Proton radiotherapy has the potential to provide state-of-the-art dose conformality in the tumor area, reducing possible adverse effects on surrounding organs at risk. However, uncertainties in the exact location of the proton Bragg peak inside the patient prevent this technique from achieving full clinical potential. In this context, in vivo verification of the range of protons in patients is key to reduce uncertainty margins. Protoacoustic range verification employs acoustic pressure waves generated by protons due to the radio-induced thermoacoustic effect to reconstruct the dose deposited in a patient during proton therapy. In this paper, we propose to use the a priori knowledge of the shape of the proton dose distribution to create a dictionary with the expected ultrasonic signals at predetermined detector locations. Using this dictionary, the reconstruction of deposited dose is performed by matching pre-calculated dictionary acoustic signals with data acquired online during treatment.

The dictionary method was evaluated on a single-field proton plan for a prostate cancer patient. Dose calculation was performed with the open-source treatment planning system matRad, while acoustic wave propagation was carried out with k-Wave. We studied the ability of the proposed dictionary method to detect range variations caused by anatomical changes in tissue density, and alterations of lateral and longitudinal beam position.

Our results show that the dictionary-based protoacoustic method was able to identify the changes in range originated by all the alterations introduced, with an average accuracy of 1.4 mm. This procedure could be used for in vivo verification, comparing the measured signals with the precalculated dictionary.

质子放疗有潜力在肿瘤区域提供最先进的剂量适形性，从而减少对处于危险中的周围器官可能产生的不利影响。然而，患者体内质子布拉格峰的确切位置的不确定性阻止了该技术获得全部临床潜力。在这种情况下，对患者质子范围进行体内验证是减少不确定性范围的关键。原声范围验证利用由质子由于无线电感应的热声效应而产生的声压波来重建在质子治疗期间沉积在患者体内的剂量。在本文中，我们建议使用先验了解质子剂量分布的形状，以在预定的检测器位置创建带有预期超声信号的字典。使用该字典，通过将预先计算的字典声学信号与治疗期间在线获取的数据进行匹配，可以重建沉积剂量。

该词典方法是针对前列腺癌患者的单视野质子计划进行评估的。使用开源治疗计划系统matRad进行剂量计算，而使用k-Wave进行声波传播。我们研究了建议的字典方法检测由组织密度的解剖变化以及横向和纵向波束位置变化引起的范围变化的能力。

我们的结果表明，基于字典的原声方法能够识别由所有引入的变化引起的范围变化，平均精度为1.4 mm。该程序可用于体内验证，将测得的信号与预先计算的字典进行比较。