arXiv subjects

Duncan Bohannon

Publications and source records attributed to Duncan Bohannon.

5 recordsLinked to original sources

arXiv2026

Circulating Lymphocytes Preservation in Lung Cancer Stereotactic Body Radiation Therapy with Ultra-Fast Proton Delivery Using Modularized Pin Ridge Filters

Purpose: Radiation-induced lymphopenia is an increasingly recognized toxicity in lung radiotherapy and has been linked to radiation exposure to circulating lymphocytes (CL). In intensity-modulated proton therapy (IMPT), prolonged pencil beam scanning (PBS) delivery may increase CL dose. We recently developed a patient-specific pin ridge filter (pRF) framework that enables ultra-fast proton delivery with a single beam energy. This study evaluated whether pRF-based lung stereotactic body radiotherapy (SBRT) plans delivered at conventional (pRFCONV) and FLASH dose rates (pRFFLASH) improve immune sparing using time-resolved blood dose accumulation and CL survival modeling. Methods: pRF plans were created for 10 lung SBRT patients previously treated with IMPT. PBS delivery simulations modeled spot delivery, scanning, and energy switching. Blood dose-volume histograms (bDVHs) were calculated with the hematological dose framework. CL survival fractions (SF) were estimated from bDVHs with saturation and linear-quadratic models derived from in-vitro survival data for CD4/CD8 CL. Results: Compared with IMPT, pRFCONV/pRFFLASH plans reduced delivery time (mean reductions: 85.3/99.9%) and irradiated blood volume per fraction (mean reductions: 52.9/81.3%). pRFCONV/pRFFLASH plans reduced blood V5cGy by 26.4/39.4%, and V50cGy by 4.5/6.9%, respectively. pRF plans improved modeled CL survival across all models and subpopulations. Unstimulated CD4/CD8 CL had the largest SF differences, for which mean saturation-model SF improved by 7.9/8.6% for pRFCONV (p=0.03/0.02) and 9.6/10.4% for pRFFLASH (p=0.02/0.01), respectively. Conclusion: pRF plans improved modeled CL survival by significantly shortening delivery time and reducing irradiation of circulating blood. Our findings suggest that pRF's ultra-fast delivery may provide a practical strategy for immune sparing in proton lung SBRT.

physics.med-ph↗

arXiv2025

Optimizing Transmission FLASH Radiotherapy for Large-Field Post-Mastectomy Breast Treatment

We investigated the effects of scanning speed, beam configuration, and dose-rate modeling on the FLASH effect in post-mastectomy proton transmission-beam (TB) planning and evaluated whether optimizing the spot-scanning path can enhance FLASH. Five left-sided post-mastectomy patients (32 Gy in 5 fractions) were replanned with single-energy (249 MeV) tangential TBs plus a clinical en face background beam. FLASH was evaluated with two models: Krieger's FLASH effectiveness model (FEM) and Folkerts' average dose-rate (ADR) framework. Plans used conventional pencil-beam scanning, split-field delivery, and GA-optimized spot sequences, with vertical scan speeds varied from 10 to 20 mm/ms. FLASH in normal tissues was defined as the percentage of voxels meeting the threshold (>= 4 Gy at >= 40 Gy/s); once a voxel met the criterion, a dose-adjustment factor of 0.67 was applied. The FLASH effect was highly sensitive to scanning pattern and model choice. Increasing vertical scan speed from 10 to 20 mm/ms increased FLASH in the CTV by 22% (ADR) and 12% (FEM); in skin it rose from 41.4% to 58.8% (ADR) and from 8.4% to 13.1% (FEM). Split-field delivery increased the temporal separation between vertical spot columns and yielded superior FLASH, including up to a 9.2 Gy reduction in CTV Dmean with ADR. GA-based optimization shortened scan time and achieved FLASH comparable to split-field delivery, with a CTV Dmean reduction of 7.87 Gy (ADR-GA) and skin Dmean reductions of 2-3 Gy. These findings indicate that FLASH outcomes depend strongly on scanning trajectory, scan speed, and model selection. In addition, path-minimizing spot-delivery optimization (e.g., GA) can further improve dose-rate distributions in healthy voxels.

physics.med-ph↗

arXiv2024

Adaptive Proton Therapy Using CBCT-Guided Digital Twins

This study aims to develop a digital twin (DT) framework to enhance adaptive proton stereotactic body radiation therapy (SBRT) for prostate cancer. Prostate SBRT has emerged as a leading option for external beam radiotherapy due to its effectiveness and reduced treatment duration. However, interfractional anatomy variations can impact treatment outcomes. This study seeks to address these uncertainties using DT concept, with the goal of improving treatment quality, potentially revolutionizing prostate radiotherapy to offer personalized treatment solutions. Our study presented a pioneering approach that leverages DT technology to enhance adaptive proton SBRT. The framework improves treatment plans by utilizing patient-specific CTV setup uncertainty, which is usually smaller than conventional clinical setups. This research contributes to the ongoing efforts to enhance the efficiency and efficacy of prostate radiotherapy, with ultimate goals of improving patient outcomes and life quality.

physics.med-ph↗

arXiv2022

A Retrospective Study on the Investigation of Potential Clinical Benefits of Online Adaptive Proton Therapy for Head and Neck Cancer

Online adaptive proton therapy (APT) is an ideal solution theoretically, which however is challenging to proton clinics. Although multiple groups have been endeavoring to develop online APT technology, there is a concern in the radiotherapy community about the necessity of online APT because of its unknown impact on treatment outcomes. Hence, we have performed a retrospective study to investigate the potential clinical effects of online APT for HN cancer patients in relative to the current offline APT via simulations. To mimic an online APT treatment course, we have recalculated and evaluated the actual dose of the current treatment plan on patient actual treatment anatomy captured by cone beam CT for each fraction. The cumulative dose of simulated online APT courses was compared to actual offline APT courses and the initially designed treatment plan dose. For patients 1 and 2, the simulated online ART course maintained a relatively higher CTV dose coverages than the offline ART course, particularly for CTV-Low, which led to an improvement of 2.66% and 4.52% in TCP of CTV-Low. For patients 3 and 4, with clinically comparable CTV dose coverages, the simulated online ART course achieved better OAR sparing than the offline ART course. The mean doses of right parotid and oral cavity were decreased from 29.52 Gy relative biological effectiveness (RBE) and 41.89 Gy RBE to 22.16 Gy RBE and 34.61 Gy RBE for patient 3, leading to a reduce of 1.67% and 3.40% in NTCP for the two organs. Compared to the current clinical practice, the retrospective study indicated that online APT tended to spare more normal tissues by achieving the clinical goal with merely half of the positional uncertainty margin. Future studies are needed to help identify the patients with large potential benefits prior to treatment to conserve scarce clinical resources.

physics.med-ph↗

arXiv2022

Feasibility Study of Hybrid Inverse Planning with Transmission Beams and Single-energy Spread-out Bragg Peaks for Proton Flash Radiotherapy

Ultra-high dose rate (FLASH) proton planning with only transmission beams (TBs) has limitations in normal tissue sparing. The single-energy spread-out Bragg peaks (SESOBPs) of FLASH dose rate have been demonstrated feasible for proton FLASH planning. A hybrid inverse optimization method was developed to combine the TBs and SESOBPs (TB-SESOBP) for FLASH planning. The SESOBPs were generated from spreading out the BPs by pre-designed general bar ridge filters and placed at the central target by range shifters to obtain a uniform dose within the target. The SESOBPs and TBs were fully sampled field-by-field allowing automatic spot selection and weighting in the optimization process. The TB-SESOBP plans were validated in comparison with the TB only (TB-only) plans and the plans with the combination of TBs and BPs (TB-BP) regarding 3D dose and dose rate distributions for five lung cases. Comparing to the TB-only plans, the mean spinal cord D1.2cc drastically reduced 41%, the mean lung V7Gy and V7.4Gy moderately reduced by up to 17% and the target dose homogeneity slightly increased in the TB-SESOBP plans. Comparable dose homogeneity was achieved in both TB-SESOBP and TB-BP plans. Besides, prominent improvements were achieved in lung sparing for the cases of relatively large targets by the TB-SESOBP plans comparing to the TB-BP plans. The targets were fully covered with the FLASH dose rate in all the three plans. For the OARs, V40Gy/s = 100% was achieved by the TB-only plans while V40Gy/s > 85% was obtained by the other two plans. We have demonstrated that the hybrid TB-SESOBP planning was feasible to achieve FLASH dose rate for proton therapy. The hybrid TB-SESOBP planning has great potential in improving OAR sparing while maintaining high target dose homogeneity, and can be potentially implemented for adaptive radiotherapy.

physics.med-ph↗