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TMAA-net: tensor-domain multi-planal anti-aliasing network for sparse-view CT image reconstruction. TMAA-net:用于稀疏视图 CT 图像重建的张量域多平面抗锯齿网络。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-12 DOI: 10.1088/1361-6560/ad8da2
Sungho Yun, Seoyoung Lee, Da-In Choi, Taewon Lee, Seungryong Cho

Objective.Among various deep-network-based sparse-view CT image reconstruction studies, the sinogram upscaling network has been predominantly employed to synthesize additional view information. However, the performance of the sinogram-based network is limited in terms of removing aliasing streak artifacts and recovering low-contrast small structures. In this study, we used a view-by-view back-projection (VVBP) tensor-domain network to overcome such limitations of the sinogram-based approaches.Approach.The proposed method offers advantages of addressing the aliasing artifacts directly in the 3D tensor domain over the 2D sinogram. In the tensor-domain network, the multi-planal anti-aliasing modules were used to remove artifacts within the coronal and sagittal tensor planes. In addition, the data-fidelity-based refinement module was also implemented to successively process output images of the tensor network to recover image sharpness and textures.Main result.The proposed method showed outperformance in terms of removing aliasing artifacts and recovering low-contrast details compared to other state-of-the-art sinogram-based networks. The performance was validated for both numerical and clinical projection data in a circular fan-beam CT configuration.Significance.We observed that view-by-view aliasing artifacts in sparse-view CT exhibit distinct patterns within the tensor planes, making them effectively removable in high-dimensional representations. Additionally, we demonstrated that the co-domain characteristics of tensor space processing offer higher generalization performance for aliasing artifact removal compared to conventional sinogram-domain processing.

在各种基于深度网络的稀疏视图 CT 图像重建研究中,主要采用正弦波上标网络来合成额外的视图信息。然而,基于正弦图的网络在去除混叠条纹伪影和恢复低对比度的小结构方面性能有限。在本研究中,我们使用了逐视图反向投影(VVBP)张量域网络来克服基于正弦图的方法的这些局限性。与二维正弦图相比,所提出的方法具有直接在三维张量域中处理混叠伪影的优势。此外,还实现了基于数据保真度的细化模块,对张量网络的输出图像进行连续处理,以恢复图像的清晰度和纹理。与其他最先进的基于正弦图的网络相比,所提出的方法在消除混叠伪影和恢复低对比度细节方面表现出色。在环形扇形光束 CT 配置中,数值和临床投影数据都验证了该方法的性能。
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引用次数: 0
Noise & mottle suppression methods for cumulative Cherenkov images of radiation therapy delivery. 放射治疗累积切伦科夫图像的噪声和斑纹抑制方法。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-12 DOI: 10.1088/1361-6560/ad8c93
Jeremy E Hallett, Petr Bruza, Michael Jermyn, Ke Li, Brian W Pogue

Purpose.Cherenkov imaging during radiotherapy provides a real time visualization of beam delivery on patient tissue, which can be used dynamically for incident detection or to review a summary of the delivered surface signal for treatment verification. Very few photons form the images, and one limitation is that the noise level per frame can be quite high, and mottle in the cumulative processed images can cause mild overall noise. This work focused on removing or suppressing noise via image postprocessing.Approach.Images were analyzed for peak-signal-to-noise and spatial frequencies present, and several established noise/mottle reduction algorithms were chosen based upon these observations. These included total variation minimization (TV-L1), non-local means filter (NLM), block-matching 3D (BM3D), alpha (adaptive) trimmed mean (ATM), and bilateral filtering. Each were applied to images acquired using a BeamSite camera (DoseOptics) imaged signal from 6x photons from a TrueBeam linac delivering dose at 600 MU min-1incident on an anthropomorphic phantom and tissue slab phantom in various configurations and beam angles. The standard denoised images were tested for PSNR, noise power spectrum (NPS) and image sharpness.Results.The average peak-signal-to-noise ratio (PSNR) increase was 17.4% for TV-L1. NLM denoising increased the average PSNR by 19.1%, BM3D processing increased it by12.1% and the bilateral filter increased the average PSNR by 19.0%. Lastly, the ATM filter resulted in the lowest average PSNR increase of 10.9%. Of all of these, the NLM and bilateral filters produced improved edge sharpness with, generally, the lowest NPS curve.Conclusion.For cumulative image Cherenkov data, NLM and the bilateral filter yielded optimal denoising with the TV-L1 algorithm giving comparable results. Single video frame Cherenkov images exhibit much higher noise levels compared to cumulative images. Noise suppression algorithms for these frame rates will likely be a different processing pipeline involving these filters incorporated with machine learning.

目的:放射治疗过程中的切伦科夫成像可实时显示光束在患者组织上的传输情况,可动态用于事件检测或查看传输表面信号的摘要,以便进行治疗验证。形成图像的光子数量很少,其局限性之一是每帧图像的噪声水平可能相当高,累积处理图像中的斑纹会导致轻微的整体噪声。这项工作的重点是通过图像后处理去除或抑制噪声:方法:分析图像的峰值信噪比和存在的空间频率,并根据这些观察结果选择几种成熟的噪声/斑纹减少算法。这些算法包括总变异最小化(TV-L1)、非局部均值滤波器(NLM)、块匹配三维(BM3D)、α(自适应)修剪均值(ATM)和双边滤波。每种方法都适用于使用 BeamSite 相机(DoseOptics)采集的图像,图像信号来自 TrueBeam 直列加速器的 6 倍光子,剂量为 600 MU/min,以各种配置和光束角度入射到人体模型和组织平板模型上。对标准去噪图像进行了PSNR、噪声功率谱(NPS)和图像清晰度测试:结果:TV-L1 的峰值信噪比(PSNR)平均提高了 17.4%。NLM 去噪使平均 PSNR 提高了 19.1%,BM3D 处理使平均 PSNR 提高了 12.1%,双边滤波器使平均 PSNR 提高了 19.0%。最后,ATM 滤波器的平均 PSNR 提高率最低,仅为 10.9%。在所有这些滤波器中,NLM 和双边滤波器提高了边缘清晰度,NPS 曲线一般也最低:结论:对于累积图像切伦科夫数据,NLM 和双边滤波器能产生最佳去噪效果,TV-L1 算法的效果与之相当。与累积图像相比,单视频帧切伦科夫图像的噪声水平要高得多。针对这些帧速率的噪声抑制算法很可能是一个不同的处理管道,其中包括这些与机器学习相结合的滤波器。
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引用次数: 0
Quantitative assessment of areal bone mineral density using multi-energy localizer radiographs from photon-counting detector CT. 使用光子计数探测器 CT 的多能量定位器射线照片定量评估骨矿物质密度。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-12 DOI: 10.1088/1361-6560/ad8da1
Sören Jasper, Joseph Swicklik, Francis Baffour, Andrea Ferrero, Ahmed O El Sadaney, Elisabeth Shanblatt, Tristan Nowak, Cynthia McCollough, Kishore Rajendran

Objective.To assess the accuracy and stability of areal bone-mineral-density (aBMD) measurements from multi-energy CT localizer radiographs acquired using photon-counting detector (PCD) CT.Approach.A European Spine Phantom (ESP) with hydroxyapatite (HA 0.5, 1.0 and 1.5 g cm-2) was scanned using clinical PCD-CT and a dual-energy x-ray absorptiometry (DXA) to compare aBMD values. To assess aBMD stability and reproducibility, PCD-localizers were acquired twice a day for one week, and once per week for five weeks. Multiple ESP anteroposterior thicknesses (18, 26, 34, and 40 cm) were achieved using a synthetic gel layer and scanned across eight tube current values for both 120 kV (15-120 mA) and 140 kV (10-80 mA). One-way analysis of variance was performed for statistical significance (p< 0.05 considered significant). Quantitative HA and water maps were reconstructed using a prototype material-decomposition software, and aBMD was calculated after background correction.In vivoperformance of PCD-based aBMD was illustrated using a patient scan acquired at 140 kV and 40 mA, and lumbar aBMD values were compared with DXA.Main results.The ESP aBMD values from PCD-localizers demonstrated excellent day-to-day stability with a coefficient-of-variation ranging from 0.42% to 0.53%, with mean absolute percentage errors (MAPE) of less than 5% for all three vertebral bodies. The coefficient-of-variation for weekly scans ranged from 0.17% to 0.60%, again with MAPE below 5% for all three vertebral bodies. Across phantom sizes and tube currents, the MAPE values varied ranging from 1.84% to 13.78% for 120 kV, and 1.38%-9.11% for 140 kV. No significant difference was found between different tube currents. For the standard phantom size, DXA showed 11.21% MAPE whereas PCD-CT showed 3.04% MAPE. For the patient scan, deviation between PCD-based aBMD values and those obtained from DXA ranged from 0.07% to 9.82% for different lumbar vertebra.Significance.This study highlights the accuracy and stability of PCD-CT localizers for measuring aBMD. We demonstrated aBMD accuracy across different sizes and showed that higher radiation doses did not inherently increase aBMD accuracy.

目的 评估使用光子计数探测器(PCD)CT 获取的多能 CT 定位器射线照片测量骨矿物质密度(aBMD)的准确性和稳定性。方法 使用临床 PCD-CT 和双能 X 射线吸收测量仪(DXA)扫描带有羟基磷灰石(HA 0.5、1.0 和 1.5 g/cm2)的欧洲脊柱模型(ESP),以比较 aBMD 值。为了评估 aBMD 的稳定性和可重复性,PCD-定位仪每天采集两次,持续一周;每周采集一次,持续五周。使用合成凝胶层模拟了多个模型的前胸厚度(18、26、34 和 40 厘米),并在 120 千伏(15-120 毫安)和 140 千伏(10-80 毫安)的八个管电流值之间进行扫描,然后进行单因素方差分析以确定统计显著性(P<0.05)。
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引用次数: 0
Imaging error reduction in radial cine-MRI with deep learning-based intra-frame motion compensation. 利用基于深度学习的帧内运动补偿,减少径向 cine-MRI 的成像误差。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-11 DOI: 10.1088/1361-6560/ad8831
Zhuojie Sui, Prasannakumar Palaniappan, Chiara Paganelli, Christopher Kurz, Guillaume Landry, Marco Riboldi

Objective.Radial cine-MRI allows for sliding window reconstruction at nearly arbitrary frame rate, promising high-speed imaging for intra-fractional motion monitoring in magnetic resonance guided radiotherapy. However, motion within the reconstruction window may determine the location of the reconstructed target to deviate from the true real-time position (target positioning errors), particularly in cases of fast breathing or for anatomical structures affected by the heartbeat. In this work, we present a proof-of-concept study aiming to enhance radial cine-MR imaging by implementing deep-learning-based intra-frame motion compensation techniques.Approach.A novel network (TransSin-UNet) was proposed to continuously estimate the final-position image of the target, corresponding to end of the frame acquisition. Within the radial k-space reconstruction window, the spatial-temporal dependencies among the sinogram representation of the spokes were modeled by a transformer encoder subnetwork, followed by a UNet subnetwork operating in the spatial domain for pixel-level fine-tuning. By simulating motion-dependent radial sampling with (tiny) golden angles, we generated datasets from 25 4D digital anthropomorphic lung cancer phantoms. The network was then trained and extensively evaluated across datasets characterized by varying azimuthal radial profile increments.Main Results.The method required additional 4.8 ms per frame over the conventional approach involving direct image reconstruction with motion-corrupted spokes. TransSin-UNet outperformed architectures relying solely on transformer encoders or UNets across all the comparative evaluations, leading to a noticeable enhancement in image quality and target positioning accuracy. The normalized root mean-squared error decreased by 50% from the initial value of 0.188 on average, whereas the mean Dice similarity coefficient of the gross tumor volume increased from 85.1% to 96.2% in the investigated cases. Furthermore, the final-positions of anatomical structures undergoing substantial intra-frame deformations were precisely derived.Significance.The proposed approach enables an effective intra-frame motion compensation, offering an opportunity to reduce errors in radial cine-MR imaging for real-time motion management.

目的:径向 cine-MRI 允许以近乎任意的帧速率进行滑动窗口重建,有望在 MRgRT 中进行高速成像,以监测瓣内运动。然而,重建窗口内的运动可能会导致重建目标的位置偏离真实的实时位置(目标定位误差),尤其是在快速呼吸或解剖结构受心跳影响的情况下。在这项工作中,我们提出了一项概念验证研究,旨在通过实施基于深度学习的帧内运动补偿技术来增强径向 cine-MR 成像:我们提出了一种新型网络(TransSin-UNet),用于持续估计目标的最终位置图像,与帧末采集相对应。在径向 k 空间重建窗口内,辐条正弦图表示之间的时空相关性由变压器编码器子网络建模,然后由在空间域运行的 UNet 子网络进行像素级微调。通过用(微小的)黄金角模拟运动相关径向采样,我们从 25 个 4D 数字拟人肺癌模型中生成了数据集。然后对网络进行了训练,并在具有不同方位径向剖面增量特征的数据集上进行了广泛评估:与使用运动破坏辐条直接重建图像的传统方法相比,该方法每帧需要额外的 4.8 毫秒。在所有比较评估中,TransSin-UNet 的性能均优于仅依赖变压器编码器或 UNet 的架构,从而显著提高了图像质量和目标定位精度。归一化均方根误差(NRMSE)比初始值 0.188 平均降低了 50%,而肿瘤总体积(GTV)的平均戴斯相似系数(DSC)则从 85.1% 提高到 96.2%。此外,还精确推导出了在帧内发生大幅变形的解剖结构的最终位置:所提出的方法能够实现有效的帧内运动补偿,为实时运动管理提供了一个减少径向 cine-MR 成像误差的机会。
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引用次数: 0
Treatment envelope of transcranial histotripsy: challenges and strategies to maximize the treatment location profile. 经颅组织电切术的治疗包络:最大化治疗位置轮廓的挑战与策略。
IF 3.3 3区 医学 Q2 ENGINEERING, BIOMEDICAL Pub Date : 2024-11-11 DOI: 10.1088/1361-6560/ad8d9f
Ning Lu, Ellen M Yeats, Jonathan R Sukovich, Timothy L Hall, Aditya S Pandey, Zhen Xu

A 750 kHz, 360-element ultrasound array has been built for transcranial histotripsy applications. This study aims to evaluate its performance to determine whether this array is adequate for treating a wide range of brain locations through a human skull. Treatment location profiles in 2 excised human skulls were experimentally characterized based on passive cavitation mapping. Full-wave acoustic simulations were performed in 8 human skulls to analyze the ultrasound propagation at shallow targets in skulls with different properties. Results showed that histotripsy successfully generated cavitation from deep to shallow targets within 5 mm from the skull surface in the skull with high SDR and small thickness, whereas in the skull with low SDR and large thickness, the treatment envelope was limited up to 16 mm from the skull surface. Simulation results demonstrated that the treatment envelope was highly dependent on the skull acoustic properties. Pre-focal pressure hotspots were observed in both simulation and experiments when targeting near the skull. For each skull, the acoustic pressure loss increases significantly for shallow targets compared to central targets due to high attenuation, large incident angles, and pre-focal pressure hotspots. Strategies including array design optimization, pose optimization, and amplitude correction, are proposed to broaden the treatment envelope. This study identifies the capabilities and limitations of the 360-element transcranial histotripsy array and suggests strategies for designing the next-generation transcranial histotripsy array to expand the treatment location profile for a future clinical trial.

我们已经建立了一个 750kHz、360 个元件的超声阵列,用于经颅组织损伤治疗。本研究旨在对其性能进行评估,以确定该阵列是否足以通过人类头骨治疗各种脑部位置。根据被动空化绘图,对 2 个切除的人类头骨中的治疗位置剖面进行了实验表征。在 8 个人类头骨中进行了全波声学模拟,以分析超声波在不同性质的头骨浅目标处的传播情况。结果显示,在高 SDR 和厚度较小的颅骨中,组织碎裂术成功地在距离颅骨表面 5 毫米的范围内产生了从深到浅的空化,而在低 SDR 和厚度较大的颅骨中,治疗包络线被限制在距离颅骨表面 16 毫米的范围内。模拟结果表明,治疗包络高度依赖于头骨的声学特性。在模拟和实验中,当目标靠近头骨时,都观察到了病灶前压力热点。对于每个头骨,由于高衰减、大入射角和前焦点压力热点,浅目标的声压损失比中心目标显著增加。研究提出了包括阵列设计优化、姿势优化和振幅校正在内的策略,以扩大治疗范围。这项研究确定了 360 元经颅组织切动阵列的能力和局限性,并提出了设计下一代经颅组织切动阵列的策略,以扩大未来临床试验的治疗位置轮廓。
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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
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
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
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Physics in medicine and biology
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