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Hybrid anatomo-functional imaging of coronary artery disease: Beneficial irrespective of its core components
摘要： Coronary artery disease (CAD) is the most common and important cause of ischemic heart disease, with major implications on global morbidity and mortality. Non-invasive testing is crucial in the diagnostic and prognostic work-up of patients with or at risk of CAD, and also to guide decision making in terms of pharmacologic and revascularization therapy. The traditional paradigm is to view anatomic (i.e., coronary computed tomography) and functional imaging (e.g., myocardial perfusion scintigraphy) tests as opposing alternatives. Such approach is too reductionist and does not capitalize on the strengths of each type of test while risking to overlook the inherent limitations. The combination of anatomic and functional tests in a logic of hybrid imaging holds the promise of overcoming the limitations inherent to anatomic and functional testing, enabling more accurate diagnosis, prognosis, and guidance for revascularization in patients with CAD.
关键词： hybrid imaging,single-photon emission computed tomography,computed tomography,Coronary artery disease
更新于2025-09-04 15:30:14
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Synthesis of gadolinium-based Bi<sub>2</sub>S<sub>3</sub> nanoparticles as cancer theranostics for dual-modality computed tomography /magnetic resonance imaging-guided photothermal therapy
摘要： Development of a safe, efficient and inexpensive multifunctional nanoplatform using a facile approach for multimodal imaging and therapeutic functions becomes more and more practically relevant but challenging. In this work, we demonstrated a novel nanocomposites (Bi2S3-Gd) for computed tomography (CT)/magnetic resonance (MR) imaging-guided photothermal therapy for cancer in vitro. It was achieved by modification of hydrophobic Bi2S3 with a smart amphiphilic gadolinium-chelated ligand. The as-prepared nanocomposites composed of low cost Bi2S3 and gadolinium complexes, showed high stability, excellent biocompatibility and good photostability. It was observed that Bi2S3-Gd nanocomposites can efficiently convert the NIR light into heat, and then suppressed the growth of tumor cells under NIR laser irradiation. Apart from serving as an effective photothermal agent, the as-prepared nanomaterials could induce an efficient contrast enhancement for both CT and MRI imaging at low concentrations of Bi and Gd, rendering more accurate diagnosis. This work suggests the potential of Bi2S3-Gd nanomaterials as a novel multifunctional nanoplatform for CT/MRI imaging-guided photothermal therapy for cancer.
关键词： photothermal therapy,magnetic resonance imaging,Bismuth sulfide,amphiphilic ligand,computed tomography imaging
更新于2025-09-04 15:30:14
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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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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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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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DukeSim: A realistic, rapid, and scanner-specific simulation framework in computed tomography
摘要： The purpose of this study was to develop a CT simulation platform that is 1) compatible with voxel-based computational phantoms, 2) capable of modeling the geometry and physics of commercial CT scanners, and 3) computationally efficient. Such a simulation platform is designed to enable the virtual evaluation and optimization of CT protocols and parameters for achieving a targeted image quality while reducing radiation dose. Given a voxelized computational phantom and a parameter file describing the desired scanner and protocol, the developed platform DukeSim calculates projection images using a combination of ray-tracing and Monte Carlo techniques. DukeSim includes detailed models for the detector quantum efficiency, quantum and electronic noise, detector crosstalk, subsampling of the detector and focal spot areas, focal spot wobbling, and the bowtie filter. DukeSim was accelerated using GPU computing. The platform was validated using physical and computational versions of a phantom (Mercury phantom). Clinical and simulated CT scans of the phantom were acquired at multiple dose levels using a commercial CT scanner (Somatom Definition Flash; Siemens Healthcare). The real and simulated images were compared in terms of image contrast, noise magnitude, noise texture, and spatial resolution. The relative error between the clinical and simulated images was less than 1.4%, 0.5%, 2.6%, and 3%, for image contrast, noise magnitude, noise texture, and spatial resolution, respectively, demonstrating the high realism of DukeSim. The runtime, dependent on the imaging task and the hardware, was approximately 2-3 minutes per rotation in our study using a computer with 4 GPUs. DukeSim, when combined with realistic human phantoms, provides the necessary toolset with which to perform large-scale and realistic virtual clinical trials in a patient and scanner-specific manner.
关键词： simulation,ray tracing,monte carlo,computational human phantoms,computed tomography,virtual clinical trial,in silico modeling,CT simulator
更新于2025-09-04 15:30:14
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The abilities of three Nickel‐Titanium mechanized systems to negotiate and shape <scp>MB</scp> 2 canals in extracted maxillary first molars. A Micro‐Computed Tomographic study
摘要： Aim To evaluate the influence of three engine-driven NiTi file systems manufactured with different NiTi alloys for the preparation of second mesiobuccal (MB2) canals in extracted maxillary first molars using a micro-computed tomography scanner (Micro-CT). Methodology Thirty maxillary molars with two canals in the mesiobuccal root were selected and randomly divided into 3 groups (n=10): Reciproc [REC; size 25, .08 taper; VDW, Munich, Germany], Prodesign R [PDR; size 25, .06 taper; Easy, Belo Horizonte, Brazil] and Mtwo [MO; size25, .06 taper; VDW, Munich, Germany]. Before and after root canal preparation of the MB2 canal, the teeth were scanned using a Micro-CT to evaluate canal transportation, centering ability, dentine thickness and volume change. The working time to achieve working length was also evaluated. All parameters were compared statistically using the Kruskal-Wallis and Dunn test for multiple comparisons, with a significance level of 5%. Results There was no significant difference among the groups regarding canal transportation and centering ability (P>0.05). However, the PDR size 25, .06 taper group had significantly lower canal volume and volume of dentine removal compared with a MO size 25, .06 taper and REC size 25, .06 taper (P<0.05). A root perforation was detected in MO size 25, .06 taper and REC size 25, .06 taper groups, respectively. Regarding the working time, the PDR size 25, .06 taper required a significantly longer time to achieve working length than MO size 25, .06 taper and REC size 25, .08 taper (P<0.05). Conclusions All NiTi systems had similar canal transportation, centering ability and increase of apical volume after preparation of MB2 canals. However, the PDR size 25, .06 taper had less volume of dentine removal, absence of root canal perforation and required a longer time to accomplish the root canal preparation.
关键词： controlled memory wire,micro-computed tomography,root canal treatment,Apical transportation
更新于2025-09-04 15:30:14
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I'm Not Sure What Bothers Me in this Chest X-Ray but an HRCT May Help?
摘要： There are some inevitable risk factors of patient exposure to problems arising from human errors, including missed subtle radiological findings, early identification of which may alter the patient outcomes. Here we are discussing a patient who presented with a prior diagnosis of seasonal allergic rhinitis with symptoms assumed to be bronchial asthma. A second review of chest radiograph after discussion over an online platform (Tabula Rasa group on Facebook) revealed some subtle findings which we missed initially. Further work-up of the case revealed some astonishing findings. This case illustrates the importance of discussing unsolved cases on online platforms with peers and also to proceed for higher imaging to detect what has been missed on plain radiography.
关键词： chest X ray,high resolution computed tomography,subtle findings
更新于2025-09-04 15:30:14
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Detection of gallbladder stones by dual-energy spectral computed tomography imaging
摘要： AIM: To evaluate the detectability of gallbladder stones by dual-energy spectral computed tomography (CT) imaging. METHODS: Totally 217 patients with surgically confirmed gallbladder stones were retrospectively analyzed who underwent single-source dual-energy CT scanning from August 2011 to December 2013. Polychromatic images were acquired. And post-processing software was used to reconstruct monochromatic (40 keV and 140 keV) images, and calcium-lipid pair-wise base substance was selected to acquire calcium base images and lipid base images. The above 5 groups of images were evaluated by two radiologists separately with 10-year experience in CT image reading. In the 5 groups of images, the cases in the positive group and negative group were counted and then the detection rate was calculated. The inter-observer agreement on the scoring results was analyzed by Kappa test, and the scoring results were analyzed by Wilcoxon test, with P < 0.05 indicating that the difference was statistically significant. The stone detection results of the 5 groups of images were analyzed by χ2 test. RESULTS: There was good inter-observer agreement (k = 0.772). In 217 patients with gallbladder stones, there was a statistically significant difference in stone visualization between spectral images (40 keV, 140 keV, calcium base and lipid base images) and polychromatic images (P < 0.05). 40 keV monochromatic images were better than 140 keV monochromatic images (4.90 ± 0.35 vs 4.53 ± 1.15, P < 0.05), and calcium base images were superior to lipid base images (4.91 ± 0.43 vs 4.77 ± 0.63, P < 0.05), but there was no statistically significant difference between 40 keV monochromatic images and calcium base images (4.90 ± 0.35 vs 4.91 ± 0.43, P > 0.05). In 217 gallbladder stone patients, there were 21, 3, 28, 5 and 12 negative stone cases in polychromatic images, 40 keV images, 140 keV images, calcium base images and lipid base images, respectively, and the differences among the five groups were statistically significant (P < 0.05). CONCLUSION: Monochromatic images and base substance images have a good clinical prospect in the iso-density stone detection.
关键词： Gallbladder stone,Spectral imaging,Computed tomography
更新于2025-09-04 15:30:14