Two-dimensional time-resolved scintillating sheet monitoring of proton pencil beam scanning FLASH mouse irradiations.
Two-dimensional time-resolved scintillating sheet monitoring of proton pencil beam scanning FLASH mouse irradiations.
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质子笔形束扫描 FLASH 小鼠照射的二维时间分辨闪烁片监测。
DOI：
10.1002/mp.17049
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发表时间：
2024
期刊：
影响因子：
3.8
通讯作者：
Poulsen,PerRugaard
中科院分区：
文献类型：
--
作者：
Kanouta,Eleni;Bruza,Petr;Johansen,JacobGraversen;Kristensen,Line;Sørensen,BritaSingers;Poulsen,PerRugaard
研究背景临床前闪光研究中的剂量学对于了解触发闪光效应的射束传输条件是必不可少的。为了解决超高剂量率质子铅笔束扫描(PBS)照射的时空特性，需要一个具有高空间和时间分辨率的探测器。目的实现一种新的基于相机的时间分辨二维(2D)监测系统，并将其应用于临床前质子铅笔束扫描(PBS)小鼠的体内照射。该片材被放置在垂直于水平PbS质子束轴的水浴中。闪烁光通过反射镜系统反射，由相机捕捉，UHDR为每秒500帧，传统剂量率为每秒4FPS。原始图像经过背景减去、几何变换、平场校正和空间滤波。该系统用于二维光斑和场分布的测量，并与辐射变色胶片进行了比较。此外，还测量了UHDR辐射的光斑位置。将测量的光斑位置与计划位置进行比较，并将相对瞬时剂量率与等效光纤耦合点闪烁体测量结果进行比较。为了在体内应用，将闪光片放置在浸泡在水浴中的非麻醉小鼠右后腿上游1厘米处。小鼠的腿和薄片都被放置在由2D射程调制器由单能质子束形成的5厘米宽的展开布拉格峰中。对于常规照射和闪光照射，确定了小鼠腿部在场内的位置。对于传统的照射，老鼠脚的位置在整个射束传递过程中都被跟踪，这是通过重新绘制进行的。对于闪光照射，测量了发射光斑的位置和相对瞬时剂量率。用该闪烁片测量的光斑和场分布在0.4 mm以内与辐射变色膜一致。在水平和垂直方向上，实测点位置与计划点位置的标准偏差分别为0.26 mm和0.35 mm。测量的相对瞬时剂量率与光纤耦合闪烁体的测量结果呈线性关系。对于体内应用，不同小鼠的腿部位置不同，在长时间的常规照射中，腿部运动可达3 mm。结论该闪烁成像系统可以监测体内UHDR质子PBS的释放，像素尺寸为0.1 mm，时间分辨率为2 ms。论证了瞬时剂量率测量的可行性，并将该系统用于验证小鼠腿部在野外的位置。
BackgroundDosimetry in pre‐clinical FLASH studies is essential for understanding the beam delivery conditions that trigger the FLASH effect. Resolving the spatial and temporal characteristics of proton pencil beam scanning (PBS) irradiations with ultra‐high dose rates (UHDR) requires a detector with high spatial and temporal resolution.PurposeTo implement a novel camera‐based system for time‐resolved two‐dimensional (2D) monitoring and apply it in vivo during pre‐clinical proton PBS mouse irradiations.MethodsTime‐resolved 2D beam monitoring was performed with a scintillation imaging system consisting of a 1 mm thick transparent scintillating sheet, imaged by a CMOS camera. The sheet was placed in a water bath perpendicular to a horizontal PBS proton beam axis. The scintillation light was reflected through a system of mirrors and captured by the camera with 500 frames per second (fps) for UHDR and 4 fps for conventional dose rates. The raw images were background subtracted, geometrically transformed, flat field corrected, and spatially filtered. The system was used for 2D spot and field profile measurements and compared to radiochromic films. Furthermore, spot positions were measured for UHDR irradiations. The measured spot positions were compared to the planned positions and the relative instantaneous dose rate to equivalent fiber‐coupled point scintillator measurements. For in vivo application, the scintillating sheet was placed 1 cm upstream the right hind leg of non‐anaesthetized mice submerged in the water bath. The mouse leg and sheet were both placed in a 5 cm wide spread‐out Bragg peak formed from the mono‐energetic proton beam by a 2D range modulator. The mouse leg position within the field was identified for both conventional and FLASH irradiations. For the conventional irradiations, the mouse foot position was tracked throughout the beam delivery, which took place through repainting. For FLASH irradiations, the delivered spot positions and relative instantaneous dose rate were measured.ResultsThe pixel size was 0.1 mm for all measurements. The spot and field profiles measured with the scintillating sheet agreed with radiochromic films within 0.4 mm. The standard deviation between measured and planned spot positions was 0.26 mm and 0.35 mm in the horizontal and vertical direction, respectively. The measured relative instantaneous dose rate showed a linear relation with the fiber‐coupled scintillator measurements. For in vivo use, the leg position within the field varied between mice, and leg movement up to 3 mm was detected during the prolonged conventional irradiations.ConclusionsThe scintillation imaging system allowed for monitoring of UHDR proton PBS delivery in vivo with 0.1 mm pixel size and 2 ms temporal resolution. The feasibility of instantaneous dose rate measurements was demonstrated, and the system was used for validation of the mouse leg position within the field.
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DOI：
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2022
期刊：
Medical Physics (Lancaster)
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DOI：
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发表时间：
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Zeitschrift für Medizinische Physik
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