Division of Radiation Oncology, H. Lee Moffitt Cancer Center, Tampa, Florida, USA.
Department of Physics, University of South Florida, Tampa, Florida, USA.
J Appl Clin Med Phys. 2009 Sep 30;10(4):64-78. doi: 10.1120/jacmp.v10i4.3080.
In this paper, we described and characterized a novel biplanar diode array, and demonstrated its applicability to dosimetric QA of the step-and-shoot IMRT. It is the first commercially available device of its kind specifically designed for measurements at varying gantry angles. The detector consists of a cylindrical PMMA phantom with two orthogonal detector boards. There are a total of 1069 p-type 1 mm wide diode detectors covering the measurement area of 20 x 20 cm2 in each of the measurement planes. The orthogonal detector arrays ensure that the dose modulation information is not lost regardless of the beam incidence angle. For absolute calibration, the dose to the reference detector is calculated at the appropriate SSD and radiological depth by the treatment planning system and is scaled by the measured accelerator output. The directly measured rotational response on the central axis shows the maximum variation of approximately +/-3% in the narrow +/-1 degree angular intervals centered on the detector boards. This variation is reduced to less than +/- 2% outside of the four similarly centered +/-5 degrees angular intervals. For all detectors, the difference between the measured and calculated dose for a plan with twelve equally spaced beams is -0.2+/-0.9%. Of eleven IMRT plans, ten passed the gamma(3%,3mm) criterion at or above 95%, while one passed at 92%. Delta4 is a useful tool for IMRT QA, allowing for essentially instantaneous on-line analysis of absolute dose errors in 3D.
在本文中，我们描述并分析了一种新型的双平面二极管阵列，并展示了其在步进和射击调强放射治疗剂量学 QA 中的适用性。这是首个专门针对不同机架角度测量而设计的商业化同类设备。探测器由一个圆柱形 PMMA 体模和两个正交探测器板组成。在每个探测器板上，共有 1069 个 p 型 1 毫米宽的二极管探测器，覆盖了 20x20cm2 的测量区域。正交探测器阵列确保了无论射束入射角如何，剂量调制信息都不会丢失。为了进行绝对校准，通过治疗计划系统计算参考探测器在适当 SSD 和放射深度处的剂量，并通过测量的加速器输出进行缩放。在中心轴上直接测量的旋转响应显示，在以探测器板为中心的 +/-1 度狭窄角度间隔内，最大变化约为 +/-3%。这种变化在四个类似的以 +/-5 度为中心的角度间隔之外减小到小于 +/-2%。对于所有探测器，对于具有 12 个等间距射束的计划，测量和计算剂量之间的差异为 -0.2+/-0.9%。在 11 个调强计划中，有 10 个通过了伽马(3%,3mm)标准，通过率为 95%或以上，而一个通过了 92%。Delta4 是一种用于调强 QA 的有用工具，允许在 3D 中对绝对剂量误差进行即时在线分析。
