Optimising proton stopping power ratio prediction with spectral cone-beam CT.

IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL
David Leibold, Dennis R Schaart, Marlies C Goorden
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引用次数: 0

Abstract

Objective: Cone-beam computed tomography (CBCT) is used for patient positioning in proton therapy, but not directly for treatment planning due to its inferior image quality compared to fan-beam CT. One way to improve its value for proton radiotherapy might be to use CBCT setups capable of extracting spectral information, which can be realised through several hardware configurations. Here, we compare different setups w.r.t. to their capability of predicting proton stopping power ratios (SPR). Approach: We investigate six different spectral CBCT realisations in a simulation study, namely a single-source setup with either a dual-layer detector or a photon-counting detector (PCD), a kVp-switching setup with either an energy-integrating detector (EID) or a PCD, and a dual-source setup with either EIDs or PCDs. Our figure of merit is the normalised Cramér-Rao Lower Bound (nCRLB) on SPR variance based on projection data. We take (cross)scatter into account, and compare ideal and realistic detector models to help guide future detector developments. Each setup is optimised w.r.t. source spectra, mAs ratios and energy bin settings (where applicable). Main results: Assuming a realistic detector response, setups with a kVp-switching source perform best, with the setup paired with an EID slightly outperforming the PCD-based setup (nCRLBs of 2.70 and 2.82, respectively). However, if the mAs ratio of the kVp-switching source is fixed, the performance of the kVp-switching setup with an EID is significantly degraded (nCRLB = 9.04) and outperformed by PCD-based setups, with nCRLBs of 3.62, 3.80 and 3.98 for the dual-source setup with two PCDs, the kVp-switching setup and the single-source setup with one PCD, respectively. Spectra with higher mean energy or wider spectral separation generally yield lower CRLB values, and avoiding the spectral distortion caused by charge sharing in direct-conversion PCDs promises to lower CRLB values by about a third. Significance: We present an extensive comparison of spectral CBCT setups for their application in proton radiotherapy, using a methodology that allows to compare their theoretical limit of performance without being influenced by the choice of reconstruction algorithm or the conversion scheme from Hounsfield units to SPR values. .

利用光谱锥束CT优化质子停止功率比预测。
目的:锥形束计算机断层扫描(CBCT)在质子治疗中用于患者定位,但由于其图像质量不如扇束CT,因此不能直接用于治疗计划。提高其在质子放射治疗中的价值的一种方法可能是使用能够提取光谱信息的CBCT设置,这可以通过几种硬件配置来实现。在这里,我们比较了不同的设置w.r.t.预测质子停止功率比(SPR)的能力。方法:我们在模拟研究中研究了六种不同的光谱CBCT实现,即带有双层探测器或光子计数探测器(PCD)的单源设置,带有能量积分探测器(EID)或PCD的kvp开关设置,以及带有EID或PCD的双源设置。我们的优点是基于投影数据的SPR方差的归一化cram - rao下限(nCRLB)。我们考虑了(交叉)散射,并比较了理想和现实的探测器模型,以帮助指导未来的探测器发展。每种设置都优化了w.r.t.源光谱、mAs比和能量仓设置(如适用)。主要结果:假设真实的探测器响应,使用kvd开关源的设置表现最佳,与EID配对的设置略优于基于pcd的设置(ncrlb分别为2.70和2.82)。然而,如果kvp开关源的mAs比是固定的,则具有EID的kvp开关装置的性能会显著下降(nCRLB = 9.04),并且优于基于PCD的装置,具有两个PCD的双源装置、具有一个PCD的kvp开关装置和单源装置的nCRLB分别为3.62、3.80和3.98。平均能量较高或光谱间距较宽的光谱通常会产生较低的CRLB值,避免直接转换pcd中电荷共享引起的光谱畸变有望使CRLB值降低约三分之一。我们对光谱CBCT装置在质子放疗中的应用进行了广泛的比较,使用了一种方法,可以比较它们的理论性能极限,而不受重建算法的选择或从霍斯菲尔德单位到SPR值的转换方案的影响。 。
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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