Design and evaluation of a variable aperture collimator for conformal radiotherapy of small animals using a microCT scanner
Design and evaluation of a variable aperture collimator for conformal radiotherapy of small animals using a microCT scanner
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DOI：
10.1118/1.2789498
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发表时间：
2007-11-01
期刊：
影响因子：
3.8
通讯作者：
Boyer, Arthur L.
中科院分区：
文献类型：
--
作者：
Graves, Edward E.;Zhou, Hu;Boyer, Arthur L.
用辐射治疗小动物一般限于用铅块成形的平面场，使剂量的空间定位和深层靶的治疗复杂化。为了使实验室放射治疗向临床放射治疗方向发展，我们研制了一种用于微型CT扫描仪射束整形的可变孔径准直器。该装置可以以高分辨率对小动物对象进行成像，并且能够在合理的曝光时间内提供治疗剂量。拟议的准直器由两个阶段，每个阶段包含六个梯形黄铜块，沿沿着一个框架移动的方式类似于相机光圈产生一个六角形孔径的可变大小。两个平台偏移30度，并针对X射线束的发散进行调整，以便在等中心处产生十二边形轮廓。开槽旋转驱动板用于向准直器块中的销施加力并影响准直器运动。该装置已通过模拟和测量进行了研究。当驱动板角度从0度增加到41度时，准直器孔径大小从0到8.5 cm变化。调整准直器所需的扭矩从0.5到5 N中心点m变化，随着驱动板角度的增加而增加。由扫描仪在等中心产生的透射轮廓显示出约为准直器孔径宽度10%的半影。准直器组件和X射线源之间的未对准可以在透射图像上识别，并通过调整准直器位置来校正。因此，这种可变孔径准直器技术是用于小动物放射治疗以及需要射束成形的其他应用中的辐射射束的可调节成形的可行且灵活的解决方案。(c)2007年美国医学物理学家协会。
Treatment of small animals with radiation has in general been limited to planar fields shaped with lead blocks, complicating spatial localization of dose and treatment of deep-seated targets. In order to advance laboratory radiotherapy toward what is accomplished in the clinic, we have constructed a variable aperture collimator for use in shaping the beam of microCT scanner. This unit can image small animal subjects at high resolution, and is capable of delivering therapeutic doses in reasonable exposure times. The proposed collimator consists of two stages, each containing six trapezoidal brass blocks that move along a frame in a manner similar to a camera iris producing a hexagonal aperture of variable size. The two stages are offset by 30 degrees and adjusted for the divergence of the x-ray beam so as to produce a dodecagonal profile at isocenter. Slotted rotating driving plates are used to apply force to pins in the collimator blocks and effect collimator motion. This device has been investigated through both simulation and measurement. The collimator aperture size varied from 0 to 8.5 cm as the driving plate angle increased from 0 to 41 degrees. The torque required to adjust the collimator varied from 0.5 to 5 N center dot m, increasing with increasing driving plate angle. The transmission profiles produced by the scanner at isocenter exhibited a penumbra of approximately 10% of the collimator aperture width. Misalignment between the collimator assembly and the x-ray source could be identified on the transmission images and corrected by adjustment of the collimator location. This variable aperture collimator technology is therefore a feasible and flexible solution for adjustable shaping of radiation beams for use in small animal radiotherapy as well as other applications in which beam shaping is desired. (c) 2007 American Association of Physicists in Medicine.