Pub Date : 2025-11-01DOI: 10.1016/j.zemedi.2024.03.004
Sepideh Hatamikia , Soraya Elmirad , Hugo Furtado , Gernot Kronreif , Elisabeth Steiner , Wolfgang Birkfellner
Intensity-based 2D/3D registration using kilo-voltage (kV) and mega-voltage (MV) on-board imaging is a promising approach for real-time tumor motion tracking. So far, the performance of the kV images as well as kV-MV image pairs for 2D/3D registration using only one gantry angle (in anterior-posterior (AP) direction) has been investigated on patient data. In stereotactic body radiation therapy (SBRT), however, various gantry angles are typically used. This study attempts to answer the question of whether automatic 2D/3D registration is possible using kV images as well as kV-MV image pairs for gantry angles other than the AP direction. We also investigated the effect of additional portal MV images paired with kV images to improve 2D/3D registration in extracting cranio-caudal (CC) and AP displacement at arbitrary gantry angles and different fractions. The kV and MV image sequences as well as 3D volume data from five patients suffering from non-small cell lung cancer undergoing SBRT were used. Diaphragm motion served as the reference signal. The CC and AP displacements resulting from the registration results were compared with the corresponding reference motion signal. Pearson correlation coefficients (R value) was used to calculate the similarity measure between reference signal and the extracted displacements resulting from the registration. Signals we found that using 2D/3D registration tumor motion in 5 degrees of freedom (DOF) with kV images and in 6 degrees of freedom with kV-MV image pairs can be extracted for most gantry angles in all patients. Furthermore, our results have shown that the use of kV-MV image pairs increases the overall chance of tumor visibility and therefore leads to more successful extraction of CC as well as AP displacements for almost all gantry angles in all patients. We observed an improvement in registration of at least 0.29% more gantry angle for all patients when we used kV-MV images compared to kV images alone. In addition, an improvement in the R-value was observed in up to 16 fractions in various patients.
{"title":"Intra-fractional lung tumor motion monitoring using arbitrary gantry angles during radiotherapy treatment","authors":"Sepideh Hatamikia , Soraya Elmirad , Hugo Furtado , Gernot Kronreif , Elisabeth Steiner , Wolfgang Birkfellner","doi":"10.1016/j.zemedi.2024.03.004","DOIUrl":"10.1016/j.zemedi.2024.03.004","url":null,"abstract":"<div><div>Intensity-based 2D/3D registration using kilo-voltage (kV) and mega-voltage (MV) on-board imaging is a promising approach for real-time tumor motion tracking. So far, the performance of the kV images as well as kV-MV image pairs for 2D/3D registration using only one gantry angle (in anterior-posterior (AP) direction) has been investigated on patient data. In stereotactic body radiation therapy (SBRT), however, various gantry angles are typically used. This study attempts to answer the question of whether automatic 2D/3D registration is possible using kV images as well as kV-MV image pairs for gantry angles other than the AP direction. We also investigated the effect of additional portal MV images paired with kV images to improve 2D/3D registration in extracting cranio-caudal (CC) and AP displacement at arbitrary gantry angles and different fractions. The kV and MV image sequences as well as 3D volume data from five patients suffering from non-small cell lung cancer undergoing SBRT were used. Diaphragm motion served as the reference signal. The CC and AP displacements resulting from the registration results were compared with the corresponding reference motion signal. Pearson correlation coefficients (R value) was used to calculate the similarity measure between reference signal and the extracted displacements resulting from the registration. Signals we found that using 2D/3D registration tumor motion in 5 degrees of freedom (DOF) with kV images and in 6 degrees of freedom with kV-MV image pairs can be extracted for most gantry angles in all patients. Furthermore, our results have shown that the use of kV-MV image pairs increases the overall chance of tumor visibility and therefore leads to more successful extraction of CC as well as AP displacements for almost all gantry angles in all patients. We observed an improvement in registration of at least 0.29% more gantry angle for all patients when we used kV-MV images compared to kV images alone. In addition, an improvement in the R-value was observed in up to 16 fractions in various patients.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 4","pages":"Pages 503-513"},"PeriodicalIF":4.2,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140764797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-01DOI: 10.1016/j.zemedi.2024.02.003
Stefan Weber , Andreas Block , Felix Bärenfänger
In recent years, access to 3D printers has become increasingly affordable. Alongside industrial and private applications, the significance of 3D printing in the clinical context is also growing. For instance, 3D printing processes enable the production of individual anatomical models that can be used to support patient communication or aid in surgical planning. While filament 3D printing is common, stereolithography (SLA) and selective laser sintering (SLS) printing processes offer higher precision. For the use of 3D printing materials in radiology, understanding their attenuation properties concerning ionizing radiation is crucial. Polymethyl methacrylate (PMMA) serves as an important reference material for radiological applications in this regard.
In this research, linear- and mass attenuation coefficients of 38 SLA-/SLS-materials from Formlabs (Somerville, Massachusetts, USA) and PMMA will be determined through intensity measurements in nuclear medicine for the radionuclides technetium-99 m and iodine-131, as well as for X-ray imaging in the range of 60 kVp - 110 kVp tube voltage. Based on the mass attenuation coefficients, correction factors in respect to PMMA will be calculated for each material. A significant number of materials exhibit a deviance within approximately 5% in respect to PMMA regardless of radiation energy. However, certain materials from the dental and industrial application show deviances up to +500% at the lower end of radiation energy spectrum. In conclusion, most materials can be considered equivalent to PMMA with only minor adjustments required. Materials with high deviances can be utilized as high-contrast materials in custom X-ray phantoms.
近年来，3D 打印机的价格越来越亲民。除工业和私人应用外，3D 打印在临床方面的重要性也在不断增加。例如，3D 打印工艺可以制作个体解剖模型，用于支持患者交流或辅助手术规划。虽然长丝三维打印很常见，但立体光刻（SLA）和选择性激光烧结（SLS）打印工艺的精度更高。要在放射学中使用 3D 打印材料，了解它们对电离辐射的衰减特性至关重要。在这方面，聚甲基丙烯酸甲酯（PMMA）是放射学应用的重要参考材料。在这项研究中，将通过在核医学中对放射性核素锝-99 m 和碘-131 的强度测量，以及在 60 kVp - 110 kVp 管电压范围内的 X 射线成像，确定来自 Formlabs 公司（美国马萨诸塞州萨默维尔市）的 38 种 SLA/SLS 材料和 PMMA 的线性和质量衰减系数。根据质量衰减系数，将计算出每种材料相对于 PMMA 的校正系数。无论辐射能量如何，许多材料与 PMMA 的偏差都在 ±5% 左右。然而，牙科和工业应用中的某些材料在辐射能谱的低端显示出高达 +500% 的偏差。总之，大多数材料可视为与 PMMA 相当，只需稍作调整。偏差较大的材料可用作定制 X 射线模型中的高对比度材料。
{"title":"Assessment of attenuation properties for SLA and SLS 3D-printing materials in X-ray imaging and nuclear medicine","authors":"Stefan Weber , Andreas Block , Felix Bärenfänger","doi":"10.1016/j.zemedi.2024.02.003","DOIUrl":"10.1016/j.zemedi.2024.02.003","url":null,"abstract":"<div><div>In recent years, access to 3D printers has become increasingly affordable. Alongside industrial and private applications, the significance of 3D printing in the clinical context is also growing. For instance, 3D printing processes enable the production of individual anatomical models that can be used to support patient communication or aid in surgical planning. While filament 3D printing is common, stereolithography (SLA) and selective laser sintering (SLS) printing processes offer higher precision. For the use of 3D printing materials in radiology, understanding their attenuation properties concerning ionizing radiation is crucial. Polymethyl methacrylate (PMMA) serves as an important reference material for radiological applications in this regard.</div><div>In this research, linear- and mass attenuation coefficients of 38 SLA-/SLS-materials from Formlabs (Somerville, Massachusetts, USA) and PMMA will be determined through intensity measurements in nuclear medicine for the radionuclides technetium-99 m and iodine-131, as well as for X-ray imaging in the range of 60 kVp - 110 kVp tube voltage. Based on the mass attenuation coefficients, correction factors in respect to PMMA will be calculated for each material. A significant number of materials exhibit a deviance within approximately <span><math><mrow><mo>±</mo></mrow></math></span>5% in respect to PMMA regardless of radiation energy. However, certain materials from the dental and industrial application show deviances up to +500% at the lower end of radiation energy spectrum. In conclusion, most materials can be considered equivalent to PMMA with only minor adjustments required. Materials with high deviances can be utilized as high-contrast materials in custom X-ray phantoms.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 4","pages":"Pages 491-502"},"PeriodicalIF":4.2,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140121807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-01DOI: 10.1016/j.zemedi.2025.07.002
Forough Jafarian-Dehkordi, Christoph Hoeschen
The application of ionizing radiation in medical diagnostics and treatments has been transformative in advancing healthcare for the benefit of patients. However, with these advancements comes the need to understand and mitigate the risks of ionizing radiation. While the role of radiation in medicine is undeniable, its potential to induce malignancies and genetic alterations requires careful application and understanding. This review provides an overview about the radiobiology of radiation risk, and then go through the evolution, challenges, and inherent uncertainties surrounding radiation risk models. In the end, it looks at the impact of the technological and methodological progress that has influenced the radiation protection and shapes our understanding of radiation risk. The search for references was conducted in Google Scholar and PubMed using the keywords ’low radiation,’ ’radiation risk,’ ’risk models,’ ’radiation protection,’ and ’uncertainty.’
{"title":"Low-Dose radiation risk in medicine: a look at risk models, challenges, and future prospects","authors":"Forough Jafarian-Dehkordi, Christoph Hoeschen","doi":"10.1016/j.zemedi.2025.07.002","DOIUrl":"10.1016/j.zemedi.2025.07.002","url":null,"abstract":"<div><div>The application of ionizing radiation in medical diagnostics and treatments has been transformative in advancing healthcare for the benefit of patients. However, with these advancements comes the need to understand and mitigate the risks of ionizing radiation. While the role of radiation in medicine is undeniable, its potential to induce malignancies and genetic alterations requires careful application and understanding. This review provides an overview about the radiobiology of radiation risk, and then go through the evolution, challenges, and inherent uncertainties surrounding radiation risk models. In the end, it looks at the impact of the technological and methodological progress that has influenced the radiation protection and shapes our understanding of radiation risk. The search for references was conducted in Google Scholar and PubMed using the keywords ’low radiation,’ ’radiation risk,’ ’risk models,’ ’radiation protection,’ and ’uncertainty.’</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 4","pages":"Pages 393-400"},"PeriodicalIF":4.2,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144719332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/j.zemedi.2024.01.001
Juan F Domínguez D , Ashley Stewart , Alex Burmester , Hamed Akhlaghi , Kieran O'Brien , Steffen Bollmann , Karen Caeyenberghs
Background
Emerging evidence suggests that traumatic brain injury (TBI) is a major risk factor for developing neurodegenerative disease later in life. Quantitative susceptibility mapping (QSM) has been used by an increasing number of studies in investigations of pathophysiological changes in TBI. However, generating artefact-free quantitative susceptibility maps in brains with large focal lesions, as in the case of moderate-to-severe TBI (ms-TBI), is particularly challenging. To address this issue, we utilized a novel two-pass masking technique and reconstruction procedure (two-pass QSM) to generate quantitative susceptibility maps (QSMxT; Stewart et al., 2022, Magn Reson Med.) in combination with the recently developed virtual brain grafting (VBG) procedure for brain repair (Radwan et al., 2021, NeuroImage) to improve automated delineation of brain areas. We used QSMxT and VBG to generate personalised QSM profiles of individual patients with reference to a sample of healthy controls.
Methods
Chronic ms-TBI patients (N = 8) and healthy controls (N = 12) underwent (multi-echo) GRE, and anatomical MRI (MPRAGE) on a 3T Siemens PRISMA scanner. We reconstructed the magnetic susceptibility maps using two-pass QSM from QSMxT. We then extracted values of magnetic susceptibility in grey matter (GM) regions (following brain repair via VBG) across the whole brain and determined if they deviate from a reference healthy control group [Z-score < −3.43 or > 3.43, relative to the control mean], with the aim of obtaining personalised QSM profiles.
Results
Using two-pass QSM, we achieved susceptibility maps with a substantial increase in quality and reduction in artefacts irrespective of the presence of large focal lesions, compared to single-pass QSM. In addition, VBG minimised the loss of GM regions and exclusion of patients due to failures in the region delineation step. Our findings revealed deviations in magnetic susceptibility measures from the HC group that differed across individual TBI patients. These changes included both increases and decreases in magnetic susceptibility values in multiple GM regions across the brain.
Conclusions
We illustrate how to obtain magnetic susceptibility values at the individual level and to build personalised QSM profiles in ms-TBI patients. Our approach opens the door for QSM investigations in more severely injured patients. Such profiles are also critical to overcome the inherent heterogeneity of clinical populations, such as ms-TBI, and to characterize the underlying mechanisms of neurodegeneration at the individual level more precisely. Moreover, this new personalised QSM profiling could in the future assist clinicians in assessing recovery and formulating a neuroscience-guided integrative rehabilitation program tailored to individual TBI patients.
{"title":"Improving quantitative susceptibility mapping for the identification of traumatic brain injury neurodegeneration at the individual level","authors":"Juan F Domínguez D , Ashley Stewart , Alex Burmester , Hamed Akhlaghi , Kieran O'Brien , Steffen Bollmann , Karen Caeyenberghs","doi":"10.1016/j.zemedi.2024.01.001","DOIUrl":"10.1016/j.zemedi.2024.01.001","url":null,"abstract":"<div><h3>Background</h3><div>Emerging evidence suggests that traumatic brain injury (TBI) is a major risk factor for developing neurodegenerative disease later in life. Quantitative susceptibility mapping (QSM) has been used by an increasing number of studies in investigations of pathophysiological changes in TBI. However, generating artefact-free quantitative susceptibility maps in brains with large focal lesions, as in the case of moderate-to-severe TBI (ms-TBI), is particularly challenging. To address this issue, we utilized a novel two-pass masking technique and reconstruction procedure (two-pass QSM) to generate quantitative susceptibility maps (QSMxT; Stewart et al., 2022, <em>Magn Reson Med</em>.) in combination with the recently developed virtual brain grafting (VBG) procedure for brain repair (Radwan et al., 2021, <em>NeuroImage</em>) to improve automated delineation of brain areas. We used QSMxT and VBG to generate personalised QSM profiles of individual patients with reference to a sample of healthy controls.</div></div><div><h3>Methods</h3><div>Chronic ms-TBI patients (<em>N</em> = 8) and healthy controls (<em>N</em> = 12) underwent (multi-echo) GRE, and anatomical MRI (MPRAGE) on a 3T Siemens PRISMA scanner. We reconstructed the magnetic susceptibility maps using two-pass QSM from QSMxT. We then extracted values of magnetic susceptibility in grey matter (GM) regions (following brain repair via VBG) across the whole brain and determined if they deviate from a reference healthy control group [Z-score < −3.43 or > 3.43, relative to the control mean], with the aim of obtaining personalised QSM profiles.</div></div><div><h3>Results</h3><div>Using two-pass QSM, we achieved susceptibility maps with a substantial increase in quality and reduction in artefacts irrespective of the presence of large focal lesions, compared to single-pass QSM. In addition, VBG minimised the loss of GM regions and exclusion of patients due to failures in the region delineation step. Our findings revealed deviations in magnetic susceptibility measures from the HC group that differed across individual TBI patients. These changes included both increases and decreases in magnetic susceptibility values in multiple GM regions across the brain.</div></div><div><h3>Conclusions</h3><div>We illustrate how to obtain magnetic susceptibility values at the individual level and to build personalised QSM profiles in ms-TBI patients. Our approach opens the door for QSM investigations in more severely injured patients. Such profiles are also critical to overcome the inherent heterogeneity of clinical populations, such as ms-TBI, and to characterize the underlying mechanisms of neurodegeneration at the individual level more precisely. Moreover, this new personalised QSM profiling could in the future assist clinicians in assessing recovery and formulating a neuroscience-guided integrative rehabilitation program tailored to individual TBI patients.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 3","pages":"Pages 357-374"},"PeriodicalIF":4.2,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139713622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/j.zemedi.2024.01.002
Saeed Izadi , Isaac Shiri , Carlos F. Uribe , Parham Geramifar , Habib Zaidi , Arman Rahmim , Ghassan Hamarneh
In positron emission tomography (PET), attenuation and scatter corrections are necessary steps toward accurate quantitative reconstruction of the radiopharmaceutical distribution. Inspired by recent advances in deep learning, many algorithms based on convolutional neural networks have been proposed for automatic attenuation and scatter correction, enabling applications to CT-less or MR-less PET scanners to improve performance in the presence of CT-related artifacts. A known characteristic of PET imaging is to have varying tracer uptakes for various patients and/or anatomical regions. However, existing deep learning-based algorithms utilize a fixed model across different subjects and/or anatomical regions during inference, which could result in spurious outputs. In this work, we present a novel deep learning-based framework for the direct reconstruction of attenuation and scatter-corrected PET from non-attenuation-corrected images in the absence of structural information in the inference. To deal with inter-subject and intra-subject uptake variations in PET imaging, we propose a novel model to perform subject- and region-specific filtering through modulating the convolution kernels in accordance to the contextual coherency within the neighboring slices. This way, the context-aware convolution can guide the composition of intermediate features in favor of regressing input-conditioned and/or region-specific tracer uptakes. We also utilized a large cohort of 910 whole-body studies for training and evaluation purposes, which is more than one order of magnitude larger than previous works. In our experimental studies, qualitative assessments showed that our proposed CT-free method is capable of producing corrected PET images that accurately resemble ground truth images corrected with the aid of CT scans. For quantitative assessments, we evaluated our proposed method over 112 held-out subjects and achieved an absolute relative error of % and a relative error of % in whole-body.
在正电子发射断层扫描（PET）中，衰减和散射校正是精确定量重建放射性药物分布的必要步骤。受深度学习最新进展的启发，许多基于卷积神经网络的算法已被提出用于自动衰减和散射校正，使其能够应用于无 CT 或无磁共振 PET 扫描仪，从而在存在 CT 相关伪影的情况下提高性能。PET 成像的一个已知特征是不同患者和/或解剖区域的示踪剂摄取量不同。然而，现有的基于深度学习的算法在推理过程中对不同受试者和/或解剖区域使用固定的模型，这可能会导致虚假输出。在这项工作中，我们提出了一种新颖的基于深度学习的框架，用于在推理中没有结构信息的情况下，从非衰减校正图像直接重建衰减和散射校正 PET。为了处理 PET 成像中的受试者间和受试者内摄取量变化，我们提出了一种新型模型，通过根据相邻切片内的上下文一致性调制卷积核来执行受试者和区域特定滤波。这样，情境感知卷积就能指导中间特征的组成，从而有利于回归输入条件和/或特定区域的示踪剂摄取量。我们还利用了一个包含 910 个全身研究数据的大型队列来进行训练和评估，其规模比之前的研究要大一个数量级以上。在实验研究中，定性评估结果表明，我们提出的无 CT 方法能够生成校正后的 PET 图像，这些图像与借助 CT 扫描校正的地面实况图像非常相似。在定量评估方面，我们对 112 名受试者进行了评估，结果表明我们提出的方法在全身的绝对相对误差为 14.30%±3.88%，相对误差为 -2.11%±2.73%。
{"title":"Enhanced direct joint attenuation and scatter correction of whole-body PET images via context-aware deep networks","authors":"Saeed Izadi , Isaac Shiri , Carlos F. Uribe , Parham Geramifar , Habib Zaidi , Arman Rahmim , Ghassan Hamarneh","doi":"10.1016/j.zemedi.2024.01.002","DOIUrl":"10.1016/j.zemedi.2024.01.002","url":null,"abstract":"<div><div>In positron emission tomography (PET), attenuation and scatter corrections are necessary steps toward accurate quantitative reconstruction of the radiopharmaceutical distribution. Inspired by recent advances in deep learning, many algorithms based on convolutional neural networks have been proposed for automatic attenuation and scatter correction, enabling applications to CT-less or MR-less PET scanners to improve performance in the presence of CT-related artifacts. A known characteristic of PET imaging is to have varying tracer uptakes for various patients and/or anatomical regions. However, existing deep learning-based algorithms utilize a fixed model across different subjects and/or anatomical regions during inference, which could result in spurious outputs. In this work, we present a novel deep learning-based framework for the direct reconstruction of attenuation and scatter-corrected PET from non-attenuation-corrected images in the absence of structural information in the inference. To deal with inter-subject and intra-subject uptake variations in PET imaging, we propose a novel model to perform subject- and region-specific filtering through modulating the convolution kernels in accordance to the contextual coherency within the neighboring slices. This way, the context-aware convolution can guide the composition of intermediate features in favor of regressing input-conditioned and/or region-specific tracer uptakes. We also utilized a large cohort of 910 whole-body studies for training and evaluation purposes, which is more than one order of magnitude larger than previous works. In our experimental studies, qualitative assessments showed that our proposed CT-free method is capable of producing corrected PET images that accurately resemble ground truth images corrected with the aid of CT scans. For quantitative assessments, we evaluated our proposed method over 112 held-out subjects and achieved an absolute relative error of <span><math><mrow><mn>14.30</mn><mo>±</mo><mn>3.88</mn></mrow></math></span>% and a relative error of <span><math><mrow><mo>-</mo><mn>2.11</mn><mo>%</mo><mo>±</mo><mn>2.73</mn></mrow></math></span>% in whole-body.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 3","pages":"Pages 304-317"},"PeriodicalIF":4.2,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139661196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 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
<div><h3>Objectives</h3><div>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.</div><div>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.</div></div><div><h3>Materials and methods</h3><div>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.</div></div><div><h3>Results</h3><div>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.</div><div>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.</div></div><div><h3>Conclusions</h3><div>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.</div><div>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.</div><div>
{"title":"Pilot study on high-resolution radiological methods for the analysis of cerebrospinal fluid (CSF) shunt valves","authors":"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","doi":"10.1016/j.zemedi.2023.11.001","DOIUrl":"10.1016/j.zemedi.2023.11.001","url":null,"abstract":"<div><h3>Objectives</h3><div>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.</div><div>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.</div></div><div><h3>Materials and methods</h3><div>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.</div></div><div><h3>Results</h3><div>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.</div><div>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.</div></div><div><h3>Conclusions</h3><div>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.</div><div>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.</div><div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 3","pages":"Pages 331-342"},"PeriodicalIF":4.2,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138679829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/j.zemedi.2023.08.007
Jonas Kleineisel , Katja Lauer , Alfio Borzì , Thorsten A. Bley , Herbert Köstler , Tobias Wech
Introduction
Deep learning-based approaches are increasingly being used for the reconstruction of accelerated MRI scans. However, presented analyses are frequently lacking in-detail evaluation of basal measures like resolution or signal-to-noise ratio. To help closing this gap, spatially resolved maps of image resolution and noise enhancement (g-factor) are determined and assessed for typical model- and data-driven MR reconstruction methods in this paper.
Methods
MR data from a routine brain scan of a patient were undersampled in retrospect at R = 4 and reconstructed using two data-driven (variational network (VN), U-Net) and two model based reconstructions methods (GRAPPA, TV-constrained compressed sensing). Local resolution was estimated by the width of the main-lobe of a local point-spread function, which was determined for every single pixel by reconstructing images with an additional small perturbation. G-factor maps were determined using a multiple replica method.
Results
GRAPPA showed good spatial resolution, but increased g-factors (1.43–1.84, 75% quartile) over all other methods. The images delivered from compressed sensing suffered most from low local resolution, in particular in homogeneous areas of the image. VN and U-Net show similar resolution with mostly moderate local blurring, slightly better for U-Net. For all methods except GRAPPA the resolution as well as the g-factors depend on the anatomy and the direction of undersampling.
Conclusion
Objective image quality parameters, local resolution and g-factors have been determined. The examined data driven methods show less local blurring than compressed sensing. The noise enhancement for reconstructions using CS, VN and U-Net is elevated at anatomical contours but is drastically reduced with respect to GRAPPA. Overall, the applied framework provides the possibility for more detailed analysis of novel reconstruction approaches incorporating non-linear and non-stationary transformations.
{"title":"Assessment of resolution and noise in magnetic resonance images reconstructed by data driven approaches","authors":"Jonas Kleineisel , Katja Lauer , Alfio Borzì , Thorsten A. Bley , Herbert Köstler , Tobias Wech","doi":"10.1016/j.zemedi.2023.08.007","DOIUrl":"10.1016/j.zemedi.2023.08.007","url":null,"abstract":"<div><h3>Introduction</h3><div>Deep learning-based approaches are increasingly being used for the reconstruction of accelerated MRI scans. However, presented analyses are frequently lacking in-detail evaluation of basal measures like resolution or signal-to-noise ratio. To help closing this gap, spatially resolved maps of image resolution and noise enhancement (g-factor) are determined and assessed for typical model- and data-driven MR reconstruction methods in this paper.</div></div><div><h3>Methods</h3><div>MR data from a routine brain scan of a patient were undersampled in retrospect at R = 4 and reconstructed using two data-driven (variational network (VN), U-Net) and two model based reconstructions methods (GRAPPA, TV-constrained compressed sensing). Local resolution was estimated by the width of the main-lobe of a local point-spread function, which was determined for every single pixel by reconstructing images with an additional small perturbation. G-factor maps were determined using a multiple replica method.</div></div><div><h3>Results</h3><div>GRAPPA showed good spatial resolution, but increased g-factors (1.43–1.84, 75% quartile) over all other methods. The images delivered from compressed sensing suffered most from low local resolution, in particular in homogeneous areas of the image. VN and U-Net show similar resolution with mostly moderate local blurring, slightly better for U-Net. For all methods except GRAPPA the resolution as well as the g-factors depend on the anatomy and the direction of undersampling.</div></div><div><h3>Conclusion</h3><div>Objective image quality parameters, local resolution and g-factors have been determined. The examined data driven methods show less local blurring than compressed sensing. The noise enhancement for reconstructions using CS, VN and U-Net is elevated at anatomical contours but is drastically reduced with respect to GRAPPA. Overall, the applied framework provides the possibility for more detailed analysis of novel reconstruction approaches incorporating non-linear and non-stationary transformations.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 3","pages":"Pages 343-356"},"PeriodicalIF":4.2,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10243559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/j.zemedi.2023.12.003
C. Katharina Renkamp , Daniela Eulenstein , Moritz Sebald , Fabian Schlüter , Carolin Buchele , Carolin Rippke , Jürgen P. Debus , Sebastian Klüter
Introduction
Patient specific quality assurance (QA) in MR-Linacs can be performed with MR-compatible ion chamber arrays. However, the presence of a static magnetic field can alter the angular response of such arrays substantially. This works investigates the suitability of two ion chamber arrays, an air-filled and a liquid-filled array, for patient specific QA at a 0.35 T MR-Linac using a static phantom.
Methods
In order to study the angular response, the two arrays were placed in a static, solid phantom and irradiated with 9.96 × 9.96 cm2 fields every 10° beam angle at a 0.35 T MR-Linac. Measurements were compared to the TPS calculated dose in terms of gamma passing rate and relative dose to the central chamber. 20 patient specific quality assurance plans were measured using the liquid-filled array.
Results
The air-filled array showed asymmetric angular response changes of central chamber dose of up to 18% and down to local 3 mm / 3% gamma rates of 20%, while only minor differences within 3% (excluding parallel irradiation and beams through the couch edges) were found for the liquid-filled ion chamber array without rotating the phantom. Patient plan QA using the liquid-filled array yielded a median local 3 mm / 3% 3D gamma passing rate of 99.8% (range 96.9%–100%).
Conclusion
A liquid-filled ionization chamber array in combination with a static phantom can be used for efficient patient specific plan QA in a single measurement set-up in a 0.35 T MR-Linac, while the air-filled ion chamber array phantom shows large angular response changes and has its limitations regarding patient specific QA measurements.
{"title":"Evaluation of 2D ion chamber arrays for patient specific quality assurance using a static phantom at a 0.35 T MR-Linac","authors":"C. Katharina Renkamp , Daniela Eulenstein , Moritz Sebald , Fabian Schlüter , Carolin Buchele , Carolin Rippke , Jürgen P. Debus , Sebastian Klüter","doi":"10.1016/j.zemedi.2023.12.003","DOIUrl":"10.1016/j.zemedi.2023.12.003","url":null,"abstract":"<div><h3>Introduction</h3><div>Patient specific quality assurance (QA) in MR-Linacs can be performed with MR-compatible ion chamber arrays. However, the presence of a static magnetic field can alter the angular response of such arrays substantially. This works investigates the suitability of two ion chamber arrays, an air-filled and a liquid-filled array, for patient specific QA at a 0.35 T MR-Linac using a static phantom.</div></div><div><h3>Methods</h3><div>In order to study the angular response, the two arrays were placed in a static, solid phantom and irradiated with 9.96 × 9.96 cm<sup>2</sup> fields every 10° beam angle at a 0.35 T MR-Linac. Measurements were compared to the TPS calculated dose in terms of gamma passing rate and relative dose to the central chamber. 20 patient specific quality assurance plans were measured using the liquid-filled array.</div></div><div><h3>Results</h3><div>The air-filled array showed asymmetric angular response changes of central chamber dose of up to 18% and down to local 3 mm / 3% gamma rates of 20%, while only minor differences within 3% (excluding parallel irradiation and beams through the couch edges) were found for the liquid-filled ion chamber array without rotating the phantom. Patient plan QA using the liquid-filled array yielded a median local 3 mm / 3% 3D gamma passing rate of 99.8% (range 96.9%–100%).</div></div><div><h3>Conclusion</h3><div>A liquid-filled ionization chamber array in combination with a static phantom can be used for efficient patient specific plan QA in a single measurement set-up in a 0.35 T MR-Linac, while the air-filled ion chamber array phantom shows large angular response changes and has its limitations regarding patient specific QA measurements.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 3","pages":"Pages 375-384"},"PeriodicalIF":4.2,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139111420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-01DOI: 10.1016/j.zemedi.2024.01.006
Jiří Valenta, Manfred Schmidt, Christoph Bert
Purpose
In medical linac quality assurance (QA), to replace film dosimetry with low-resolution 2-D ionization chamber array measurements, to validate the procedures, and to perform a comprehensive sensitivity analysis.
Methods
A 2-D ionization chamber array with a spatial resolution of 7.62 mm was deployed to perform the following tests: Junction tests, MLC transmission test, beam profile constancy vs. gantry angle test, beam profile constancy vs. low dose delivery test, and beam energy constancy vs. low dose delivery test. Test validation and sensitivity analyses based on short- and long-term statistics of the test results were performed.
Results
All selected mechanical and dosimetry tests could be successfully performed with a 2-D array. Considering the tolerance limits recommended by the AAPM Task Group 142 report (2009), sensitivities of 99.0% or better and specificities ranging from 99.5% to 99.9% could be achieved in all tests when the proper metrics were chosen.
Conclusions
The results showed that a low-resolution 2-D ionization chamber array could replace film dosimetry without having to sacrifice high test sensitivity. Its implementation in the routine clinical linac QA program may involve considerable QA time savings.
{"title":"Implementation and validation of 2-D-array based tests in routine linac quality assurance","authors":"Jiří Valenta, Manfred Schmidt, Christoph Bert","doi":"10.1016/j.zemedi.2024.01.006","DOIUrl":"10.1016/j.zemedi.2024.01.006","url":null,"abstract":"<div><h3>Purpose</h3><div>In medical linac quality assurance (QA), to replace film dosimetry with low-resolution 2-D ionization chamber array measurements, to validate the procedures, and to perform a comprehensive sensitivity analysis.</div></div><div><h3>Methods</h3><div>A 2-D ionization chamber array with a spatial resolution of 7.62 mm was deployed to perform the following tests: Junction tests, MLC transmission test, beam profile constancy vs. gantry angle test, beam profile constancy vs. low dose delivery test, and beam energy constancy vs. low dose delivery test. Test validation and sensitivity analyses based on short- and long-term statistics of the test results were performed.</div></div><div><h3>Results</h3><div>All selected mechanical and dosimetry tests could be successfully performed with a 2-D array. Considering the tolerance limits recommended by the AAPM Task Group 142 report (2009), sensitivities of 99.0% or better and specificities ranging from 99.5% to 99.9% could be achieved in all tests when the proper metrics were chosen.</div></div><div><h3>Conclusions</h3><div>The results showed that a low-resolution 2-D ionization chamber array could replace film dosimetry without having to sacrifice high test sensitivity. Its implementation in the routine clinical linac QA program may involve considerable QA time savings.</div></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"35 3","pages":"Pages 270-281"},"PeriodicalIF":4.2,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139898425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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