SIMSEB: Unlocking the Dosimetric Potential of Sequential Boost Plans in VMAT Through Simultaneous Optimization

Abstract

was irradiated with 20 Gy of X-ray so that an irradiated part and a nonirradiated part were formed. After X-ray irradiation, Free radical imaging by DNP-MRI was performed. In addition, T1-weighted MRI images were obtained. Results: The EPR signal of Tempol capillaries were decreased depending on irradiation dose. In addition, a linear relationship between the spins of tempol radical and the irradiation dose was observed. The reduction rate of Tempol radical was 1.483/Gy. The gel phantom including Tempol radical was clearly visualized by DNP-MRI. Although the enhancement of gel phantom was observed in whole area before radiation treatment, the signal enhancement in half region (it is irradiated region by Linac) was decreased after radiation. In the T1-weighted MRI images, no signal change was observed between the X-ray irradiated part and the non-irradiated part. EPR signal of tempol in the capillary was decreased depending on radiation dose. Because hydroxyl radicals are generated by X-ray irradiation, Tempol was oxidized at first. After then, oxidized Tempol might be reduced by GSH in the gel phase. On the other hand, DNP-MR imaging of the phantom with radiation treatment was clearly visualized the site of the free radical reaction between Tempol/GSH gel with ROS. It is suggesting that the Tempol/GSH gel phantom would be useful for the redox sensor for radiation treatment. Conclusion: The distribution of free radical generation produced by X-ray irradiation was visualized by DNP-MRI with Tempol/GSH phantom.