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Note on uncertainty in Monte Carlo dose calculations and its relation to microdosimetry 关于蒙特卡洛剂量计算的不确定性及其与微剂量测定的关系的说明。
IF 2.4 4区 医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Zeitschrift fur Medizinische Physik
Pub Date : 2024-08-01 DOI: 10.1016/j.zemedi.2022.11.012

Purpose

The Type A standard uncertainty in Monte Carlo (MC) dose calculations is usually determined using the “history by history” method. Its applicability is based on the assumption that the central limit theorem (CLT) can be applied such that the dispersion of repeated calculations can be modeled by a Normal distribution. The justification for this assumption, however, is not obvious. The concept of stochastic quantities used in the field of microdosimetry offers an alternative approach to assess uncertainty. This leads to a new and simple expression.

Methods

The value of the MC determined absorbed dose is considered a random variable which is comparable to the stochastic quantity specific energy, z. This quantity plays an important role in microdosimetry and in the definition of the quantity absorbed dose, D. One of the main features of z is that it is itself the product of two other random variables, specifically of the mean dose contribution in a ‘single event’ and of the mean number of such events. The term ‘single event’ signifies the sum of energies imparted by all correlated particles to the matter in a given volume. The similarity between the MC calculated absorbed dose and the specific energy is used to establish the ‘event by event’ method for the determination of the uncertainty. MC dose calculations were performed to test and compare both methods.

Results

It is shown that the dispersion of values obtained by MC dose calculations indeed depend on the product of the mean absorbed dose per event, and the number of events. Applying methods to obtain the variance of a product of two random variables, a simple formula for the assessment of uncertainties is obtained which is slightly different from the ‘history by history’ method. Interestingly, both formulas yield indistinguishable results. This finding is attributed to the large number of histories used in MC simulations. Due to the fact that the values of a MC calculated absorbed dose are the product of two approximately Normal distributions it can be demonstrated that the resulting product is also approximately normally distributed.

Conclusions

The event by event approach appears to be more suitable than the history by history approach because it takes into account the randomness of the number of events involved in MC dose calculations. Under the condition of large numbers of histories, however, both approaches lead to the same simple expression for the determination of uncertainty in MC dose calculations. It is suggested to replace the formula currently used by the new expression. Finally, it turned out that the concept and ideas that were developed in the field of microdosimetry already 50 years ago can be usefully applied also in MC calculations.

目的：蒙特卡罗（MC）剂量计算中的 A 类标准不确定性通常采用 "逐历史 "法确定。其适用性基于这样一个假设，即可以应用中心极限定理（CLT），从而使重复计算的分散性可以用正态分布来模拟。然而，这一假设的合理性并不明显。微观模拟领域使用的随机量概念为评估不确定性提供了另一种方法。这导致了一种新的简单表达方式：z 的主要特征之一是它本身是其他两个随机变量的乘积，特别是 "单一事件 "中的平均剂量贡献和此类事件的平均数量。单个事件 "是指在给定体积内，所有相关粒子对物质产生的能量总和。利用 MC 计算的吸收剂量与特定能量之间的相似性，可以建立 "逐个事件 "的方法来确定不确定性。为了测试和比较这两种方法，还进行了 MC 剂量计算：结果表明，通过 MC 剂量计算获得的数值的离散性确实取决于每个事件的平均吸收剂量与事件数量的乘积。应用获得两个随机变量乘积方差的方法，可以得到一个评估不确定性的简单公式，该公式与 "逐历史 "法略有不同。有趣的是，这两个公式得出的结果并无差别。这一发现归因于 MC 模拟中使用了大量的历史记录。由于 MC 计算的吸收剂量值是两个近似正态分布的乘积，因此可以证明所得到的乘积也是近似正态分布的：结论：逐个事件的方法似乎比逐个历史的方法更合适，因为它考虑到了 MC 剂量计算所涉及的事件数量的随机性。不过，在历史数据较多的情况下，这两种方法都能得出相同的简单表达式来确定 MC 剂量计算的不确定性。建议用新的表达式取代目前使用的公式。最后，事实证明，50 年前在微剂量测定领域提出的概念和想法也可以有效地应用于 MC 计算。
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引用次数: 0
Automated shape-independent assessment of the spatial distribution of proton density fat fraction in vertebral bone marrow 与形状无关的椎骨骨髓质子密度脂肪部分空间分布自动评估。
IF 2.4 4区 医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Zeitschrift fur Medizinische Physik
Pub Date : 2024-08-01 DOI: 10.1016/j.zemedi.2022.12.004

This work proposes a method for automatic standardized assessment of bone marrow volume and spatial distribution of the proton density fat fraction (PDFF) in vertebral bodies. Intra- and interindividual variability in size and shape of vertebral bodies is a challenge for comparable interindividual evaluation and monitoring of changes in the composition and distribution of bone marrow due to aging and/or intervention. Based on deep learning image segmentation, bone marrow PDFF of single vertebral bodies is mapped to a cylindrical template and corrected for the inclination with respect to the horizontal plane. The proposed technique was applied and tested in a cohort of 60 healthy (30 males, 30 females) individuals. Obtained bone marrow volumes and mean PDFF values are comparable to former manual and (semi-)automatic approaches. Moreover, the proposed method allows shape-independent characterization of the spatial PDFF distribution inside vertebral bodies.

这项研究提出了一种自动标准化评估椎体中骨髓体积和质子密度脂肪分数（PDFF）空间分布的方法。椎体的大小和形状在个体内和个体间存在差异，这对可比的个体间评估和监测因老化和/或干预引起的骨髓组成和分布变化是一个挑战。基于深度学习图像分割，单个椎体的骨髓PDFF被映射到一个圆柱模板上，并校正了相对于水平面的倾斜度。所提出的技术在 60 名健康人（30 名男性，30 名女性）中进行了应用和测试。获得的骨髓体积和平均 PDFF 值与以前的手动和（半）自动方法相当。此外，所提出的方法还能不受形状影响地描述椎体内部的空间 PDFF 分布。
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引用次数: 0
Development and clinical implementation of a digital system for risk assessments for radiation therapy 放射治疗风险评估数字系统的开发和临床应用
IF 2.4 4区 医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Zeitschrift fur Medizinische Physik
Pub Date : 2024-08-01 DOI: 10.1016/j.zemedi.2023.08.003

Before introducing new treatment techniques, an investigation of hazards due to unintentional radiation exposures is a reasonable activity for proactively increasing patient safety. As dedicated software is scarce, we developed a tool for risk assessment to design a quality management program based on best practice methods, i.e., process mapping, failure modes and effects analysis and fault tree analysis. Implemented as a web database application, a single dataset was used to describe the treatment process and its failure modes. The design of the system and dataset allowed failure modes to be represented both visually as fault trees and in a tabular form. Following the commissioning of the software for our department, previously conducted risk assessments were migrated to the new system after being fully re-assessed which revealed a shift in risk priorities. Furthermore, a weighting factor was investigated to bring risk levels of the migrated assessments into perspective. The compensation did not affect high priorities but did re-prioritize in the midrange of the ranking. We conclude that the tool is suitable to conduct multiple risk assessments and concomitantly keep track of the overall quality management activities.

在引入新的治疗技术之前，调查无意辐射照射造成的危害是主动提高患者安全的合理活动。由于缺乏专用软件，我们开发了一种风险评估工具，以最佳实践方法为基础设计质量管理计划，即流程映射、故障模式与影响分析和故障树分析。该工具以网络数据库应用程序的形式实施，使用单一数据集来描述治疗过程及其失效模式。系统和数据集的设计允许以故障树和表格的形式直观地表示故障模式。在本部门启用该软件后，先前进行的风险评估在经过全面重新评估后被转移到新系统中，评估结果显示风险优先级发生了变化。此外，还对加权系数进行了调查，以便对已迁移评估的风险等级进行评估。补偿并没有影响到高优先级，但确实重新调整了中等级别的优先级。我们得出的结论是，该工具适用于进行多重风险评估，并同时跟踪整体质量管理活动。
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引用次数: 0
Population-based model selection for an accurate estimation of time-integrated activity using non-linear mixed-effects modelling 利用非线性混合效应建模，为准确估算时间积分活动选择基于人群的模型。
IF 2.4 4区 医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Zeitschrift fur Medizinische Physik
Pub Date : 2024-08-01 DOI: 10.1016/j.zemedi.2023.01.007

Purpose

Personalized treatment planning in Molecular Radiotherapy (MRT) with accurately determining the absorbed dose is highly desirable. The absorbed dose is calculated based on the Time-Integrated Activity (TIA) and the dose conversion factor. A crucial unresolved issue in MRT dosimetry is which fit function to use for the TIA calculation. A data-driven population-based fitting function selection could help solve this problem. Therefore, this project aims to develop and evaluate a method for accurately determining TIAs in MRT, which performs a Population-Based Model Selection within the framework of the Non-Linear Mixed-Effects (NLME-PBMS) model.

Methods

Biokinetic data of a radioligand for the Prostate-Specific Membrane Antigen (PSMA) for cancer treatment were used. Eleven fit functions were derived from various parameterisations of mono-, bi-, and tri-exponential functions. The functions' fixed and random effects parameters were fitted (in the NLME framework) to the biokinetic data of all patients. The goodness of fit was assumed acceptable based on the visual inspection of the fitted curves and the coefficients of variation of the fitted fixed effects. The Akaike weight, the probability that the model is the best among the whole set of considered models, was used to select the fit function most supported by the data from the set of functions with acceptable goodness of fit. NLME-PBMS Model Averaging (MA) was performed with all functions having acceptable goodness of fit. The Root-Mean-Square Error (RMSE) of the calculated TIAs from individual-based model selection (IBMS), a shared-parameter population-based model selection (SP-PBMS) reported in the literature, and the functions from NLME-PBMS method to the TIAs from MA were calculated and analysed. The NLME-PBMS (MA) model was used as the reference as this model considers all relevant functions with corresponding Akaike weights.

Results

The function f3a=A1e-λ1+λphyst+A2e-λphyst was selected as the function most supported by the data with an Akaike weight of (54 ± 11) %. Visual inspection of the fitted graphs and the RMSE values show that the NLME model selection method has a relatively better or equivalent performance than the IBMS or SP-PBMS methods. The RMSEs of the IBMS, SP-PBMS, and NLME-PBMS (f3a) methods are 7.4%, 8.8%, an

目的：在分子放射治疗（MRT）中，精确确定吸收剂量的个性化治疗计划是非常理想的。吸收剂量是根据时间综合活动（TIA）和剂量转换系数计算得出的。在 MRT 剂量测定中，一个尚未解决的关键问题是在计算 TIA 时应使用哪种拟合函数。基于数据的人群拟合函数选择有助于解决这一问题。因此，本项目旨在开发和评估一种在 MRT 中准确确定 TIA 的方法，该方法在非线性混合效应（NLME-PBMS）模型框架内执行基于人群的模型选择：方法：使用用于治疗癌症的前列腺特异性膜抗原（PSMA）放射性配体的生物动力学数据。通过对单、双和三指数函数的不同参数设置，得出了 11 个拟合函数。这些函数的固定效应和随机效应参数（在 NLME 框架内）与所有患者的生物动力学数据进行了拟合。根据对拟合曲线和拟合固定效应变异系数的目测，假定拟合优度是可以接受的。Akaike 权重是指模型在所有考虑的模型中成为最佳模型的概率，用于从拟合优度可接受的函数集中选择数据最支持的拟合函数。对所有拟合优度可接受的函数进行 NLME-PBMS 模型平均（MA）。计算并分析了基于个体的模型选择（IBMS）、文献中报道的基于共享参数的群体模型选择（SP-PBMS）以及 NLME-PBMS 方法的函数与 MA 的 TIA 计算结果的均方根误差（RMSE）。NLME-PBMS（MA）模型被用作参考，因为该模型考虑了所有相关函数及相应的 Akaike 权重：结果：函数[公式：见正文]被选为数据支持率最高的函数，其 Akaike 权重为 (54 ± 11) %。对拟合图形和均方根误差值的目测表明，NLME 模型选择方法比 IBMS 或 SP-PBMS 方法具有更好或同等的性能。IBMS、SP-PBMS 和 NLME-PBMS (f3a) 方法的均方根误差分别为 7.4%、8.8% 和 2.4%：我们开发了一种基于群体的方法，包括拟合函数选择在内的程序，用于确定计算特定放射性药物、器官和生物动力学数据集的 MRT TIA 的最佳拟合函数。该技术结合了药代动力学的标准实践方法，即基于 Akaike 权重的模型选择和 NLME 模型框架。
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引用次数: 0
Characterizing Off-center MRI with ZTE 利用中兴通讯对偏离中心的磁共振成像进行特征描述。
IF 2.4 4区 医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Zeitschrift fur Medizinische Physik
Pub Date : 2024-08-01 DOI: 10.1016/j.zemedi.2022.09.002

Purpose

To maximize acquisition bandwidth in zero echo time (ZTE) sequences, readout gradients are already switched on during the RF pulse, creating unwanted slice selectivity. The resulting image distortions are amplified especially when the anatomy of interest is not located at the isocenter. We aim to characterize off-center ZTE MRI of extremities such as the shoulder, knee, and hip, adjusting the carrier frequency of the RF pulse excitation for each TR.

Methods

In ZTE MRI, radial encoding schemes are used, where the distorted slice profile due to the finite RF pulse length rotates with the k-space trajectory. To overcome these modulations for objects far away from the magnet isocenter, the frequency of the RF pulse is shifted for each gradient setting so that artifacts do not occur at a given off-center target position. The sharpness of the edges in the images were calculated and the ZTE acquisition with off-center excitation was compared to an acquisition with isocenter excitation both in phantom and in vivo off-center MRI of the shoulder, knee, and hip at 1.5 and 3T MRI systems.

Results

Distortion and blurriness artifacts on the off-center MRI images of the phantom, in vivo shoulder, knee, and hip images were mitigated with off-center excitation without time or noise penalty, at no additional computational cost.

Conclusion

The off-center excitation allows ZTE MRI of the shoulder, knee, and hip for high-bandwidth image acquisitions for clinical settings, where positioning at the isocenter is not possible.

目的：为了在零回波时间（ZTE）序列中最大限度地提高采集带宽，读出梯度已在射频脉冲期间开启，从而产生了不必要的切片选择性。特别是当感兴趣的解剖结构不在等中心时，所产生的图像失真会被放大。我们的目标是对肩部、膝部和髋部等四肢偏离中心的 ZTE MRI 进行表征，调整每个 TR 的射频脉冲激励载波频率：在 ZTE MRI 中，使用的是径向编码方案，由于射频脉冲长度有限，切片轮廓会随着 k 空间轨迹旋转而扭曲。为了克服这些对远离磁体等中心的物体的调制，射频脉冲的频率在每个梯度设置中都会发生偏移，这样在给定的偏离中心的目标位置就不会出现伪影。我们计算了图像边缘的清晰度，并在 1.5T 和 3T 磁共振成像系统中，将偏离中心激励的 ZTE 采集与等中心激励的采集进行了比较：结果：模型、体内肩部、膝部和髋部偏离中心核磁共振成像上的畸变和模糊伪影通过偏离中心激励得到了缓解，没有时间或噪声损失，也没有额外的计算成本：结论：偏离中心的激励允许对肩部、膝部和髋部进行中兴磁共振成像，从而在无法定位等中心的临床环境中进行高带宽图像采集。
{"title":"Characterizing Off-center MRI with ZTE","authors":"","doi":"10.1016/j.zemedi.2022.09.002","DOIUrl":"10.1016/j.zemedi.2022.09.002","url":null,"abstract":"<div><h3>Purpose</h3><p>To maximize acquisition bandwidth in zero echo time (ZTE) sequences, readout gradients are already switched on during the RF pulse, creating unwanted slice selectivity. The resulting image distortions are amplified especially when the anatomy of interest is not located at the isocenter. We aim to characterize off-center ZTE MRI of extremities such as the shoulder, knee, and hip, adjusting the carrier frequency of the RF pulse excitation for each TR.</p></div><div><h3>Methods</h3><p>In ZTE MRI, radial encoding schemes are used, where the distorted slice profile due to the finite RF pulse length rotates with the k-space trajectory. To overcome these modulations for objects far away from the magnet isocenter, the frequency of the RF pulse is shifted for each gradient setting so that artifacts do not occur at a given off-center target position. The sharpness of the edges in the images were calculated and the ZTE acquisition with off-center excitation was compared to an acquisition with isocenter excitation both in phantom and <em>in vivo</em> off-center MRI of the shoulder, knee, and hip at 1.5 and 3T MRI systems.</p></div><div><h3>Results</h3><p>Distortion and blurriness artifacts on the off-center MRI images of the phantom, <em>in vivo</em> shoulder, knee, and hip images were mitigated with off-center excitation without time or noise penalty, at no additional computational cost.</p></div><div><h3>Conclusion</h3><p>The off-center excitation allows ZTE MRI of the shoulder, knee, and hip for high-bandwidth image acquisitions for clinical settings, where positioning at the isocenter is not possible.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"34 3","pages":"Pages 446-455"},"PeriodicalIF":2.4,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000940/pdfft?md5=88ef93407ba6cb137dc9ea24421d0b25&pid=1-s2.0-S0939388922000940-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40679315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Process failure mode and effects analysis for external beam radiotherapy: Introducing a literature-based template and a novel action priority 外照射放射治疗的过程失效模式与效应分析：引入基于文献的模板和新的行动优先级。
IF 2.4 4区 医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Zeitschrift fur Medizinische Physik
Pub Date : 2024-08-01 DOI: 10.1016/j.zemedi.2024.02.002

Purpose

The first aim of the study was to create a general template for analyzing potential failures in external beam radiotherapy, EBRT, using the process failure mode and effects analysis (PFMEA). The second aim was to modify the action priority (AP), a novel prioritization method originally introduced by the Automotive Industry Action Group (AIAG), to work with different severity, occurrence, and detection rating systems used in radiation oncology.

Methods and materials

The AIAG PFMEA approach was employed in combination with an extensive literature survey to develop the EBRT-PFMEA template. Subsets of high-risk failure modes found through the literature survey were added to the template where applicable. Our modified AP for radiation oncology (RO AP) was defined using a weighted sum of severity, occurrence, and detectability. Then, Monte Carlo simulations were conducted to compare the original AIAG AP, the RO AP, and the risk priority number (RPN). The results of the simulations were used to determine the number of additional corrective actions per failure mode and to parametrize the RO AP to our department’s rating system.

Results

An EBRT-PFMEA template comprising 75 high-risk failure modes could be compiled. The AIAG AP required 1.7 additional corrective actions per failure mode, while the RO AP ranged from 1.3 to 3.5, and the RPN required 3.6. The RO AP could be parametrized so that it suited our rating system and evaluated severity, occurrence, and detection ratings equally to the AIAG AP.

Conclusions

An adjustable EBRT-PFMEA template is provided which can be used as a practical starting point for creating institution-specific templates. Moreover, the RO AP introduces transparent action levels that can be adapted to any rating system.

目的：本研究的第一个目的是创建一个通用模板，用于使用过程故障模式和影响分析（PFMEA）分析外照射放射治疗（EBRT）中的潜在故障。第二个目的是修改行动优先级（AP），这是一种新颖的优先级排序方法，最初由汽车工业行动小组（AIAG）推出，用于放射肿瘤学中不同的严重性、发生率和检测评级系统：采用 AIAG PFMEA 方法并结合广泛的文献调查，开发出 EBRT-PFMEA 模板。通过文献调查发现的高风险失效模式子集被添加到适用的模板中。我们使用严重性、发生率和可探测性的加权和来定义放射肿瘤学的修正 AP（RO AP）。然后，进行蒙特卡罗模拟，比较原始 AIAG AP、RO AP 和风险优先级编号 (RPN)。模拟结果用于确定每种故障模式下额外纠正措施的数量，并根据我们部门的评级系统对 RO AP 进行参数化：结果：可以编制一个包含 75 种高风险故障模式的 EBRT-PFMEA 模板。AIAG AP 要求对每种失效模式采取 1.7 项额外纠正措施，而 RO AP 的范围在 1.3 至 3.5 之间，RPN 要求采取 3.6 项额外纠正措施。RO AP 可以进行参数化，使其适合我们的评级系统，对严重性、发生率和检测评级的评估与 AIAG AP 相同：提供了一个可调整的 EBRT-PFMEA 模板，可作为创建特定机构模板的实用起点。此外， RO AP 引入了透明的行动级别，可适用于任何评级系统。
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引用次数: 0
A body mass index-based method for “MR-only” abdominal MR-guided adaptive radiotherapy 基于体重指数的 "纯磁共振 "腹部磁共振引导自适应放射治疗方法。
IF 2.4 4区 医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Zeitschrift fur Medizinische Physik
Pub Date : 2024-08-01 DOI: 10.1016/j.zemedi.2022.12.001

Purpose

Dose calculation for MR-guided radiotherapy (MRgRT) at the 0.35 T MR-Linac is currently based on deformation of planning CTs (defCT) acquired for each patient. We present a simple and robust bulk density overwrite synthetic CT (sCT) method for abdominal treatments in order to streamline clinical workflows.

Method

Fifty-six abdominal patient treatment plans were retrospectively evaluated. All patients had been treated at the MR-Linac using MR datasets for treatment planning and plan adaption and defCT for dose calculation. Bulk density CTs (4M-sCT) were generated from MR images with four material compartments (bone, lung, air, soft tissue). The relative electron densities (RED) for bone and lung were extracted from contoured CT structure average REDs. For soft tissue, a correlation between BMI and RED was evaluated. Dose was recalculated on 4M-sCT and compared to dose distributions on defCTs assessing dose differences in the PTV and organs at risk (OAR).

Results

Mean RED of bone was 1.17 ± 0.02, mean RED of lung 0.17 ± 0.05. The correlation between BMI and RED for soft tissue was statistically significant (p < 0.01). PTV dose differences between 4M-sCT and defCT were Dmean: −0.4 ± 1.0%, D1%: −0.3 ± 1.1% and D95%: −0.5 ± 1.0%. OARs showed D2%: −0.3 ± 1.9% and Dmean: −0.1 ± 1.4% differences. Local 3D gamma index pass rates (2%/2mm) between dose calculated using 4M-sCT and defCT were 96.8 ± 2.6% (range 89.9–99.6%).

Conclusion

The presented method for sCT generation enables precise dose calculation for MR-only abdominal MRgRT.

目的：目前，在 0.35 T MR-Linac 上进行磁共振引导放疗 (MRgRT) 的剂量计算基于为每位患者获取的计划 CT（defCT）的变形。我们针对腹部治疗提出了一种简单、稳健的体密度覆盖合成 CT（sCT）方法，以简化临床工作流程：方法：我们对 56 例腹部患者的治疗计划进行了回顾性评估。所有患者均在磁共振Linac接受过治疗，治疗计划和计划调整使用磁共振数据集，剂量计算使用defCT。大体密度 CT（4M-sCT）由四个物质区（骨、肺、空气、软组织）的磁共振图像生成。骨和肺的相对电子密度（RED）是从轮廓 CT 结构平均 RED 中提取的。对于软组织，则评估了 BMI 与 RED 之间的相关性。在 4M-sCT 上重新计算剂量，并与 defCT 上的剂量分布进行比较，评估 PTV 和危险器官 (OAR) 的剂量差异：结果：骨的平均 RED 为 1.17 ± 0.02，肺的平均 RED 为 0.17 ± 0.05。体重指数（BMI）与软组织 RED 之间的相关性具有统计学意义（P 平均值：-0.4 ± 1.0）：-0.4 ± 1.0%, D1%:-0.3±1.1%，D95%：-0.5 ± 1.0%.OAR 显示 D2%：-0.3 ± 1.9%，D95%：-0.5 ± 1.0%：-0.3 ± 1.9% 和 Dmean：差异为-0.1 ± 1.4%。使用4M-sCT和defCT计算的剂量之间的局部三维伽马指数通过率（2%/2mm）为96.8 ± 2.6%（范围89.9-99.6%）：结论：所介绍的 sCT 生成方法可精确计算仅磁共振腹部 MRgRT 的剂量。
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引用次数: 0
Re-evaluation of the prospective risk analysis for artificial-intelligence driven cone beam computed tomography-based online adaptive radiotherapy after one year of clinical experience 基于人工智能驱动的锥形束计算机断层扫描在线自适应放射治疗一年后的前瞻性风险分析再评估。
IF 2.4 4区 医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Zeitschrift fur Medizinische Physik
Pub Date : 2024-08-01 DOI: 10.1016/j.zemedi.2024.05.001

Cone-beam computed tomography (CBCT)-based online adaptation is increasingly being introduced into many clinics. Upon implementation of a new treatment technique, a prospective risk analysis is required and enhances workflow safety. We conducted a risk analysis using Failure Mode and Effects Analysis (FMEA) upon the introduction of an online adaptive treatment programme (Wegener et al., Z Med Phys. 2022).

A prospective risk analysis, lacking in-depth clinical experience with a treatment modality or treatment machine, relies on imagination and estimates of the occurrence of different failure modes. Therefore, we systematically documented all irregularities during the first year of online adaptation, namely all cases in which quality assurance detected undesired states potentially leading to negative consequences. Additionally, the quality of automatic contouring was evaluated. Based on those quantitative data, the risk analysis was updated by an interprofessional team. Furthermore, a hypothetical radiation therapist-only workflow during adaptive sessions was included in the prospective analysis, as opposed to the involvement of an interprofessional team performing each adaptive treatment.

A total of 126 irregularities were recorded during the first year. During that time period, many of the previously anticipated failure modes (almost) occurred, indicating that the initial prospective risk analysis captured relevant failure modes. However, some scenarios were not anticipated, emphasizing the limits of a prospective risk analysis. This underscores the need for regular updates to the risk analysis. The most critical failure modes are presented together with possible mitigation strategies. It was further noted that almost half of the reported irregularities applied to the non-adaptive treatments on this treatment machine, primarily due to a manual plan import step implemented in the institution’s workflow.

基于锥形束计算机断层扫描（CBCT）的在线适应技术正越来越多地被引入许多诊所。在实施新的治疗技术时，需要进行前瞻性风险分析，以提高工作流程的安全性。我们采用失效模式及影响分析法（FMEA）对引入在线自适应治疗方案进行了风险分析（Wegener 等人，Z Med Phys.）前瞻性风险分析由于缺乏对治疗模式或治疗设备的深入临床经验，只能依赖于对不同故障模式发生率的想象和估计。因此，我们系统地记录了第一年在线适应期间的所有异常情况，即质量保证检测到可能导致不良后果的不期望状态的所有案例。此外，我们还对自动轮廓绘制的质量进行了评估。根据这些定量数据，跨专业团队对风险分析进行了更新。此外，在前瞻性分析中还包括了适应性治疗过程中仅由放射治疗师参与的假设工作流程，而不是由跨专业团队参与执行每次适应性治疗。第一年共记录了 126 起违规事件。在此期间，许多之前预计的故障模式（几乎）都发生了，这表明最初的前瞻性风险分析捕捉到了相关的故障模式。然而，有些情况是没有预料到的，这强调了前瞻性风险分析的局限性。这强调了定期更新风险分析的必要性。最关键的失效模式与可能的缓解战略一并列出。我们还注意到，在报告的不规范情况中，几乎有一半适用于该治疗机上的非适应性治疗，这主要是由于该机构的工作流程中实施了手动计划导入步骤。
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引用次数: 0
Prospective risk analysis of the online-adaptive artificial intelligence-driven workflow using the Ethos treatment system 对使用 Ethos 治疗系统的在线自适应人工智能驱动工作流程进行前瞻性风险分析。
IF 2.4 4区 医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING
Zeitschrift fur Medizinische Physik
Pub Date : 2024-08-01 DOI: 10.1016/j.zemedi.2022.11.004

Purpose

The recently introduced Varian Ethos system allows adjusting radiotherapy treatment plans to anatomical changes on a daily basis. The system uses artificial intelligence to speed up the process of creating adapted plans, comes with its own software solutions and requires a substantially different workflow. A detailed analysis of possible risks of the associated workflow is presented.

Methods

A prospective risk analysis of the adaptive workflow with the Ethos system was performed using Failure Modes and Effects Analysis (FMEA). An interprofessional team collected possible adverse events and evaluated their severity as well as their chance of occurrence and detectability. Measures to reduce the risks were discussed.

Results

A total of 122 events were identified, and scored. Within the 20 events with the highest-ranked risks, the following were identified: Challenges due to the stand-alone software solution with very limited connectivity to the existing record and verify software and digital patient file, unfamiliarity with the new software and its limitations and the adaption process relying on results obtained by artificial intelligence. The risk analysis led to the implementation of additional quality assurance measures in the workflow.

Conclusions

The thorough analysis of the risks associated with the new treatment technique was the basis for designing details of the workflow. The analysis also revealed challenges to be addressed by both, the vendor and customers. On the vendor side, this includes improving communication between their different software solutions. On the customer side, this especially includes establishing validation strategies to monitor the results of the black box adaption process making use of artificial intelligence.

目的：最近推出的瓦里安 Ethos 系统可以每天根据解剖结构的变化调整放射治疗计划。该系统利用人工智能来加快制定适应性计划的过程，并配有自己的软件解决方案，所需的工作流程也大不相同。本文对相关工作流程可能存在的风险进行了详细分析：方法：使用故障模式和影响分析（FMEA）对使用 Ethos 系统的适应性工作流程进行了前瞻性风险分析。一个跨专业小组收集了可能发生的不良事件，并评估了其严重程度、发生几率和可探测性。讨论了降低风险的措施：共确定了 122 个事件并进行了评分。在风险最高的 20 个事件中，确定了以下几点：由于独立软件解决方案与现有记录和验证软件以及数字病人档案的连接非常有限而带来的挑战，对新软件及其局限性的不熟悉，以及适应过程依赖于人工智能获得的结果。通过风险分析，在工作流程中实施了额外的质量保证措施：对新治疗技术相关风险的全面分析是设计工作流程细节的基础。分析还揭示了供应商和客户需要应对的挑战。在供应商方面，这包括改善不同软件解决方案之间的沟通。在客户方面，这尤其包括制定验证策略，利用人工智能监控黑盒适应过程的结果。
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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 : 2024-08-01 DOI: 10.1016/S0939-3889(24)00060-6
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