| 61. |
- Liebi, Marianne, 1984, et al.
(författare)
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Small-angle X-ray scattering tensor tomography: Model of the three-dimensional reciprocal-space map, reconstruction algorithm and angular sampling requirements
- 2018
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Ingår i: Acta Crystallographica Section A: Foundations and Advances. - 2053-2733. ; 74:1, s. 12-24
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Tidskriftsartikel (refereegranskat)abstract
- Small-angle X-ray scattering tensor tomography, which allows reconstruction of the local three-dimensional reciprocal-space map within a three-dimensional sample as introduced by Liebi et al. [Nature (2015), 527, 349-352], is described in more detail with regard to the mathematical framework and the optimization algorithm. For the case of trabecular bone samples from vertebrae it is shown that the model of the three-dimensional reciprocal-space map using spherical harmonics can adequately describe the measured data. The method enables the determination of nanostructure orientation and degree of orientation as demonstrated previously in a single momentum transfer q range. This article presents a reconstruction of the complete reciprocal-space map for the case of bone over extended ranges of q. In addition, it is shown that uniform angular sampling and advanced regularization strategies help to reduce the amount of data required.The mathematical framework and reconstruction algorithm for small-angle scattering tensor tomography are introduced in detail, as well as strategies which help to reduce the amount of data and therewith the measurement time required. Experimental validation is provided for the application to trabecular bone.
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| 62. |
- Mürer, Fredrik K., et al.
(författare)
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Quantifying the hydroxyapatite orientation near the ossification front in a piglet femoral condyle using X-ray diffraction tensor tomography
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- While a detailed knowledge of the hierarchical structure and morphology of the extracellular matrix is considered crucial for understanding the physiological and mechanical properties of bone and cartilage, the orientation of collagen fibres and carbonated hydroxyapatite (HA) crystallites remains a debated topic. Conventional microscopy techniques for orientational imaging require destructive sample sectioning, which both precludes further studies of the intact sample and potentially changes the microstructure. In this work, we use X-ray diffraction tensor tomography to image non-destructively in 3D the HA orientation in a medial femoral condyle of a piglet. By exploiting the anisotropic HA diffraction signal, 3D maps showing systematic local variations of the HA crystallite orientation in the growing subchondral bone and in the adjacent mineralized growth cartilage are obtained. Orientation maps of HA crystallites over a large field of view (~ 3 × 3 × 3 mm3) close to the ossification (bone-growth) front are compared with high-resolution X-ray propagation phase-contrast computed tomography images. The HA crystallites are found to predominantly orient with their crystallite c-axis directed towards the ossification front. Distinct patterns of HA preferred orientation are found in the vicinity of cartilage canals protruding from the subchondral bone. The demonstrated ability of retrieving 3D orientation maps of bone-cartilage structures is expected to give a better understanding of the physiological properties of bones, including their propensity for bone-cartilage diseases.
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| 63. |
- Nordebo, Sven, 1963-, et al.
(författare)
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A parametric model for the changes in the complex valued conductivity of a lung during tidal breathing
- 2018
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 51:20
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Tidskriftsartikel (refereegranskat)abstract
- Classical homogenization theory based on the Hashin-Shtrikman coated ellipsoids is used to model the changes in the complex valued conductivity (or admittivity) of a lung during tidal breathing. Here, the lung is modeled as a two-phase composite material where the alveolar air-filling corresponds to the inclusion phase. The theory predicts a linear relationship between the real and the imaginary parts of the change in the complex valued conductivity of a lung during tidal breathing, and where the loss cotangent of the change is approximately the same as of the effective background conductivity and hence easy to estimate. The theory is illustrated with numerical examples based on realistic parameter values and frequency ranges used with electrical impedance tomography (EIT). The theory may be potentially useful for imaging and clinical evaluations in connection with lung EIT for respiratory management and control.
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| 64. |
- Penen, Florent, 1987, et al.
(författare)
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Time of Flight Secondary Ion Mass Spectrometry imaging for precise localization of zirconium-labelled trastuzumab in xenograft cancer tumour tissues
- 2022
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Ingår i: Microchemical Journal. - : Elsevier BV. - 0026-265X. ; 181
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Tidskriftsartikel (refereegranskat)abstract
- The human epidermal growth factor receptor 2 (HER2) specific radiotracer zirconium-Desferrioxamine(DFO)-trastuzumab was visualized ex-vivo by Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) imaging in ovarian and breast cancer xenograft tumor sections. Heterogeneous spatial distribution of [90Zr+] ions re-flected the heterogeneous localization of trastuzumab, observed in parallel by immunohistochemistry staining in HER2+ tumors. Our results show that ToF-SIMS imaging is a quick and sensitive technique to image zirconium labelled biologics at microscale in tissues.
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| 65. |
- Phillips, Rachel, et al.
(författare)
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Visual Blood Loss Estimation Accuracy : Directions for Future Research Based on a Systematic Literature Review
- 2020
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Ingår i: Proceedings of the 2020 HFES 64th International Annual Meeting. - : Sage Publications. ; , s. 1411-1415
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Konferensbidrag (refereegranskat)abstract
- Visual blood loss estimation occurs in a variety of medical contexts and may impact everything from interventions by immediate responders to the likelihood of receiving blood transfusions in a hospital setting. However, research suggests that visual blood loss estimation is inaccurate for laypeople and medical professionals. The aim of the current study was to conduct a systematic literature review to determine the current state of knowledge on visual blood loss estimation accuracy and identify directions for future research. A structured search resulted in 1799 titles that were subsequently screened. A total of 72 articles were coded for comparison. Based on the evaluation, several gaps were identified, most notably related to factors of the situation that may influence estimation accuracy such as blood flow and victim/patient gender. Directions for future research are proposed based on identified gaps.
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| 66. |
- Pierantoni, Maria, et al.
(författare)
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Muscular loading affects the 3D structure of both the mineralized rudiment and growth plate at early stages of bone formation
- 2021
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Ingår i: Bone. - : Elsevier BV. - 8756-3282. ; 145
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Tidskriftsartikel (refereegranskat)abstract
- Fetal immobilization affects skeletal development and can lead to severe malformations. Still, how mechanical load affects embryonic bone formation is not fully elucidated. This study combines mechanobiology, image analysis and developmental biology, to investigate the structural effects of muscular loading on embryonic long bones. We present a novel approach involving a semi-automatic workflow, to study the spatial and temporal evolutions of both hard and soft tissues in 3D without any contrast agent at micrometrical resolution. Using high-resolution phase-contrast-enhanced X-ray synchrotron microtomography, we compare the humeri of Splotch-delayed embryonic mice lacking skeletal muscles with healthy littermates. The effects of skeletal muscles on bone formation was studied from the first stages of mineral deposition (Theiler Stages 23 and 24) to just before birth (Theiler Stage 27). The results show that muscle activity affects both growth plate and mineralized regions, especially during early embryonic development. When skeletal muscles were absent, there was reduced mineralization, altered tuberosity size and location, and, at early embryonic stages, decreased chondrocyte density, size and elongation compared to littermate controls. The proposed workflow enhances our understanding of mechanobiology of early bone formation and could be implemented for the study of other complex biological tissues.
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| 67. |
- Piri, Reza, et al.
(författare)
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Aortic wall segmentation in F-18-sodium fluoride PET/CT scans: Head-to-head comparison of artificial intelligence-based versus manual segmentation
- 2022
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Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1532-6551 .- 1071-3581. ; 29:4, s. 2001-2010
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Tidskriftsartikel (refereegranskat)abstract
- Background We aimed to establish and test an automated AI-based method for rapid segmentation of the aortic wall in positron emission tomography/computed tomography (PET/CT) scans. Methods For segmentation of the wall in three sections: the arch, thoracic, and abdominal aorta, we developed a tool based on a convolutional neural network (CNN), available on the Research Consortium for Medical Image Analysis (RECOMIA) platform, capable of segmenting 100 different labels in CT images. It was tested on F-18-sodium fluoride PET/CT scans of 49 subjects (29 healthy controls and 20 angina pectoris patients) and compared to data obtained by manual segmentation. The following derived parameters were compared using Bland-Altman Limits of Agreement: segmented volume, and maximal, mean, and total standardized uptake values (SUVmax, SUVmean, SUVtotal). The repeatability of the manual method was examined in 25 randomly selected scans. Results CNN-derived values for volume, SUVmax, and SUVtotal were all slightly, i.e., 13-17%, lower than the corresponding manually obtained ones, whereas SUVmean values for the three aortic sections were virtually identical for the two methods. Manual segmentation lasted typically 1-2 hours per scan compared to about one minute with the CNN-based approach. The maximal deviation at repeat manual segmentation was 6%. Conclusions The automated CNN-based approach was much faster and provided parameters that were about 15% lower than the manually obtained values, except for SUVmean values, which were comparable. AI-based segmentation of the aorta already now appears as a trustworthy and fast alternative to slow and cumbersome manual segmentation.
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| 68. |
- Piri, R., et al.
(författare)
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Common carotid segmentation in F-18-sodium fluoride PET/CT scans: Head-to-head comparison of artificial intelligence-based and manual method
- 2023
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Ingår i: Clinical Physiology and Functional Imaging. - : Wiley. - 1475-0961 .- 1475-097X. ; 43:2, s. 71-77
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Tidskriftsartikel (refereegranskat)abstract
- Background Carotid atherosclerosis is a major cause of stroke, traditionally diagnosed late. Positron emission tomography/computed tomography (PET/CT) with F-18-sodium fluoride (NaF) detects arterial wall micro-calcification long before macro-calcification becomes detectable by ultrasound, CT or magnetic resonance imaging. However, manual PET/CT processing is time-consuming and requires experience. We compared a convolutional neural network (CNN) approach with manual segmentation of the common carotids. Methods Segmentation in NaF-PET/CT scans of 29 healthy volunteers and 20 angina pectoris patients were compared for segmented volume (Vol) and mean, maximal, and total standardized uptake values (SUVmean, SUVmax, and SUVtotal). SUVmean was the average of SUVmeans within the VOI, SUVmax the highest SUV in all voxels in the VOI, and SUVtotal the SUVmean multiplied by the Vol of the VOI. Intra and Interobserver variability with manual segmentation was examined in 25 randomly selected scans. Results Bias for Vol, SUVmean, SUVmax, and SUVtotal were 1.33 +/- 2.06, -0.01 +/- 0.05, 0.09 +/- 0.48, and 1.18 +/- 1.99 in the left and 1.89 +/- 1.5, -0.07 +/- 0.12, 0.05 +/- 0.47, and 1.61 +/- 1.47, respectively, in the right common carotid artery. Manual segmentation lasted typically 20 min versus 1 min with the CNN-based approach. Mean Vol deviation at repeat manual segmentation was 14% and 27% in left and right common carotids. Conclusions CNN-based segmentation was much faster and provided SUVmean values virtually identical to manually obtained ones, suggesting CNN-based analysis as a promising substitute of slow and cumbersome manual processing.
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| 69. |
- Piri, R., et al.
(författare)
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"Global" cardiac atherosclerotic burden assessed by artificial intelligence-based versus manual segmentation in F-18-sodium fluoride PET/CT scans: Head-to-head comparison
- 2022
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Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1071-3581 .- 1532-6551. ; 29:5, s. 2531-2539
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Tidskriftsartikel (refereegranskat)abstract
- Background Artificial intelligence (AI) is known to provide effective means to accelerate and facilitate clinical and research processes. So in this study it was aimed to compare a AI-based method for cardiac segmentation in positron emission tomography/computed tomography (PET/CT) scans with manual segmentation to assess global cardiac atherosclerosis burden. Methods A trained convolutional neural network (CNN) was used for cardiac segmentation in F-18-sodium fluoride PET/CT scans of 29 healthy volunteers and 20 angina pectoris patients and compared with manual segmentation. Parameters for segmented volume (Vol) and mean, maximal, and total standardized uptake values (SUVmean, SUVmax, SUVtotal) were analyzed by Bland-Altman Limits of Agreement. Repeatability with AI-based assessment of the same scans is 100%. Repeatability (same conditions, same operator) and reproducibility (same conditions, two different operators) of manual segmentation was examined by re-segmentation in 25 randomly selected scans. Results Mean (+/- SD) values with manual vs. CNN-based segmentation were Vol 617.65 +/- 154.99 mL vs 625.26 +/- 153.55 mL (P = .21), SUVmean 0.69 +/- 0.15 vs 0.69 +/- 0.15 (P = .26), SUVmax 2.68 +/- 0.86 vs 2.77 +/- 1.05 (P = .34), and SUVtotal 425.51 +/- 138.93 vs 427.91 +/- 132.68 (P = .62). Limits of agreement were - 89.42 to 74.2, - 0.02 to 0.02, - 1.52 to 1.32, and - 68.02 to 63.21, respectively. Manual segmentation lasted typically 30 minutes vs about one minute with the CNN-based approach. The maximal deviation at manual re-segmentation was for the four parameters 0% to 0.5% with the same and 0% to 1% with different operators. Conclusion The CNN-based method was faster and provided values for Vol, SUVmean, SUVmax, and SUVtotal comparable to the manually obtained ones. This AI-based segmentation approach appears to offer a more reproducible and much faster substitute for slow and cumbersome manual segmentation of the heart.
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| 70. |
- Polymeri, Erini, et al.
(författare)
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Deep learning-based quantification of PET/CT prostate gland uptake : association with overall survival
- 2020
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Ingår i: Clinical Physiology and Functional Imaging. - Chichester : Blackwell Publishing. - 1475-0961 .- 1475-097X. ; 40:2, s. 106-113
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To validate a deep-learning (DL) algorithm for automated quantification of prostate cancer on positron emission tomography/computed tomography (PET/CT) and explore the potential of PET/CT measurements as prognostic biomarkers. Material and methods: Training of the DL-algorithm regarding prostate volume was performed on manually segmented CT images in 100 patients. Validation of the DL-algorithm was carried out in 45 patients with biopsy-proven hormone-naïve prostate cancer. The automated measurements of prostate volume were compared with manual measurements made independently by two observers. PET/CT measurements of tumour burden based on volume and SUV of abnormal voxels were calculated automatically. Voxels in the co-registered 18F-choline PET images above a standardized uptake value (SUV) of 2·65, and corresponding to the prostate as defined by the automated segmentation in the CT images, were defined as abnormal. Validation of abnormal voxels was performed by manual segmentation of radiotracer uptake. Agreement between algorithm and observers regarding prostate volume was analysed by Sørensen-Dice index (SDI). Associations between automatically based PET/CT biomarkers and age, prostate-specific antigen (PSA), Gleason score as well as overall survival were evaluated by a univariate Cox regression model. Results: The SDI between the automated and the manual volume segmentations was 0·78 and 0·79, respectively. Automated PET/CT measures reflecting total lesion uptake and the relation between volume of abnormal voxels and total prostate volume were significantly associated with overall survival (P = 0·02), whereas age, PSA, and Gleason score were not. Conclusion: Automated PET/CT biomarkers showed good agreement to manual measurements and were significantly associated with overall survival. © 2019 The Authors. Clinical Physiology and Functional Imaging published by John Wiley & Sons Ltd on behalf of Scandinavian Society of Clinical Physiology and Nuclear Medicine
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