Rajapakse Arith, Outwater Coral, Brivio Davide, Sajo Erno, Zygmanski Piotr
Department of Radiation Oncology, Dana Farber Cancer Institute and Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Department of Radiation Oncology, Dana Farber Cancer Institute, Boston, Massachusetts, USA.
Med Phys. 2025 May;52(5):3258-3269. doi: 10.1002/mp.17756. Epub 2025 Mar 19.
In x-ray radiography and computed tomography (CT), absorbed dose is deposited in a radiation detector array in the form of charge carriers and collected. While these modalities are the standard for clinical imaging during the radiation therapy process, they require the use of bulk materials and adequate operating voltages. These constraints leave space for an imaging/dosimetry niche favoring low profile, low power, and non-invasive modalities.
The conversion of therapeutic radiation to absorbed dose begins with the generation of high energy electrons. If utilized correctly, the high energy particle currents (HEC) offer a unique prospect for a novel form of imaging and dosimetry. In this paper, we establish the theoretical and experimental framework behind the sensing of HEC by measuring currents in various homogeneous and heterogeneous phantoms and comparing the measured signals to both one-dimensional particle transport and Monte Carlo (MC) based simulations.
The experimental setup for HEC sensing consists of pairs of complementary electrodes placed upstream and downstream of the object or phantom in question. When irradiated with 6MV x-rays, two signals, s, and s, were collected with zero external bias. These signals are coupled to each other due to the distribution of HEC inside the phantom. Both homogeneous (water) and heterogeneous (water and bone) phantoms were irradiated, and the measured signals were reviewed against simulations (MCNP6, CEPXS).
The measured signals s and s (as a function of water equivalent thickness [WET]) for homogeneous phantoms matched the trends established by the corresponding radiation transport simulations; indicating that these signals convey information about the distribution of HEC inside the phantoms. Based on these findings, new signal metrics, α and β, were formalized and used to quantify the scanning of heterogeneous phantoms.
In this work, we demonstrated that information about the internal composition of an object can be obtained through HEC sensing. Specifically, the distribution of HEC inside of an object resulting from x-ray irradiation was measured using a simple system of planar electrodes and agreed well with radiation transport simulations. HEC sensing has the potential to be a disruptive method of imaging with its low power, low profile, and non-invasive nature.
在X射线摄影和计算机断层扫描（CT）中，吸收剂量以电荷载流子的形式沉积在辐射探测器阵列中并被收集。虽然这些模态是放射治疗过程中临床成像的标准，但它们需要使用块状材料和足够的工作电压。这些限制为有利于低轮廓、低功耗和非侵入性模态的成像/剂量测定领域留出了空间。
治疗性辐射向吸收剂量的转换始于高能电子的产生。如果正确利用，高能粒子电流（HEC）为一种新型成像和剂量测定形式提供了独特的前景。在本文中，我们通过测量各种均匀和非均匀体模中的电流，并将测量信号与一维粒子输运和基于蒙特卡罗（MC）的模拟进行比较，建立了HEC传感背后的理论和实验框架。
HEC传感的实验装置由放置在所研究物体或体模上游和下游的成对互补电极组成。当用6MV X射线照射时，在零外部偏置下收集两个信号s和s。由于体模内部HEC的分布，这些信号相互耦合。对均匀（水）和非均匀（水和骨）体模都进行了照射，并将测量信号与模拟（MCNP6、CEPX S）进行了对比。
均匀体模的测量信号s和s（作为水等效厚度[WET]的函数）与相应辐射输运模拟建立的趋势相匹配；表明这些信号传达了体模内部HEC分布的信息。基于这些发现，新的信号指标α和β被形式化，并用于量化非均匀体模的扫描。
在这项工作中，我们证明了可以通过HEC传感获得有关物体内部组成的信息。具体而言，使用简单的平面电极系统测量了X射线照射导致的物体内部HEC分布，并且与辐射输运模拟结果吻合良好。HEC传感凭借其低功耗、低轮廓和非侵入性的特性，有潜力成为一种具有颠覆性的成像方法。
