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. 2023 Nov 8;68(22):10.1088/1361-6560/ad02d6.
doi: 10.1088/1361-6560/ad02d6.

A stochastic model of blood flow to calculate blood dose during radiotherapy

Chris Beekman  1 , Julia D Withrow  2 , Camilo M Correa Alfonso  2 , Shreya P Pathak  2 , Robert J Dawson  2 , Natalia Carrasco-Rojas  2 , Andrew R Sforza  2 , Carlos G Colon  2 , Wesley E Bolch  2 , Clemens Grassberger  1   3 , Harald Paganetti  1
Affiliations

A stochastic model of blood flow to calculate blood dose during radiotherapy

Chris Beekman et al. Phys Med Biol. .

Abstract

Purpose. Lymphopenia is a common side effect in patients treated with radiotherapy, potentially caused by direct cell killing of circulating lymphocytes in the blood. To investigate this hypothesis, a method to assess dose to circulating lymphocytes is needed.Methods. A stochastic model to simulate systemic blood flow in the human body was developed based on a previously designed compartment model. Blood dose was obtained by superimposing the spatiotemporal distribution of blood particles with a time-varying dose rate field, and used as a surrogate for dose to circulating lymphocytes. We discuss relevant theory on compartmental modeling and how to combine it with models of explicit organ vasculature.Results. A general workflow was established which can be used for any anatomical site. Stochastic compartments can be replaced by explicit models of organ vasculatures for improved spatial resolution, and tumor compartments can be dynamically assigned. Generating a patient-specific blood flow distribution takes about one minute, fast enough to investigate the effect of varying treatment parameters such as the dose rate. Furthermore, the anatomical structures contributing most to the overall blood dose can be identified, which could potentially be used for lymphocyte-sparing treatment planning.Conclusion. The ability to report the blood dose distribution during radiotherapy is imperative to test and act upon the current paradigm that radiation-induced lymphopenia is caused by direct cell killing of lymphocytes in the blood. We have built a general model that can do so for various treatment sites. The presented framework is publicly available athttp://github.com/mghro/hedos.

Keywords: Weibull distribution; blood dose; blood flow; organ vasculature; stochastic compartment model; tranfer function.

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Figures

Figure 1.
Figure 1.
a) Simplified depiction of the compartmental model. Stochastic compartments can be replaced by models of explicit vasculature as indicated. In b), the full list of included structures and their relative blood volume as maintained throughout the simulation. Reference values from ICRP 89 are also indicated.
Figure 2.
Figure 2.
Splitting off the tumor compartment from the original organ compartment.
Figure 3.
Figure 3.
Left: Phantom vasculature of the brain color coded for blood flow. Right: Centerlines are extracted, and its vertices (green) registered to a patient which is represented by orthogonal slices of the dose distribution. A mesh rendering of the patient brain is also shown for clarity (grey).
Figure 4.
Figure 4.
Fractional blood dose distributions (left) and the dose contributions of different structures (right). Top row: only lung and heart are considered and with particles describing uncorrelated motion. Middle row: explicit vasculature tracking in the lung and a random walk in the heart. Bottom row: explicit vasculature tracking in the lung and a random walk in all other indicated structures. Vertical axis: number of particles out of 100,000.
Figure 5.
Figure 5.
Fractional (right) and summed (right) blood dose distributions.
See this image and copyright information in PMC

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