Program Information
Computing the Blood DVH
D Craft1*, C Grassberger2 , (1) Massachusetts General Hospital, Cambridge, AA, (2) Massachusetts General Hospital, Boston, MA
Presentations
TH-EF-FS1-4 (Thursday, August 3, 2017) 1:00 PM - 3:00 PM Room: Four Seasons 1
Purpose: While dose-volume-histograms have been the workhorse of treatment planning and response modeling for decades, computing a DVH for the blood has not been described. White blood cells, in particular lymphocytes, are sensitive to low levels of radiation (in plating studies, 1.65 Gy of radiation killed 90% of the human lymphocytes), and it is increasingly known that radiation therapy can deplete levels of lymphocytes, which is correlated with organ toxicities and possibly tumor eradication.
Methods: We describe a patient-specific blood flow model coupled with a dynamic simulation of the radiation delivery process. For the blood simulation, we use a compartmentalized (“zero D”) approach which models blood as flow rates and delay times between different organ compartments of the body. This information is scaled using the patient's resting heart rate and weight. For the dose delivery information, which in general could be protons (passive scattering or scanned beams) or photons (IMRT, VMAT, or 3D conformal), we assume we have a photon plan given by a DICOM file in static delivery mode (3D or step-and-shoot). Given the machine's dose rate, we map each field onto the patient and use the blood flow coupled with the dosimetry of each field, to compute the field-wise blood volume-dose relationship. Mixing time considerations for blood are used to justify decoupling the individual beam angles (by assuming mixing between beam angles) for the blood impact computations.
Results: We demonstrate the computation of a blood DVH for a brain case and an esophageal case. We also present preliminary data which relates the blood DVH to white blood cell counts taken over the course of therapy.
Conclusion: We propose to include the blood DVH into treatment planning, in general and particularly for plans which involve radiation dose to organs of significant blood flow, like heart, liver, kidneys, and brain.
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