Zeitschrift fur Medizinische Physik最新文献_第4页

Physical wedge as a tool for radiochromic film calibration 物理楔子作为放射色膜校准的工具

IF 2.4 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2025-05-01 DOI: 10.1016/j.zemedi.2023.05.008

Stevan Pecić , Miloš Vićić , Ivan Belča , Strahinja Stojadinović , Borko Nidžović , Ljubomir Kurij , Slobodan Dević

Reliable calibration is one of the major challenges in using radiochromic films (RCF) for radiation dosimetry. In this study the feasibility of using dose gradients produced by a physical wedge (PW) for RCF calibration was investigated. The aim was to establish an efficient and reproducible method for calibrating RCF using a PW. Film strips were used to capture the wedge dose profile for five different exposures and the acquired scans were processed to generate corresponding net optical density wedge profiles. The proposed method was compared to the benchmark calibration, following the guidelines for precise calibration using uniform dose fields. The results of the benchmark comparison presented in this paper showed that using a single film strip for measuring wedge dose profile is sufficient for estimating a reliable calibration curve within the recorded dose range. Furthermore, the PW calibration can be extrapolated or extended by using multiple gradients for the optimal coverage of the desired calibration dose range. The method outlined in this paper can be readily replicated using the equipment and expertise commonly found in a radiotherapy center. Once the dose profile and central axis attenuation coefficient of the PW are determined, they can serve as a reference for a variety of calibrations using different types and batches of film. This investigation demonstrated that the calibration curves obtained with the presented PW calibration method are within the bounds of the measurement uncertainty evaluated for the conventional uniform dose field calibration method.

可靠的校准是使用放射性致色膜（RCF）进行辐射剂量测定的主要挑战之一。本研究探讨了利用物理楔（PW）产生的剂量梯度进行RCF校准的可行性。目的是建立一种使用PW校准RCF的有效和可重复的方法。使用薄膜条捕获五种不同曝光的楔形剂量分布图，并对获得的扫描进行处理以生成相应的净光密度楔形分布图。按照均匀剂量场精确校准的指导方针，将所提出的方法与基准校准进行了比较。本文给出的基准对比结果表明，在记录的剂量范围内，用单个薄膜条测量楔形剂量分布足以估计出可靠的校准曲线。此外，PW校准可以通过使用多个梯度来外推或扩展，以获得所需校准剂量范围的最佳覆盖范围。本文概述的方法可以使用放射治疗中心常见的设备和专业知识很容易地复制。一旦确定了PW的剂量分布和中轴衰减系数，就可以作为使用不同类型和批次的薄膜进行各种校准的参考。研究表明，所提出的PW校准方法得到的校准曲线在常规均匀剂量场校准方法的测量不确定度范围内。

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引用次数: 0

Comparison of different neurite density metrics with brain asymmetry evaluation 不同神经突密度指标与脑不对称评价的比较

IF 2.4 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2025-05-01 DOI: 10.1016/j.zemedi.2023.07.003

Ivan I. Maximov , Lars T. Westlye

The standard diffusion MRI model with intra- and extra-axonal water pools offers a set of microstructural parameters describing brain white matter architecture. However, non-linearities in the standard model and diffusion data contamination by noise and imaging artefacts make estimation of diffusion metrics challenging. In order to develop reliable diffusion approaches and to avoid computational model degeneracy, additional theoretical assumptions allowing stable numerical implementations are required. Advanced diffusion approaches allow for estimation of intra-axonal water fraction (AWF), describing a key structural characteristic of brain tissue. AWF can be interpreted as an indirect measure or proxy of neurite density and has a potential as useful clinical biomarker. Established diffusion approaches such as white matter tract integrity, neurite orientation dispersion and density imaging (NODDI), and spherical mean technique provide estimates of AWF within their respective theoretical frameworks. In the present study, we estimated AWF metrics using different diffusion approaches and compared measures of brain asymmetry between the different metrics in a sub-sample of 182 subjects from the UK Biobank. Multivariate decomposition by mean of linked independent component analysis revealed that the various AWF proxies derived from the different diffusion approaches reflect partly non-overlapping variance of independent components, with distinct anatomical distributions and sensitivity to age. Further, voxel-wise analysis revealed age-related differences in AWF-based brain asymmetry, indicating less apparent left-right hemisphere difference with higher age. Finally, we demonstrated that NODDI metrics suffer from a quite strong dependence on used numerical algorithms and post-processing pipeline. The analysis based on AWF metrics strongly depends on the used diffusion approach and leads to poorly reproducible results.

具有轴突内和轴突外水池的标准弥散MRI模型提供了一组描述脑白质结构的微结构参数。然而，标准模型中的非线性和受噪声和成像伪影污染的扩散数据使得扩散度量的估计具有挑战性。为了开发可靠的扩散方法并避免计算模型退化，需要允许稳定数值实现的附加理论假设。先进的扩散方法允许估计轴突内水分数（AWF），描述脑组织的关键结构特征。AWF可以被解释为神经突密度的间接测量或代理，具有潜在的有用的临床生物标志物。已建立的扩散方法，如白质束完整性、神经突取向弥散和密度成像（NODDI）和球面平均技术，在各自的理论框架内提供了AWF的估计。在本研究中，我们使用不同的扩散方法估计了AWF指标，并比较了来自英国生物银行的182名受试者的不同指标之间的大脑不对称测量。通过关联独立分量分析进行多元分解，发现不同扩散方法得到的AWF指标部分反映了独立分量的非重叠方差，具有不同的解剖分布和对年龄的敏感性。此外，体素分析揭示了基于awf的大脑不对称性的年龄相关差异，表明年龄越大，左右半球差异越不明显。最后，我们证明了NODDI指标非常依赖于所使用的数值算法和后处理管道。基于AWF指标的分析强烈依赖于所使用的扩散方法，导致结果的可重复性很差。

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引用次数: 0

Gamma radiation detector selection for CT scanner CT扫描仪伽玛辐射探测器的选择

IF 2.4 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2025-05-01 DOI: 10.1016/j.zemedi.2023.07.006

Kajal Kumari, Mayank Goswami

Three types of gamma radiation detectors associated with distributed electronics namely, NaI (Tl), HPGe and

{LaBr}_{3} (C e)

are compared primarily focusing on electronic noise and scattering noise. Additionally, detectors of same make, material, size and electronics are also compared. A methodology is proposed to select the most suitable detector for computed tomography (CT) among the available options. Standard deviation parameter is employed to estimate electronic noise without performing CT experiment. Kanpur theorem-1(KT-1) is used to estimate the scattering noise quantitatively after verifying its sensitivity to scattering noise. The impact of scattering noise on CT profiles is evaluated using dice similarity dice coefficient. A good resemblance between KT-1 and dice coefficient is observed. A maximum difference of 56% in scattering noise is observed when five detectors used simultaneously instead of single detector whereas a discrepancy of 85% is observed between different types of radiation detectors. As far as ease of handling, operational and capital cost is concern one has to compromise minimum 12% of accuracy in CT reconstruction if NaI (Tl) detector is used with respect to best alternative available.

The proposed methodology can be applied to measurement that require minimal scattering interference data other than CT experiments. The manufacturer can add noise level of detector as a characteristic parameter in the data sheet.

比较了三种与分布式电子学相关的伽马辐射探测器，即NaI （Tl）、HPGe和LaBr3(Ce)，主要关注电子噪声和散射噪声。此外，还对相同制造、材料、尺寸和电子器件的探测器进行了比较。提出了一种方法，以选择最合适的检测器的计算机断层扫描（CT）中可用的选项。在不进行CT实验的情况下，采用标准差参数估计电子噪声。在验证了Kanpur定理1（KT-1）对散射噪声的敏感性后，利用Kanpur定理1对散射噪声进行了定量估计。利用骰子相似系数评价了散射噪声对CT轮廓的影响。观察到KT-1和骰子系数之间有很好的相似性。同时使用5个探测器而不是单个探测器时，散射噪声的最大差异为56%，而不同类型的辐射探测器之间的差异为85%。考虑到操作、操作和资金成本，如果使用NaI （Tl）检测器作为最佳替代方案，则必须在CT重建中牺牲至少12%的准确性。该方法可应用于CT实验以外的散射干扰最小的测量。制造商可以在数据表中添加探测器的噪声级作为特征参数。

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引用次数: 0

Editorial Board + Consulting Editorial Board 编辑委员会+咨询编辑委员会

IF 2.4 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2025-05-01 DOI: 10.1016/S0939-3889(25)00044-3

引用次数: 0

Quality assurance and temporal stability of a 1.5 T MRI scanner for MR-guided Photon and Particle Therapy 用于核磁共振引导光子和粒子治疗的1.5 T MRI扫描仪的质量保证和时间稳定性

IF 2.4 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2025-05-01 DOI: 10.1016/j.zemedi.2023.04.004

Stefan Dorsch , Katharina Paul , Cedric Beyer , Christian P Karger , Oliver Jäkel , Jürgen Debus , Sebastian Klüter

Purpose

To describe performance measurements, adaptations and time stability over 20 months of a diagnostic MR scanner for integration into MR-guided photon and particle radiotherapy.

Material and methods

For realization of MR-guided photon and particle therapy (MRgRT/MRgPT), a 1.5 T MR scanner was installed at the Heidelberg Ion Beam Therapy Center. To integrate MRI into the treatment process, a flat tabletop and dedicated coil holders for flex coils were used, which prevent deformation of the patient external contour and allow for the use of immobilization tools for reproducible positioning. The signal-to-noise ratio (SNR) was compared for the diagnostic and therapy-specific setup using the flat couch top and flexible coils for the a) head & neck and b) abdominal region as well as for different bandwidths and clinical pulse sequences. Additionally, a quality assurance (QA) protocol with monthly measurements of the ACR phantom and measurement of geometric distortions for a large field-of-view (FOV) was implemented to assess the imaging quality parameters of the device over the course of 20 months.

Results

The SNR measurements showed a decreased SNR for the RT-specific as compared to the diagnostic setup of (a) 26% to 34% and (b) 11% to 33%. No significant bandwidth dependency for this ratio was found. The longitudinal assessment of the image quality parameters with the ACR and distortion phantom confirmed the long-term stability of the MRI device.

Conclusion

A diagnostic MRI was commissioned for use in MR-guided particle therapy. Using a radiotherapy specific setup, a high geometric accuracy and signal homogeneity was obtained after some adaptions and the measured parameters were shown to be stable over a period of 20 months.

目的描述诊断性磁共振扫描仪集成到磁共振引导光子和粒子放射治疗中的性能测量，适应性和时间稳定性超过20个月。材料和方法为了实现核磁共振引导光子和粒子治疗（MRgRT/MRgPT），在海德堡离子束治疗中心安装了一台1.5 T核磁共振扫描仪。为了将MRI整合到治疗过程中，使用了一个扁平的桌面和专用的弯曲线圈支架，以防止患者外部轮廓变形，并允许使用固定工具进行可重复定位。比较诊断和治疗特定设置的信噪比（SNR），使用平沙发顶和柔性线圈作为a)头；颈部和腹部区域以及不同的带宽和临床脉冲序列。此外，实施了质量保证（QA）方案，每月测量ACR模体和测量大视场（FOV）的几何畸变，以评估设备在20个月内的成像质量参数。结果信噪比测量显示，与诊断设置(a) 26%至34%和(b) 11%至33%相比，rt特异性的信噪比降低。该比率没有发现明显的带宽依赖关系。利用ACR和畸变模体对图像质量参数进行纵向评估，证实了该MRI装置的长期稳定性。结论磁共振诊断技术可用于磁共振引导粒子治疗。使用放射治疗专用装置，经过一些调整后获得了高几何精度和信号均匀性，并且测量参数在20个月的时间内显示稳定。

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引用次数: 0

Silicone phantoms fabricated with multi-material extrusion 3D printing technology mimicking imaging properties of soft tissues in CT 采用多材料挤压3D打印技术制作模拟软组织CT成像特性的硅胶模型

IF 2.4 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2025-05-01 DOI: 10.1016/j.zemedi.2023.05.007

Sepideh Hatamikia , Laszlo Jaksa , Gernot Kronreif , Wolfgang Birkfellner , Joachim Kettenbach , Martin Buschmann , Andrea Lorenz

Recently, 3D printing has been widely used to fabricate medical imaging phantoms. So far, various rigid 3D printable materials have been investigated for their radiological properties and efficiency in imaging phantom fabrication. However, flexible, soft tissue materials are also needed for imaging phantoms for simulating several clinical scenarios where anatomical deformations is important. Recently, various additive manufacturing technologies have been used to produce anatomical models based on extrusion techniques that allow the fabrication of soft tissue materials. To date, there is no systematic study in the literature investigating the radiological properties of silicone rubber materials/fluids for imaging phantoms fabricated directly by extrusion using 3D printing techniques. The aim of this study was to investigate the radiological properties of 3D printed phantoms made of silicone in CT imaging. To achieve this goal, the radiodensity as described as Hounsfield Units (HUs) of several samples composed of three different silicone printing materials were evaluated by changing the infill density to adjust their radiological properties. A comparison of HU values with a Gammex Tissue Characterization Phantom was performed. In addition, a reproducibility analysis was performed by creating several replicas for specific infill densities. A scaled down anatomical model derived from an abdominal CT was also fabricated and the resulting HU values were evaluated. For the three different silicone materials, a spectrum ranging from −639 to +780 HU was obtained on CT at a scan setting of 120 kVp. In addition, using different infill densities, the printed materials were able to achieve a similar radiodensity range as obtained in different tissue-equivalent inserts in the Gammex phantom (238 HU to −673 HU). The reproducibility results showed good agreement between the HU values of the replicas compared to the original samples, confirming the reproducibility of the printed materials. A good agreement was observed between the HU target values in abdominal CT and the HU values of the 3D-printed anatomical phantom in all tissues.

近年来，3D打印技术被广泛应用于医学成像幻影的制造。到目前为止，人们已经研究了各种刚性3D打印材料的放射学性能和成像幻影制造的效率。然而，灵活的软组织材料也需要成像的幻影，以模拟几种临床场景，其中解剖变形是重要的。最近，各种增材制造技术已被用于生产基于挤压技术的解剖模型，从而可以制造软组织材料。迄今为止，文献中还没有系统的研究硅橡胶材料/流体的放射学特性，用于使用3D打印技术直接挤压制造的成像幻影。本研究的目的是探讨三维打印的硅胶模型在CT成像中的放射学特性。为了实现这一目标，通过改变填充密度来调整其放射学性能，评估了由三种不同硅酮印刷材料组成的几个样品的放射密度，即霍斯菲尔德单位（HUs）。将HU值与Gammex组织表征幻影进行比较。此外，通过创建特定填充密度的多个副本进行再现性分析。我们还制作了一个由腹部CT得出的按比例缩小的解剖模型，并对所得的HU值进行了评估。对于三种不同的有机硅材料，在扫描设置为120 kVp的CT上获得了−639至+780 HU的光谱。此外，使用不同的填充密度，打印材料能够获得与Gammex模型中不同组织等效插入物相似的辐射密度范围（238 HU至- 673 HU）。再现性结果表明，与原始样品相比，复制品的HU值吻合良好，证实了印刷材料的再现性。腹部CT HU目标值与3d打印解剖模体各组织HU值吻合良好。

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引用次数: 0

A modular system of flexible receive-only coil arrays for 3 T Magnetic Resonance Imaging 用于3t磁共振成像的柔性仅接收线圈阵列的模块化系统

IF 2.4 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2025-05-01 DOI: 10.1016/j.zemedi.2023.05.002

Lena Nohava, Michael Obermann, Roberta Frass-Kriegl, Onisim Soanca, Elmar Laistler

Flexible form-fitting radiofrequency coils provide high signal-to-noise ratio (SNR) for magnetic resonance imaging (MRI), and in array configuration large anatomical areas of interest can be covered. We propose a modular system - “ModFlex”- of flexible lightweight 4-channel coaxial coil arrays for 3 T MRI. We investigated the performance difference between commercial reference coils and 8- and 16-channel ModFlex receive-only array systems. In vivo, six anatomical targets in four regions of interest – the neck, the ankle, the spine and the hip – were imaged with the novel coil array system. The versatility of ModFlex and the robustness of the coil characteristics for different use cases is demonstrated. We measured an SNR gain for 4 out of 6 and similar SNR for 2 out of 6 anatomical target regions as compared to commercial reference coils. Parallel imaging capabilities are comparable to standard coils in hip and neck imaging, but ModFlex outperforms standard coils in ankle and spine imaging. High SNR combined with high acceleration possibilities enables faster imaging workflows and/or high-resolution MR acquisitions. The coil’s versatility is beneficial for use cases with varying subject sizes and could improve patient comfort.

柔性贴合射频线圈为磁共振成像（MRI）提供高信噪比（SNR），并且在阵列配置中可以覆盖感兴趣的大解剖区域。我们提出了一种模块化系统-“ModFlex”-用于3t MRI的柔性轻质4通道同轴线圈阵列。我们研究了商用参考线圈与8通道和16通道ModFlex仅接收阵列系统之间的性能差异。在体内，使用新型线圈阵列系统对颈部、脚踝、脊柱和髋关节四个感兴趣区域的六个解剖目标进行成像。演示了ModFlex的多功能性和线圈特性在不同用例中的鲁棒性。与商业参考线圈相比，我们测量了6个解剖目标区域中4个的信噪比增益和6个解剖目标区域中2个的相似信噪比。在髋关节和颈部成像方面，ModFlex的并行成像能力与标准线圈相当，但在踝关节和脊柱成像方面，ModFlex的性能优于标准线圈。高信噪比结合高加速度的可能性，实现更快的成像工作流程和/或高分辨率MR采集。线圈的多功能性有利于不同受试者大小的用例，可以提高患者的舒适度。

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引用次数: 0

Characterization of a new radiochromic film (LD-V1) using mammographic beam qualities 一种新的放射致色膜（LD-V1）的特征利用乳房x线摄影光束质量

IF 2.4 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2025-05-01 DOI: 10.1016/j.zemedi.2023.05.004

Erika Nakajima, Hitoshi Sato

Purpose

Radiochromic film (RCF) is a detector that can obtain a two-dimensional dose distribution with high resolution; it is widely used in medical and industrial fields. Several types of RCFs exist based on their application. The type of RCF mainly used for mammography dose assessment has been discontinued; however, a new type of RCF (LD-V1) has been distributed as a successor. Since the medical use of LD-V1 has rarely been studied, we investigated the response characteristics of LD-V1 in mammography.

Methods

Measurements were performed using Mo/Mo and Rh/Ag on a Senographe Pristina mammography device (GE, Fairfield, CT, USA). The reference air kerma was measured using a parallel-plate ionization chamber (PPIC) (C-MA, Applied Engineering Inc, Tokyo, Japan). Pieces of LD-V1 film model were irradiated at the same position where the reference air kerma in air was measured by the PPIC. Irradiation was performed using the time scale method based on the load on the equipment. Two methods of irradiation were considered: placing the detector in air and on the phantom. The LD-V1 was scanned five times at 72 dpi in RGB (48 bit) mode using a flatbed scanner (ES-G11000, Seiko Epson Corp, Nagano, Japan) 24 h following irradiation. The response ratio of the reference air kerma and the air kerma obtained from the LD-V1 were compared and examined for each beam quality and air kerma range.

Results and discussion

When the beam quality was altered, the response ratio varied from 0.8 to 1.2 with respect to the measurement value of the PPIC; however, some outliers were observed. Response ratios were highly variable in the low-dose range; however, as the air kerma increased, the ratios approached 1. Thus, LD-V1 does not need calibration for each beam quality used in mammography. LD-V1 enables air kerma evaluation by creating air kerma response curves under certain X-ray conditions used in mammography.

Conclusion

We suggest that the dose range be limited to 12 mGy or more to keep the response variation with beam qualities below ±20%. If further measurement is required for reducing the response variation, the dose range should be shifted to a higher dose range.

目的放射致色膜（RCF）是一种能够获得二维高分辨率剂量分布的检测器；广泛应用于医疗和工业领域。根据它们的应用程序，存在几种类型的rcf。主要用于乳房x线摄影剂量评估的RCF类型已停止使用；然而，一种新型的RCF （LD-V1）已被分发作为继任者。由于LD-V1的医学应用很少被研究，我们研究了LD-V1在乳房x光检查中的反应特征。方法在Senographe Pristina乳房x线摄影设备（GE, Fairfield， CT， USA）上使用Mo/Mo和Rh/Ag进行测量。参考空气温度采用平行板电离室（PPIC）测量（C-MA，应用工程公司，东京，日本）。在PPIC测量空气中参考空气浓度的同一位置照射LD-V1膜模型片。辐照采用基于设备负荷的时间尺度法。考虑了两种辐照方法：将探测器放置在空气中和放置在假体上。辐照24小时后，使用平板扫描仪（ES-G11000，精工爱普生公司，日本长野）在RGB（48位）模式下以72 dpi扫描LD-V1 5次。比较了参考空气克尔玛和从LD-V1获得的空气克尔玛的响应比，并检查了每个光束质量和空气克尔玛范围。结果与讨论当光束质量改变时，相对于PPIC测量值的响应比在0.8 ~ 1.2之间变化；然而，也观察到一些异常值。在低剂量范围内，反应率变化很大；然而，随着空气质量的增加，比值接近1。因此，LD-V1不需要对乳房x光检查中使用的每个光束质量进行校准。LD-V1通过在乳房x射线检查中使用的某些x射线条件下创建空气角反应曲线来进行空气角评价。结论建议将辐照剂量控制在12 mGy及以上，使辐照响应随光束质量的变化小于±20%。如果需要进一步测量以减小响应变化，则应将剂量范围转移到更高的剂量范围。

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引用次数: 0

Evaluation of proton and carbon ion beam models in TReatment Planning for Particles 4D (TRiP4D) referring to a commercial treatment planning system 参考商业处理计划系统，评估粒子处理计划4D （TRiP4D）中的质子和碳离子束模型

IF 2.4 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2025-05-01 DOI: 10.1016/j.zemedi.2023.06.002

Yinxiangzi Sheng , Lennart Volz , Weiwei Wang , Marco Durante , Christian Graeff

Purpose

To investigate the accuracy of the treatment planning system (TPS) TRiP4D in reproducing doses computed by the clinically used TPS SyngoRT.

Methods

Proton and carbon ion beam models in TRiP4D were converted from SyngoRT. Cubic plans with different depths in a water-tank phantom (WP) and previously treated and experimentally verified patient plans from SyngoRT were recalculated in TRiP4D. The target mean dose deviation (ΔD_mean,T) and global gamma index (2%–2 mm for the absorbed dose and 3%–3mm for the RBE-weighted dose with 10% threshold) were evaluated.

Results

The carbon and proton absorbed dose gamma passing rates (γ-PRs) were ≥99.93% and ΔD_mean,T smaller than −0.22%. On average, the RBE-weighted dose D_mean,T was −1.26% lower for TRiP4D than SyngoRT for cubic plans. In TRiP4D, the faster analytical ‘low dose approximation’ (Krämer, 2006) was used, while SyngoRT used a stochastic implementation (Krämer, 2000). The average ΔD_{mean, T} could be reduced to −0.59% when applying the same biological effect calculation algorithm. However, the dose recalculation time increased by a factor of 79–477. ΔD_mean,T variation up to −2.27% and −2.79% was observed for carbon absorbed and RBE-weighted doses in patient plans. The γ-PRs were ≥93.92% and ≥91.83% for patient plans, except for one proton beam with a range shifter (γ-PR of 64.19%).

Conclusion

The absorbed dose between TRiP4D and SyngoRT were identical for both proton and carbon ion plans in the WP. Compared to SyngoRT, TRiP4D underestimated the target RBE-weighted dose; however more efficient in RBE-weighted dose calculation. Large variation for proton beam with range shifter was observed. TRiP4D will be used to evaluate doses delivered to moving targets. Uncertainties inherent to the 4D-dose reconstruction calculation are expected to be significantly larger than the dose errors reported here. For this reason, the residual differences between TRiP4D and SyngoRT observed in this study are considered acceptable.

The study was approved by the Institutional Research Board of Shanghai Proton and Heavy Ion Center (approval number SPHIC-MP-2020-04, RS).

目的探讨治疗计划系统（TPS） TRiP4D复制临床使用的TPS SyngoRT计算剂量的准确性。方法将质子和碳离子束模型从SyngoRT转换为TRiP4D。在TRiP4D中重新计算水箱幻影（WP）中不同深度的立方平面图和先前经过SyngoRT治疗和实验验证的患者平面图。评估了目标平均剂量偏差（ΔDmean，T）和总体伽马指数（吸收剂量为2%-2 mm， 10%阈值的rbe加权剂量为3%-3mm）。结果碳、质子吸收剂量γ通过率(γ- pr)≥99.93%,γ- pr≥ΔDmean,T < - 0.22%。在立方方案中，TRiP4D的rbe加权剂量Dmean，T平均比SyngoRT低- 1.26%。在TRiP4D中，使用了更快的分析“低剂量近似”（Krämer, 2006），而SyngoRT使用了随机实现（Krämer, 2000）。采用相同的生物效应计算算法，平均ΔDmean， T可降至−0.59%。然而，剂量重新计算时间增加了79-477倍。ΔDmean，在患者计划中，碳吸收剂量和rbe加权剂量的T变化高达- 2.27%和- 2.79%。患者计划γ-PR≥93.92%和≥91.83%，除了一个质子束带范围移位器（γ-PR为64.19%）。结论TRiP4D和SyngoRT在质子和碳离子计划下的吸收剂量相同。与SyngoRT相比，TRiP4D低估了靶rbe加权剂量；但在rbe加权剂量计算中更有效。用移程器对质子束进行了较大的变化。TRiP4D将用于评估运送到移动目标的剂量。4d剂量重建计算固有的不确定性预计将明显大于本文报道的剂量误差。因此，本研究中观察到的TRiP4D与SyngoRT的残留差异是可以接受的。本研究已获上海市质子重离子中心机构研究委员会批准（批准文号SPHIC-MP-2020-04， RS）。

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引用次数: 0

Rapid whole-brain quantitative MT imaging 快速全脑定量MT成像

IF 2.4 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2025-02-01 DOI: 10.1016/j.zemedi.2023.02.005

Roya Afshari , Francesco Santini , Rahel Heule , Craig H. Meyer , Josef Pfeuffer , Oliver Bieri

Purpose

To provide a robust whole-brain quantitative magnetization transfer (MT) imaging method that is not limited by long acquisition times.

Methods

Two variants of a spiral 2D interleaved multi-slice spoiled gradient echo (SPGR) sequence are used for rapid quantitative MT imaging of the brain at 3 T. A dual flip angle, steady-state prepared, double-contrast method is used for combined B₁ and-T₁ mapping in combination with a single-contrast MT-prepared acquisition over a range of different saturation flip angles (50 deg to 850 deg) and offset frequencies (1 kHz and 10 kHz). Five sets (containing minimum 6 to maximum 18 scans) with different MT-weightings were acquired. In addition, main magnetic field inhomogeneities (ΔB₀) were measured from two Cartesian low-resolution 2D SPGR scans with different echo times. Quantitative MT model parameters were derived from all sets using a two-pool continuous-wave model analysis, yielding the pool-size ratio, F, their exchange rate, k_f, and their transverse relaxation time, T_2r.

Results

Whole-brain quantitative MT imaging was feasible for all sets with total acquisition times ranging from 7:15 min down to 3:15 min. For accurate modeling, B₁-correction was essential for all investigated sets, whereas ΔB₀-correction showed limited bias for the observed maximum off-resonances at 3 T.

Conclusion

The combination of rapid B₁-T₁ mapping and MT-weighted imaging using a 2D multi-slice spiral SPGR research sequence offers excellent prospects for rapid whole-brain quantitative MT imaging in the clinical setting.

目的提供一种不受采集时间限制的全脑定量磁化转移成像方法。方法采用两种不同的螺旋二维交错多层破坏梯度回波（SPGR）序列，在3 t时对大脑进行快速定量MT成像。采用双翻转角度、稳态制备的双对比度方法，在不同的饱和翻转角度（50°至850°）和偏移频率（1 kHz和10 kHz）范围内，结合单对比度MT制备的采集，进行B1和t1的组合成像。获得了5组不同mt权重的扫描（包含最少6到最多18次扫描）。此外，通过两次不同回波时间的笛卡尔低分辨率二维SPGR扫描测量了主磁场不均匀性（ΔB0）。使用双池连续波模型分析从所有集合中获得定量MT模型参数，得到池大小比F、它们的汇率kf和它们的横向弛豫时间T2r。结果全脑定量MT成像对所有集都是可行的，总采集时间从7:15 min到3:15 min不等。为了准确建模，b1校正对所有研究集都是必不可少的。结论快速B1-T1定位与二维多层螺旋SPGR研究序列的MT加权成像相结合，为临床快速全脑定量MT成像提供了良好的前景。

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