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Computational Modeling of Microbeam Irradiation in Microvasculature Network

W Gu1, M Alp2, L Dong3, B Teo3, T Li3, K Sheng1, J Zou3*, (1) UCLA School of Medicine, Los Angeles, CA, (2) Covenant Health, Knoxville, TN, (3) University of Pennsylvania, Philadelphia, PA

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose:
Preclinical studies show superior normal tissue sparing in Microbeam Radiation Therapy while maintaining effective tumor damage. The vascular structure is suggested to be related to the enhanced therapeutic ratio. In this work, an in silico microvasculature network is built. Both uniform beam (UB) and microbeam (MB) irradiation are modeled to assess damage in the microvasculature.

Methods:
A spherical microvasculature network is built with 1-mm radius and surrounded by microvessels with a thickness of 250µm. The stochastic structure is first generated with node density, branch angle, and length distribution from experimental data. Then the vessel radius and blood flow are acquired by Murray’s and Poiseuille’s laws in an iterative way. The radiation damage is modeled by stochastic dose-dependent endothelial cell damage that leads to breakage of dysfunctional vascular branches. Both UB and MB irradiation are simulated. For UB, the integrated dose varies from 0Gy to 25Gy. The MB field has the same integrated dose. The peak-width is 50µm, the peak-to-peak distance is 200µm, and the peak-to-valley dose ratio (PVDR) varies from 5 to 150.

Results:
The model shows decreased vessel damage under MB irradiation compared with UB. Higher PVDR leads to better preservation of blood supply. Under an integrated dose of 5Gy and a PVDR between 5-150, the survival fraction of vascular length after MB irradiation is improved by 6-38% compared with UB, the mean distance of points in the tissue to the nearest vessel is improved from 171µm to 160-121µm. MB better preserves vessels of low flow rate. The mean flow rate of surviving vessels is 5-23% lower after MB compared to UB.

Conclusion:
A computational model is developed to simulate the microvascular structure and blood supply. Radiation damage is further applied to the model to investigate the effect of microbeam therapy in the microvasculature level.

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