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Bimodal PET/MRI generative reconstruction based on VAE architectures. 基于 VAE 架构的双模态 PET/MRI 成像重建。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-11 DOI: 10.1088/1361-6560/ad9133
Valentin Gautier, Alexandre Bousse, Florent Sureau, Claude Comtat, Voichita Maxim, Bruno Sixou

•Objective:In this study, we explore positron emission tomography(PET)/magnetic resonance imaging (MRI) joint reconstruction within a deeplearning (DL) framework, introducing a novel synergistic method. •Approach:We propose a new approach based on a variational autoencoder (VAE)constraint combined with the alternating direction method of multipliers (ADMM)optimization technique. We compare several VAE architectures, including jointVAE, mixture of experts (MoE) and product of experts (PoE), to determine theoptimal latent representation for the two modalities. We trained then evaluatedthe architectures on a brain PET/MRI dataset. •Main results:We showed that our approach takes advantage of each modalitysharing information to each other, which results in improved peak signal-to-noiseratio (PSNR) and structural similarity (SSIM) as compared with traditionalreconstruction methods, particularly for short acquisition times. We find that theone particular architecture, MMJSD, is the most effective for our methodology. •Significance:The proposed method outperforms classical approaches especiallyin noisy and undersampled conditions by making use of the two modalities together to compensate for the missing information.

-目标:在本研究中,我们在深度学习(DL)框架内探索了正电子发射断层成像(PET)/磁共振成像(MRI)联合重建,并引入了一种新型协同方法。我们比较了几种 VAE 架构,包括联合 VAE、专家混合(MoE)和专家乘积(PoE),以确定两种模态的最佳潜表征。我们在脑 PET/MRI 数据集上对这些架构进行了训练和评估。主要结果:我们的研究表明,与传统的重建方法相比,我们的方法利用了每种模态相互共享信息的优势,从而提高了峰值信噪比(PSNR)和结构相似性(SSIM),尤其是在短采集时间内。我们发现,MMJSD 这一特定架构对我们的方法最为有效。意义:通过利用两种模态共同补偿缺失信息,我们提出的方法在噪声和采样不足的条件下优于传统方法。
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引用次数: 0
Novel Bragg peak characterization method using proton flux measurements on plastic scintillators. 利用质子通量测量塑料闪烁体的新型布拉格峰表征方法。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-11 DOI: 10.1088/1361-6560/ad8da0
D R Guerreiro, J G Saraiva, L Peralta, C Rodrigues, M Rovituso, E van der Wal, Dennis R Schaart, P Crespo, H Simões, J M Sampaio

Objective. Bragg peak measurements play a key role in the beam quality assurance in proton therapy. Used as base data for the treatment planning softwares, the accuracy of the data is crucial when defining the range of the protons in the patient.Approach. In this paper a protocol to reconstruct a Pristine Bragg Peak exploring the direct correlation between the particle flux and the dose deposited by particles is presented. Proton flux measurements at the HollandPTC and FLUKA Monte Carlo simulations are used for this purpose. This new protocol is applicable to plastic scintillator detectors developed for Quality Assurance applications. In order to obtain the Bragg curve using a plastic fiber detector, a PMMA phantom with a decoupled and moveable stepper was designed. The step phantom allows to change the depth of material in front of the fiber detector during irradiations. The Pristine Bragg Peak reconstruction protocol uses the measured flux of particles at each position and multiplies it by the average dose obtained from the Monte Carlo simulation at each position.Main results. The results show that with this protocol it is possible to reconstruct the Bragg Peak with an accuracy of about 470µm, which is in accordance with the tolerances set by the AAPM.Significance. It has the advantage to be able to overcome the quenching problem of scintillators in the high ionization density region of the Bragg peak.

textit{Objective}.布拉格峰测量在质子治疗的射束质量保证中起着关键作用。作为治疗计划软件的基础数据,数据的准确性对于确定患者体内的质子范围、保护健康组织以及正确的容积剂量分布都至关重要。方法本文介绍了重建原始布拉格峰的方案,以探索粒子通量与粒子沉积剂量之间的直接相关性。为此使用了在荷兰粒子物理中心(HollandPTC)进行的质子通量测量和 FLUKA 蒙特卡罗模拟。这一新方案适用于为质量保证应用而开发的塑料闪烁探测器。为了使用塑料光纤探测器获得布拉格曲线,设计了一个带有去耦合可移动步进装置的 PMMA 模型。阶梯模型允许在辐照过程中改变光纤探测器前的材料深度。原始布拉格峰重建协议使用在每个位置测得的粒子通量,并乘以在每个位置蒙特卡洛模拟得到的平均剂量。文本{主要结果} 结果表明,使用该协议可以重建布拉格峰,精度约为 470 微米,符合 AAPM 规定的公差。此外,还讨论了协议的改进和进一步的应用。意义它的优点是能够克服闪烁体在布拉格峰高电离密度区域的淬火问题。
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引用次数: 0
Inter-center comparison of proton range verification prototypes with an anthropomorphic head phantom. 质子射程验证原型与拟人头部模型的中心间比较。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-11 DOI: 10.1088/1361-6560/ad8856
Fernando Hueso-González, Jonathan Berthold, Patrick Wohlfahrt, Thomas Bortfeld, Chirasak Khamfongkhruea, Sebastian Tattenberg, Melek Zarifi, Joost Verburg, Christian Richter

Objective. To compare in reproducible and equalized conditions the performance of two independent proton range verification systems based on prompt gamma-ray detectors from two different proton therapy centers.Approach. An anthropomorphic head phantom with calibrated stopping power, serving as ground truth, was irradiated with comparable treatment plans, spot positions and energies in both facilities. Clinical beam current, tumor contour and dose were used. The absolute range measurement was compared to the expected value according to the ground truth. The statistical precision was assessed by repeating each measurement ten times. Sensitivity to relative range shifts was evaluated by introducing 2 mm and 5 mm plastic slabs on half of the field.Main results. The resulting absolute range accuracy was within 2.4 mm in all cases. Relative range shifts were detected with deviations lower than 14%.Significance. The performance of both systems was deemed worthy of clinical application for the detection of range deviations. This study represents the first comparison of independent prompt gamma-ray-based proton range verification systems under equalized conditions with realistic treatment fields and beam currents.

目的: 在可重复和均衡的条件下,比较两个不同质子治疗中心的两个独立质子量程验证系统的性能。比较两个不同质子治疗中心基于瞬发伽马射线探测器的独立质子范围验证系统在可重复和均衡条件下的性能。方法:在两家质子治疗中心,以校准停止功率的拟人化头部模型作为基础数据,采用可比的治疗方案、光斑位置和能量对其进行辐照。使用临床射束电流、肿瘤轮廓和剂量。绝对范围测量结果与根据基本真相得出的预期值进行比较。每次测量重复十次,以评估统计精度。通过在半场引入 2 毫米和 5 毫米的塑料板,对相对量程偏移的敏感性进行了评估。在所有情况下,绝对测距精度都在 2.4 毫米以内。检测到的相对测距偏差低于 14%。两套系统的性能都值得临床应用于测距偏差的检测。这项研究首次比较了基于伽马射线的独立质子射程验证系统在均衡条件下的实际治疗场和射束电流。
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引用次数: 0
The influence of daily imaging and target margin reduction on secondary cancer risk in image-guided and adaptive proton therapy. 在图像引导和自适应质子治疗中,每日成像和靶边缘缩小对继发性癌症风险的影响。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-11 DOI: 10.1088/1361-6560/ad8da3
A Smolders, K Czerska, Z Celicanin, A Lomax, F Albertini

Objective. Image-guided and adaptive proton therapy rely on daily CBCT or CT imaging, which increases radiation dose and radiation-induced cancer risk. Online adaptation however also reduces setup uncertainty, and the additional risk might be compensated by reducing the setup robustness margin. This work developed a framework to investigate how much this robustness margin should be reduced to offset the secondary cancer risk from additional imaging dose and applied it to proton therapy for head-and-neck cancer.Approach. For five patients with head-and-neck cancer, voxel-wise CT and CBCT imaging doses were estimated with Monte Carlo radiation transport simulations, calibrated with air and PMMA phantom measurements. The total dose of several image-guided and adaptive treatments protocols was calculated by summing the planning CT dose, daily and weekly CBCT or CT dose, and therapy dose, robustly optimized with setup margins between 0 and 4 mm. These were compared to a reference protocol with 4 mm setup margin without daily imaging. All plans further used 3% range robustness. Organ-wise excess absolute risk (EAR) of cancer was calculated with three models to determine at which setup margin the total EAR of image-guided and adaptive treatment protocols was equal to the total EAR of the reference.Results. The difference between the simulated and measured CT and CBCT doses was within 10%. Using the Monte Carlo models, we found that a 1 mm setup margin reduction was sufficient for most patients, treatment protocols, and cancer risk models to compensate the additional risk imposed by daily and weekly imaging. For some protocols, even a smaller reduction sufficed, depending on the imaging frequency and type. The risk reduction by reducing the margin was mainly due to reducing the risk for carcinomas in the brain and, for some patients, the oral cavity.Significance. Our framework allows to compare an increased imaging dose with the reduced treatment dose from margin reductions in terms of radiation-induced cancer risk. It is extendable to different treatment sites, modalities, and imaging protocols, in clinic-specific or even patient-specific assessments.

目的:图像引导和自适应质子治疗依赖于每天的 CBCT 或 CT 成像,这会增加辐射剂量和辐射诱发癌症的风险。本研究开发了一个框架,用于研究应减少多少稳健性裕度,以抵消额外成像剂量带来的次生癌症风险,并将其应用于头颈癌的质子治疗。通过将计划 CT 剂量、每日和每周 CBCT 或 CT 剂量以及治疗剂量相加,计算出几种图像引导和自适应治疗方案的总剂量,并根据 0 至 4 毫米的设置余量进行了稳健优化。这些数据与设置裕度为 4 毫米且不进行每日成像的参考方案进行了比较。所有方案都进一步使用了 3% 范围的稳健性。通过三种模型计算器官癌症超额绝对风险(EAR),以确定在哪个设置裕度下,图像引导和自适应治疗方案的总EAR等于参考方案的总EAR。使用蒙特卡洛模型,我们发现对于大多数患者、治疗方案和癌症风险模型来说,减少 1 毫米的设置余量足以补偿每日和每周成像带来的额外风险。对于某些方案,根据成像频率和类型,甚至更小的减少幅度也足够了。通过降低边际值来降低风险的主要原因是降低了脑癌的风险,对某些患者来说还降低了口腔癌的风险:我们的框架可以从辐射诱发癌症风险的角度,将增加的成像剂量与减少边缘所减少的治疗剂量进行比较。该框架可扩展到不同的治疗部位、模式和成像方案,并可针对特定诊所甚至特定患者进行评估。
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引用次数: 0
Investigation of scatter energy window width and count levels for deep learning-based attenuation map estimation in cardiac SPECT/CT imaging. 研究基于深度学习的心脏 SPECT/CT 成像衰减图估算的散射能量窗口宽度和计数水平。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-11 DOI: 10.1088/1361-6560/ad8b09
Yuan Chen, P Hendrik Pretorius, Yongyi Yang, Michael A King, Clifford Lindsay

Objective.Deep learning (DL) is becoming increasingly important in generating attenuation maps for accurate attenuation correction (AC) in cardiac perfusion SPECT imaging. Typically, DL models take inputs from initial reconstructed SPECT images, which are performed on the photopeak window and often also on scatter windows. While prior studies have demonstrated improvements in DL performance when scatter window images are incorporated into the DL input, the comprehensive analysis of the impact of employing different scatter windows remains unassessed. Additionally, existing research mainly focuses on applying DL to SPECT scans obtained at clinical standard count levels. This study aimed to assess utilities of DL from two aspects: (1) investigating the impact when different scatter windows were used as input to DL, and (2) evaluating the performance of DL when applied on SPECT scans acquired at a reduced count level.Approach.We utilized 1517 subjects, with 386 subjects for testing and the remaining 1131 for training and validation.Main results.The results showed that as scatter window width increased from 4% to 30%, a slight improvement was observed in DL estimated attenuation maps. The application of DL models to quarter-count (¼-count) SPECT scans, compared to full-count scans, showed a slight reduction in performance. Nonetheless, discrepancies across different scatter window configurations and between count levels were minimal, with all normalized mean square error (NMSE) values remaining within 2.1% when comparing the different DL attenuation maps to the reference CT maps. For attenuation corrected SPECT slices using DL estimated maps, NMSE values were within 0.5% when compared to CT correction.Significance.This study, leveraging an extensive clinical dataset, showed that the performance of DL seemed to be consistent across the use of varied scatter window settings. Moreover, our investigation into reduced count studies indicated that DL could provide accurate AC even at a ¼-count level.

目的:深度学习(DL)在生成衰减图以对心脏灌注 SPECT 成像进行精确衰减校正方面正变得越来越重要。通常情况下,深度学习模型的输入来自初始重建的 SPECT 图像,这些图像是在光峰窗上执行的,通常也在散射窗上执行。虽然之前的研究表明,将散射窗图像纳入 DL 输入时,DL 性能会有所改善,但对采用不同散射窗的影响的全面分析仍有待评估。此外,现有研究主要侧重于将 DL 应用于以临床标准计数水平获得的 SPECT 扫描。本研究旨在从两个方面评估 DL 的实用性:1)调查不同散射窗作为 DL 输入时的影响;2)评估 DL 应用于以较低计数水平获取的 SPECT 扫描时的性能:主要结果:结果显示,随着散射窗宽度从 4% 增加到 30%,DL 估算的衰减图略有改善。与全计数扫描相比,将 DL 模型应用于四分之一计数(¼-计数)SPECT 扫描的性能略有下降。不过,不同散射窗配置和不同计数水平之间的差异很小,将不同的DL衰减图与参考CT图进行比较时,所有归一化均方误差(NMSE)值都保持在2.1%以内。对于使用 DL 估算图进行衰减校正的 SPECT 切片,与 CT 校正相比,归一化均方误差值在 0.5%以内:本研究利用广泛的临床数据集显示,在使用不同的散射窗设置时,DL 的性能似乎是一致的。此外,我们对减少计数研究的调查表明,即使是在¼计数水平,DL也能提供准确的衰减校正。
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引用次数: 0
Verification of linear energy transfer optimized carbon-ion radiotherapy. 验证优化碳离子放射治疗的线性能量传递。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-07 DOI: 10.1088/1361-6560/ad8fec
Hideyuki Mizuno, Taku Nakaji, Sung Hyun Lee, Dousatsu Sakata, Katsumi Aoki, Kota Mizushima, Linh Tran, Anatoly B Rosenfeld, Taku Inaniwa

Objective: Linear energy transfer (LET) verification was conducted using a silicon-on-insulator (SOI) microdosimeter during the commissioning of LET-optimized carbon-ion radiotherapy. This advanced treatment technique is expected to improve local control rates, especially in hypoxic tumors. Approach: An SOI microdosimeter with a cylindrical sensitive volume of 30 μm diameter and 5 μm thickness was used. Simple cubic plans and patient plans using the carbon-ion beams were created by treatment planning system, and the calculated LETd values were compared with the measured LETd values obtained by the SOI microdosimeter. Main results: Reasonable agreement between the measured and calculated LETd was seen in the plateau region of depth LETd profile, whereas the measured LETd were below the calculated LETd in the peak region, specifically where LETd exceeds 75 keV/μm. The discrepancy in the peak region may arise from the uncertainties in the calibration process of the SOI microdosimeter. Excluding the peak region, the average ratio and standard deviation between measured and calculated LETd values were 0.996 and 7%, respectively. Significance: This verification results in the initiation of clinical trials for LET-optimized carbon-ion radiotherapy at QST Hospital, National Institutes for Quantum Science and Technology.

目的:在 LET 优化碳离子放射治疗的调试过程中,使用硅绝缘体(SOI)微剂量计进行了线性能量传递(LET)验证。这种先进的治疗技术有望提高局部控制率,尤其是对缺氧性肿瘤:使用了一个直径为 30 微米、厚度为 5 微米的圆柱形敏感体积 SOI 微剂量计。通过治疗计划系统创建简单的立方体计划和使用碳离子束的患者计划,并将计算出的 LETd 值与 SOI 微透镜测量出的 LETd 值进行比较:在 LETd 深度剖面的高原区,测量值与计算值基本一致,而在峰值区,特别是 LETd 超过 75 keV/μm 的地方,测量值低于计算值。峰值区域的差异可能是 SOI 微探针校准过程中的不确定性造成的。除去峰值区域,LETd 测量值和计算值的平均比值和标准偏差分别为 0.996 和 7%:通过此次验证,国家量子科学与技术研究所 QST 医院将启动 LET 优化碳离子放射治疗的临床试验。
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引用次数: 0
Effects of spot size errors in DynamicARC pencil beam scanning proton therapy planning. DynamicARC 铅笔束扫描质子治疗规划中光斑尺寸误差的影响。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-07 DOI: 10.1088/1361-6560/ad8feb
Suresh Rana, Anatoly B Rosenfeld

Objective: Spot size stability is crucial in pencil beam scanning (PBS) proton therapy, and variations in spot size can disrupt dose distributions. Recently, a novel proton beam delivery method known as DynamicARC PBS scanning has been introduced. The current study investigates the dosimetric impact of spot size errors in DynamicARC proton therapy for head and neck (HNC), prostate, and lung cancers. Approach: Robustly optimized DynamicARC proton therapy plans were created for HNC (n=4), prostate (n=4), and lung (n=4) cancer patients. Spot size errors of ±10%, ±15%, and ±20% were introduced, and their effects on target coverage (D95% and D99%), homogeneity index (HI), and organ-at-risk (OAR) doses were analyzed across different cancer sites. Main Results: HNC and lung cancer plans showed greater vulnerability to spot size errors, with reductions in target coverage of up to 4.8% under -20% spot size errors. Dose homogeneity was also more affected in these cases, with HI degrading by 0.12 in lung cancer. Prostate cancer demonstrated greater resilience to spot size variations, even under errors of ±20%. For spot size errors ±10%, the oral cavity, parotid glands, and constrictor muscles experienced Dmean deviations within ±1.2%, while deviations were limited to ±0.5% for D10% of the bladder and rectum and ±0.3% for V20Gy(RBE) of the lungs. The robustness analysis indicated that lung cancer plans were most susceptible to robustness reductions caused by spot size errors, while HNC plans demonstrated moderate sensitivity. Conversely, prostate cancer plans demonstrated high robustness, experiencing only minimal reductions in target coverage. Significance: While the ±10% spot size tolerance is appropriate in the majority of the cases, lung cancer plans may require more stringent criteria. As DynamicARC becomes clinically available, measuring spot size errors in practice will be essential to validate these findings and refine tolerance thresholds for clinical use.

目的:在铅笔束扫描(PBS)质子治疗中,光斑尺寸的稳定性至关重要,光斑尺寸的变化会破坏剂量分布。最近,一种名为 DynamicARC PBS 扫描的新型质子束输送方法问世。目前的研究调查了光斑尺寸误差对头颈部(HNC)、前列腺癌和肺癌的动态ARC质子治疗的剂量学影响:为 HNC(4 人)、前列腺癌(4 人)和肺癌(4 人)患者创建了稳健优化的 DynamicARC 质子治疗计划。引入了±10%、±15%和±20%的光斑大小误差,并分析了它们对不同癌症部位的靶点覆盖率(D95%和D99%)、均匀性指数(HI)和风险器官(OAR)剂量的影响:HNC和肺癌计划更容易受到光斑尺寸误差的影响,在光斑尺寸误差为-20%的情况下,目标覆盖率最多可降低4.8%。在这些情况下,剂量均匀性受到的影响也更大,肺癌的 HI 降低了 0.12。前列腺癌对光斑尺寸变化的适应能力更强,即使在误差为±20%的情况下也是如此。在光斑尺寸误差为±10%的情况下,口腔、腮腺和收缩肌的 Dmean 偏差在±1.2%以内,而膀胱和直肠的 D10% 偏差限制在±0.5%,肺的 V20Gy(RBE) 偏差限制在±0.3%。稳健性分析表明,肺癌计划最容易受到光斑尺寸误差导致的稳健性降低的影响,而 HNC 计划则表现出中等敏感性。相反,前列腺癌计划则表现出较高的稳健性,目标覆盖率的降低幅度很小:虽然±10% 的光斑大小容差在大多数情况下都是合适的,但肺癌计划可能需要更严格的标准。随着 DynamicARC 在临床上的应用,在实践中测量光斑大小误差对验证这些发现和完善临床使用的容差阈值至关重要。
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引用次数: 0
IPEM topical report: the first UK survey of cone beam CT dose indices in radiotherapy verification imaging for adult patients. IPEM 专题报告:英国首次对成年患者放疗验证成像中锥束 CT 剂量指数的调查。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-06 DOI: 10.1088/1361-6560/ad88d1
Tim J Wood, Anne T Davis, James Earley, Sue Edyvean, Una Findlay, Rebecca Lindsay, Rosaleen Plaistow, Matthew Williams

Cone beam CT is integral to most modern radiotherapy treatments. The application of daily and repeat CBCT imaging can lead to high imaging doses over a large volume of tissue that extends beyond the treatment site. Hence, it is important to ensure exposures are optimised to keep doses as low as reasonably achievable, whilst ensuring images are suitable for the clinical task. This IPEM topical report presents the results of the first UK survey of dose indices in radiotherapy CBCT. Dose measurements, as defined by the cone beam dose index (CBDIw), were collected along with protocol information for seven treatment sites. Where a range of optimised protocols were available in a centre, a sample of patient data demonstrating the variation in protocol use were requested. Protocol CBDIwvalues were determined from the average dosimetry data for each type of linear accelerator, and median CBDIwand scan length were calculated for each treatment site at each centre. Median CBDIwvalues were compared and summary statistics derived that enable the setting of national dose reference levels (DRLs). A total of 63 UK radiotherapy centres contributed data. The proposed CBDIwDRLs are; prostate 20.6 mGy, gynaecological 20.8 mGy, breast 5.0 mGy, 3D-lung 6.0 mGy, 4D-lung 11.8 mGy, brain 3.5 mGy and head/neck 4.2 mGy. However, large differences between models of imaging system were noted. Where centres had pro-active optimisation strategies in place, such as sized based protocols with selection criteria, dose reductions on the 'average' patient were possible compared with vendor defaults. Optimisation of scan length was noted in some clinical sites, with Elekta users tending to fit different collimators for prostate imaging (relatively short) compared with gynaecological treatments (longest). This contrasts with most Varian users who apply the default scan length in most cases.

锥形束 CT 是大多数现代放射治疗不可或缺的组成部分。每天重复进行 CBCT 成像会导致大量组织的成像剂量增大,甚至超出治疗部位。因此,在确保图像适合临床任务的同时,还必须确保对曝光进行优化,以保持尽可能低的剂量。 这份 IPEM 专题报告介绍了英国首次对 CBCT 放射治疗中的剂量指数进行调查的结果。我们收集了锥形束剂量指数(CBDIw)所定义的剂量测量值以及七个治疗点的方案信息。如果某中心有一系列优化方案,则要求提供患者数据样本,以证明方案使用的差异。根据每种直线加速器的平均剂量测定数据确定方案 CBDIw 值,并计算出每个中心每个治疗点的 CBDIw 中位数和扫描长度。对 CBDIw 中位值进行比较,并得出汇总统计数据,以便制定国家剂量参考水平 (DRL)。建议的 CBDIw DRL 为:前列腺 20.6 mGy、妇科 20.8 mGy、乳腺 5.0 mGy、3D 肺 6.0 mGy、4D 肺 11.8 mGy、脑 3.5 mGy 和头颈部 4.2 mGy。然而,不同型号的成像系统之间存在很大差异。如果中心采取了积极的优化策略,例如基于尺寸的方案,并制定了选择标准,那么与供应商的默认值相比,"普通 "患者的剂量就有可能降低。一些临床中心对扫描长度进行了优化,Elekta 用户倾向于为前列腺成像(相对较短)和妇科治疗(最长)安装不同的准直器。这与大多数瓦里安用户在大多数情况下使用默认扫描长度形成鲜明对比。
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引用次数: 0
Inhomogeneity detection within a head-sized phantom using tracking of charged nuclear fragments in ion beam therapy. 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。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-06 DOI: 10.1088/1361-6560/ad8870
Renato Félix-Bautista, Laura Ghesquière-Diérickx, Pamela Ochoa-Parra, Laurent Kelleter, Gernot Echner, Jürgen Debus, Oliver Jäkel, Mária Martišíková, Tim Gehrke

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.

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。
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引用次数: 0
A framework to model charge sharing and pulse pileup for virtual imaging trials of photon-counting CT. 为光子计数 CT 虚拟成像试验建立电荷共享和脉冲堆积模型的框架。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-06 DOI: 10.1088/1361-6560/ad8b0a
Shobhit Sharma, Stevan Vrbaški, Mridul Bhattarai, Ehsan Abadi, Renata Longo, Ehsan Samei

Objective.This study describes the development, validation, and integration of a detector response model that accounts for the combined effects of x-ray crosstalk, charge sharing, and pulse pileup in photon-counting detectors.Approach.The x-ray photon transport was simulated using Geant4, followed by analytical charge sharing simulation in MATLAB. The analytical simulation models charge clouds with Gaussian-distributed charge densities, which are projected on a 3×3 pixel neighborhood of interaction location to compute detected counts. For pulse pileup, a prior analytical method for redistribution of energy-binned counts was implemented for delta pulses. The x-ray photon transport and charge sharing components were validated using experimental data acquired on the CdTe-based Pixirad-1/Pixie-III detector using monoenergetic beams at 26, 33, 37, and 50 keV. The pulse pileup implementation was verified with a comparable Monte Carlo simulation. The model output without pulse pileup was used to generate spatio-energetic response matrices for efficient simulation of scanner-specific photon-counting CT (PCCT) images with DukeSim, with pulse pileup modeled as a post-processing step on simulated projections. For analysis, images for the Gammex multi-energy phantom and the XCAT chest phantom were simulated at 120 kV, both with and without pulse pileup for a range of doses (27-1344 mAs). The XCAT images were evaluated qualitatively at 120 mAs, while images for the Gammex phantom were evaluated quantitatively for all doses using measurements of attenuation coefficients and Calcium concentrations.Main results.Reasonable agreement was observed between simulated and experimental spectra with Mean Absolute Percentage Error Values (MAPE) between 10%and 31%across all incident energies and detector modes. The increased pulse pileup from increased dose affected attenuation coefficients and calcium concentrations, with an effect on calcium quantification as high as MAPE of 28%.Significance.The presented approach demonstrates the viability of the model for enabling VITs to assess and optimize the clinical performance of PCCT.

目标:本研究描述了探测器响应模型的开发、验证和集成,该模型考虑了光子计数探测器中 X 射线串扰、电荷共享和脉冲堆积的综合影响:方法:使用 Geant4 对 X 射线光子传输进行模拟,然后在 MATLAB 中对电荷共享进行分析模拟。分析模拟以高斯分布电荷密度的电荷云为模型,将其投射到相互作用位置的 3x3 像素邻域上,以计算检测到的计数。对于脉冲堆积,对三角脉冲实施了能量分档计数再分布的先验分析方法。利用基于碲镉合金的 Pixirad-1/Pixie-III探测器获得的实验数据,使用 26、33、37 和 50 千伏的单能量光束,对 X 射线光子传输和电荷共享组件进行了验证。脉冲堆积的实施通过类似的蒙特卡罗模拟进行了验证。无脉冲堆积的模型输出被用于生成空间能量响应矩阵,以便使用 DukeSim 高效模拟扫描仪专用的光子计数 CT(PCCT)图像,并将脉冲堆积建模为模拟投影的后处理步骤。为了进行分析,我们在 120 kV 电压下模拟了 Gammex 多能量模型和 XCAT 胸部模型的图像,并在一定剂量(27-1344 mAs)范围内模拟和不模拟了脉冲堆积。XCAT 图像在 120 mAs 时进行了定性评估,而 Gammex 模型的图像则通过测量衰减系数和钙浓度对所有剂量进行了定量评估:主要结果:在所有入射能量和探测器模式下,模拟光谱和实验光谱的平均绝对百分比误差值 (MAPE) 在 10%-31% 之间,两者之间具有合理的一致性。剂量增加导致的脉冲堆积增加影响了衰减系数和钙浓度,对钙定量的影响高达 28% 的 MAPE:意义:所介绍的方法证明了该模型的可行性,可使 VIT 评估和优化 PCCT 的临床性能。
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Physics in medicine and biology
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