Department of Radiation Oncology, Medical University of Vienna/AKH Wien, Vienna, Austria; Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna, Vienna, Austria.
Radiother Oncol. 2013 Dec;109(3):356-60. doi: 10.1016/j.radonc.2013.10.022. Epub 2013 Nov 18.
The applicability of various detectors for small field dosimetry and whether there are differences in the detector response when irradiated with FF- and FFF-beams was investigated.
Output factors of 6 and 10 MV FF- and FFF-beams were measured with 14 different online detectors using field sizes between 10 × 10 and 0.6 × 0.6 cm(2) at a depth of 5 cm of water in isocentric conditions. Alanine pellets with a diameter of 5 and 2.5mm were used as reference dosimeters for field sizes down to 1.2 × 1.2 and 0.6 × 0.6 cm(2), respectively. The ratio of the relative output measured with the online detectors to the relative output measured with alanine was evaluated (referred to as dose response ratio).
The dose response ratios of two different shielded diodes measured with 10 MV FF-beams deviated substantially by 2-3% compared to FFF-beams at a field size of 0.6 × 0.6 cm(2). This difference was less pronounced for 6 MV FF- and FFF-beams. For all other detectors the dose response ratios of FF- and FFF-beams showed no significant difference.
The dose response ratios of the majority of the detectors agreed within the measurement uncertainty when irradiated with FF- and FFF-beams. Of all investigated detectors, the microDiamond and the unshielded diodes would require only small corrections which make them suitable candidates for small field dosimetry in FF- and FFF-beams.
研究了不同探测器在小射野剂量测量中的适用性，以及在照射 FF 和 FFF 射束时探测器响应是否存在差异。
在水深处 5cm 的等中心条件下，使用 14 种不同的在线探测器，测量了 6 和 10 MV FF 和 FFF 射束的输出因子，射野大小为 10×10cm²至 0.6×0.6cm²。直径为 5mm 和 2.5mm 的 Alanine 小球分别被用作 1.2×1.2cm²及以下射野的参考剂量计。评估了在线探测器测量的相对输出与 Alanine 测量的相对输出的比值（称为剂量响应比）。
与 FFF 射束相比，在 0.6×0.6cm²的射野尺寸下，两种不同屏蔽二极管在 10 MV FF 射束下测量的剂量响应比偏差较大，为 2-3%。对于 6 MV FF 和 FFF 射束，这种差异不那么明显。对于所有其他探测器，FF 和 FFF 射束的剂量响应比没有显著差异。
当用 FF 和 FFF 射束照射时，大多数探测器的剂量响应比在测量不确定度范围内是一致的。在所研究的所有探测器中，microDiamond 和非屏蔽二极管仅需要较小的校正，这使得它们成为 FF 和 FFF 射束中小射野剂量测量的合适候选者。
