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Automated planning of curved needle channels in 3D printed patient-tailored applicators for cervical cancer brachytherapy. 自动规划用于宫颈癌近距离治疗的 3D 打印患者定制涂抹器中的弯曲针道。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-25 DOI: 10.1088/1361-6560/ad8b08
Robin Straathof, Sharline M van Vliet-Pérez, Inger-Karine K Kolkman-Deurloo, Linda S G L Wauben, Remi A Nout, Ben J M Heijmen, Linda Rossi, Jenny Dankelman, Nick J van de Berg

Purpose.Patient-tailored intracavitary/interstitial (IC/IS) brachytherapy (BT) applicators may increase dose conformity in cervical cancer patients. Current configuration planning methods in these custom applicators rely on manual specification or a small set of (straight) needles. This work introduces and validates a two-stage approach for establishing channel configurations in the 3D printed patient-tailored ARCHITECT applicator.Methods.For each patient, the patient-tailored applicator shape was based on the first BT application with a commercial applicator and integrated connectors to a commercial (Geneva) intrauterine tube and two lunar ring channels. First, a large candidate set was generated of channels that steer the needle to desired poses in the target region and are contained in the applicator. The channels' centrelines were represented by Bézier curves. Channels running between straight target segments and entry points were optimised and refined to ensure (dynamic) feasibility. Second, channel configurations were selected using geometric coverage optimisation. This workflow was applied to establish patient-tailored geometries for twenty-two patients previously treated using the Venezia applicator. Treatment plans were automatically generated using the in-house developed algorithm BiCycle. Plans for the clinically used configuration,TPclin, and patient-tailored configuration,TParch, were compared.Results.Channel configurations could be generated in clinically feasible time (median: 2651 s, range 1826-3812 s). AllTParchandTPclinplans were acceptable, but planning aims were more frequently attained with patient-tailored configurations (115/132 versus 100/132 instances). Median CTVIRD98and bladderD2cm3doses significantly improved (p<0.001 andp<0.01 respectively) inTParchplans in comparison withTPclinplans, and in approximately half of the patients dosimetric indices improved.Conclusion.Automated patient-tailored BT channel configuration planning for 3D printed applicators is clinically feasible. A treatment planning study showed that all plans met planning limits for the patient-tailored configurations, and in selected cases improved the plan quality in comparison with commercial applicator configurations.

目的 为患者量身定制的腔内/间质(IC/IS)近距离放射治疗(BT)应用器可提高宫颈癌患者的剂量一致性。目前这些定制涂抹器的配置规划方法依赖于手动规范或一小套(直)针。这项工作介绍并验证了一种两阶段方法,用于在 3D 打印的患者定制的 ARCHITECT 应用器中建立通道配置。 对于每位患者,患者定制的应用器形状是基于首次使用商用应用器进行的 BT 应用,以及与商用(日内瓦)宫内管和两个月环通道的集成连接器。首先,我们生成了一个庞大的候选通道集,这些通道可将针引导至目标区域的理想位置,并包含在涂抹器中。这些通道的中心线由贝塞尔曲线表示。对直线目标段和入口点之间的通道进行了优化和细化,以确保(动态)可行性。其次,使用几何覆盖优化来选择通道配置。这一工作流程被用于为之前使用 Venezia 治疗仪治疗过的 22 名患者建立适合患者的几何图形。治疗计划通过内部开发的 BiCycle 算法自动生成。对临床常用配置 TPclin 和患者定制配置 TParch 的计划进行了比较。所有 TParch 和 TPclin 计划均可接受,但患者定制的配置更能达到计划目标(115/132 对 100/132)。与 TPclin 计划相比,TParch 计划的中位 CTVIRD98 和膀胱 D2cm3 剂量明显提高(分别为 p< 0.001 和 p< 0.01),约有一半患者的剂量指数得到改善。治疗计划研究表明,所有计划都符合患者定制配置的计划限制,在某些情况下,与商用涂抹器配置相比,计划质量有所提高。
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引用次数: 0
Novel frequency selective B1focusing passive Lenz resonators for substantial MRI signal-to-noise ratio amplification. 用于大幅提高磁共振成像信噪比的新型频率选择性 B1 聚焦无源伦茨谐振器。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-22 DOI: 10.1088/1361-6560/ad965b
Aaron Earl Hodgson, Yurii Shepelytskyi, Viktoriia Batarchuk, Nedal Al Taradeh, Vira Grynko, Mitchell S Albert

Objective: The need for increased sensitivity in magnetic resonance imaging (MRI) is crucial for its advancement as an imaging modality. The development of passive Lenz Resonators for effective RF magnetic field focusing will improve MRI sensitivity via local amplification of MRI signal, thereby leading to more efficient diagnosis and patient treatment.

Approach: While there are methods for amplifying the signal from specific nuclei in MRI, such as hyperpolarization, a general solution will be more advantageous and would work in combination with these preexisting methods. While the Lenz Lens proposed such a general solution based on Lenz's law and the reciprocity principle, it came at the cost of limited signal enhancement. In this work, the first-in-kind prototype Lenz Resonator was conceived and examined as a general frequency-selective passive flux-focusing element for significant MRI signal enhancement. A 3.0 T Philips Achieva MRI was used to compare the signal from a phantom in the presence of Lenz Lenses, Lenz Resonators, and control trials with neither component.

Main results: An MRI investigation demonstrated an experimental amplification of the signal-to-noise ratio up to 80% using an MRI insert of two coaxial Lenz Resonators due to superior B1 magnetic field focusing. The resonators displayed consistent amplification, nearly independent of their x-position within the MRI bore.

Significance: This behavior demonstrates the feasibility of imaging large objects of varying shapes without penalties for signal amplification using Lenz Resonators. The Lenz Resonators versatility in geometrical design and consistent signal amplifying abilities between pulse sequences should allow for the development of Lenz Resonators suitable for most commonly used MRI setups.

目的:提高磁共振成像(MRI)的灵敏度对其作为一种成像方式的发展至关重要。开发用于有效射频磁场聚焦的无源伦茨谐振器将通过局部放大磁共振成像信号来提高磁共振成像的灵敏度,从而提高诊断和治疗病人的效率:虽然有一些方法可以放大磁共振成像中特定细胞核的信号,如超极化,但通用解决方案将更具优势,并能与这些现有方法结合使用。虽然伦兹透镜根据伦兹定律和互惠原理提出了这样一种通用解决方案,但其代价是信号增强效果有限。在这项工作中,我们构思并研究了首个原型伦兹谐振器,将其作为一种通用的频率选择性被动磁通聚焦元件,以显著增强磁共振成像信号。我们使用 3.0 T 飞利浦 Achieva 核磁共振成像仪,比较了在使用伦茨透镜、伦茨谐振器和对照试验中均未使用这两种元件的情况下模型的信号:一项磁共振成像研究表明,由于 B1 磁场聚焦效果出色,使用两个同轴伦茨谐振器的磁共振成像插件可将信噪比放大至 80%。谐振器显示出一致的放大效果,几乎与它们在核磁共振成像孔内的 x 位置无关:意义:这证明了使用伦茨谐振器对不同形状的大型物体进行成像而不影响信号放大的可行性。伦茨谐振器在几何设计上的多样性和不同脉冲序列之间一致的信号放大能力,使得伦茨谐振器的开发适用于大多数常用的磁共振成像装置。
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引用次数: 0
ML-EM based dual tracer PET image reconstruction with inclusion of prompt gamma attenuation. 基于 ML-EM 的双示踪剂 PET 图像重建,包含及时伽马衰减。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-22 DOI: 10.1088/1361-6560/ad9660
Elisabeth Pfaehler, Debora Niekämper, Juergen J Scheins, Nadim Jon Shah, Christoph W Lerche

Objective: Conventionally, if two metabolic processes are of interest for image analysis, two separate, sequential PET scans are performed. However, sequential PET scans cannot simultaneously display the metabolic targets. The concurrent study of two simultaneous PET scans could provide new insights into the causes of diseases. Approach: In this work, we propose a reconstruction algorithm for the simultaneous injection of a β+-emitter emitting only annihilation photons and a β+-γ-emitter emitting annihilation photons and an additional prompt γ-photon. As in previous works, the γ-photon is used to identify events originating from the β+-γ-emitter. However, due to e.g. attenuation, the γ-photon is often not detected and not all events can correctly be associated with the β+-γ-emitter as they are detected as double coincidences. In contrast to previous works, we estimate this number of double coincidences with origin in the β+-γ, emitter including the attenuation of the prompt γ, and incorporate this estimation in the forward-projection of the ML-EM algorithm. For evaluation, we simulate different scenarios with varying objects and attenuation maps. The nuclide 18F serves as β+-emitter, while 44Sc functions as β+-γ emitter. The performance of the algorithm is assessed by calculating the residual error of the β+-γ-emitter in the reconstructed β+-emitter image. Additionally, the intensity values in the simulated cylinders of the ground truth (GT) and the reconstructed images are compared. Main Results: The remaining activity in the β+-emitter image varied from 0.4% to 3.7%. The absolute percentage difference between GT and reconstructed intensity for the pure β+ emitter images was found to be between 3.0 and 7.4% for all cases. The absolute percentage difference between GT and reconstructed intensity for the β+-γ emitter images ranged from 8.7 to 10.4% for all simulated cases. Significance: These results demonstrate that our approach can reconstruct two separate images with a good quantitation accurac.

目的:传统上,如果图像分析涉及两个代谢过程,则需要进行两次单独的顺序正电子发射计算机断层扫描。然而,顺序 PET 扫描无法同时显示代谢目标。同时进行两次正电子发射计算机断层扫描研究可为了解疾病的原因提供新的视角:在这项工作中,我们提出了一种重建算法,用于同时注入只发射湮灭光子的 β+ 发射器和发射湮灭光子及额外γ-光子的 β+-γ 发射器。与之前的研究一样,γ 光子用于识别来自 β+-γ 发射器的事件。然而,由于衰减等原因,γ 光子往往无法被探测到,而且并非所有事件都能正确地与β+-γ 发射器相关联,因为它们会被探测为双重重合。与之前的工作不同,我们估算了起源于 β+-γ 发射器的双重重合事件的数量,包括提示 γ 的衰减,并将这一估算纳入 ML-EM 算法的前向投影中。为了进行评估,我们用不同的对象和衰减图模拟了不同的情况。核素 18F 作为 β+- 发射体,而 44Sc 作为 β+-γ 发射体。通过计算重建的 β+-γ 发射器图像中 β+-γ 发射器的残余误差来评估该算法的性能。此外,还比较了地面实况(GT)和重建图像中模拟圆柱体的强度值:β+ 发射器图像中的剩余活动从 0.4% 到 3.7% 不等。在所有情况下,纯 β+ 发射器图像的 GT 强度与重建强度之间的绝对百分比差异在 3.0% 到 7.4% 之间。在所有模拟案例中,β+-γ 发射器图像的 GT 与重建强度之间的绝对百分比差异在 8.7% 到 10.4% 之间:这些结果表明,我们的方法可以重建两幅独立的图像,并具有良好的定量准确性。
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引用次数: 0
Diffusion equation quantification: selective enhancement algorithm for bone metastasis lesions in CT images. 扩散方程量化:CT 图像中骨转移病灶的选择性增强算法。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-22 DOI: 10.1088/1361-6560/ad965c
Yusuke Anetai, Kentaro Doi, Hideki Takegawa, Yuhei Koike, Midori Yui, Asami Yoshida, Kazuki Hirota, Ken Yoshida, Teiji Nishio, Jun'ichi Kotoku, Mitsuhiro Nakamura, Satoaki Nakamura

Objective: Diffusion equation imaging processing is promising to enhance images showing lesions of bone metastasis (LBM). The Perona-Malik diffusion (PMD) model, which has been widely used and studied, is an anisotropic diffusion processing method to denoise or extract objects from an image effectively. However, the smoothing characteristics of PMD or its related method hinder extraction and enhancement of soft tissue regions of medical image such as computed tomography (CT), typically leaving an indistinct region with ambient tissues. Moreover, PMD expands the border region of the objects. A novel diffusion methodology must be used to enhance the LBM region effectively. Approach. For this study, we originally developed a diffusion equation quantification (DEQ) method that uses a filter function to selectively provide modulated diffusion according to the original locations of objects in an image. The structural similarity index measure (SSIM) and Lie derivative image analysis (LDIA) L-value map were used to evaluate image quality and processing. Main results. We determined superellipse function with its order n=4 for the LBM region. DEQ was found to be more effective at contrasting LBM for various LBM CT images than PMD or its improved models. DEQ yields enhancement agreeing with the indications of positron emission tomography despite complex lesions of bone metastasis comprising osteoblastic, osteoclastic, mixed tissues, and metal artifacts, which is innovative. Moreover, DEQ retained high quality of image (SSIM > 0.95), and achieved a low mean value of the L-value (< 0.001), indicative of our intended selective diffusion compared to other PMD models. Significance. Our method improved the visibility of mixed tissue lesions, which can assist computer visional framework and can help radiologists to produce accurate diagnose of LBM regions which are frequently overlooked in radiology findings because of the various degrees of visibility in CT images.

目的:扩散方程成像处理在增强显示骨转移瘤(LBM)病变的图像方面大有可为。佩罗纳-马利克扩散(PMD)模型是一种各向异性扩散处理方法,可有效地从图像中去噪或提取对象,已被广泛应用和研究。然而,PMD 或其相关方法的平滑特性阻碍了计算机断层扫描(CT)等医学图像中软组织区域的提取和增强,通常会留下一个模糊不清的环境组织区域。此外,PMD 还会扩大物体的边界区域。要有效增强 LBM 区域,必须采用一种新颖的扩散方法。在这项研究中,我们最初开发了一种扩散方程量化(DEQ)方法,该方法使用滤波函数,根据图像中物体的原始位置有选择性地提供调制扩散。结构相似性指数测量(SSIM)和Lie导数图像分析(LDIA)L值图用于评估图像质量和处理。我们为 LBM 区域确定了阶数为 n=4 的超椭圆函数。与 PMD 或其改进模型相比,DEQ 在各种 LBM CT 图像的 LBM 对比方面更为有效。尽管骨转移瘤病变复杂,包括成骨细胞、破骨细胞、混合组织和金属伪影,但 DEQ 所产生的增强效果与正电子发射断层扫描的适应症一致,这一点具有创新性。此外,DEQ 保持了较高的图像质量(SSIM > 0.95),L 值的平均值较低(< 0.001),这表明与其他 PMD 模型相比,我们的选择性扩散是有意义的。我们的方法提高了混合组织病变的可见度,这有助于计算机视觉框架,并能帮助放射科医生准确诊断 LBM 区域,由于 CT 图像的可见度不同,这些区域在放射科检查结果中经常被忽略。
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引用次数: 0
Automated treatment planning with deep reinforcement learning for head-and-neck (HN) cancer intensity modulated radiation therapy (IMRT). 利用深度强化学习对头颈部(HN)癌症进行强度调制放射治疗(IMRT)的自动治疗规划。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-22 DOI: 10.1088/1361-6560/ad965d
Dongrong Yang, Xin Wu, Xinyi Li, Ryan Mansfield, Yibo Xie, Qiuwen Wu, Q Jackie Wu, Yang Sheng

Purpose: To develop a deep reinforcement learning (DRL) agent to self-interact with the treatment planning system (TPS) to automatically generate intensity modulated radiation therapy (IMRT) treatment plans for head-and-neck (HN) cancer with consistent organ-at-risk (OAR) sparing performance. Methods: With IRB approval, one hundred and twenty HN patients receiving IMRT were included. The DRL agent was trained with 20 patients. During each inverse optimization process, the intermediate dosimetric endpoints' value, dose volume constraints value and structure objective function loss were collected as the DRL states. By adjusting the objective constraints as actions, the agent learned to seek optimal rewards by balancing OAR sparing and planning target volume (PTV) coverage. Reward computed from current dose-volume-histogram (DVH) endpoints and clinical objectives were sent back to the agent to update action policy during model training. The trained agent was evaluated with the rest 100 patients. Results: The DRL agent was able to generate a clinically acceptable IMRT plan within 12.4±3.1 minutes without human intervention. DRL plans showed lower PTV maximum dose (109.2%) compared to clinical plans (112.4%) (p<.05). Average median dose of left parotid, right parotid, oral cavity, larynx, pharynx of DRL plans were 15.6Gy, 12.2Gy, 25.7Gy, 27.3Gy and 32.1Gy respectively, comparable to 17.1 Gy,15.7Gy, 24.4Gy, 23.7Gy and 35.5Gy of corresponding clinical plans. The maximum dose of cord+5mm, brainstem and mandible were also comparable between the two groups. In addition, DRL plans demonstrated reduced variability, as evidenced by smaller 95% confidence intervals. The total MU of the DRL plans was 1611 vs 1870 (p<.05) of clinical plans. The results signaled the DRL's consistent planning strategy compared to the planners' occasional back-and-forth decision-making during planning. Conclusion: The proposed deep reinforcement learning (DRL) agent is capable of efficiently generating HN IMRT plans with consistent quality. .

目的: 开发一种深度强化学习(DRL)代理,使其能够与治疗计划系统(TPS)进行自我交互,从而为头颈部(HN)癌症自动生成强度调制放射治疗(IMRT)治疗计划,并具有一致的风险器官(OAR)疏通性能。对 20 名患者进行了 DRL 代理训练。在每次逆优化过程中,收集中间剂量学终点值、剂量体积约束值和结构目标函数损失作为 DRL 状态。通过调整作为行动的目标约束条件,代理学会了通过平衡 OAR sparing 和计划目标容积(PTV)覆盖率来寻求最佳奖励。在模型训练过程中,根据当前剂量-体积-历史图(DVH)终点和临床目标计算出的奖励被发送回代理,以更新行动策略。结果: DRL 代理能够在 12.4±3.1 分钟内生成临床上可接受的 IMRT 计划,无需人工干预。与临床计划(112.4%)相比,DRL 计划显示出更低的 PTV 最大剂量(109.2%)(p
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引用次数: 0
On the microdosimetric characterisation of the radiation quality of a carbon-ion beam and the effect of the target volume thickness. 碳离子束辐射质量的微观模拟特性及靶体积厚度的影响。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-22 DOI: 10.1088/1361-6560/ad965e
Gabriele Parisi, Giulio Magrin, Claudio Verona, Gianluca Verona-Rinati, Sandra Barna, Cynthia Meouchi, Francesco Romano, Giuseppe Schettino

Objective - Microdosimetry is gaining increasing interest in particle therapy. Thanks to the advancements in microdosimeter technologies and the increasing number of experimental studies carried out in hadron therapy frameworks, it is proving to be a reliable experimental technique for radiation quality characterisation, quality assurance, and radiobiology studies. However, considering the variety of detectors used for microdosimetry, it is important to ensure the consistency of microdosimetric results measured with different types of microdosimeters. Approach - This work presents a novel multi-thickness microdosimeter and a methodology to characterise the radiation quality of a clinical carbon-ion beam. The novel device is a diamond detector made of three sensitive volumes (SV) of different thicknesses: 2, 6 and 12 μm. The SVs, which operate simultaneously, were accurately aligned and laterally positioned within 3mm. This allignement allowed for a comparison of the results with a negligible impact of the SVs alignment and their lateral positioning, ensuring the homogeneity of the measured radiation quality. An experimental campaign was carried out at MedAustron using a carbon-ion beam of typical clinical energy (284.7MeV/u). Main results - The measurement results allowed for a meticulous interpretation of its radiation quality, highlighting the effect of the SV thickness. The consistency of the microdosimetric spectra measured by detectors of different thicknesses is discussed by critically analysing the spectra and the differences observed. Significance - The methodology presented will be highly valuable for future experiments investigating the effects of the target volume size in radiobiology and could be easily adapted to the other particles employed in hadron therapy for clinical (i.e. protons) and for research purposes (e.g. helium, lithium and oxygen ions).

目的 - 微剂量测定技术在粒子治疗领域越来越受到关注。由于微剂量计技术的进步以及在强子治疗框架内开展的实验研究数量不断增加,微剂量计已被证明是一种可靠的实验技术,可用于辐射质量表征、质量保证和放射生物学研究。然而,考虑到用于微剂量测定的探测器种类繁多,确保使用不同类型微剂量计测量的微剂量测定结果的一致性非常重要。这种新型装置是由三个不同厚度(2、6 和 12 μm)的敏感体 (SV) 组成的金刚石探测器。同时工作的 SV 经过精确对准,横向定位在 3 毫米以内。这种对齐方式可以对结果进行比较,SV 对齐及其横向定位的影响可以忽略不计,从而确保了测量辐射质量的一致性。在 MedAustron 公司使用典型临床能量(284.7MeV/u)的碳离子束进行了一次实验。通过对光谱和观察到的差异进行批判性分析,讨论了不同厚度探测器测得的微剂量测定光谱的一致性。
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引用次数: 0
Dual virtual non-contrast imaging: a Bayesian quantitative approach to determine radiotherapy quantities from contrast-enhanced DECT images. 双虚拟非对比成像:从对比增强 DECT 图像确定放疗量的贝叶斯定量方法。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-22 DOI: 10.1088/1361-6560/ad965f
Mohsen Beikali Soltani, Hugo Bouchard

Objective: Contrast agents in CT scans can compromise the accuracy of dose calculations in radiation therapy planning, especially for particle therapy. This often requires an additional non-contrast CT scan, increasing radiation exposure and introducing potential registration errors. Our goal is to resolve these issues by accurately estimating radiotherapy parameters from dual virtual non-contrast (dual-VNC) images generated by contrast-enhanced dual-energy CT (DECT) scans, while accounting for noise and variability in tissue composition. Approach: A new Bayesian model is introduced to estimate dual-VNC Hounsfield units from contrast-enhanced DECT data. The model defines a prior distribution that describes tissue variations in terms of elemental compositions and mass densities. Multiple reference tissues are used to estimate variations across human tissues. A likelihood distribution is also defined to model the noise contained in CT data. The model is thoroughly validated in a simulated environment including 12 virtual patients under low and high iodine uptake scenarios, while incorporating noise and beam hardening effects. The eigentissue decomposition (ETD) technique is used to derive elemental compositions and parameters critical for radiotherapy from the dual-VNC images, such as electron density (ρe), particle stopping power (SPR), and photon energy absorption coefficient (EAC) Main results: The proposed method yields accurate voxelwise estimations for ρe, SPR, and EAC, with root mean square errors of 3.09%, 3.14%, and 1.34% for highly-enhanced tissues, compared to 5.93%, 6.39%, and 17.11% when the presence of contrast agent is ignored. It also demonstrates robustness to systematic shifts in tissue composition and bandwidth variations in the prior distribution, resulting in overall uncertainties down to 1.13%, 1.33%, and 0.86% for ρe, SPR, and EAC in soft tissues; 1.17%, 1.32%, and 1.34% in enhanced soft tissues; and 4.34%, 4.00%, and 2.50% in bone. Significance: The proposed method accurately derives radiotherapy parameters from contrast-enhanced DECT data and demonstrates robustness against systematic errors in reference data, highlighting its potential for clinical use.

目的:CT 扫描中的造影剂会影响放射治疗计划中剂量计算的准确性,尤其是粒子治疗。这通常需要额外的非对比 CT 扫描,从而增加了辐射量并带来潜在的登记错误。我们的目标是解决这些问题,从对比度增强双能 CT(DECT)扫描生成的双虚拟非对比度(dual-VNC)图像中准确估算放疗参数,同时考虑噪声和组织成分的可变性:方法:介绍一种新的贝叶斯模型,用于从对比度增强 DECT 数据中估算双 VNC Hounsfield 单位。该模型定义了一个先验分布,以元素组成和质量密度来描述组织的变化。使用多个参考组织来估计人体组织的变化。此外,还定义了一个似然分布来模拟 CT 数据中的噪声。该模型在模拟环境中进行了全面验证,包括在低碘摄入量和高碘摄入量情况下的 12 位虚拟病人,同时结合了噪声和光束硬化效应。利用电子组织分解(ETD)技术,从双 VNC 图像中得出对放疗至关重要的元素组成和参数,如电子密度(ρe)、粒子停止功率(SPR)和光子能量吸收系数(EAC) 主要结果:对于高度增强的组织,所提出的方法能准确地按体素估算出ρe、SPR和EAC,均方根误差分别为3.09%、3.14%和1.34%,而在忽略造影剂存在的情况下,均方根误差分别为5.93%、6.39%和17.11%。它还显示出对组织成分系统性变化和先验分布带宽变化的鲁棒性,使软组织中ρe、SPR 和 EAC 的总体不确定性分别降至 1.13%、1.33% 和 0.86%;增强软组织中分别为 1.17%、1.32% 和 1.34%;骨骼中分别为 4.34%、4.00% 和 2.50%:所提出的方法能从对比增强 DECT 数据中准确推导出放疗参数,并对参考数据中的系统误差表现出稳健性,突出了其在临床应用中的潜力。
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引用次数: 0
Comparison of contrast-enhanced ultrasound imaging (CEUS) and super-resolution ultrasound (SRU) for the quantification of ischaemia flow redistribution: a theoretical study. 对比增强超声成像(CEUS)与超分辨率超声成像(SRU)在量化缺血血流再分布方面的比较:理论研究。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-22 DOI: 10.1088/1361-6560/ad9231
Lachlan J M B Arthur, Vasiliki Voulgaridou, Mairead B Butler, Georgios Papageorgiou, Weiping Lu, Steven R McDougall, Vassilis Sboros

The study of microcirculation can reveal important information related to pathology. Focusing on alterations that are represented by an obstruction of blood flow in microcirculatory regions may provide an insight into vascular biomarkers. The current in silico study assesses the capability of contrast enhanced ultrasound (CEUS) and super-resolution ultrasound imaging (SRU) flow-quantification to study occlusive actions in a microvascular bed, particularly the ability to characterise known and model induced flow behaviours. The aim is to investigate theoretical limits with the use of CEUS and SRU in order to propose realistic biomarker targets relevant for clinical diagnosis. Results from CEUS flow parameters display limitations congruent with prior investigations. Conventional resolution limits lead to signals dominated by large vessels, making discrimination of microvasculature specific signals difficult. Additionally, some occlusions lead to weakened parametric correlation against flow rate in the remainder of the network. Loss of correlation is dependent on the degree to which flow is redistributed, with comparatively minor redistribution correlating in accordance with ground truth measurements for change in mean transit time,dMTT(CEUS,R = 0.85; GT,R = 0.82) and change in peak intensity,dIp(CEUS,R = 0.87; GT,R = 0.96). Major redistributions, however, result in a loss of correlation, demonstrating that the effectiveness of time-intensity curve parameters is influenced by the site of occlusion. Conversely, results from SRU processing provides accurate depiction of the anatomy and dynamics present in the vascular bed, that extends to individual microvessels. Correspondence between model vessel structure displayed in SRU maps with the ground truth was>91%for cases of minor and major flow redistributions. In conclusion, SRU appears to be a highly promising technology in the quantification of subtle flow phenomena due ischaemia induced vascular flow redistribution.

微循环研究可以揭示与病理学相关的重要信息。当前的硅学研究评估了 CEUS 和 SRU 流量量化技术研究微血管床闭塞作用的能力,特别是描述已知和模型诱导的流动行为的能力。其目的是研究使用 CEUS 和即将在 SRU 中使用的粒子追踪技术的理论限制,以便提出与临床诊断相关的实际生物标记目标。CEUS血流参数的结果显示出与之前研究一致的局限性。传统的分辨率限制导致大血管信号占主导地位,使微血管特异性信号难以分辨 。此外,一些闭塞会导致参数与网络其余部分流速的相关性减弱 。相关性的丧失取决于血流被重新分配的程度,相对较小的重新分配与平均通过时间 dM T T(CEUS,R = 0.85;GT,R = 0.82)变化和峰值强度 dIp(CEUS,R = 0.87; GT,R = 0.96)变化的地面实况测量结果相关。然而,主要的重新分布会导致相关性丧失,这表明 TIC 相关参数的有效性取决于闭塞的位置。相反,SRU 处理的结果能准确 描述血管床的解剖结构和动态,并延伸到单个微血管。SRU 地图中显示的模型血管结构与地面实况之间的相关性在轻微和重大血流再分布情况下均大于 91%。总之,SRU 似乎是一种非常有前途的技术,可用于量化缺血引起的血管血流再分布造成的微妙血流现象。
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引用次数: 0
Resolution-dependent MRI-to-CT translation for orthotopic breast cancer models using deep learning. 利用深度学习实现正位乳腺癌模型的分辨率依赖性 MRI-CT 转换
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-21 DOI: 10.1088/1361-6560/ad9076
Dagnachew Tessema Ambaye, Abel Worku Tessema, Jiwoo Jeong, Jiwon Ryu, Tosol Yu, Jimin Lee, Hyungjoon Cho

Objective.This study aims to investigate the feasibility of utilizing generative adversarial networks (GANs) to synthesize high-fidelity computed tomography (CT) images from lower-resolution MR images. The goal is to reduce patient exposure to ionizing radiation while maintaining treatment accuracy and accelerating MR image acquisition. The primary focus is to determine the extent to which low-resolution MR images can be utilized to generate high-quality CT images through a systematic study of spatial resolution-dependent magnetic resonance imaging (MRI)-to-CT image conversion.Approach.Paired MRI-CT images were acquired from healthy control and tumor models, generated by injecting MDA-MB-231 and 4T1 tumor cells into the mammary fat pad of nude and BALB/c mice to ensure model diversification. To explore various MRI resolutions, we downscaled the highest-resolution MR image into three lower resolutions. Using a customized U-Net model, we automated region of interest masking for both MRI and CT modalities with precise alignment, achieved through three-dimensional affine paired MRI-CT registrations. Then our customized models, Nested U-Net GAN and Attention U-Net GAN, were employed to translate low-resolution MR images into high-resolution CT images, followed by evaluation with separate testing datasets.Main Results.Our approach successfully generated high-quality CT images (0.142mm2) from both lower-resolution (0.282mm2) and higher-resolution (0.142mm2) MR images, with no statistically significant differences between them, effectively doubling the speed of MR image acquisition. Our customized GANs successfully preserved anatomical details, addressing the typical loss issue seen in other MRI-CT translation techniques across all resolutions of MR image inputs.Significance.This study demonstrates the potential of using low-resolution MR images to generate high-quality CT images, thereby reducing radiation exposure and expediting MRI acquisition while maintaining accuracy for radiotherapy.

目的: 本研究旨在探讨利用生成对抗网络(GAN)从低分辨率磁共振图像合成高保真 CT 图像的可行性。目的是在保持治疗准确性和加速 MR 图像采集的同时,减少患者暴露于电离辐射的机会。 Approach. Paired MRI-CT images were acquired from healthy control and tumor models, generated by injecting MDA-MB-231 and 4T1 tumor cells into the mammary fat pad of nude and BALB/c mice to ensure model diversification.为了探索不同的 MRI 分辨率,我们将最高分辨率的 MR 图像降频为三个较低分辨率的图像。我们使用定制的 U-Net 模型,通过三维仿射配对 MRI-CT 注册,自动对 MRI 和 CT 模式进行精确配准的感兴趣区掩蔽。然后,我们使用定制模型--嵌套 U-Net 生成对抗网络(NUGAN)和注意力 U-Net 生成对抗网络(AUGAN)--将低分辨率 MR 图像转化为高分辨率 CT 图像,并使用单独的测试数据集进行评估。 主要结果 我们的方法成功地从低分辨率(0.282 平方毫米)和高分辨率(0.142 平方毫米)MR 图像生成了高质量 CT 图像(0.142 平方毫米),两者之间没有显著的统计学差异,有效地将 MR 图像采集速度提高了一倍。我们定制的 GAN 成功地保留了解剖细节,解决了其他 MRI-CT 转换技术在所有分辨率 MR 图像输入中都会出现的典型损失问题。
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引用次数: 0
Feasibility study of modularized pin ridge filter implementation in proton FLASH planning for liver stereotactic ablative body radiotherapy. 在质子 FLASH 计划中实施模块化针脊滤波器进行肝脏立体定向消融体放射治疗的可行性研究。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-21 DOI: 10.1088/1361-6560/ad95d6
Chaoqiong Ma, Xiaofeng Yang, Jufri Setianegara, Yinan Wang, Yuan Gao, David S Yu, Pretesh Patel, Jun Zhou

We previously developed a FLASH planning framework for streamlined pin-ridge-filter (pin-RF) design, demonstrating its feasibility for single-energy proton FLASH planning. In this study, we refined the pin-RF design for easy assembly using reusable modules, focusing on its application in liver stereotactic ablative body radiotherapy (SABR). This framework generates an intermediate intensity-modulated proton therapy (IMPT) plan and translates it into step widths and thicknesses of pin-RFs for a single-energy FLASH plan. Parameters like energy spacing, monitor unit limit, and spot quantity were adjusted during IMPT planning, resulting in pin-RFs assembled using predefined modules with widths from 1 to 6 mm, each with a water-equivalent-thickness of 5 mm. This approach was validated on three liver SABR cases. FLASH doses, quantified using the FLASH effectiveness model at 1 to 5 Gy thresholds, were compared to conventional IMPT (IMPT-CONV) doses to assess clinical benefits. The highest demand for 6 mm width modules, moderate for 2-4 mm, and minimal for 1- and 5-mm modules were shown across all cases. At lower dose thresholds, the two-beam case reduced indicators including liver V21Gy and skin Dmax by >19.4%, while the three-beam cases showed reductions ≤11.4%, indicating the need for higher fractional beam doses for an enhanced FLASH effect. Positive clinical benefits were seen only in the two-beam case at the 5 Gy threshold. At the 1 Gy threshold, the two-beam FLASH plan outperformed the IMPT-CONV plan, reducing dose indicators for all relevant normal tissues by up to 31.2%. In contrast, the three-beam cases showed negative clinical benefits, with skin Dmax and liver V21Gy increasing by up to 17.4% due to lower fractional beam doses and closer beam arrangements. This study evaluated the feasibility of modularizing streamlined pin-RFs in single-energy proton FLASH planning for liver SABR, offering guidance on optimal module composition and strategies to enhance FLASH planning.

我们之前开发了一种用于简化针脊过滤器(pin-RF)设计的 FLASH 计划框架,证明了其在单能量质子 FLASH 计划中的可行性。在本研究中,我们改进了针脊过滤器的设计,使其能够使用可重复使用的模块进行简易组装,重点关注其在肝脏立体定向消融体放射治疗(SABR)中的应用。该框架可生成中间强度调制质子治疗(IMPT)计划,并将其转化为单能量 FLASH 计划中针-RF 的阶梯宽度和厚度。在 IMPT 计划期间,对能量间隔、监控单元限制和光斑数量等参数进行调整,从而使用宽度为 1 到 6 毫米的预定义模块组装出针-RF,每个模块的水等效厚度为 5 毫米。这种方法在三个肝脏 SABR 病例中得到了验证。在 1 到 5 Gy 的阈值下,使用 FLASH 效能模型量化的 FLASH 剂量与传统的 IMPT(IMPT-CONV)剂量进行了比较,以评估临床效益。在所有病例中,6 毫米宽模块的需求量最大,2-4 毫米模块的需求量适中,1 毫米和 5 毫米模块的需求量最小。在较低的剂量阈值下,双光束病例的肝脏V21Gy和皮肤Dmax等指标降低了19.4%以上,而三光束病例则降低了≤11.4%,这表明需要更高的部分光束剂量来增强FLASH效果。只有在 5 Gy 临界值下的双光束病例才有积极的临床疗效。在 1 Gy 临界值时,双光束 FLASH 方案优于 IMPT-CONV 方案,可将所有相关正常组织的剂量指标降低 31.2%。与此相反,三光束病例显示出负面的临床效益,皮肤Dmax和肝脏V21Gy增加了17.4%,原因是部分光束剂量更低,光束排列更紧密。这项研究评估了在肝脏SABR的单能质子FLASH计划中将流线型针式RF模块化的可行性,为最佳模块组成和增强FLASH计划的策略提供了指导。
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引用次数: 0
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