Inhomogeneity detection within a head-sized phantom using tracking of charged nuclear fragments in ion beam therapy.

IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL
Renato Félix-Bautista, Laura Ghesquière-Diérickx, Pamela Ochoa-Parra, Laurent Kelleter, Gernot Echner, Jürgen Debus, Oliver Jäkel, Mária Martišíková, Tim Gehrke
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Abstract

Objective.The highly conformal carbon-ion radiotherapy is associated with an increased sensitivity of the dose distributions to internal changes in the patient during the treatment course. Hence, monitoring methodologies capable of detecting such changes are of vital importance. We established experimental setup conditions to address the sensitivity of a monitoring approach based on secondary-fragment tracking for detecting clinically motivated air cavity dimensions in a homogeneous head-sized PMMA phantom in 40 mm depth.Approach.The air cavities were positioned within the entrance channel of a treatment field of 50 mm diameter at three lateral positions. The measured secondary-fragment emission profiles were compared to a reference measurement without cavities. The experiments were conducted at the Heidelberg Ion-Beam Therapy Center in Germany at typical doses and dose rates.Main results.Significances above a detectability threshold of 2σfor the larger cavities (20 mm diameter and 4 mm thickness, and 20 mm diameter and 2 mm thickness) across the entire treatment field. The smallest cavity of 10 mm diameter and 2 mm thickness, which is on the lower limit of clinical interest, could not be detected at any position. We also demonstrated that it is feasible to reconstruct the lateral position of the cavity on average within 2.8 mm, once the cavity is detected. This is sufficient for the clinicians to estimate medical effects of such a cavity and to decide about the need for a control imaging CT.Significance.This investigation defines well-controlled reference conditions for the evaluation of the performance of any kind of treatment monitoring method and its capability to detect internal changes within head-sized objects. Four air cavities with volumes between 0.31 cm3and 1.26 cm3were narrowed down around the detectability threshold of this secondary-fragment-based monitoring method.

利用离子束疗法中的带电核碎片跟踪技术检测头部大小的模型内的不均匀性。
目的:高适形碳离子放射治疗会增加剂量分布对治疗过程中患者体内变化的敏感性。因此,能够检测到这种变化的监测方法至关重要。我们建立了实验设置条件,以解决基于二次碎片跟踪的监测方法的灵敏度问题,该方法可在深度为 40 毫米的均质头部尺寸 PMMA 模型中检测临床上需要的气穴尺寸:方法:将气穴放置在直径为 50 毫米的治疗场入口通道内的三个横向位置。测量到的二次碎片发射轮廓与没有气穴的参考测量结果进行了比较。实验在德国海德堡离子束治疗中心以典型剂量和剂量率进行:在整个治疗场中,较大的空腔(直径 20 毫米、厚度 4 毫米,以及直径 20 毫米、厚度 2 毫米)的显著性高于 2+sigma 的可检测阈值。直径为 10 毫米、厚度为 2 毫米的最小空腔处于临床关注的下限,在任何位置都无法检测到。我们还证明,一旦检测到龋洞,平均在 2.8 毫米内重建龋洞的横向位置是可行的。这足以让临床医生估计蛀牙对医疗的影响,并决定是否需要进行 CT 对照成像:这项研究为评估各种治疗监测方法的性能及其检测头部大小物体内部变化的能力确定了良好的参考条件。体积从 0.31 cm3 到 1.26 cm3 的气腔被缩小到了这种基于二次碎片监测方法的可检测阈值附近。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Physics in medicine and biology
Physics in medicine and biology 医学-工程:生物医学
CiteScore
6.50
自引率
14.30%
发文量
409
审稿时长
2 months
期刊介绍: The development and application of theoretical, computational and experimental physics to medicine, physiology and biology. Topics covered are: therapy physics (including ionizing and non-ionizing radiation); biomedical imaging (e.g. x-ray, magnetic resonance, ultrasound, optical and nuclear imaging); image-guided interventions; image reconstruction and analysis (including kinetic modelling); artificial intelligence in biomedical physics and analysis; nanoparticles in imaging and therapy; radiobiology; radiation protection and patient dose monitoring; radiation dosimetry
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