-reading current integrator is developed for high time-resolution and low-noise ion beam diagnostics under both continuous-wave and pulsed operating conditions. The system combines a low-leakage transimpedance front-end with a hybrid digitization architecture based on charge-balancing and voltage-to-frequency conversion. The input current is converted into a pulse stream corresponding to discrete charge quanta, enabling event-driven measurement with temporal resolution down to 0.5 ms while preserving a wide dynamic range and high linearity. The system further enables real-time pulse selection for instantaneous dose-rate estimation and reconstruction of time-dependent beam structures. A deterministic beam-interrupt signal is generated within <1 us upon reaching a predefined charge threshold, enabling fast feedback control. Additional functionalities, including threshold- and slope-based gating as well as phase-sensitive detection, enhance performance under noisy or modulated beam conditions. Calibration with precision current sources and beamline detectors demonstrates stable operation with excellent linearity and timing fidelity. The proposed system provides a compact and flexible platform for next-generation ion beam diagnostics requiring fast response, large dynamic range, and time-resolved measurement.

physics.ins-det↗

arXiv2025

Mapping of discrete range modulated proton radiograph to water-equivalent path length using machine learning

Objective. Proton beams enable localized dose delivery. Accurate range estimation is essential, but planning still relies on X-ray CT, which introduces uncertainty in stopping power and range. Proton CT measures water equivalent thickness directly but suffers resolution loss from multiple Coulomb scattering. We develop a data driven method that reconstructs water equivalent path length (WEPL) maps from energy resolved proton radiographs, bypassing intermediate reconstructions. Approach. We present a machine learning pipeline for WEPL from high dimensional radiographs. Data were generated with the TOPAS Monte Carlo toolkit, modeling a clinical nozzle and a patient CT. Proton energies spanned 70-230 MeV across 72 projection angles. Principal component analysis reduced input dimensionality while preserving signal. A conditional GAN with gradient penalty was trained for WEPL prediction using a composite loss (adversarial, MSE, SSIM, perceptual) to balance sharpness, accuracy, and stability. Main results. The model reached a mean relative WEPL deviation of 2.5 percent, an SSIM of 0.97, and a proton radiography gamma index passing rate of 97.1 percent (2 percent delta WEPL, 3 mm distance-to-agreement) on a simulated head phantom. Results indicate high spatial fidelity and strong structural agreement. Significance. WEPL can be mapped directly from proton radiographs with deep learning while avoiding intermediate steps. The method mitigates limits of analytic techniques and may improve treatment planning. Future work will tune the number of PCA components, include detector response, explore low dose settings, and extend multi angle data toward full proton CT reconstruction; it is compatible with clinical workflows.

physics.med-ph↗

arXiv2023

Proton FLASH irradiation platform for small animal setup at Chang Gung Memorial Hospital

Background : Proton flash therapy is an emergency research topic in radiation therapy since the Varian announced the promising results from the first in human clinical trial of Flash therapy recently. However, it still needs a lot of researches on this topic, not only to understand the mechanism of the radiobiological effects but also to develop an appropriate dose monitoring system. Purpose : In this study we setup an experimental station for small animal proton Flash irradiation in a clinical machine. The dose monitoring system is able to provide real-time irradiation dose and irradiation time structure. Methods : The dose monitoring system includes homebrewed transmission ionization chamber (TIC), plastic scintillator based beam position monitor, and Poor Man Faraday Cup (FC). Both TIC and FC are equipped with a homebrewed fast reading current integral electronics device. The imaging guidance system comprises a moveable CT, laser, as well as attaching a bead on the body surface of the mouse can accurately guide the testing small animal in position. Results : The dose monitoring system can provide the time structure of delivered dose rate within 1 ms time resolution. Experimental testing results show that the highest dose in one pulse of 230 MeV proton that can be delivered to the target is about 20 Gy during 199 ms pulse period at 100 Gy/s dose rate. Conclusion : A proton research irradiation platform dedicated for studying small animal Flash biological effects has been established at Chang Gung Memorial Hospital. The final setup data represent a reference for the beam users to plan the experiments as well as for the improvement of the facility.

physics.med-ph↗