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Accuracy of Calcium Scoring calculated from contrast-enhanced Coronary Computed Tomography Angiography using a dual-layer spectral CT: A comparison of Calcium Scoring from real and virtual non-contrast data
摘要： Modern non-invasive evaluation of Coronary Artery Disease (CAD) requires non-contrast low dose Computed Tomography (CT) imaging for determination of Calcium Scoring (CACS) and contrast-enhanced imaging for evaluation of vascular stenosis. Several methods for calculation of CACS from contrast-enhanced images have been proposed before. The main principle for that is generation of virtual non-contrast images by iodine subtraction from a contrast-enhanced spectral CT dataset. However, those techniques have some limitations: Dual-Source CT imaging can lead to increased radiation exposure, and switching of the tube voltage (rapid kVp switching) can be associated with slower rotation speed of the gantry and is thus prone to motion artefacts that are especially critical in cardiac imaging. Both techniques cannot simultaneously acquire spectral data. A novel technique to overcome these difficulties is spectral imaging with a dual-layer detector. After absorption of the lower energetic photons in the first layer, the second layer detects a hardened spectrum of the emitted radiation resulting in registration of two different energy spectra at the same time. The objective of the present investigation was to evaluate the accuracy of virtual non-contrast CACS computed from spectral data in comparison to standard non-contrast imaging.
关键词： virtual non-contrast data,Coronary Computed Tomography Angiography,Calcium Scoring,dual-layer spectral CT
更新于2025-09-04 15:30:14
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Near-infrared Zeeman spectroscopy for the spatially resolved measurement of helium emission spectra in Heliotron J
摘要： A passive spectroscopic method that can measure spatially resolved emission spectra only by observing from a single diagnostic port without assuming plasma symmetry was applied to the stellarator-heliotron device Heliotron J. The emission spectra from the inboard and outboard sides were separated using the difference in their Zeeman effects. On the basis of the fact that in a spectrum as a function of the wavelength, the magnitude of the wavelength splitting by the Zeeman effect relative to the Doppler broadening increases with the wavelength, the method was applied to a near-infrared helium emission line (He I 1s2s 3S?1s2p 3P, 1083 nm), and it was confirmed that the uncertainty in the separated spectra was reduced compared with that in the application to visible emission lines. From the emissivity of the separated spectra, the local recycling flux was evaluated using the inverse photon efficiency method.
关键词： Zeeman effect,plasma surface interaction,stellarator,recycling,plasma spectroscopy,tomography
更新于2025-09-04 15:30:14
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Optical coherence tomography imaging of the basal ganglia: feasibility and brief review
摘要： Optical coherence tomography (OCT) is a promising medical imaging technique that uses light to capture real-time cross-sectional images from biological tissues in micrometer resolution. Commercially available optical coherence tomography systems are employed in diverse applications, including art conservation and diagnostic medicine, notably in cardiology and ophthalmology. Application of this technology in the brain may enable distinction between white matter and gray matter, and obtainment of detailed images from within the encephalon. We present, herein, the in vivo implementation of OCT imaging in the rat brain striatum. For this, two male 60-day-old rats (Rattus norvegicus, Albinus variation, Wistar) were stereotactically implanted with guide cannulas into the striatum to guide a 2.7-French diameter high-definition OCT imaging catheter (Dragonfly, St. Jude Medical, USA). Obtained images were compared with corresponding histologically stained sections to collect imaging samples. A brief analysis of OCT technology and its current applications is also reported, as well as intra-cerebral OCT feasibility on brain mapping during neurosurgical procedures.
关键词： Basal ganglia,Optical coherence tomography (OCT),Rat brain,Histology,Thalamus,Brain imaging
更新于2025-09-04 15:30:14
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Absorbed doses in salivary and thyroid glands from panoramic radiography and cone beam computed tomography
摘要： Introduction: Panoramic radiography and cone beam computed tomography (CBCT) are very important in the diagnosis of oral diseases, however patients are exposed to the risk of ionizing radiation. This paper describes our study aimed at comparing absorbed doses in the salivary glands and thyroid due to panoramic radiography and CBCT and estimating radiation induced cancer risk associated with those methods. Methods: Absorbed doses of two CBCT equipment (i?CAT? Next Generation and SCANORA? 3D) and a digital panoramic device (ORTHOPANTOMOGRAPH? OP200D) were measured using thermoluminescent dosimeters loaded in an anthropomorphic phantom on sublingual, submandibular, parotid and thyroid glands. Results: Absorbed doses in the i?CAT? device ranged between 0.02 (+/?0.01) and 2.23 mGy (+/?0.03), in the SCANORA? device ranged from 0.01 (+/?0.01) to 2.96 mGy (+/?0.29) and in the ORTHOPANTOMOGRAPH? OP200D ranged between 0.04 mGy and 0.78 mGy. The radiation induced cancer risk was highlighted in the salivary glands, which received higher doses. The protocols that offer the highest risk of cancer are the high resolution protocols of CBCT equipment. Conclusion: CBCT exposes patients to higher levels of radiation than panoramic radiography, so the risks and benefits of each method should be considered. The doses in CBCT were dependent on equipment and exposure parameters, therefore adequate selection minimizes the radiation dose.
关键词： Radiation dose,Cone beam computed tomography,Thermoluminescent dosimetry,Panoramic radiograph
更新于2025-09-04 15:30:14
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Organ doses evaluation for chest computed tomography procedures with TL dosimeters: Comparison with Monte Carlo simulations
摘要： Purpose: To evaluate organ doses in routine and low‐dose chest computed tomography (CT) protocols using an experimental methodology. To compare experimental results with results obtained by the National Cancer Institute dosimetry system for CT (NCICT) organ dose calculator. To address the differences on organ dose measurements using tube current modulation (TCM) and fixed tube current protocols. Methods: An experimental approach to evaluate organ doses in pediatric and adult anthropomorphic phantoms using thermoluminescent dosimeters (TLDs) was employed in this study. Several analyses were performed in order to establish the best way to achieve the main results in this investigation. The protocols used in this study were selected after an analysis of patient data collected from the Institute of Radiology of the School of Medicine of the University of S?o Paulo (InRad). The image quality was evaluated by a radiologist from this institution. Six chest adult protocols and four chest pediatric protocols were evaluated. Lung doses were evaluated for the adult phantom and lung and thyroid doses were evaluated for the pediatric phantom. The irradiations were performed using both a GE and a Philips CT scanner. Finally, organ doses measured with dosimeters were compared with Monte Carlo simulations performed with NCICT. Results: After analyzing the data collected from all CT examinations performed during a period of 3 yr, the authors identified that adult and pediatric chest CT are among the most applied protocol in patients in that clinical institution, demonstrating the relevance on evaluating organ doses due to these examinations. With regards to the scan parameters adopted, the authors identified that using 80 kV instead of 120 kV for a pediatric chest routine CT, with TCM in both situations, can lead up to a 28.7% decrease on the absorbed dose. Moreover, in comparison to the standard adult protocol, which is performed with fixed mAs, TCM, and ultra low‐dose protocols resulted in dose reductions of up to 35.0% and 90.0%, respectively. Finally, the percent differences found between experimental and Monte Carlo simulated organ doses were within a 20% interval. Conclusions: The results obtained in this study measured the impact on the absorbed dose in routine chest CT by changing several scan parameters while the image quality could be potentially preserved.
关键词： Monte Carlo simulations,computed tomography,dosimetry/exposure assessment,organ dose,image quality
更新于2025-09-04 15:30:14
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Infrared microscopy in the study of cellular biochemistry
摘要： This is a personal overview of the background, motivation and objectives in the application of infrared spectromicroscopy techniques to the study of cellular biochemistry, as detailed in a presentation given at WIRMS2017. It was not the aim of the presentation, nor is it the aim of the present article, to be a systematic review of the field of biological IR microscopy. Rather, it highlights the motivation for the author to use IR microscopy in biological research, with an emphasis on experiments that address specific questions in biochemical and cellular research. It also comments on the role of conventional light sources and synchrotron radiation in these experiments and justifies the use of synchrotron light in their implementation. The synchrotron advantage for experiments on live cells is reassessed in view of recent developments in the technology of IR light sources, in particular the introduction of novel designs of mid-infrared lasers. Finally, future applications of synchrotron IR light to the field are discussed with respect to the introduction of near-field techniques for IR imaging and spectroscopy of cellular samples, such as sSNOM and AFM-IR.
关键词： Metabolism,Infrared microscopy,Tomography,Synchrotron radiation,Live cells
更新于2025-09-04 15:30:14
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Error-Splitting Forward Model for Iterative Reconstruction in X-ray Computed Tomography and application with Gauss-Markov-Potts prior
摘要： In order to enhance image quality for controlling the interior of a volume in industry, model-based iterative reconstruction (MBIR) methods in 3D X-ray Computed Tomography (CT) have shown their efficiency compared to analytical reconstruction methods. MBIR methods enforce a prior model on the volume to reconstruct and make fusion of the information contained in the prior model and the projection data. The projections have many uncertainties which have very different origins in 3D CT. They are taken into account in MBIR methods but, despite of their different origins, they are in general gathered in only one term in the forward model. In this paper, we propose to derive a new forward model by adding a further error term in the Poisson statistics of photon-count, corresponding to the deviation of the monochromatic model with respect to the actual polychromacy of the rays. A Taylor expansion of the Poisson log-likelihood leads us to a new algebraic forward model accounting for two terms of uncertainties : we call it the error-splitting forward model. Different prior models are assigned to each of distinguished uncertainties : measurement uncertainties are modeled as Gaussian, while linear model uncertainties are modeled as heavy-tailed to bring robustness to the reconstruction process. We give strategies to fix the parameters of the error-splitting forward model. Next, we use it in a full MBIR method with Gauss-Markov-Potts prior model on the volume, in order to reconstruct piecewise-constant objects for non-destructive testing in industry. Compared to the conventional forward model, we show in our experiments that the use of the error-splitting forward model with Gauss-Markov-Potts prior combines better robustness and accuracy.
关键词： 3D Computed Tomography,iterative reconstruction,Gauss-Markov-Potts,error-splitting,forward model,Bayesian approach,non-destructive testing
更新于2025-09-04 15:30:14
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PET Image Reconstruction Using Deep Image Prior
摘要： Recently deep neural networks have been widely and successfully applied in computer vision tasks and attracted growing interests in medical imaging. One barrier for the application of deep neural networks to medical imaging is the need of large amounts of prior training pairs, which is not always feasible in clinical practice. This is especially true for medical image reconstruction problems, where raw data are needed. Inspired by the deep image prior framework, in this work we proposed a personalized network training method where no prior training pairs are needed, but only the patient’ own prior information. The network is updated during the iterative reconstruction process using the patient specific prior information and measured data. We formulated the maximum likelihood estimation as a constrained optimization problem and solved it using the alternating direction method of multipliers (ADMM) algorithm. Magnetic resonance imaging (MRI) guided Positron emission tomography (PET) reconstruction was employed as an example to demonstrate the effectiveness of the proposed framework. Quantification results based on simulation and real data show that the proposed reconstruction framework can outperform Gaussian post-smoothing and anatomically-guided reconstructions using the kernel method or the neural network penalty.
关键词： positron emission tomography,unsupervised learning,Medical image reconstruction,deep neural network
更新于2025-09-04 15:30:14
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Progression of retinitis pigmentosa on multimodal imaging: the PREP‐1 study
摘要： Importance: It is important to establish reliable outcome measures to detect progression in retinitis pigmentosa (RP). Background: To evaluate progression of RP using multimodal imaging, including spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence (FAF) and microperimetry (MP). Design: Retrospective longitudinal study at a tertiary teaching hospital. Participants: 205 eyes of 106 patients with RP with 1-5 years of follow-up. Methods: Demographics and visual acuity (VA) were recorded, and each modality was graded at baseline and every annual follow-up. SD-OCT was graded for the width of ellipsoid zone (EZ), FAF was graded for the diameter and area of the hyperautofluorescent ring (if present), and MP was graded for mean, central and paracentral sensitivity. Spearman’s correlation was used to measure correlations at baseline. Mixed effects models were used to estimate the annual change of each parameter, adjusted for disease duration. Main outcome measures: Rate of progression. Results: The median VA at baseline was 75 letters and was positively correlated with mean and central sensitivity (r: 0.372 and 0.394; p=0.01 for both). All parameters (except paracentral sensitivity) were strongly correlated with each other (r: 0.673-0.991; p<0.001 for all). The annual rates of change for each parameter were as follows: VA, -2.3 letters (p<0.001); EZ, -151um (p<0.001); ring diameter, -132um (p<0.001); ring area, -0.4mm2 (p<0.001); mean sensitivity, -0.3 dB (p<0.001); central sensitivity, -0.7 dB (p<0.001); paracentral sensitivity, -0.4 dB (p<0.001). Conclusion and relevance: Structural and functional measures are well correlated in RP and can reliable measure disease progression within the course of a year.
关键词： Optical Coherence Tomography,Multimodal Imaging,Microperimetry,Fundus Autofluorescence,Disease Progression
更新于2025-09-04 15:30:14
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Intraoperative detection of blood vessels with an imaging needle during neurosurgery in humans
摘要： Intracranial hemorrhage can be a devastating complication associated with needle biopsies of the brain. Hemorrhage can occur to vessels located adjacent to the biopsy needle as tissue is aspirated into the needle and removed. No intraoperative technology exists to reliably identify blood vessels that are at risk of damage. To address this problem, we developed an “imaging needle” that can visualize nearby blood vessels in real time. The imaging needle contains a miniaturized optical coherence tomography probe that allows differentiation of blood flow and tissue. In 11 patients, we were able to intraoperatively detect blood vessels (diameter, >500 mm) with a sensitivity of 91.2% and a specificity of 97.7%. This is the first reported use of an optical coherence tomography needle probe in human brain in vivo. These results suggest that imaging needles may serve as a valuable tool in a range of neurosurgical needle interventions.
关键词： intracranial hemorrhage,optical coherence tomography,neurosurgery,blood vessel detection,imaging needle
更新于2025-09-04 15:30:14