Department of Medical Physics, University Hospital of Heraklion, Staurakia, 71110 Crete, Greece.
Med Phys. 2011 Feb;38(2):830-5. doi: 10.1118/1.3538924.
To introduce a novel laser-based optical-CT scanner for the readout of three-dimensional (3D) radiation dosimeters.
The scanner employs a diode laser, a cylindrical lens, a motorized linear rail, a rotation stage, and a charge-coupled device camera. The scanner operates in a translate-rotate fashion and may be set up in two configurations depending on the orientation of the cylindrical lens. The attenuation coefficient versus dose response was determined for a normoxic N-vinylpyrrolidone based polymer gel dosimeter. Cylindrical dosimeters, 2 cm diameter, were homogenously irradiated to known doses up to 60 Gy using a 6 MV linear accelerator. For a test irradiation, a 5 cm diameter dosimeter was irradiated along its cylindrical axis using a rectangular 1 cm x 1 cm irradiation beam. The dose readout of this scanner was compared to the corresponding readout of a common wide illumination and area detector optical-CT scanner.
The attenuation coefficient versus dose response of the laser-based system was found to be linear up to 60 Gy (r2 = 0.997) compared to the wide field illumination based optical-CT scanner, which exhibits linearity up to 32 Gy (r2 = 0.996). The noise in the reconstructed attenuation coefficient maps was +/- 7.2 x 10(-2) mm(-1) versus +/- 9.5 x 10(-3) mm(-1) for the laser-based system and the wide field illumination system, respectively.
We have developed a novel laser-based optical-CT scanner, which is capable of generating fast 3D dosimetric data using a scattering polymer gel dosimeter. Our data demonstrate that the dose readout of this scanner preserves the advantage of existing laser-based optical-CT scanners in providing measurements, which are minimally affected by scattered light. For accurate reconstruction of the attenuation coefficients, noise reduction techniques need to be applied.
介绍一种用于读取三维（3D）辐射剂量计的新型基于激光的光学 CT 扫描仪。
该扫描仪采用二极管激光器、柱面透镜、电动线性导轨、旋转台和电荷耦合器件（CCD）相机。扫描仪采用平移-旋转方式工作，可根据柱面透镜的方向设置两种配置。在正常氧合 N-乙烯基吡咯烷酮基聚合物凝胶剂量计的情况下，确定了衰减系数与剂量的响应关系。使用 6 MV 线性加速器，将直径为 2 cm 的圆柱形剂量计均匀照射至已知剂量，最高可达 60 Gy。对于测试照射，使用矩形 1 cm x 1 cm 照射束沿其圆柱轴照射直径为 5 cm 的剂量计。将此扫描仪的剂量读取与常见的宽照明和区域探测器光学 CT 扫描仪的相应读取进行了比较。
与基于宽场照明的光学 CT 扫描仪相比，基于激光的系统的衰减系数与剂量响应在 60 Gy 范围内呈线性（r2 = 0.997），而后者在 32 Gy 范围内呈线性（r2 = 0.996）。与基于宽场照明的系统相比，在重建的衰减系数图中，激光系统的噪声分别为 +/- 7.2 x 10(-2) mm(-1) 和 +/- 9.5 x 10(-3) mm(-1)。
我们开发了一种新型的基于激光的光学 CT 扫描仪，该扫描仪能够使用散射聚合物凝胶剂量计快速生成 3D 剂量数据。我们的数据表明，该扫描仪的剂量读取保留了现有基于激光的光学 CT 扫描仪的优势，即提供受散射光影响最小的测量结果。为了准确重建衰减系数，需要应用降噪技术。
