Zeitschrift fur Medizinische Physik最新文献_第7页

Pilot study on high-resolution radiological methods for the analysis of cerebrospinal fluid (CSF) shunt valves 用于分析脑脊液（CSF）分流阀的高分辨率放射学方法试点研究

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2023-12-15 DOI: 10.1016/j.zemedi.2023.11.001

Martin P. Pichotka, Moritz Weigt, Mukesch J. Shah, Maximilian F. Russe, Thomas Stein, T. Billoud, Jürgen Beck, Jakob Straehle, Christopher L. Schlett, Dominik v. Elverfeldt, Marco Reisert

<h3>Objectives</h3><p>Despite their life-saving capabilities, cerebrospinal fluid (CSF) shunts exhibit high failure rates, with a large fraction of failures attributed to the regulating valve. Due to a lack of methods for the detailed analysis of valve malfunctions, failure mechanisms are not well understood, and valves often have to be surgically explanted on the mere suspicion of malfunction.</p><p>The presented pilot study aims to demonstrate radiological methods for comprehensive analysis of CSF shunt valves, considering both the potential for failure analysis in design optimization, and for future clinical in-vivo application to reduce the number of required shunt revision surgeries. The proposed method could also be utilized to develop and support in situ repair methods (e.g. by lysis or ultrasound) of malfunctioning CSF shunt valves.</p><h3>Materials and methods</h3><p>The primary methods described are contrast-enhanced radiographic time series of CSF shunt valves, taken in a favorable projection geometry at low radiation dose, and the machine-learning-based diagnosis of CSF shunt valve obstructions. Complimentarily, we investigate CT-based methods capable of providing accurate ground truth for the training of such diagnostic tools. Using simulated test and training data, the performance of the machine-learning diagnostics in identifying and localizing obstructions within a shunt valve is evaluated regarding per-pixel sensitivity and specificity, the Dice similarity coefficient, and the false positive rate in the case of obstruction free test samples.</p><h3>Results</h3><p>Contrast enhanced subtraction radiography allows high-resolution, time-resolved, low-dose analysis of fluid transport in CSF shunt valves. Complementarily, photon-counting micro-CT allows to investigate valve obstruction mechanisms in detail, and to generate valid ground truth for machine learning-based diagnostics.</p><p>Machine-learning-based detection of valve obstructions in simulated radiographies shows promising results, with a per-pixel sensitivity >70%, per-pixel specificity >90%, a median Dice coefficient >0.8 and <10% false positives at a detection threshold of 0.5.</p><h3>Conclusions</h3><p>This ex-vivo study demonstrates obstruction detection in cerebro-spinal fluid shunt valves, combining radiological methods with machine learning under conditions compatible to future in-vivo application.</p><p>Results indicate that high-resolution contrast-enhanced subtraction radiography, possibly including time-series data, combined with machine-learning image analysis, has the potential to strongly improve the diagnostics of CSF shunt valve failures. The presented method is in principle suitable for in-vivo application, considering both measurement geometry and radiological dose. Further research is needed to validate these results on real-world data and to refine the employed methods.</p><p>In combination, the presented methods enable comprehensive analysis

目的尽管脑脊液（CSF）分流器具有挽救生命的功能，但其故障率很高，其中很大一部分故障归咎于调节阀。本试验研究旨在展示全面分析脑脊液分流瓣膜的放射学方法，既考虑到在优化设计中进行故障分析的潜力，也考虑到未来在临床活体应用中减少所需分流改造手术的数量。所提出的方法还可用于开发和支持故障 CSF 分流瓣膜的原位修复方法（如通过裂解或超声波）。此外，我们还研究了基于 CT 的方法，这些方法能够为此类诊断工具的训练提供准确的地面实况。使用模拟测试和训练数据，评估了机器学习诊断在识别和定位分流瓣内阻塞方面的性能，包括每像素灵敏度和特异性、Dice 相似系数以及无阻塞测试样本的假阳性率。作为补充，光子计数微型计算机断层扫描可以详细研究瓣膜阻塞机制，并为基于机器学习的诊断生成有效的基本事实。基于机器学习的瓣膜阻塞检测在模拟射线照片中显示出良好的结果，每像素灵敏度为 70%，每像素特异度为 90%，中位 Dice 系数为 0.8，在检测阈值为 0.5 时，假阳性率为 10%。结果表明，高分辨率对比度增强减影射线摄影（可能包括时间序列数据）与机器学习图像分析相结合，有可能极大地改善脑脊液分流瓣膜故障的诊断。考虑到测量的几何形状和放射剂量，所介绍的方法原则上适用于体内应用。需要开展进一步的研究，以便在真实世界的数据上验证这些结果，并完善所采用的方法。结合这些方法，可以对瓣膜故障机制进行全面分析，为改进脑脊液分流瓣膜的产品开发和临床诊断铺平道路。

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引用次数: 0

Bandinhaltsverzeichnis 2023 2023 年目录

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2023-11-01 DOI: 10.1016/S0939-3889(23)00132-0

引用次数: 0

Acknowledgements to the Consulting Editorial Board and the Reviewers 向顾问编委会和审稿人致谢

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2023-11-01 DOI: 10.1016/j.zemedi.2023.09.003

引用次数: 0

Mitteilungen der Deutschen Gesellschaft für Medizinische Physik e.V. 德国医学物理学协会

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2023-11-01 DOI: 10.1016/j.zemedi.2023.10.006

Aus dem Vorstand

引用次数: 0

SSRMP Recommendations No 9: Reference dosimetry in low and medium energy x-ray beams SSRMP 建议 9：中低能量 X 射线束的参考剂量测定

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2023-11-01 DOI: 10.1016/j.zemedi.2022.12.003

Maria M Aspradakis , Thierry Buchillier , Götz Kohler , Christian Kottler , Jérôme Krayenbühl

The SSRMP recommendations on reference dosimetry in kilovolt beams as used in radiation therapy were revised to establish current practice in Switzerland.

The recommendations specify the dosimetry formalism, reference class dosimeter systems and conditions used for the calibration of low and medium energy x-ray beams. Practical guidance is provided on the determination of the beam quality specifier and all corrections required for converting instrument readings to absorbed dose to water. Guidance is also provided on the determination of relative dose under non-reference conditions and on the cross calibration of instruments.

The effect of lack of electron equilibrium and influence of contaminant electrons when using thin window plane parallel chambers at x-ray tube potentials higher than 50 kV is elaborated in an appendix. In Switzerland the calibration of the reference system used for dosimetry is regulated by law. METAS and IRA are the authorities providing this calibration service to the radiotherapy departments. The last appendix of these recommendations summarise this calibration chain.

SSRMP 对放射治疗中使用的千伏光束参考剂量测定建议进行了修订，以确立瑞士的现行做法。该建议规定了剂量测定形式、参考类剂量计系统以及用于校准低能量和中等能量 X 射线光束的条件。该建议书提供了实用指南，指导如何确定光束质量规格，以及将仪器读数转换为水吸收剂量所需的所有修正。附录中详细阐述了在 X 射线管电位高于 50 千伏的情况下使用薄窗平面平行腔时缺乏电子平衡的影响和杂质电子的影响。在瑞士，用于剂量测定的参考系统的校准受法律约束。METAS 和 IRA 是为放射治疗部门提供校准服务的机构。本建议书的最后一个附录总结了这一校准链。

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引用次数: 0

Determination of the dose rate around a HDR 192Ir brachytherapy source with the microDiamond and the microSilicon detector 利用微型钻石和微型硅探测器测定高清 192Ir 近距离放射源周围的剂量率

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2023-11-01 DOI: 10.1016/j.zemedi.2022.07.004

Giulio Rossi , Thomas Failing , Mark Gainey , Michael Kollefrath , Frank Hensley , Klemens Zink , Dimos Baltas

<div><p><strong>Purpose:</strong> To employ the microDiamond and the microSilicon detector (mDD and mSD, both PTW-Freiburg, Germany) to determine the dose rate around a HDR <sup>192</sup>Ir brachytherapy source (model mHDR-v2r, Elekta AB, Sweden).</p><p><strong>Methods:</strong> The detectors were calibrated with a <sup>60</sup>Co beam at the PTW Calibration Laboratory. Measurements around the <sup>192</sup>Ir source were performed inside a PTW MP3 water phantom. The detectors were placed at selected points of measurement at radial distances <em>r</em>, ranging from 0.5 to 10 cm, keeping the polar angle <em>θ</em> = 90°. Additional measurements were performed with the mSD at fixed distances <em>r</em> = 1, 3 and 5 cm, with <em>θ</em> varying from 0 to 150°, 0 to 166°, and 0 to 168°, respectively. The corresponding mDD readings were already available from a previous work (Rossi et al., 2020). The beam quality correction factor of both detectors, as well as a phantom effect correction factor to account for the difference between the experimental geometry and that assumed in the TG-43 formalism, were determined using the Monte Carlo (MC) toolkit EGSnrc. The beam quality correction factor was factorized into energy dependence and volume-averaging correction factors. Using the abovementioned MC-based factors, the dose rate to water at the different points of measurement in TG-43 conditions was obtained from the measured readings, and was compared to the dose rate calculated according to the TG-43 formalism.</p><p><strong>Results:</strong> The beam quality correction factor was considerably closer to unity for the mDD than for the mSD. The energy dependence of the mDD showed a very weak radial dependence, similar to the previous findings showing a weak angular dependence as well (Rossi et al., 2020). Conversely, the energy dependence of the mSD decreased significantly with increasing distances, and also showed a considerably more pronounced angular dependence, especially for the smallest angles. The volume-averaging showed a similar radial dependence for both detectors: the correction had a maximal impact at 0.5 cm and then approached unity for larger distances, as expected. Concerning the angular dependence, the correction for the mSD was also similar to the one previously determined for the mDD (Rossi et al., 2020): a maximal impact was observed at <em>θ</em> = 0°, with values tending to unity for larger angles. In general, the volume-averaging was less pronounced for the mSD due to the smaller sensitive volume radius. After the application of the MC-based factors, differences between mDD dose rate measurements and TG-43 dose rate calculations ranged from −2.6% to +4.3%, with an absolute average difference of 1.0%. For the mSD, the differences ranged from −3.1% to +5.2%, with an absolute average difference of 1.0%. For both detectors, all differences but one were within the combined uncertainty (<em>k</em> = 2). The differences of the mSD from the mD

目的：采用微钻石和微硅探测器（mDD 和 mSD，均为德国 PTW-Freiburg）确定 HDR 192Ir 近距离放射源（型号 mHDR-v2r，瑞典 Elekta AB）周围的剂量率：在 PTW 校准实验室用 60Co 射束对探测器进行了校准。192Ir 放射源周围的测量在 PTW MP3 水模型内进行。探测器被放置在选定的测量点上，径向距离 r 从 0.5 厘米到 10 厘米不等，保持极角 θ = 90°。在固定距离 r = 1、3 和 5 厘米处使用 mSD 进行了额外测量，θ 分别为 0 至 150°、0 至 166°、0 至 168°。相应的 mDD 读数可从以前的工作中获得（Rossi 等人，2020 年）。使用蒙特卡罗（MC）工具包 EGSnrc 确定了两个探测器的光束质量校正因子以及幻影效应校正因子，以考虑到实验几何形状与 TG-43 形式中假设的几何形状之间的差异。光束质量校正因子被分解为能量依赖校正因子和体积平均校正因子。利用上述基于 MC 的因子，从测量读数中获得了 TG-43 条件下不同测量点的水剂量率，并与根据 TG-43 形式主义计算的剂量率进行了比较：结果：与 mSD 相比，mDD 的光束质量校正因子更接近于统一。mDD 的能量依赖性显示出非常微弱的径向依赖性，这与之前显示出微弱角度依赖性的研究结果类似（Rossi 等人，2020 年）。相反，mSD 的能量依赖性随着距离的增加而显著降低，同时也显示出明显的角度依赖性，尤其是在最小角度时。两个探测器的体积平均值都显示出类似的径向依赖性：校正在 0.5 厘米处影响最大，然后如预期的那样，在更大的距离上接近于 1。关于角度依赖性，对 mSD 的校正也与之前为 mDD 确定的校正相似（Rossi 等人，2020 年）：在 θ = 0° 时影响最大，角度越大，校正值越趋于统一。一般来说，由于敏感体积半径较小，mSD 的体积平均化不太明显。应用基于 MC 的因子后，mDD 剂量率测量值与 TG-43 剂量率计算值之间的差异从 -2.6% 到 +4.3%，绝对平均差异为 1.0%。对于 mSD，差异范围从 -3.1% 到 +5.2%，绝对平均差异为 1.0%。对于这两种探测器来说，除了一个之外，所有的差异都在综合不确定度（k = 2）范围之内。mSD 与 mDD 的差异从 -3.9% 到 +2.6%，绝大多数差异都在综合不确定度（k = 2）范围内。对于 θ ≠ 0°，即使不使用基于 MC 的光束质量校正因子，mDD 也能提供足够精确的结果，与 TG-43 剂量率计算结果的差异从 -1.9% 到 +3.4%，始终在综合不确定性（k = 2）范围内：mDD 和 mSD 显示出一致的结果，似乎非常适合测量 HDR 192Ir 近距离放射源周围的剂量率。需要对探测器的响应进行 MC 鉴定，以确定射束质量校正因子，并考虑能量依赖性和/或体积平均，尤其是对于 mSD。我们的研究结果支持使用 mDD 和 mSD 进行放射源质量保证、TPS 验证和 TG-43 参数确定。

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引用次数: 0

Development and validation of an optimal GATE model for proton pencil-beam scanning delivery 开发和验证用于质子铅笔束扫描传输的最佳 GATE 模型

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2023-11-01 DOI: 10.1016/j.zemedi.2022.10.008

Ali Asadi , Azadeh Akhavanallaf , Seyed Abolfazl Hosseini , Naser Vosoughi , Habib Zaidi

Objective

To develop and validate a versatile Monte Carlo (MC)-based dose calculation engine to support MC-based dose verification of treatment planning systems (TPSs) and quality assurance (QA) workflows in proton therapy.

Methods

The GATE MC toolkit was used to simulate a fixed horizontal active scan-based proton beam delivery (SIEMENS IONTRIS). Within the nozzle, two primary and secondary dose monitors have been designed to enable the comparison of the accuracy of dose estimation from MC simulations with respect to physical QA measurements. The developed beam model was validated against a series of commissioning measurements using pinpoint chambers and 2D array ionization chambers (IC) in terms of lateral profiles and depth dose distributions. Furthermore, beam delivery module and treatment planning has been validated against the literature deploying various clinical test cases of the AAPM TG‐119 (c-shape phantom) and a prostate patient.

Results

MC simulations showed excellent agreement with measurements in the lateral depth-dose parameters and spread-out Bragg peak (SOBP) characteristics within a maximum relative error of 0.95 mm in range, 1.83% in entrance to peak ratio, 0.27% in mean point-to-point dose difference, and 0.32% in peak location. The mean relative absolute difference between MC simulations and measurements in terms of absorbed dose in the SOBP region was 0.93% ± 0.88%. Clinical phantom studies showed a good agreement compared to research TPS (relative error for TG-119 planning target volume PTV-D₉₅ ∼ 1.8%; and for prostate PTV-D₉₅ ∼ −0.6%).

Conclusion

We successfully developed a MC model for the pencil beam scanning system, which appears reliable for dose verification of the TPS in combination with QA information, prior to patient treatment.

目的开发并验证基于蒙特卡罗（MC）的多功能剂量计算引擎，以支持质子治疗中基于MC的治疗计划系统（TPS）剂量验证和质量保证（QA）工作流程。方法使用GATE MC工具包模拟基于固定水平主动扫描的质子束输送（SIEMENS IONTRIS）。在喷嘴内，设计了两个主要和次要剂量监测器，以便比较 MC 模拟与物理 QA 测量的剂量估算准确性。利用针尖室和二维阵列电离室（IC）进行了一系列调试测量，从横向剖面和深度剂量分布方面对所开发的射束模型进行了验证。结果 MC 模拟结果显示，横向深度剂量参数和扩散布拉格峰（SOBP）特性与测量结果非常吻合，最大相对误差范围为 0.95 毫米，入口与峰值比为 1.83%，平均点对点剂量差为 0.27%，峰值位置为 0.32%。就 SOBP 区域的吸收剂量而言，MC 模拟与测量之间的平均相对绝对差值为 0.93% ± 0.88%。临床模型研究显示，与 TPS 研究相比，两者的一致性很好（TG-119 规划靶体积 PTV-D95 的相对误差 ∼ 1.8%；前列腺 PTV-D95 的相对误差 ∼ -0.6%）。

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引用次数: 0

Small field proton irradiation for in vivo studies: Potential and limitations when adapting clinical infrastructure 用于体内研究的小场质子辐照：改造临床基础设施的潜力和局限性

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2023-11-01 DOI: 10.1016/j.zemedi.2022.10.002

Monika Clausen , Sirinya Ruangchan , Arame Sotoudegan , Andreas F. Resch , Barbara Knäusl , Hugo Palmans , Dietmar Georg

Purpose

To evaluate the dosimetric accuracy for small field proton irradiation relevant for pre-clinical in vivo studies using clinical infrastructure and technology. In this context additional beam collimation and range reduction was implemented.

Methods and materials

The clinical proton beam line employing pencil beam scanning (PBS) was adapted for the irradiation of small fields at shallow depths. Cylindrical collimators with apertures of 15, 12, 7 and 5 mm as well as two different range shifter types, placed at different distances relative to the target, were tested: a bolus range shifter (BRS) attached to the collimator and a clinical nozzle mounted range shifter (CRS) placed at a distance of 72 cm from the collimator. The Monte Carlo (MC) based dose calculation engine implemented in the clinical treatment planning system (TPS) was commissioned for these two additional hardware components. The study was conducted with a phantom and cylindrical target sizes between 2 and 25 mm in diameter following a dosimetric end-to-end test concept.

Results

The setup with the CRS provided a uniform dose distribution across the target. An agreement of better than 5% between the planned dose and the measurements was obtained for a target with 3 mm diameter (collimator 5 mm). A 2 mm difference between the collimator and the target diameter (target being 2 mm smaller than the collimator) sufficed to cover the whole target with the planned dose in the setup with CRS. Using the BRS setup (target 8 mm, collimator 12 mm) resulted in non-homogeneous dose distributions, with a dose discrepancy of up to 10% between the planned and measured doses.

Conclusion

The clinical proton infrastructure with adequate beam line adaptations and a state-of-the-art TPS based on MC dose calculations enables small animal irradiations with a high dosimetric precision and accuracy for target sizes down to 3 mm.

目的利用临床基础设施和技术，评估与临床前体内研究相关的小场质子辐照的剂量测定精度。方法和材料采用铅笔束扫描（PBS）的临床质子束线适用于浅层小场辐照。测试了孔径分别为 15、12、7 和 5 毫米的圆柱形准直器以及两种不同类型的射程移动器，它们与目标的相对距离各不相同：一种是与准直器相连的栓状射程移动器 (BRS)，另一种是安装在临床喷嘴上的射程移动器 (CRS)，与准直器的距离为 72 厘米。临床治疗计划系统（TPS）中基于蒙特卡罗（MC）的剂量计算引擎被用于这两个额外的硬件组件。研究使用了一个模型和直径在 2 毫米到 25 毫米之间的圆柱形靶，采用了端到端剂量测定测试概念。对于直径为 3 毫米的目标（准直器为 5 毫米），计划剂量与测量值的一致性优于 5%。准直器与靶直径相差 2 毫米（靶比准直器小 2 毫米），在使用 CRS 的设置中，计划剂量足以覆盖整个靶。结论临床质子基础设施具有足够的束流线适应性和基于 MC 剂量计算的最先进的 TPS，能够以高剂量测定精度和准确度对目标尺寸小至 3 毫米的小动物进行辐照。

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引用次数: 1

Dosimetric validation of the couch and coil model for high-field MR-linac treatment planning 用于高场磁共振线性治疗规划的床和线圈模型的剂量学验证

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2023-11-01 DOI: 10.1016/j.zemedi.2023.02.002

Hans Lynggaard Riis , Rasmus Lübeck Christiansen , Nina Tilly , David Tilly

Purpose

The precision of the dose delivery in radiation therapy with high-field MR-linacs is challenging due to the substantial variation in the beam attenuation of the patient positioning system (PPS) (the couch and coils) as a function of the gantry angle. This work aimed to compare the attenuation of two PPSs located at two different MR-linac sites through measurements and calculations in the treatment planning system (TPS).

Methods

Attenuation measurements were performed at every 1° gantry angle at the two sites with a cylindrical water phantom with a Farmer chamber inserted along the rotational axis of the phantom. The phantom was positioned with the chamber reference point (CRP) at the MR-linac isocentre. A compensation strategy was applied to minimise sinusoidal measurement errors due to, e.g. air cavity or setup. A series of tests were performed to assess the sensitivity to measurement uncertainties. The dose to a model of the cylindrical water phantom with the PPS added was calculated in the TPS (Monaco v5.4 as well as in a development version Dev of an upcoming release), for the same gantry angles as for the measurements. The TPS PPS model dependency of the dose calculation voxelisation resolution was also investigated.

Results

A comparison of the measured attenuation of the two PPSs yielded differences of less than 0.5% for most gantry angles. The maximum deviation between the attenuation measurements for the two different PPSs exceeded ±1% at two specific gantry angles 115° and 245°, where the beam traverses the most complex PPS structures. The attenuation increases from 0% to 25% in 15° intervals around these angles. The measured and calculated attenuation, as calculated in v5.4, was generally within 1-2% with a systematic overestimation of the attenuation for gantry angles around 180°, as well as a maximum error of 4-5% for a few discrete angles in 10° gantry angle intervals around the complex PPS structures. The PPS modelling was improved compared to v5.4 in Dev, especially around 180°, and the results of those calculations were within ±1%, but with a similar 4% maximum deviation for the most complex PPS structures.

Conclusions

Generally, the two tested PPS structures exhibit very similar attenuation as a function of the gantry angle, including the angles with a steep change in attenuation. Both TPS versions, v5.4 and Dev delivered clinically acceptable accuracy of the calculated dose, as the differences in the measurements were overall better than ±2%. Additionally, Dev improved the accuracy of the dose calculation to ±1% for gantry angles around 180°.

目的由于患者定位系统（PPS）（治疗床和线圈）的射束衰减随龙门架角度的变化而有很大差异，因此在使用高场磁共振线性加速器进行放射治疗时，剂量投放的精确性具有挑战性。这项工作的目的是通过在治疗计划系统（TPS）中进行测量和计算，比较位于两个不同磁共振线阵部位的两个 PPS 的衰减情况。方法在两个部位每隔 1° 的龙门角度用一个圆柱形水模型进行衰减测量，模型中沿旋转轴插入一个 Farmer 腔。模型的定位是将腔体参考点（CRP）置于磁共振成像仪的等中心。采用了补偿策略，以尽量减少由于气腔或设置等原因造成的正弦测量误差。为评估对测量不确定性的敏感性，进行了一系列测试。在 TPS（Monaco v5.4，以及即将发布的开发版本 Dev）中计算了添加了 PPS 的圆柱形水体模型的剂量，龙门角度与测量时相同。结果比较两种 PPS 的测量衰减结果发现，在大多数龙门角度下，两者之间的差异小于 0.5%。在两个特定的龙门角度 115° 和 245°，两种不同 PPS 的衰减测量值之间的最大偏差超过 ±1%，在这两个角度，光束穿过最复杂的 PPS 结构。在这两个角度周围，衰减以 15° 的间隔从 0% 增加到 25%。在 v5.4 中计算的测量和计算衰减一般在 1-2% 的范围内，180° 左右的龙门角度的衰减被系统性高估，而在复杂 PPS 结构周围 10°龙门角度间隔内的几个离散角度的最大误差为 4-5%。与 Dev5.4 版相比，PPS 建模有所改进，尤其是在 180° 附近，计算结果在 ±1% 以内，但对于最复杂的 PPS 结构，最大偏差也同样为 4%。两个 TPS 版本（v5.4 和 Dev）都能提供临床上可接受的计算剂量精度，因为测量结果的差异总体上小于 ±2%。此外，Dev 将 180° 左右龙门角度的剂量计算精度提高到 ±1%。

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引用次数: 0

The Medical Device Regulation and its impact on device development and research in Germany 《医疗器械条例》及其对德国器械研发的影响。

IF 2 4区医学 Q2 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Zeitschrift fur Medizinische Physik

Pub Date : 2023-11-01 DOI: 10.1016/j.zemedi.2023.09.002

Mark E. Ladd

引用次数: 0