Evaluation of a pixelated large format CMOS sensor for x-ray microbeam radiotherapy
Evaluation of a pixelated large format CMOS sensor for x-ray microbeam radiotherapy
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DOI：
10.1002/mp.13971
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发表时间：
2020-01-06
期刊：
影响因子：
3.8
通讯作者：
Sedgwick, Iain
中科院分区：
文献类型：
--
作者：
Flynn, Samuel;Price, Tony;Sedgwick, Iain
目的目前的微束剂量测量技术和程序通常依赖于放射变色薄膜或小体积电离室来分别进行2D和1D的验证和质量保证。虽然这些方法具有很好的临床和临床前放射治疗的特点，但它们是非瞬时的，不提供实时的资料信息。这项工作的目的是确定新开发的vM1212探测器，一种像素化的CMOS(互补金属氧化物半导体)成像传感器，用于原位和活体验证X射线微束。方法在德国慕尼黑Helmholtz中心220KVP小型动物辐射研究平台(SARRP)的vM1212探测器上进行实验。一块3x3 cm(2)的正方形EBT3薄膜被放置在标记的非纤维卡的顶部，该卡覆盖在传感器的敏感硅上。一厘米的水当量的药丸材料被放置在胶片的顶部以供建立。探测器的响应与Epson Expression 10000XL平板扫描仪进行了比较，扫描仪使用了FilmQA Pro和三通道剂量测量。这也与使用450微米硅作为探测器替代品的单独曝光和使用光学显微镜剂量学方法的蔡司Axio Imager 2显微镜进行了比较。使用标称宽度范围为25、50、75和100微米的微束准直器狭缝来比较光束分布并确定探测器和两种薄膜测量对不同微束的灵敏度。结果该探测器能够实时测量峰和谷的轮廓，与EBT3胶片所需的24小时自我显影相比，有显著的减少。由于发散，观测到的半高全宽(FWHM)值大于标称狭缝宽度，范围从130到190微米。两种方法在峰谷剂量比(PVDR)、峰峰间隔和半高宽方面是一致的，但在微束的相对强度上观察到不同的探测器。结论本研究表明，像素化的cmos传感器可用于微束放射治疗的实时剂量测量，但vM1212探测器的像素间距较大，限制了结果的即时应用。
Purpose Current techniques and procedures for dosimetry in microbeams typically rely on radiochromic film or small volume ionization chambers for validation and quality assurance in 2D and 1D, respectively. Whilst well characterized for clinical and preclinical radiotherapy, these methods are noninstantaneous and do not provide real time profile information. The objective of this work is to determine the suitability of the newly developed vM1212 detector, a pixelated CMOS (complementary metal-oxide-semiconductor) imaging sensor, for in situ and in vivo verification of x-ray microbeams. Methods Experiments were carried out on the vM1212 detector using a 220 kVp small animal radiation research platform (SARRP) at the Helmholtz Centre Munich. A 3 x 3 cm(2) square piece of EBT3 film was placed on top of a marked nonfibrous card overlaying the sensitive silicon of the sensor. One centimemter of water equivalent bolus material was placed on top of the film for build-up. The response of the detector was compared to an Epson Expression 10000XL flatbed scanner using FilmQA Pro with triple channel dosimetry. This was also compared to a separate exposure using 450 mu m of silicon as a surrogate for the detector and a Zeiss Axio Imager 2 microscope using an optical microscopy method of dosimetry. Microbeam collimator slits with range of nominal widths of 25, 50, 75, and 100 mu m were used to compare beam profiles and determine sensitivity of the detector and both film measurements to different microbeams. Results The detector was able to measure peak and valley profiles in real-time, a significant reduction from the 24 hr self-development required by the EBT3 film. Observed full width at half maximum (FWHM) values were larger than the nominal slit widths, ranging from 130 to 190 mu m due to divergence. Agreement between the methods was found for peak-to-valley dose ratio (PVDR), peak to peak separation and FWHM, but a difference in relative intensity of the microbeams was observed between the detectors. Conclusions The investigation demonstrated that pixelated CMOS sensors could be applied to microbeam radiotherapy for real-time dosimetry in the future, however the relatively large pixel pitch of the vM1212 detector limit the immediate application of the results.