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Nava TS, Nussbaumer M, Tysome JR, Sutcliffe MPF. Sound and Noise Sources in Sonotubometry: An Investigation of Eustachian Tube Assessment. Ann Biomed Eng 2024:10.1007/s10439-024-03526-9. [PMID: 38740729 DOI: 10.1007/s10439-024-03526-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 04/20/2024] [Indexed: 05/16/2024]
Abstract
This research aims to enhance the understanding of the acoustic processes occurring during sonotubometry, a method used to assess the Eustachian tube (ET) function. Recent advancements in digital signal processing enable a more comprehensive data analysis. In this project, a silicone model of the ET was developed to systematically study the existing noise and sound sources. These measurements were then compared with recordings from human subjects. Three distinct 'noise sources' were identified, which can influence the assessment of the ET opening using transmission measurements of the imposed signal: sound leakage from the speaker, a clicking noise at the initiation of ET opening, and rumbling/swallowing noise. Through spectral analysis, it was also possible to ascertain the spectral and temporal occurrence of these sound and noise types. The silicone model exhibited remarkable similarity to the healthy human ET, making it a robust experimental model for investigating the acoustics of sonotubometry. The findings underscore the significance of delving deeper into the analysed sound, as the noise occurring during sonotubometry can be easily misconstrued as an actual ET opening. Particularly, careful consideration is warranted when evaluating data involving clicking and swallowing noise.
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Affiliation(s)
- Tobia Sebastiano Nava
- Department of Engineering, University of Cambridge, Trumpington St, Cambridge, CB2 1PZ, UK.
| | - Maximilian Nussbaumer
- Department of Engineering, University of Cambridge, Trumpington St, Cambridge, CB2 1PZ, UK
| | - James R Tysome
- Department of Otorhinolaryngology, Cambridge University Hospitals, Hills Rd, Cambridge, CB2 0QQ, UK
| | - Michael P F Sutcliffe
- Department of Engineering, University of Cambridge, Trumpington St, Cambridge, CB2 1PZ, UK
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2
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Khorisantono PA, Huang 黃飛揚 FY, Sutcliffe MPF, Fletcher PC, Farooqi IS, Grabenhorst F. A Neural Mechanism in the Human Orbitofrontal Cortex for Preferring High-Fat Foods Based on Oral Texture. J Neurosci 2023; 43:8000-8017. [PMID: 37845034 PMCID: PMC10669766 DOI: 10.1523/jneurosci.1473-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 09/17/2023] [Accepted: 09/19/2023] [Indexed: 10/18/2023] Open
Abstract
Although overconsumption of high-fat foods is a major driver of weight gain, the neural mechanisms that link the oral sensory properties of dietary fat to reward valuation and eating behavior remain unclear. Here we combine novel food-engineering approaches with functional neuroimaging to show that the human orbitofrontal cortex (OFC) translates oral sensations evoked by high-fat foods into subjective economic valuations that guide eating behavior. Male and female volunteers sampled and evaluated nutrient-controlled liquid foods that varied in fat and sugar ("milkshakes"). During oral food processing, OFC activity encoded a specific oral-sensory parameter that mediated the influence of the foods' fat content on reward value: the coefficient of sliding friction. Specifically, OFC responses to foods in the mouth reflected the smooth, oily texture (i.e., mouthfeel) produced by fatty liquids on oral surfaces. Distinct activity patterns in OFC encoded the economic values associated with particular foods, which reflected the subjective integration of sliding friction with other food properties (sugar, fat, viscosity). Critically, neural sensitivity of OFC to oral texture predicted individuals' fat preferences in a naturalistic eating test: individuals whose OFC was more sensitive to fat-related oral texture consumed more fat during ad libitum eating. Our findings suggest that reward systems of the human brain sense dietary fat from oral sliding friction, a mechanical food parameter that likely governs our daily eating experiences by mediating interactions between foods and oral surfaces. These findings identify a specific role for the human OFC in evaluating oral food textures to mediate preference for high-fat foods.SIGNIFICANCE STATEMENT Fat and sugar enhance the reward value of food by imparting a sweet taste and rich mouthfeel but also contribute to overeating and obesity. Here we used a novel food-engineering approach to realistically quantify the physical-mechanical properties of high-fat liquid foods on oral surfaces and used functional neuroimaging while volunteers sampled these foods and placed monetary bids to consume them. We found that a specific area of the brain's reward system, the orbitofrontal cortex, detects the smooth texture of fatty foods in the mouth and links these sensory inputs to economic valuations that guide eating behavior. These findings can inform the design of low-calorie fat-replacement foods that mimic the impact of dietary fat on oral surfaces and neural reward systems.
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Affiliation(s)
- Putu A Khorisantono
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, United Kingdom
| | - Fei-Yang Huang 黃飛揚
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, United Kingdom
- Department of Experimental Psychology, University of Oxford, Oxford OX1 3TA, United Kingdom
| | - Michael P F Sutcliffe
- Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, United Kingdom
| | - Paul C Fletcher
- Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom
| | - I Sadaf Farooqi
- Wellcome Trust-MRC Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom
| | - Fabian Grabenhorst
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, United Kingdom
- Department of Experimental Psychology, University of Oxford, Oxford OX1 3TA, United Kingdom
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3
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Tokgoz A, Wang S, Sastry P, Sun C, Figg NL, Huang Y, Bennett MR, Sinha S, Gillard JH, Sutcliffe MPF, Teng Z. Association of Collagen, Elastin, Glycosaminoglycans, and Macrophages With Tissue Ultimate Material Strength and Stretch in Human Thoracic Aortic Aneurysms: A Uniaxial Tension Study. J Biomech Eng 2022; 144:101001. [PMID: 35274123 DOI: 10.1115/1.4054060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Indexed: 11/08/2022]
Abstract
Fiber structures and pathological features, e.g., inflammation and glycosaminoglycan (GAG) deposition, are the primary determinants of aortic mechanical properties which are associated with the development of an aneurysm. This study is designed to quantify the association of tissue ultimate strength and extensibility with the structural percentage of different components, in particular, GAG, and local fiber orientation. Thoracic aortic aneurysm (TAA) tissues from eight patients were collected. Ninety-six tissue strips of thickened intima, media, and adventitia were prepared for uni-extension tests and histopathological examination. Area ratios of collagen, elastin, macrophage and GAG, and collagen fiber dispersion were quantified. Collagen, elastin, and GAG were layer-dependent and the inflammatory burden in all layers was low. The local GAG ratio was negatively associated with the collagen ratio (r2 = 0.173, p < 0.05), but positively with elastin (r2 = 0.037, p < 0.05). Higher GAG deposition resulted in larger local collagen fiber dispersion in the media and adventitia, but not in the intima. The ultimate stretch in both axial and circumferential directions was exclusively associated with elastin ratio (axial: r2 = 0.186, p = 0.04; circumferential: r2 = 0.175, p = 0.04). Multivariate analysis showed that collagen and GAG contents were both associated with ultimate strength in the circumferential direction, but not with the axial direction (collagen: slope = 27.3, GAG: slope = -18.4, r2 = 0.438, p = 0.002). GAG may play important roles in TAA material strength. Their deposition was found to be associated positively with the local collagen fiber dispersion and negatively with ultimate strength in the circumferential direction.
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Affiliation(s)
- Aziz Tokgoz
- Department of Engineering, University of Cambridge, Cambridge CB2 1TN, UK
| | - Shuo Wang
- Department of Radiology, University of Cambridge, Cambridge CB2 1TN, UK; Digital Medical Research Center, School of Basic Medical Sciences, Fudan University, Shanghai 200437, China; Shanghai Key Laboratory of MICCAI, Shanghai, China
| | - Priya Sastry
- Division of Cardiovascular Medicine, Department of Medicine, University of Cambridge, Cambridge CB2 1TN, UK
| | - Chang Sun
- Department of Radiology, University of Cambridge, Cambridge CB2 1TN, UK
| | - Nichola L Figg
- Digital Medical Research Center, School of Basic Medical Sciences, Fudan University, Shanghai 200437, China
| | - Yuan Huang
- Department of Radiology, University of Cambridge, Cambridge CB2 1TN, UK; Centre for Mathematical and Statistical Analysis of Multimodal Clinical Imaging, University of Cambridge, Cambridge CB2 1TN, UK
| | - Martin R Bennett
- Division of Cardiovascular Medicine, Department of Medicine, University of Cambridge, Cambridge CB2 1TN, UK
| | - Sanjay Sinha
- Division of Cardiovascular Medicine, Department of Medicine, University of Cambridge, Cambridge CB2 1TN, UK
| | | | - Michael P F Sutcliffe
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK
| | - Zhongzhao Teng
- Department of Engineering, University of Cambridge, Cambridge CB2 1TN, UK; Department of Radiology, University of Cambridge, Level 5, Box 218, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, UK; Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing 100083, China; Nanjing Jingsan Medical Science and Technology, Ltd., Jiangsu, China
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4
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Lei IM, Jiang C, Lei CL, de Rijk SR, Tam YC, Swords C, Sutcliffe MPF, Malliaras GG, Bance M, Huang YYS. 3D printed biomimetic cochleae and machine learning co-modelling provides clinical informatics for cochlear implant patients. Nat Commun 2021; 12:6260. [PMID: 34716306 PMCID: PMC8556326 DOI: 10.1038/s41467-021-26491-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 10/06/2021] [Indexed: 02/07/2023] Open
Abstract
Cochlear implants restore hearing in patients with severe to profound deafness by delivering electrical stimuli inside the cochlea. Understanding stimulus current spread, and how it correlates to patient-dependent factors, is hampered by the poor accessibility of the inner ear and by the lack of clinically-relevant in vitro, in vivo or in silico models. Here, we present 3D printing-neural network co-modelling for interpreting electric field imaging profiles of cochlear implant patients. With tuneable electro-anatomy, the 3D printed cochleae can replicate clinical scenarios of electric field imaging profiles at the off-stimuli positions. The co-modelling framework demonstrated autonomous and robust predictions of patient profiles or cochlear geometry, unfolded the electro-anatomical factors causing current spread, assisted on-demand printing for implant testing, and inferred patients' in vivo cochlear tissue resistivity (estimated mean = 6.6 kΩcm). We anticipate our framework will facilitate physical modelling and digital twin innovations for neuromodulation implants.
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Affiliation(s)
- Iek Man Lei
- Department of Engineering, University of Cambridge, Cambridge, United Kingdom.,The Nanoscience Centre, University of Cambridge, Cambridge, United Kingdom
| | - Chen Jiang
- Department of Engineering, University of Cambridge, Cambridge, United Kingdom.,Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom.,Department of Electronic Engineering, Tsinghua University, Beijing, 100084, China
| | - Chon Lok Lei
- Institute of Translational Medicine, Faculty of Health Sciences, University of Macau, Taipa, Macau.,Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Simone Rosalie de Rijk
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Yu Chuen Tam
- Emmeline Centre for Hearing Implants, Addenbrookes Hospital, Cambridge, United Kingdom
| | - Chloe Swords
- Department of Physiology, Development and Neurosciences, Cambridge, United Kingdom
| | | | - George G Malliaras
- Department of Engineering, University of Cambridge, Cambridge, United Kingdom
| | - Manohar Bance
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom.
| | - Yan Yan Shery Huang
- Department of Engineering, University of Cambridge, Cambridge, United Kingdom. .,The Nanoscience Centre, University of Cambridge, Cambridge, United Kingdom.
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5
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Häusler KA, Braun D, Liu NC, Penrose F, Sutcliffe MPF, Allen MJ. Evaluation of the repeatability of kinetic and temporospatial gait variables measured with a pressure-sensitive treadmill for dogs. Am J Vet Res 2020; 81:922-929. [PMID: 33251838 DOI: 10.2460/ajvr.81.12.922] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To evaluate intrasession and intersession repeatability of measurements for temporospatial and kinetic variables obtained with a pressure-sensitive treadmill designed for gait analysis of dogs. ANIMALS 16 client-owned dogs. PROCEDURES The influence of treadmill speed on accuracy of ground reaction force (GRF) measurements was assessed by simulated gait analysis at 0 to 7.5 km/h with a custom test device. A similar test was performed with 1 client-owned dog ambulating on the treadmill at 5 speeds (3 to 7 km/h) for GRF calculations. Fifteen client-owned dogs were then walked on the treadmill at 3 km/h for collection of temporospatial and kinetic data. Intrasession repeatability was determined by comparing 2 sets of measurements obtained ≤ 2 hours apart. Intersession repeatability was determined by comparing the first set of these measurements with those for a second session ≥ 4 days later. Intraclass correlation coefficients (ICCs; consistency test) and difference ratios were calculated to assess repeatability. RESULTS Increases in treadmill speed yielded a mean 9.1% decrease in weight-normalized force data at belt speeds of up to 7.5 km/h for the test device, compared with the value when the treadmill belt was stationary. Results were similar for the dog at increasing treadmill speeds (mean decrease, 12.4%). For temporospatial data, intrasession ICCs were > 0.9 and intersession ICCs ranged from 0.75 to 0.9; for GRFs, intrasession and intersession ICCs ranged from 0.68 to 0.97 and from 0.35 to 0.78, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Repeatability of temporospatial data for healthy dogs was good to excellent; results for kinetic data varied. Further research is needed to investigate use of this system for gait analysis with larger samples of dogs and dogs with lameness.
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6
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Avgoulas EI, Sutcliffe MPF, Linderman SW, Birman V, Thomopoulos S, Genin GM. Adhesive-based tendon-to-bone repair: failure modelling and materials selection. J R Soc Interface 2020; 16:20180838. [PMID: 30966948 DOI: 10.1098/rsif.2018.0838] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Surgical reattachment of tendon to bone is a procedure marked by high failure rates. For example, nearly all rotator cuff repairs performed on elderly patients with massive tears ultimately result in recurrence of tearing. These high failure rates have been attributed to stress concentrations that arise due to the mechanical mismatch between tendon and bone. Although recent studies have identified potential adhesives with mechanical properties tuned to alleviate these stress concentrations, and thereby delay the onset of failure, resistance to the progression of failure has not been studied. Here, we refined the space of adhesive material properties that can improve surgical attachment by considering the fracture process. Using cohesive zone modelling and physiologically relevant values of mode I and mode II adhesive fracture toughnesses, we predicted the maximum displacement and strength at failure of idealized, adhesively bonded tendon-to-bone repairs. Repair failure occurred due to excessive relative displacement of the tendon and bone tissues for strong and compliant adhesives. The failure mechanism shifted to rupture of the entire repair for stiffer adhesives below a critical shear strength. Results identified a narrow range of materials on an Ashby chart that are suitable for adhesive repair of tendon to bone, including a range of elastomers and porous solids.
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Affiliation(s)
- Evangelos I Avgoulas
- 1 Department of Engineering, University of Cambridge , Trumpington Street, Cambridge CB2 1PZ , UK
| | - Michael P F Sutcliffe
- 1 Department of Engineering, University of Cambridge , Trumpington Street, Cambridge CB2 1PZ , UK
| | - Stephen W Linderman
- 2 Department of Orthopaedic Surgery, Washington University School of Medicine , St Louis, MO 63131 , USA
| | - Victor Birman
- 3 Missouri Science and Technology Global-St Louis, and Department of Mechanical and Aerospace Engineering , St Louis, MO 63131 , USA
| | - Stavros Thomopoulos
- 4 Department of Orthopedic Surgery, Columbia University , New York, NY 10032 , USA.,5 Department of Biomedical Engineering, Columbia University , New York, NY 10032 , USA
| | - Guy M Genin
- 6 NSF Science and Technology Center for Engineering Mechanobiology, Department of Mechanical and Aerospace Engineering, Washington University , St Louis, MO 63130 , USA
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7
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Shelley LEA, Sutcliffe MPF, Thomas SJ, Noble DJ, Romanchikova M, Harrison K, Bates AM, Burnet NG, Jena R. Associations between voxel-level accumulated dose and rectal toxicity in prostate radiotherapy. Phys Imaging Radiat Oncol 2020; 14:87-94. [PMID: 32582869 PMCID: PMC7301619 DOI: 10.1016/j.phro.2020.05.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/15/2020] [Accepted: 05/18/2020] [Indexed: 12/25/2022]
Abstract
Background and Purpose Associations between dose and rectal toxicity in prostate radiotherapy are generally poorly understood. Evaluating spatial dose distributions to the rectal wall (RW) may lead to improvements in dose-toxicity modelling by incorporating geometric information, masked by dose-volume histograms. Furthermore, predictive power may be strengthened by incorporating the effects of interfraction motion into delivered dose calculations.Here we interrogate 3D dose distributions for patients with and without toxicity to identify rectal subregions at risk (SRR), and compare the discriminatory ability of planned and delivered dose. Material and Methods Daily delivered dose to the rectum was calculated using image guidance scans, and accumulated at the voxel level using biomechanical finite element modelling. SRRs were statistically determined for rectal bleeding, proctitis, faecal incontinence and stool frequency from a training set (n = 139), and tested on a validation set (n = 47). Results SRR patterns differed per endpoint. Analysing dose to SRRs improved discriminative ability with respect to the full RW for three of four endpoints. Training set AUC and OR analysis produced stronger toxicity associations from accumulated dose than planned dose. For rectal bleeding in particular, accumulated dose to the SRR (AUC 0.76) improved upon dose-toxicity associations derived from planned dose to the RW (AUC 0.63). However, validation results could not be considered significant. Conclusions Voxel-level analysis of dose to the RW revealed SRRs associated with rectal toxicity, suggesting non-homogeneous intra-organ radiosensitivity. Incorporating spatial features of accumulated delivered dose improved dose-toxicity associations. This may be an important tool for adaptive radiotherapy in the future.
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Affiliation(s)
- Leila E A Shelley
- Cancer Research UK VoxTox Research Group, Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.,Edinburgh Cancer Centre, Western General Hospital, Edinburgh EH4 2XU, United Kingdom.,Department of Engineering, University of Cambridge, Trumpington St, Cambridge CB21PZ, United Kingdom
| | - Michael P F Sutcliffe
- Cancer Research UK VoxTox Research Group, Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.,Department of Engineering, University of Cambridge, Trumpington St, Cambridge CB21PZ, United Kingdom
| | - Simon J Thomas
- Cancer Research UK VoxTox Research Group, Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.,Department of Medical Physics and Clinical Engineering, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom
| | - David J Noble
- Cancer Research UK VoxTox Research Group, Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.,Department of Oncology, University of Cambridge, Cambridge Biomedical Campus, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom
| | - Marina Romanchikova
- Cancer Research UK VoxTox Research Group, Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.,National Physical Laboratory, Teddington TW11 0JE, United Kingdom
| | - Karl Harrison
- Cancer Research UK VoxTox Research Group, Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.,Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Amy M Bates
- Cancer Research UK VoxTox Research Group, Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.,Cambridge Clinical Trials Unit, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom
| | - Neil G Burnet
- Cancer Research UK VoxTox Research Group, Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.,University of Manchester, Manchester Academic Health Science Centre, Manchester M13 9PL, United Kingdom
| | - Raj Jena
- Cancer Research UK VoxTox Research Group, Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, Addenbrooke's Hospital, Cambridge CB2 0QQ, United Kingdom.,Department of Oncology, University of Cambridge, Cambridge Biomedical Campus, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom
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8
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Shelley LEA, Sutcliffe MPF, Harrison K, Scaife JE, Parker MA, Romanchikova M, Thomas SJ, Jena R, Burnet NG. Autosegmentation of the rectum on megavoltage image guidance scans. Biomed Phys Eng Express 2019; 5:025006. [PMID: 31057946 PMCID: PMC6466640 DOI: 10.1088/2057-1976/aaf1db] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 11/07/2018] [Accepted: 11/19/2018] [Indexed: 11/12/2022]
Abstract
Autosegmentation of image guidance (IG) scans is crucial for streamlining and optimising delivered dose calculation in radiotherapy. By accounting for interfraction motion, daily delivered dose can be accumulated and incorporated into automated systems for adaptive radiotherapy. Autosegmentation of IG scans is challenging due to poorer image quality than typical planning kilovoltage computed tomography (kVCT) systems, and the resulting reduction of soft tissue contrast in regions such as the pelvis makes organ boundaries less distinguishable. Current autosegmentation solutions generally involve propagation of planning contours to the IG scan by deformable image registration (DIR). Here, we present a novel approach for primary autosegmentation of the rectum on megavoltage IG scans acquired during prostate radiotherapy, based on the Chan-Vese algorithm. Pre-processing steps such as Hounsfield unit/intensity scaling, identifying search regions, dealing with air, and handling the prostate, are detailed. Post-processing features include identification of implausible contours (nominally those affected by muscle or air), 3D self-checking, smoothing, and interpolation. In cases where the algorithm struggles, the best estimate on a given slice may revert to the propagated kVCT rectal contour. Algorithm parameters were optimised systematically for a training cohort of 26 scans, and tested on a validation cohort of 30 scans, from 10 patients. Manual intervention was not required. Comparing Chan-Vese autocontours with contours manually segmented by an experienced clinical oncologist achieved a mean Dice Similarity Coefficient of 0.78 (SE < 0.011). This was comparable with DIR methods for kVCT and CBCT published in the literature. The autosegmentation system was developed within the VoxTox Research Programme for accumulation of delivered dose to the rectum in prostate radiotherapy, but may have applicability to further anatomical sites and imaging modalities.
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Affiliation(s)
- L E A Shelley
- University of Cambridge, Department of Engineering, Cambridge, United Kingdom
- Addenbrooke's Hospital, Department of Medical Physics and Clinical Engineering, Cambridge, United Kingdom
- Cambridge University Hospitals NHS Foundation Trust, Cancer Research UK VoxTox Research Group, Cambridge, United Kingdom
| | - M P F Sutcliffe
- University of Cambridge, Department of Engineering, Cambridge, United Kingdom
- Cambridge University Hospitals NHS Foundation Trust, Cancer Research UK VoxTox Research Group, Cambridge, United Kingdom
| | - K Harrison
- Cambridge University Hospitals NHS Foundation Trust, Cancer Research UK VoxTox Research Group, Cambridge, United Kingdom
- University of Cambridge, Cavendish Laboratory, Cambridge, United Kingdom
| | - J E Scaife
- Gloucestershire Oncology Centre, Cheltenham General Hospital, Cheltenham, United Kingdom
| | - M A Parker
- Cambridge University Hospitals NHS Foundation Trust, Cancer Research UK VoxTox Research Group, Cambridge, United Kingdom
- University of Cambridge, Cavendish Laboratory, Cambridge, United Kingdom
| | - M Romanchikova
- Cambridge University Hospitals NHS Foundation Trust, Cancer Research UK VoxTox Research Group, Cambridge, United Kingdom
- National Physical Laboratory, Teddington, United Kingdom
| | - S J Thomas
- Addenbrooke's Hospital, Department of Medical Physics and Clinical Engineering, Cambridge, United Kingdom
- Cambridge University Hospitals NHS Foundation Trust, Cancer Research UK VoxTox Research Group, Cambridge, United Kingdom
| | - R Jena
- Cambridge University Hospitals NHS Foundation Trust, Cancer Research UK VoxTox Research Group, Cambridge, United Kingdom
- Addenbrooke's Hospital, Oncology Centre, Cambridge, United Kingdom
| | - N G Burnet
- Cambridge University Hospitals NHS Foundation Trust, Cancer Research UK VoxTox Research Group, Cambridge, United Kingdom
- University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
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9
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Wang S, Tokgoz A, Huang Y, Zhang Y, Feng J, Sastry P, Sun C, Figg N, Lu Q, Sutcliffe MPF, Teng Z, Gillard JH. Bayesian Inference-Based Estimation of Normal Aortic, Aneurysmal and Atherosclerotic Tissue Mechanical Properties: From Material Testing, Modeling and Histology. IEEE Trans Biomed Eng 2019; 66:2269-2278. [PMID: 30703001 DOI: 10.1109/tbme.2018.2886681] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE Mechanical properties of healthy, aneurysmal, and atherosclerotic arterial tissues are essential for assessing the risk of lesion development and rupture. Strain energy density function (SEDF) has been widely used to describe these properties, where material constants of the SEDF are traditionally determined using the ordinary least square (OLS) method. However, the material constants derived using OLS are usually dependent on initial guesses. METHODS To avoid such dependencies, Bayesian inference-based estimation was used to fit experimental stress-stretch curves of 312 tissue strips from 8 normal aortas, 19 aortic aneurysms, and 21 carotid atherosclerotic plaques to determine the constants, C1, D1, and D2 of the modified Mooney-Rivlin SEDF. RESULTS Compared with OLS, material constants varied much less with prior in the Bayesian inference-based estimation. Moreover, fitted material constants differed amongst distinct tissue types. Atherosclerotic tissues associated with the biggest D2, an indicator of the rate of increase in stress during stretching, followed by aneurysmal tissues and those from normal aortas. Histological analyses showed that C1 and D2 were associated with elastin content and details of the collagen configuration, specifically, waviness and dispersion, in the structure. CONCLUSION Bayesian inference-based estimation robustly determines material constants in the modified Mooney-Rivlin SEDF and these constants can reflect the inherent physiological and pathological features of the tissue structure. SIGNIFICANCE This study suggested a robust procedure to determine the material constants in SEDF and demonstrated that the obtained constants can be used to characterize tissues from different types of lesions, while associating with their inherent microstructures.
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10
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Kim DJ, Kim H, Park DH, Lee HJ, Czosnyka Z, Sutcliffe MPF, Czosnyka M. Finite Element Model for Hydrocephalus and Idiopathic Intracranial Hypertension. Acta Neurochir Suppl 2017; 122:157-9. [PMID: 27165898 DOI: 10.1007/978-3-319-22533-3_32] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Hydrocephalus and idiopathic intracranial hypertension (IIH) are neuropathies associated with disturbed cerebrospinal fluid dynamics. Several finite element (FE) brain models were suggested to simulate the pathological changes in hydrocephalus, but with overly simplified assumptions regarding the properties of the brain parenchyma. This study proposes a two-dimensional FE brain model, capable of simulating both hydrocephalus and IIH by incorporating poro-hyperelasticity of the brain and detailed structural information (i.e., sulci).
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Affiliation(s)
- Dong-Joo Kim
- Department of Brain and Cognitive Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul, 136-713, South Korea.
| | - Hakseung Kim
- Department of Brain and Cognitive Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul, 136-713, South Korea
| | - Dae-Hyeon Park
- Department of Brain and Cognitive Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul, 136-713, South Korea
| | - Hack-Jin Lee
- Department of Brain and Cognitive Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul, 136-713, South Korea
| | - Zofia Czosnyka
- Department of Neurosurgery, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK
| | | | - Marek Czosnyka
- Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
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Yeap PL, Noble DJ, Harrison K, Bates AM, Burnet NG, Jena R, Romanchikova M, Sutcliffe MPF, Thomas SJ, Barnett GC, Benson RJ, Jefferies SJ, Parker MA. Automatic contour propagation using deformable image registration to determine delivered dose to spinal cord in head-and-neck cancer radiotherapy. Phys Med Biol 2017; 62:6062-6073. [PMID: 28573978 PMCID: PMC5952263 DOI: 10.1088/1361-6560/aa76aa] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To determine delivered dose to the spinal cord, a technique has been developed to propagate manual contours from kilovoltage computed-tomography (kVCT) scans for treatment planning to megavoltage computed-tomography (MVCT) guidance scans. The technique uses the Elastix software to perform intensity-based deformable image registration of each kVCT scan to the associated MVCT scans. The registration transform is then applied to contours of the spinal cord drawn manually on the kVCT scan, to obtain contour positions on the MVCT scans. Different registration strategies have been investigated, with performance evaluated by comparing the resulting auto-contours with manual contours, drawn by oncologists. The comparison metrics include the conformity index (CI), and the distance between centres (DBC). With optimised registration, auto-contours generally agree well with manual contours. Considering all 30 MVCT scans for each of three patients, the median CI is \documentclass[12pt]{minimal}
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}{}$0.759 \pm 0.003$ \end{document}0.759±0.003, and the median DBC is (\documentclass[12pt]{minimal}
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}{}$0.87 \pm 0.01$ \end{document}0.87±0.01) mm. An intra-observer comparison for the same scans gives a median CI of \documentclass[12pt]{minimal}
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}{}$0.820 \pm 0.002$ \end{document}0.820±0.002 and a DBC of (\documentclass[12pt]{minimal}
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}{}$0.64 \pm 0.01$ \end{document}0.64±0.01) mm. Good levels of conformity are also obtained when auto-contours are compared with manual contours from one observer for a single MVCT scan for each of 30 patients, and when they are compared with manual contours from six observers for two MVCT scans for each of three patients. Using the auto-contours to estimate organ position at treatment time, a preliminary study of 33 patients who underwent radiotherapy for head-and-neck cancers indicates good agreement between planned and delivered dose to the spinal cord.
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Affiliation(s)
- P L Yeap
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
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12
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Shelley LEA, Scaife JE, Romanchikova M, Harrison K, Forman JR, Bates AM, Noble DJ, Jena R, Parker MA, Sutcliffe MPF, Thomas SJ, Burnet NG. Delivered dose can be a better predictor of rectal toxicity than planned dose in prostate radiotherapy. Radiother Oncol 2017; 123:466-471. [PMID: 28460825 PMCID: PMC5486775 DOI: 10.1016/j.radonc.2017.04.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 04/03/2017] [Accepted: 04/05/2017] [Indexed: 01/23/2023]
Abstract
Background and purpose For the first time, delivered dose to the rectum has been calculated and accumulated throughout the course of prostate radiotherapy using megavoltage computed tomography (MVCT) image guidance scans. Dosimetric parameters were linked with toxicity to test the hypothesis that delivered dose is a stronger predictor of toxicity than planned dose. Material and methods Dose–surface maps (DSMs) of the rectal wall were automatically generated from daily MVCT scans for 109 patients within the VoxTox research programme. Accumulated-DSMs, representing total delivered dose, and planned-DSMs, from planning CT data, were parametrised using Equivalent Uniform Dose (EUD) and ‘DSM dose-width’, the lateral dimension of an ellipse fitted to a discrete isodose cluster. Associations with 6 toxicity endpoints were assessed using receiver operator characteristic curve analysis. Results For rectal bleeding, the area under the curve (AUC) was greater for accumulated dose than planned dose for DSM dose-widths up to 70 Gy. Accumulated 65 Gy DSM dose-width produced the strongest spatial correlation (AUC 0.664), while accumulated EUD generated the largest AUC overall (0.682). For proctitis, accumulated EUD was the only reportable predictor (AUC 0.673). Accumulated EUD was systematically lower than planned EUD. Conclusions Dosimetric parameters extracted from accumulated DSMs have demonstrated stronger correlations with rectal bleeding and proctitis, than planned DSMs.
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Affiliation(s)
- L E A Shelley
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Department of Medical Physics and Clinical Engineering, Cambridge University Hospitals NHS Foundation Trust, United Kingdom; Department of Engineering, University of Cambridge, United Kingdom.
| | - J E Scaife
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Department of Oncology, University of Cambridge, United Kingdom
| | - M Romanchikova
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Department of Medical Physics and Clinical Engineering, Cambridge University Hospitals NHS Foundation Trust, United Kingdom
| | - K Harrison
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Cavendish Laboratory, University of Cambridge, United Kingdom
| | - J R Forman
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Cambridge Clinical Trials Unit, Cambridge University Hospitals NHS Foundation Trust, United Kingdom
| | - A M Bates
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Department of Oncology, University of Cambridge, United Kingdom
| | - D J Noble
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Department of Oncology, University of Cambridge, United Kingdom
| | - R Jena
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Department of Oncology, University of Cambridge, United Kingdom
| | - M A Parker
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Cavendish Laboratory, University of Cambridge, United Kingdom
| | - M P F Sutcliffe
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Department of Engineering, University of Cambridge, United Kingdom
| | - S J Thomas
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Department of Medical Physics and Clinical Engineering, Cambridge University Hospitals NHS Foundation Trust, United Kingdom
| | - N G Burnet
- Cambridge University Hospitals NHS Foundation Trust, Department of Oncology, United Kingdom; Department of Oncology, University of Cambridge, United Kingdom
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Douglas GR, Brown AJ, Gillard JH, Bennett MR, Sutcliffe MPF, Teng Z. Impact of Fiber Structure on the Material Stability and Rupture Mechanisms of Coronary Atherosclerotic Plaques. Ann Biomed Eng 2017; 45:1462-1474. [PMID: 28361184 PMCID: PMC5415591 DOI: 10.1007/s10439-017-1827-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 03/22/2017] [Indexed: 12/19/2022]
Abstract
The rupture of an atherosclerotic plaque in the coronary circulation remains the main cause of heart attack. As a fiber-oriented structure, the fiber structure, in particular in the fibrous cap (FC), may affect both loading and material strength in the plaque. However, the role of fiber orientation and dispersion in plaque rupture is unclear. Local orientation and dispersion of fibers were calculated for the shoulder regions, mid FC, and regions with intimal thickening (IT) from histological images of 16 human coronary atherosclerotic lesions. Finite element analysis was performed to assess the effect of these properties on mechanical conditions. Fibers in shoulder regions had markedly reduced alignment (Median [interquartile range] 12.9° [6.6, 18.0], p < 0.05) compared with those in mid FC (6.1° [5.5, 9.0]) and IT regions (6.7° [5.1, 8.6]). Fiber dispersion was highest in shoulders (0.150 [0.121, 0.192]), intermediate in IT (0.119 [0.103, 0.144]), and lowest in mid FC regions (0.093 [0.081, 0.105], p < 0.05). When anisotropic properties were considered, stresses were significantly higher for the mid FC (p = 0.030) and IT regions (p = 0.002) and no difference was found for the shoulder or global regions. Shear (sliding) stress between fibers in each region and their proportion of maximum principal stress were: shoulder (25.8 kPa [17.1, 41.2], 12.4%), mid FC (13.9 kPa [5.8, 29.6], 13.8%), and IT (36.5 kPa [25.9, 47.3], 15.5%). Fiber structure within the FC has a marked effect on principal stresses, resulting in considerable shear stress between fibers. Fiber structure including orientation and dispersion may determine mechanical strength and thus rupture of atherosclerotic plaques.
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Affiliation(s)
- Graeham R Douglas
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, UK
| | - Adam J Brown
- Division of Cardiovascular Medicine, University of Cambridge, Cambridge, UK
| | - Jonathan H Gillard
- Department of Radiology, School of Clinical Medicine, University of Cambridge, Box 218, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK
| | - Martin R Bennett
- Division of Cardiovascular Medicine, University of Cambridge, Cambridge, UK
| | - Michael P F Sutcliffe
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, UK.
| | - Zhongzhao Teng
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, UK. .,Department of Radiology, School of Clinical Medicine, University of Cambridge, Box 218, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK.
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14
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Fletcher TL, Wirthl B, Kolias AG, Adams H, Hutchinson PJA, Sutcliffe MPF. Modelling of Brain Deformation After Decompressive Craniectomy. Ann Biomed Eng 2016; 44:3495-3509. [PMID: 27278343 PMCID: PMC5112297 DOI: 10.1007/s10439-016-1666-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 05/28/2016] [Indexed: 02/05/2023]
Abstract
Hyperelastic finite element models, with either an idealized cylindrical geometry or with realistic craniectomy geometries, were used to explore clinical issues relating to decompressive craniectomy. The potential damage in the brain tissue was estimated by calculating the volume of material exceeding a critical shear strain. Results from the idealized model showed how the potentially damaged volume of brain tissue increased with an increasing volume of brain tissue herniating from the skull cavity and with a reduction in craniectomy area. For a given herniated volume, there was a critical craniectomy diameter where the volume exceeding a critical shear strain fell to zero. The effects of details at the craniectomy edge, specifically a fillet radius and a chamfer on the bone margin, were found to be relatively slight, assuming that the dura is retained to provide effective protection. The location in the brain associated with volume expansion and details of the material modeling were found to have a relatively modest effect on the predicted damage volume. The volume of highly sheared material in the realistic models of the craniectomy varied roughly in line with differences in the craniectomy area.
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Affiliation(s)
- Tim L Fletcher
- Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, UK
| | - Barbara Wirthl
- Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, UK
| | - Angelos G Kolias
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Hadie Adams
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
| | - Peter J A Hutchinson
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK
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15
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Thomas SJ, Romanchikova M, Harrison K, Parker MA, Bates AM, Scaife JE, Sutcliffe MPF, Burnet NG. Recalculation of dose for each fraction of treatment on TomoTherapy. Br J Radiol 2016; 89:20150770. [PMID: 26728661 PMCID: PMC4986496 DOI: 10.1259/bjr.20150770] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Objective: The VoxTox study, linking delivered dose to toxicity requires recalculation of typically 20–37 fractions per patient, for nearly 2000 patients. This requires a non-interactive interface permitting batch calculation with multiple computers. Methods: Data are extracted from the TomoTherapy® archive and processed using the computational task-management system GANGA. Doses are calculated for each fraction of radiotherapy using the daily megavoltage (MV) CT images. The calculated dose cube is saved as a digital imaging and communications in medicine RTDOSE object, which can then be read by utilities that calculate dose–volume histograms or dose surface maps. The rectum is delineated on daily MV images using an implementation of the Chan–Vese algorithm. Results: On a cluster of up to 117 central processing units, dose cubes for all fractions of 151 patients took 12 days to calculate. Outlining the rectum on all slices and fractions on 151 patients took 7 h. We also present results of the Hounsfield unit (HU) calibration of TomoTherapy MV images, measured over an 8-year period, showing that the HU calibration has become less variable over time, with no large changes observed after 2011. Conclusion: We have developed a system for automatic dose recalculation of TomoTherapy dose distributions. This does not tie up the clinically needed planning system but can be run on a cluster of independent machines, enabling recalculation of delivered dose without user intervention. Advances in knowledge: The use of a task management system for automation of dose calculation and outlining enables work to be scaled up to the level required for large studies.
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Affiliation(s)
- Simon J Thomas
- 1 Cambridge University Hospitals NHS Foundation Trust, Department of Medical Physics and Clinical Engineering, Addenbrooke's Hospital, Cambridge, UK.,2 Cancer Research UK VoxTox Research Group, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
| | - Marina Romanchikova
- 1 Cambridge University Hospitals NHS Foundation Trust, Department of Medical Physics and Clinical Engineering, Addenbrooke's Hospital, Cambridge, UK.,2 Cancer Research UK VoxTox Research Group, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
| | - Karl Harrison
- 2 Cancer Research UK VoxTox Research Group, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,3 Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, UK
| | - Michael A Parker
- 2 Cancer Research UK VoxTox Research Group, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,3 Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, UK
| | - Amy M Bates
- 2 Cancer Research UK VoxTox Research Group, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,4 Department of Oncology, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge, UK
| | - Jessica E Scaife
- 2 Cancer Research UK VoxTox Research Group, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,5 Department of Oncology, University of Cambridge, Cambridge Biomedical Campus, Addenbrooke's Hospital, Cambridge, UK
| | - Michael P F Sutcliffe
- 2 Cancer Research UK VoxTox Research Group, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,6 Department of Engineering, University of Cambridge, Cambridge, UK
| | - Neil G Burnet
- 2 Cancer Research UK VoxTox Research Group, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,5 Department of Oncology, University of Cambridge, Cambridge Biomedical Campus, Addenbrooke's Hospital, Cambridge, UK
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16
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Teng Z, Feng J, Zhang Y, Sutcliffe MPF, Huang Y, Brown AJ, Jing Z, Lu Q, Gillard JH. A uni-extension study on the ultimate material strength and extreme extensibility of atherosclerotic tissue in human carotid plaques. J Biomech 2015; 48:3859-67. [PMID: 26472304 PMCID: PMC4655866 DOI: 10.1016/j.jbiomech.2015.09.037] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 09/16/2015] [Accepted: 09/24/2015] [Indexed: 12/26/2022]
Abstract
Atherosclerotic plaque rupture occurs when mechanical loading exceeds its material strength. Mechanical analysis has been shown to be complementary to the morphology and composition for assessing vulnerability. However, strength and stretch thresholds for mechanics-based assessment are currently lacking. This study aims to quantify the ultimate material strength and extreme extensibility of atherosclerotic components from human carotid plaques. Tissue strips of fibrous cap, media, lipid core and intraplaque hemorrhage/thrombus were obtained from 21 carotid endarterectomy samples of symptomatic patients. Uni-extension test with tissue strips was performed until they broke or slid. The Cauchy stress and stretch ratio at the peak loading of strips broken about 2 mm away from the clamp were used to characterize their ultimate strength and extensibility. Results obtained indicated that ultimate strength of fibrous cap and media were 158.3 [72.1, 259.3] kPa (Median [Inter quartile range]) and 247.6 [169.0, 419.9] kPa, respectively; those of lipid and intraplaque hemorrhage/thrombus were 68.8 [48.5, 86.6] kPa and 83.0 [52.1, 124.9] kPa, respectively. The extensibility of each tissue type were: fibrous cap – 1.18 [1.10, 1.27]; media – 1.21 [1.17, 1.32]; lipid – 1.25 [1.11, 1.30] and intraplaque hemorrhage/thrombus – 1.20 [1.17, 1.44]. Overall, the strength of fibrous cap and media were comparable and so were lipid and intraplaque hemorrhage/thrombus. Both fibrous cap and media were significantly stronger than either lipid or intraplaque hemorrhage/thrombus. All atherosclerotic components had similar extensibility. Moreover, fibrous cap strength in the proximal region (closer to the heart) was lower than that of the distal. These results are helpful in understanding the material behavior of atherosclerotic plaques.
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Affiliation(s)
- Zhongzhao Teng
- Department of Radiology, University of Cambridge, UK; Department of Engineering, University of Cambridge, UK.
| | - Jiaxuan Feng
- Department of Vascular Surgery, Changhai Hospital, Shanghai, China
| | - Yongxue Zhang
- Department of Vascular Surgery, Changhai Hospital, Shanghai, China
| | | | - Yuan Huang
- Department of Radiology, University of Cambridge, UK
| | - Adam J Brown
- Division of Cardiovascular Medicine, University of Cambridge, UK
| | - Zaiping Jing
- Department of Vascular Surgery, Changhai Hospital, Shanghai, China
| | - Qingsheng Lu
- Department of Vascular Surgery, Changhai Hospital, Shanghai, China
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17
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Scaife JE, Thomas SJ, Harrison K, Romanchikova M, Sutcliffe MPF, Forman JR, Bates AM, Jena R, Parker MA, Burnet NG. Accumulated dose to the rectum, measured using dose-volume histograms and dose-surface maps, is different from planned dose in all patients treated with radiotherapy for prostate cancer. Br J Radiol 2015. [PMID: 26204919 PMCID: PMC4730972 DOI: 10.1259/bjr.20150243] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
OBJECTIVE We sought to calculate accumulated dose (DA) to the rectum in patients treated with radiotherapy for prostate cancer. We were particularly interested in whether dose-surface maps (DSMs) provide additional information to dose-volume histograms (DVHs). METHODS Manual rectal contours were obtained for kilovoltage and daily megavoltage CT scans for 10 participants from the VoxTox study (380 scans). Daily delivered dose recalculation was performed using a ray-tracing algorithm. Delivered DVHs were summated to create accumulated DVHs. The rectum was considered as a cylinder, cut and unfolded to produce daily delivered DSMs; these were summated to produce accumulated DSMs. RESULTS Accumulated dose-volumes were different from planned in all participants. For one participant, all DA levels were higher and all volumes were larger than planned. For four participants, all DA levels were lower and all volumes were smaller than planned. For each of these four participants, ≥1% of pixels on the accumulated DSM received ≥5 Gy more than had been planned. CONCLUSION Differences between accumulated and planned dose-volumes were seen in all participants. DSMs were able to identify differences between DA and planned dose that could not be appreciated from the DVHs. Further work is needed to extract the dose data embedded in the DSMs. These will be correlated with toxicity as part of the VoxTox Programme. ADVANCES IN KNOWLEDGE DSMs are able to identify differences between DA and planned dose that cannot be appreciated from DVHs alone and should be incorporated into future studies investigating links between DA and toxicity.
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Affiliation(s)
- Jessica E Scaife
- 1 Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,2 Department of Oncology, University of Cambridge, Cambridge Biomedical Campus, Addenbrooke's Hospital, Cambridge, UK
| | - Simon J Thomas
- 1 Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,3 Medical Physics Department, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Karl Harrison
- 1 Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,4 Department of Physics, University of Cambridge, Cavendish Laboratory, Cambridge, UK
| | - Marina Romanchikova
- 1 Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,3 Medical Physics Department, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Michael P F Sutcliffe
- 1 Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,5 Department of Engineering, University of Cambridge, Cambridge, UK
| | - Julia R Forman
- 1 Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,6 Cambridge Clinical Trials Unit, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
| | - Amy M Bates
- 1 Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,2 Department of Oncology, University of Cambridge, Cambridge Biomedical Campus, Addenbrooke's Hospital, Cambridge, UK
| | - Raj Jena
- 1 Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,2 Department of Oncology, University of Cambridge, Cambridge Biomedical Campus, Addenbrooke's Hospital, Cambridge, UK
| | - M Andrew Parker
- 1 Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,4 Department of Physics, University of Cambridge, Cavendish Laboratory, Cambridge, UK
| | - Neil G Burnet
- 1 Cancer Research UK VoxTox Research Group, Department of Oncology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.,2 Department of Oncology, University of Cambridge, Cambridge Biomedical Campus, Addenbrooke's Hospital, Cambridge, UK
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18
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Teng Z, Feng J, Zhang Y, Huang Y, Sutcliffe MPF, Brown AJ, Jing Z, Gillard JH, Lu Q. Layer- and Direction-Specific Material Properties, Extreme Extensibility and Ultimate Material Strength of Human Abdominal Aorta and Aneurysm: A Uniaxial Extension Study. Ann Biomed Eng 2015; 43:2745-59. [PMID: 25905688 PMCID: PMC4611020 DOI: 10.1007/s10439-015-1323-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Accepted: 04/12/2015] [Indexed: 11/26/2022]
Abstract
Mechanical analysis has the potential to provide complementary information to aneurysm morphology in assessing its vulnerability. Reliable calculations require accurate material properties of individual aneurysmal components. Quantification of extreme extensibility and ultimate material strength of the tissue are important if rupture is to be modelled. Tissue pieces from 11 abdomen aortic aneurysm (AAA) from patients scheduled for elective surgery and from 8 normal aortic artery (NAA) from patients who scheduled for kidney/liver transplant were collected at surgery and banked in liquid nitrogen with the use of Cryoprotectant solution to minimize frozen damage. Prior to testing, specimen were thawed and longitudinal and circumferential tissue strips were cut from each piece and adventitia, media and thrombus if presented were isolated for the material test. The incremental Young’s modulus of adventitia of NAA was direction-dependent at low stretch levels, but not the media. Both adventitia and media had a similar extreme extensibility in the circumferential direction, but the adventitia was much stronger. For aneurysmal tissues, no significant differences were found when the incremental moduli of adventitia, media or thrombus in both directions were compared. Adventitia and media from AAA had similar extreme extensibility and ultimate strength in both directions and thrombus was the weakest material. Adventitia and media from AAA were less extensible compared with those of NAA, but the ultimate strength remained similar. The material properties, including extreme extensibility and ultimate strength, of both healthy aortic and aneurysmal tissues were layer-dependent, but not direction-dependent.
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Affiliation(s)
- Zhongzhao Teng
- Department of Radiology, School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Box 218, Cambridge, CB2 0QQ, UK.
- Department of Engineering, University of Cambridge, Cambridge, UK.
| | - Jiaxuan Feng
- Department of Vascular Surgery, Changhai Hospital, 168 Changhai Rd., Shanghai, 200433, China
| | - Yongxue Zhang
- Department of Radiology, School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Box 218, Cambridge, CB2 0QQ, UK
- Department of Vascular Surgery, Changhai Hospital, 168 Changhai Rd., Shanghai, 200433, China
| | - Yuan Huang
- Department of Radiology, School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Box 218, Cambridge, CB2 0QQ, UK
| | | | - Adam J Brown
- Division of Cardiovascular Medicine, University of Cambridge, Cambridge, UK
| | - Zaiping Jing
- Department of Vascular Surgery, Changhai Hospital, 168 Changhai Rd., Shanghai, 200433, China
| | - Jonathan H Gillard
- Department of Radiology, School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Box 218, Cambridge, CB2 0QQ, UK
| | - Qingsheng Lu
- Department of Vascular Surgery, Changhai Hospital, 168 Changhai Rd., Shanghai, 200433, China.
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Kim H, Min BK, Park DH, Hawi S, Kim BJ, Czosnyka Z, Czosnyka M, Sutcliffe MPF, Kim DJ. Porohyperelastic anatomical models for hydrocephalus and idiopathic intracranial hypertension. J Neurosurg 2015; 122:1330-40. [PMID: 25658783 DOI: 10.3171/2014.12.jns14516] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Brain deformation can be seen in hydrocephalus and idiopathic intracranial hypertension (IIH) via medical images. The phenomenology of local effects, brain shift, and raised intracranial pressure and herniation are textbook concepts. However, there are still uncertainties regarding the specific processes that occur when brain tissue is subject to the mechanical stress of different temporal and spatial profiles of the 2 neurological disorders. Moreover, recent studies suggest that IIH and hydrocephalus may be diseases with opposite pathogenesis. Nevertheless, the similarities and differences between the 2 subjects have not been thoroughly investigated. METHODS An anatomical porohyperelastic finite element model was used to assess the brain tissue responses associated with hydrocephalus and IIH. The same set of boundary conditions, with the exception of brain loading for development of the transmantle pressure gradient, was applied for the 2 models. The distribution of stress and strain during tissue distortion is described by the mechanical parameters. RESULTS The results of both the hydrocephalus and IIH models correlated with pathological characteristics. For the hydrocephalus model, periventricular edema was associated with the presence of positive volumetric strain and void ratio in the lateral ventricle horns. By contrast, the IIH model revealed edema across the cerebral mantle, including the centrum semiovale, with a positive void ratio and volumetric strain. CONCLUSIONS The model simulates all the clinical features in correlation with the MR images obtained in patients with hydrocephalus and IIH, thus providing support for the role of the transmantle pressure gradient and capillary CSF absorption in CSF-related brain deformation. The finite element methods can be used for a better understanding of the pathophysiological mechanisms of neurological disorders associated with parenchymal volumetric fluctuation.
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Affiliation(s)
- Hakseung Kim
- 1Department of Brain and Cognitive Engineering, Korea University
| | - Byoung-Kyong Min
- 1Department of Brain and Cognitive Engineering, Korea University
| | - Dae-Hyeon Park
- 1Department of Brain and Cognitive Engineering, Korea University
| | - Stanley Hawi
- 1Department of Brain and Cognitive Engineering, Korea University
| | - Byung-Jo Kim
- 2Department of Neurology, Korea University College of Medicine, Seoul, South Korea
| | - Zofia Czosnyka
- 3Department of Neurosurgery, Addenbrooke's Hospital, University of Cambridge; and
| | - Marek Czosnyka
- 3Department of Neurosurgery, Addenbrooke's Hospital, University of Cambridge; and
| | | | - Dong-Joo Kim
- 1Department of Brain and Cognitive Engineering, Korea University
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Abstract
Decompressive craniectomy (DC), an operation whereby part of the skull is removed, is used in the management of patients with brain swelling. While the aim of DC is to reduce intracranial pressure, there is the risk that brain deformation and mechanical strain associated with the operation could damage the brain tissue. The nature and extent of the resulting strain regime is poorly understood at present. Finite element (FE) models of DC can provide insight into this applied strain and hence assist in deciding on the best surgical procedures. However there is uncertainty about how well these models match experimental data, which are difficult to obtain clinically. Hence there is a need to validate any modelling approach outside the clinical setting. This paper develops an axisymmetric FE model of an idealised DC to assess the key features of such an FE model which are needed for an accurate simulation of DC. The FE models are compared with an experimental model using gelatin hydrogel, which has similar poro-viscoelastic material property characteristics to brain tissue. Strain on a central plane of the FE model and the front face of the experimental model, deformation and load relaxation curves are compared between experiment and FE. Results show good agreement between the FE and experimental models, providing confidence in applying the proposed FE modelling approach to DC. Such a model should use material properties appropriate for brain tissue and include a more realistic whole head geometry.
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Affiliation(s)
- Tim L. Fletcher
- Department of Engineering, University of Cambridge, Cambridge, United Kingdom
| | - Angelos G. Kolias
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital & University of Cambridge, Cambridge, United Kingdom
| | - Peter J. A. Hutchinson
- Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital & University of Cambridge, Cambridge, United Kingdom
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Kim DJ, Carrera E, Czosnyka M, Keong N, Smielewski P, Balédent O, Sutcliffe MPF, Pickard JD, Czosnyka Z. Cerebrospinal compensation of pulsating cerebral blood volume in hydrocephalus. Neurol Res 2013; 32:587-92. [DOI: 10.1179/174313209x455673] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Li ZY, Taviani V, Tang T, Sutcliffe MPF, Gillard JH. The hemodynamic effects of in-tandem carotid artery stenosis: implications for carotid endarterectomy. J Stroke Cerebrovasc Dis 2010; 19:138-45. [PMID: 20189090 DOI: 10.1016/j.jstrokecerebrovasdis.2009.03.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Revised: 03/04/2009] [Accepted: 03/09/2009] [Indexed: 10/19/2022] Open
Abstract
OBJECTIVES It remains controversial whether patients with severe disease of the internal carotid artery and a coexisting stenotic lesion downstream would benefit from a carotid endarterectomy (CEA) of the proximal lesion. The aim of this study was to simulate the hemodynamic and wall shear effects of in-tandem internal carotid artery stenosis using a computational fluid dynamic (CFD) idealized model to give insight into the possible consequences of CEA on these lesions. METHODS A CFD model of steady viscous flow in a rigid tube with two asymmetric stenoses was introduced to simulate blood flow in arteries with multiple constrictions. The effect of varying the distance between the two stenoses, and the severity of the upstream stenosis on the pressure and wall shear stress (WSS) distributions on the second plaque, was investigated. The influence of the relative positions of the two stenoses was also assessed. RESULTS The distance between the plaques was found to have minimal influence on the overall hemodynamic effect except for the presence of a zone of low WSS (range -20 to 30 dyne/cm2) adjacent to both lesions when the two stenoses were sufficiently close (<4 times the arterial diameter). The upstream stenosis was protective if it was larger than the downstream stenosis. The relative positions of the stenoses were found to influence the WSS but not the pressure distribution. CONCLUSIONS The geometry and positions of the lesions need to be considered when considering the hemodynamic effects of an in-tandem stenosis. Low WSS is thought to cause endothelial dysfunction and initiate atheroma formation. The fact that there was a flow recirculation zone with low WSS in between the two stenoses may demonstrate how two closely positioned plaques may merge into one larger lesion. Decision making for CEA may need to take into account the hemodynamic situation when an in-tandem stenosis is found. CFD may aid in the risk stratification of patients with this problem.
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Affiliation(s)
- Zhi-Yong Li
- University Department of Radiology, Cambridge University Hospitals National Health Service Foundation Trust, United Kingdom.
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Kim DJ, Kasprowicz M, Carrera E, Castellani G, Zweifel C, Lavinio A, Smielewski P, Sutcliffe MPF, Pickard JD, Czosnyka M. The monitoring of relative changes in compartmental compliances of brain. Physiol Meas 2009; 30:647-59. [PMID: 19498218 DOI: 10.1088/0967-3334/30/7/009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The study aimed to develop a computational method for assessing relative changes in compartmental compliances within the brain: the arterial bed and the cerebrospinal space. The method utilizes the relationship between pulsatile components in the arterial blood volume, arterial blood pressure (ABP) and intracranial pressure (ICP). It was verified by using clinical recordings of intracranial pressure plateau waves, when massive vasodilatation accompanying plateau waves produces changes in brain compliances of the arterial bed (C(a)) and compliance of the cerebrospinal space (C(i)). Ten patients admitted after head injury with a median Glasgow Coma Score of 6 were studied retrospectively. ABP was directly monitored from the radial artery. Changes in the cerebral arterial blood volume were assessed using Transcranial Doppler (TCD) ultrasonography by digital integration of inflow blood velocity. During plateau waves, ICP increased (P = 0.001), CPP decreased (P = 0.001), ABP remained constant (P = 0.532), blood flow velocity decreased (P = 0.001). Calculated compliance of the arterial bed C(a) increased significantly (P = 0.001); compliance of the CSF space C(i) decreased (P = 0.001). We concluded that the method allows for continuous monitoring of relative changes in brain compartmental compliances. Plateau waves affect the balance between vascular and CSF compartments, which is reflected by the inverse change of compliance of the cerebral arterial bed and global compliance of the CSF space.
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Affiliation(s)
- Dong-Joo Kim
- Academic Neurosurgical Unit, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK. Department of Engineering, University of Cambridge, Cambridge, UK
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Lilikakis A, Sutcliffe MPF. The effect of vancomycin addition to the compression strength of antibiotic-loaded bone cements. Int Orthop 2009; 33:815-9. [PMID: 18283457 PMCID: PMC2903084 DOI: 10.1007/s00264-008-0521-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Revised: 12/21/2007] [Accepted: 01/03/2008] [Indexed: 10/22/2022]
Abstract
The purpose of this study was to record the effect of the addition of vancomycin on the compression strength of antibiotic-loaded bone cement and to compare the results with the international standards (ISO 5833-2). The formulations tested were: Palamed G and Copal. Vancomycin concentrations of 2.5%, 5% and 10% per powder weight were added. Samples of Palamed G with 5% vancomycin and non-standardised mixing procedures were also tested. The ISO requirements for the testing procedures were followed. None of the combinations tested fall short of the ISO standards for compression strength. Copal with 10% and Palamed G with 5% vancomycin and non-standardised mixing procedures, however, did not significantly exceed them. The addition of up to 5% vancomycin per powder weight to the Palamed G and Copal bone cements can be considered safe. Care should be given to the mixing procedure of the cement, as it significantly affects its compression strength.
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Barrett SRH, Sutcliffe MPF, Howarth S, Li ZY, Gillard JH. Experimental measurement of the mechanical properties of carotid atherothrombotic plaque fibrous cap. J Biomech 2009; 42:1650-5. [PMID: 19464014 DOI: 10.1016/j.jbiomech.2009.04.025] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Revised: 03/31/2009] [Accepted: 04/17/2009] [Indexed: 11/29/2022]
Abstract
Eleven carotid atherothrombotic plaque samples were harvested from patients. Three samples that were highly calcified were discarded, while eight yielded results. The elastic properties of the material were estimated by fitting the measured indentation response to finite element simulations. The methodology was refined and its accuracy quantified using a synthetic rubber. The neo-Hookean form of the material model gave a good fit to the measured response of the tissue. The inferred shear modulus mu was found to be in the range 7-100 kPa, with a median value of 11 kPa. A review of published materials data showed a wide range of material properties for human atherothrombotic tissue. The effects of anisotropy and time dependency in these published results were highlighted. The present measurements were comparable to the static radial compression tests of Lee et al, 1991 [Structure-dependent dynamic behaviour of fibrous caps from human atherosclerotic plaques. Circulation 83, 1764-1770].
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Affiliation(s)
- S R H Barrett
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK
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Taviani V, Sutcliffe MPF, Wong P, Li ZY, Young V, Graves MJ, Gillard JH. In vivo non-invasive high resolution MR-based method for the determination of the elastic modulus of arterial vessels. Annu Int Conf IEEE Eng Med Biol Soc 2009; 2008:5569-72. [PMID: 19163979 DOI: 10.1109/iembs.2008.4650476] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The mechanical properties of arterial walls have long been recognized to play an essential role in the development and progression of cardiovascular disease (CVD). Early detection of variations in the elastic modulus of arteries would help in monitoring patients at high cardiovascular risk stratifying them according to risk. An in vivo, non-invasive, high resolution MR-phase-contrast based method for the estimation of the time-dependent elastic modulus of healthy arteries was developed, validated in vitro by means of a thin walled silicon rubber tube integrated into an existing MR-compatible flow simulator and used on healthy volunteers. A comparison of the elastic modulus of the silicon tube measured from the MRI-based technique with direct measurements confirmed the method's capability. The repeatability of the method was assessed. Viscoelastic and inertial effects characterizing the dynamic response of arteries in vivo emerged from the comparison of the pressure waveform and the area variation curve over a period. For all the volunteers who took part in the study the elastic modulus was found to be in the range 50-250 kPa, to increase during the rising part of the cycle, and to decrease with decreasing pressure during the downstroke of systole and subsequent diastole.
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Affiliation(s)
- Valentina Taviani
- Department of Engineering, University of Cambridge, CB21PZ UK. vt232@ cam.ac.uk
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