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A Dynamic Model for Radiobiological Response of Spinal Cord to Radiation Damage

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J Li

J Li*, M Chan , C Shi , Memorial Sloan-Kettering Cancer Center, Basking Ridge, NJ


SU-I-GPD-T-656 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: Evaluation of spinal cord dose tolerance for retreatment requires an estimate of cord damage from previous irradiation. When the spinal cord is irradiated, multiple types of surrounding cells coordinate their responses to the radiation damages. This study is to model time dependent cellular interactions within irradiated spinal cord which has not been addressed in previous studies.

Methods: We developed a three-dimensional ordinary differential equation model of cellular interaction consisting of a radiation injury, an inflammatory mediator and a repairing agent. After initial radiation damage, a cellular injury can be either reduced or extended through competing processes of inflammatory and repairing responses. Inflammatory mediator can be excited by injury or suppressed by repairing agents. Finally a repairing agent is recruited by the reduced inflammatory responses and radiation injury through a sigmoidal coupling function and is cleared with an intrinsic rate. Model parameters can be chosen so that its behaviors resemble experimental results.

Results: The model exhibits behavior similar to what is observed in experimental results: when the amount of initial radiation damage is small, the inflammatory response decreases gradually after increasing significantly at the onset. The radiation injury is being repaired with new cells regenerated. On the other hand, when the initial radiation dose is large, the inflammatory response continues to increase and causes more cellular damages. The cellular repair process is suppressed and this in turn induces more inflammatory response. Eventually the feedback processes become so unstable that both the inflammatory response and injury increase exponentially

Conclusion: A three-dimensional model is constructed to simulate the inflammatory and repairing responses to the spinal cord radiation damage. In general, the model can exhibit important features observed in experimental studies. Validation through comparison with experimental and clinical data will lead to a better estimate of time dependent cord tolerance for retreatment dose.

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