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Modeling Blood Volume and Circulating Lymphocytes as a Critical Organ in Radiation Therapy

R Hobbs1*, S Ellsworth2 , S Grossman1 , (1) Johns Hopkins University, Baltimore, MD, (2) University of Indiana, Indianapolis, Indiana


(Tuesday, 7/31/2018) 3:45 PM - 4:15 PM

Room: Exhibit Hall | Forum 9

Purpose: Radiation Therapy irradiates blood and its components such as lymphocytes as the blood traverses the radiation field. Lymphopenia is a common consequence of chemo-radiation treatments and overall survival has been directly correlated in a wide range of disease types to lymphocyte count post-therapy. We propose a model that calculates dose to circulating blood on a patient-specific basis to estimate dose to circulating blood cells including lymphocytes.

Methods: Beam dose maps and CT data including MU per beam were exported from Pinnacle treatment planning system and loaded into in-house software. Anatomical information such as total blood volume, blood flow rate and blood content per tissue type were taken from the literature. Dose to blood “voxels� was calculated as the blood “voxels� flow through the beams, where the blood was assumed to redistribute evenly throughout the body after each beam and dose volume histograms (DVHs) to the circulating blood and lymphocytes were created.

Results: DVHs were compared between different modalities: small field vs. large field in prostate cancer, SBRT vs. IMRT in pancreas cancer, FFF vs. non-FFF, EBRT vs. HDR brachytherapy for endo-rectal cancer, ¹�³Pd seed implant vs. EBRT for prostate cancer and ¹³¹I vs. EBRT for thyroid cancer.

Conclusion: Blood volume can be used as a surrogate for estimating lymphocyte toxicity and should be considered when planning. The proposed model can be used to compare treatment plan and modalities to assist in reducing the lymphocyte toxicity.


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