Devices and methods to directly measure absolute absorbed dose to water in non-standard complex beams in a radiotherapy clinical setting

放射治疗的目的是利用放射损伤肿瘤细胞，使其死亡（坏死）或无法繁殖（不育）。治疗效果与辐射剂量传递的准确性直接相关，而辐射剂量传递本身包括从辐射传递系统校准一直到剂量传递的几个步骤。目前的剂量学方案需要一个所谓的“参考”条件进行校准，传统上这是放射治疗交付设置的良好反映。然而，随着放射治疗递送技术的最新发展（例如MR-linac，断层治疗，射波刀，体积调制电弧治疗（VMAT），扫描质子束等），使用大静态场尺寸递送的低剂量/低剂量率辐射部分已经普遍转变为使用小，高度调制，复杂的场以相对高剂量率动态递送的高剂量部分。因此，患者的治疗条件（和放疗单位）正与参考校准条件相距甚远。这导致了更多的不确定性，或剂量测定中最严重的错误。我们的NSERC发现拨款的目标是通过创新和开发新一代的放射治疗探测器或修改现有的探测器和检测技术，在高度复杂的辐射输送模式中进行剂量测量，减少辐射剂量测定的不确定性，并大大减少用户错误的可能性。为此，研究的主要目标是：1)开发一种新的3d打印，便携式和完全可成像的水热量计，适合日常临床使用；2)使用(1)中提出的绝对剂量计，不仅可以在临床中以安全、准确的方式显示绝对剂量测量的可行性，而且还可以确定传统探测器的校正因子，这对许多这些新的、复杂的递送技术的未来剂量测定方案至关重要。基于我们之前将新的剂量计技术推向市场并为现代放射治疗新方案的发展做出贡献的实践改变剂量学的成功，我们的研究计划将对整体改善辐射剂量不确定性和减少小型和非标准辐射剂量测定的操作误差产生强烈的积极影响。

The goal of radiation therapy is to use radiation to damage tumor cells to an extent that they are either dead (necrotic), or not viable to reproduce (sterile). The treatment outcome is directly correlated with the accuracy of radiation dose delivery which itself is comprised of several steps starting from radiation delivery system calibration all the way to dose delivery. Current dosimetry protocols require a so-called `reference' conditions for calibration which traditionally has been a good reflection of radiotherapy delivery setup. However, with more recent novel developments in radiotherapy delivery technology (e.g. MR-linac, Tomotherapy, CyberKnife, Volumetric Modulated Arc Therapy (VMAT), scanned proton beams, etc.), there has been a general shift from low dose / low dose rate radiation fractions delivered using large static field sizes, to delivery of high dose fractions using small, highly modulated, complex fields dynamically delivered at relatively high dose rates. As such, the patient treatment conditions (and RT delivery units) are becoming far removed from reference calibration conditions. This has led to added uncertainties, or worst errors in dosimetry. The goal of our NSERC discovery grant is to reduce radiation dosimetry uncertainty and drastically decrease possibility of user error by innovating and developing new generation of detectors in radiation therapy or modification of current detectors and detection techniques for dose measurement in highly complex radiation delivery modalities. To that end, the main objectives of the research are: 1) To develop a new 3-D printed, portable and fully image-able water calorimeter appropriate for everyday clinical use; 2) to use the proposed absolute dosimeter in (1) to not only show feasibility of absolute dose measurement in a safe and accurate way in clinic, but to also determine correction factors for traditional detectors that will be essential to future dosimetry protocols in many of these new and complex delivery technologies. Building on our previous practice-changing dosimetry success of bringing new dosimeter technologies to market and contributing to the development of new protocols in modern RT, our research program will have strong positive impact on overall improvement of radiation dose uncertainty and reducing operator error in small and non-standard radiation dosimetry.