arXiv subjects

Xiaochun Wang

Publications and source records attributed to Xiaochun Wang.

5 recordsLinked to original sources

arXiv2026

Ridge-filter crosstalk in conformal proton FLASH planning: dependence on beamlet pitch and iterative mitigation

Objective: Patient-specific ridge filters (PSRFs) can enable conformal single-energy proton FLASH delivery without energy switching. However, converting optimized spot-based dose distributions into physically adjacent ridge-filter structures may introduce inter-beamlet modulation errors not captured by conventional isolated-spot optimization. This study characterized ridge-filter (RF) crosstalk, evaluated its dependence on the beam-width-to-pitch relationship, and developed an iterative mitigation strategy. Approach: A Monte Carlo dose influence matrix was generated for monoenergetic proton beamlets passing through RFs of varying thickness. A baseline spot-weighted IMPT plan was optimized to meet dose constraints and converted into PSRF geometries. PSRF dose distributions were calculated by explicitly modeling the PSRF in the scanned beam path. RF crosstalk was quantified by comparing PSRF and baseline IMPT plans. Lateral beamlet spacings of 8, 10, 12, and 15 mm were evaluated using gamma analysis, DVH metrics, and mean relative dose difference. An iterative re-optimization method was tested in water-phantom and patient CT geometries. Results: RF crosstalk produced hot and cold spots, reducing agreement between PSRF and baseline IMPT plans. For the same spot size and target geometry, crosstalk increased as beamlet spacing decreased. Iterative re-optimization substantially reduced dose discrepancies, lowering the mean relative dose difference in the target from 8.9% to 3.4% in water and from 3.7% to 1.8% in CT. Significance: RF crosstalk is an important source of dose inconsistency in ridge-filter-based conformal proton FLASH planning. Its dependence on the beam-width-to-pitch relationship and mitigation through iterative re-optimization provide a practical framework for improving the accuracy and robustness of patient-specific single-energy proton FLASH delivery.

physics.med-ph↗

arXiv2025

Language modulates vision: Evidence from neural networks and human brain-lesion models

Comparing information structures in between deep neural networks (DNNs) and the human brain has become a key method for exploring their similarities and differences. Recent research has shown better alignment of vision-language DNN models, such as CLIP, with the activity of the human ventral occipitotemporal cortex (VOTC) than earlier vision models, supporting the idea that language modulates human visual perception. However, interpreting the results from such comparisons is inherently limited due to the "black box" nature of DNNs. To address this, we combined model-brain fitness analyses with human brain lesion data to examine how disrupting the communication pathway between the visual and language systems causally affects the ability of vision-language DNNs to explain the activity of the VOTC. Across four diverse datasets, CLIP consistently captured unique variance in VOTC neural representations, relative to both label-supervised (ResNet) and unsupervised (MoCo) models. This advantage tended to be left-lateralized at the group level, aligning with the human language network. Analyses of 33 stroke patients revealed that reduced white matter integrity between the VOTC and the language region in the left angular gyrus was correlated with decreased CLIP-brain correspondence and increased MoCo-brain correspondence, indicating a dynamic influence of language processing on the activity of the VOTC. These findings support the integration of language modulation in neurocognitive models of human vision, reinforcing concepts from vision-language DNN models. The sensitivity of model-brain similarity to specific brain lesions demonstrates that leveraging manipulation of the human brain is a promising framework for evaluating and developing brain-like computer models.

q-bio.NC↗

arXiv2024

Mimicking large spot-scanning radiation fields for proton FLASH preclinical studies with a robotic motion platform

Previously, a synchrotron-based horizontal proton beamline (87.2 MeV) was successfully commissioned to deliver radiation doses in FLASH and conventional dose rate modes to small fields and volumes. In this study, we developed a strategy to increase the effective radiation field size using a custom robotic motion platform to automatically shift the positions of biological samples. The beam was first broadened with a thin tungsten scatterer and shaped by customized brass collimators for irradiating cell/organoid cultures in 96-well plates (a 7-mm-diameter circle) or for irradiating mice (1-cm2 square). Motion patterns of the robotic platform were written in G-code, with 9-mm spot spacing used for the 96-well plates and 10.6-mm spacing for the mice. The accuracy of target positioning was verified with a self-leveling laser system. The dose delivered in the experimental conditions was validated with EBT-XD film attached to the 96-well plate or the back of the mouse. Our film-measured dose profiles matched Monte Carlo calculations well (1D gamma pass rate >95%). The FLASH dose rates were 113.7 Gy/s for cell/organoid irradiation and 191.3 Gy/s for mouse irradiation. These promising results indicate that this robotic platform can be used to effectively increase the field size for preclinical experiments with proton FLASH.

physics.med-ph↗

arXiv2012

Nuclear Shell Structure Evolution Theory

The Self-similar-structure shell model (SSM) comes from the evolution of the conventional shell model (SM) and keeps the energy level of SM single particle harmonic oscillation motion. In SM, single particle motion is the positive harmonic oscillation and in SSM, the single particle motion is the negative harmonic oscillation. In this paper a nuclear evolution equation (NEE) is proposed. NEE describes the nuclear evolution process from gas state to liquid state and reveals the relations among SM, SSM and liquid drop model (DM). Based upon SSM and NEE theory, we propose the solution to long-standing problem of nuclear shell model single particle spin-orbit interaction energy . We demonstrate that the single particle motion in normal nuclear ground state is the negative harmonic oscillation of SSM[1][2][3][4] Key words: negative harmonic oscillation, nuclear evolution equation, self-similar shell model

nucl-th↗

arXiv2012

Spin-Orbit Interaction of Nuclear Shell Structure

Single particle spin-orbit interaction energy problem in nuclear shell structure is solved through negative harmonic oscillator in the self-similar-structure shell model (SSM) [4] and considering quarks' contributions on single particle spin and orbit momentum. The paper demonstrates that single particle motion in normal nuclei is described better by SSM negative harmonic oscillator than conventional shell model positive harmonic oscillator[1][2][3]. The proposed theoretical formula for spin orbit interaction energy agrees well to experiment measurements.

nucl-th↗