Lárraga-Gutiérrez José Manuel, Ballesteros-Zebadúa Paola, Rodríguez-Ponce Miguel, García-Garduño Olivia Amanda, de la Cruz Olga Olinca Galván
Departamento de Física, Universidad Autónoma Metropolitana, Unidad Iztapalapa, México D.F., Mexico. Laboratorio de Física Médica, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, C.P. 14269, México, D.F., Mexico. Unidad de Radioneurocirugía, Instituto Nacional de Neurología y Neurocirugía, Insurgentes sur 3877, C.P. 14269, México, D.F., Mexico.
Phys Med Biol. 2015 Jan 21;60(2):905-24. doi: 10.1088/0031-9155/60/2/905. Epub 2015 Jan 7.
A CVD based radiation detector has recently become commercially available from the manufacturer PTW-Freiburg (Germany). This detector has a sensitive volume of 0.004 mm(3), a nominal sensitivity of 1 nC Gy(-1) and operates at 0 V. Unlike natural diamond based detectors, the CVD diamond detector reports a low dose rate dependence. The dosimetric properties investigated in this work were dose rate, angular dependence and detector sensitivity and linearity. Also, percentage depth dose, off-axis dose profiles and total scatter ratios were measured and compared against equivalent measurements performed with a stereotactic diode. A Monte Carlo simulation was carried out to estimate the CVD small beam correction factors for a 6 MV photon beam. The small beam correction factors were compared with those obtained from stereotactic diode and ionization chambers in the same irradiation conditions The experimental measurements were performed in 6 and 15 MV photon beams with the following square field sizes: 10 × 10, 5 × 5, 4 × 4, 3 × 3, 2 × 2, 1.5 × 1.5, 1 × 1 and 0.5 × 0.5 cm. The CVD detector showed an excellent signal stability (<0.2%) and linearity, negligible dose rate dependence (<0.2%) and lower response angular dependence. The percentage depth dose and off-axis dose profiles measurements were comparable (within 1%) to the measurements performed with ionization chamber and diode in both conventional and small radiotherapy beams. For the 0.5 × 0.5 cm, the measurements performed with the CVD detector showed a partial volume effect for all the dosimetric quantities measured. The Monte Carlo simulation showed that the small beam correction factors were close to unity (within 1.0%) for field sizes ≥1 cm. The synthetic diamond detector had high linearity, low angular and negligible dose rate dependence, and its response was energy independent within 1% for field sizes from 1.0 to 5.0 cm. This work provides new data showing the performance of the CVD detector compared against a high spatial resolution diode. It also presents a comparison of the CVD small beam correction factors with those of diode and ionization chamber for a 6 MV photon beam.
一种基于化学气相沉积（CVD）的辐射探测器最近已由德国的PTW - 弗莱堡制造商投入商业使用。该探测器的灵敏体积为0.004立方毫米，标称灵敏度为1纳库仑每戈瑞，工作电压为0伏。与天然金刚石探测器不同，CVD金刚石探测器显示出低剂量率依赖性。在这项工作中研究的剂量学特性包括剂量率、角度依赖性以及探测器的灵敏度和线性度。此外，还测量了百分深度剂量、离轴剂量分布和总散射比，并与使用立体定向二极管进行的等效测量结果进行了比较。进行了蒙特卡罗模拟，以估计6兆伏光子束的CVD小射野校正因子。将小射野校正因子与在相同照射条件下从立体定向二极管和电离室获得的校正因子进行了比较。实验测量是在6兆伏和15兆伏光子束中进行的，射野尺寸如下：10×10、5×5、4×4、3×3、2×2、1.5×1.5、1×1和0.5×0.5平方厘米。CVD探测器显示出出色的信号稳定性（<0.2%）和线性度，可忽略不计的剂量率依赖性（<0.2%）以及较低的响应角度依赖性。在常规和小放疗射野中，百分深度剂量和离轴剂量分布测量结果与使用电离室和二极管进行的测量结果相当（在1%以内）。对于0.5×0.5平方厘米的射野，使用CVD探测器进行的测量显示出在所测量的所有剂量学量中都存在部分体积效应。蒙特卡罗模拟表明，对于射野尺寸≥1厘米，小射野校正因子接近1（在1.0%以内）。合成金刚石探测器具有高线性度、低角度依赖性且剂量率依赖性可忽略不计，并且对于1.0至5.0厘米的射野尺寸，其响应在1%以内与能量无关。这项工作提供了新的数据，展示了CVD探测器与高空间分辨率二极管相比的性能。它还给出了6兆伏光子束的CVD小射野校正因子与二极管和电离室校正因子的比较结果。
