The INTRABEAM system (Carl Zeiss Meditec AG, Jena, Germany) is an electronic brachytherapy (eBT) device designed for intraoperative radiotherapy applications. To date, the INTRABEAM x-ray source has not been characterized according to the AAPM TG-43 specifications for brachytherapy sources. This restricts its modelling in commercial treatment planning systems (TPSs), with the consequence that the doses to organs at risk are unknown. The aim of this work is to characterize the INTRABEAM source according to the TG-43 brachytherapy dosimetry protocol. The dose distribution in water around the source was determined with Monte Carlo (MC) calculations. For the validation of the MC model, depth dose calculations along the source longitudinal axis were compared with measurements using a soft x-ray ionization chamber (PTW 34013) and two synthetic diamond detectors (microDiamond PTW TN60019). In our results, the measurements in water agreed with the MC model calculations within uncertainties. The use of the microDiamond detector yielded better agreement with MC calculations, within estimated uncertainties, compared to the ionization chamber at points of steeper dose gradients. The radial dose function showed a steep fall-off close to the INTRABEAM source (10 mm) with a gradient higher than that of commonly used brachytherapy radionuclides (¹⁹²Ir, ¹²⁵I and ¹⁰³Pd), with values of 2.510, 1.645 and 1.232 at 4, 6 and 8 mm, respectively. The radial dose function partially flattens at larger distances with a fall-off comparable to that of the Xoft Axxent (iCAD, Inc., Nashua, NH) eBT system. The simulated 2D polar anisotropy close to the bare probe walls showed deviations from unity of up to 55% at 10 mm and 155. This work presents the MC calculated TG-43 parameters for the INTRABEAM, which constitute the necessary data for the characterization of the source as required by a TPS used in clinical dose calculations.

INTRABEAM 系统（Carl Zeiss Meditec AG，耶拿，德国）是一种电子近距离放射治疗 (eBT) 设备，专为术中放射治疗应用而设计。迄今为止，INTRABEAM X 射线源尚未根据 AAPM TG-43 近距离放射治疗源规范进行表征。这限制了其在商业治疗计划系统（TPS）中的建模，导致处于危险中的器官的剂量未知。这项工作的目的是根据 TG-43 近距离放射治疗剂量测定协议表征 INTRABEAM 源。通过蒙特卡罗 (MC) 计算确定源周围水中的剂量分布。为了验证 MC 模型，将沿源纵轴的深度剂量计算与使用软 X 射线电离室 (PTW 34013) 和两个合成金刚石探测器 (microDiamond PTW TN60019) 的测量进行了比较。在我们的结果中，水中的测量结果与 MC 模型计算结果一致，但存在不确定性。与电离室相比，在剂量梯度更陡的点，使用 microDiamond 检测器在估计的不确定性范围内与 MC 计算产生了更好的一致性。径向剂量函数显示靠近 INTRABEAM 源 (10 mm) 的陡峭下降，其梯度高于常用的近距离放射治疗放射性核素（¹⁹² Ir、¹²⁵ I 和¹⁰³ Pd），在处的值为 2.510、1.645 和 1.232。分别为 4、6 和 8 毫米。径向剂量函数在较大距离处部分变平，其衰减与 Xoft Axxent（iCAD, Inc.，纳舒厄，新罕布什尔州）eBT 系统相当。靠近裸露探头壁的模拟 2D 极各向异性显示，在 10 mm 和 155 处，与统一的偏差高达 55%。这项工作介绍了 MC 计算的 INTRABEAM TG-43 参数，这些参数构成了表征临床剂量计算中使用的 TPS 所需的来源。