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Quantification of image artifacts from navigation markers in dynamic guided implant surgery and the effect on registration performance in different clinical scenarios
摘要： Purpose: Different navigation markers in dynamic guided implant surgery could cause different degrees of artifacts, which would affect the accuracy and efficiency of the implant navigation system. This study aimed to quantify artifacts caused by navigation markers made of different materials and to evaluate their effects on registration accuracy under various oral conditions. Materials and Methods: Four U-shaped tubes with different navigation markers (440c stainless steel, silicon nitride, zirconium oxide, and aluminium oxide) were produced by three-dimensional printing. Four kinds of maxillary plaster models were prepared to stimulate four tooth crown conditions. U-shaped tubes combined with different tooth models were scanned using cone beam computed tomography (CBCT). The size of artifacts from different navigation markers and registration rate were measured. Abrasion performance of navigation markers was evaluated by scanning electron microscopy (SEM) images. Results: Aluminium oxide navigation markers showed the fewest artifacts. Silicon nitride markers caused fewer artifacts than zirconium oxide and 440c stainless steel ones (P < .05) and had the best registration performance under all tooth crown conditions with the lowest volume of abrasion. Registration data suggested aluminium oxide worked badly under artificial crown and natural tooth conditions for its lower radiopacity, and zirconium oxide worked undesirably in edentulous conditions. 440c stainless steel was worst in all dental conditions. Conclusion: Navigation markers made of silicon nitride have the best overall performance and perform the best in registration under all circumstances owing to less artifact generation, better radiopacity, and desirable abrasion resistance. Silicon nitride can be regarded as an ideal material, including but not limited to oral implant navigator-guided surgery.
关键词： Dental implants,Navigation marker,Cone-Beam Computed Tomography,Artefacts,Dynamic guided,Registration
更新于2025-09-09 09:28:46
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Evaluation of vascular changes in intermediate uveitis and retinal vasculitis using swept-source wide-field optical coherence tomography angiography
摘要： Purpose To evaluate vascular changes in patients with intermediate uveitis with or without retinal vasculitis using swept-source wide-field optical coherence tomography angiography (OCTA). Methods This is a prospective cross-sectional study. Consecutive patients with intermediate uveitis were evaluated using wide-field OCTA. Wide-field OCTA and en-face OCT images were analysed for the presence of capillary non-perfusion and reduced perfusion, disruption of ellipsoid zone, and abnormalities on en-face wide-field retinal thickness maps, respectively, and compared with fluorescein angiography (FA) findings in a subcohort. results 164 eyes of 88 patients with intermediate uveitis were included. Areas of capillary non-perfusion and reduced perfusion were more frequently observed in the choroidal OCTA slab (33.3% and 49.4%), choriocapillaris (CC; 31.4% and 48%) and deep capillary plexus (DCP; 9.6% and 34.6%) than in the superficial capillary plexus (SCP; 5% and 26.3%), respectively. Intermediate uveitis with vasculitis presented more frequently with non-perfusion and hypoperfusion in the DCP (p=0.003 and p=0.05, respectively) and SCP (p=0.007 and p=0.005, respectively) than intermediate uveitis without vasculitis. Peripheral capillary leakage on FA correlated with the presence of perivascular, macular and generalised thickening on en-face wide-field thickness maps (p=0.007). Ischaemia on FA was significantly associated with non-perfusion on wide-field OCTA in SCP and DCP (p=0.019 and p=0.027, respectively). Conclusion Changes in the choroid, CC and DCP are more frequently found than in the SCP on wide-field OCTA in intermediate uveitis. While wide-field OCTA is a reliable tool to detect capillary non-perfusion in intermediate uveitis, it was not helpful in determining disease activity. Trial registration number NCT02811536.
关键词： vascular changes,swept-source wide-field optical coherence tomography angiography,retinal vasculitis,intermediate uveitis
更新于2025-09-09 09:28:46
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Exploring the Capability of HAADF-STEM Techniques to Characterize Graphene Distribution in Nanocomposites by Simulations
摘要： This paper explores the capability of scanning transmission electron microscopy (STEM) techniques in determining the dispersion degree of graphene layers within the carbon matrix by using simulated high-angle annular dark-field (HAADF) images. Results ensure that unmarked graphene layers are only detectable if their orientation is parallel to the microscope beam. Additionally, gold-marked graphene layers allow evaluating the dispersion degree in structural composites. Moreover, electron tomography has been demonstrated to provide truthfully 3D distribution of the graphene sheets inside the matrix when an appropriate reconstruction algorithm and 2D projections including channelling effect are used.
关键词： HAADF-STEM,electron tomography,nanocomposites,dispersion degree,graphene
更新于2025-09-08 09:54:54
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Inter-relationship between retinal and choroidal vasculatures using optical coherence tomography angiography in normal eyes
摘要： Purpose: To quantify vascular and structural macular variables in healthy eyes and to investigate correlations between these variables and age using optical coherence tomography angiography. Materials and methods: A total of 261 eyes of 261 subjects with normal fundus were included. Central macular thickness, ganglion cell layer to inner plexiform layer thickness, outer retina layer thickness, subfoveal choroidal thickness, and choroidal vascularity index were measured using optical coherence tomography. Foveal avascular zone area, vascular density, and flow void area were measured using optical coherence tomography angiography. Results: Vascular density in the superficial capillary plexus was correlated with central macular thickness, ganglion cell layer to inner plexiform layer thickness, and outer retina layer thickness (P < 0.001, P = 0.004, and P < 0.001, respectively). Vascular density in the deep capillary plexus was correlated with central macular thickness and outer retina layer thickness (P = 0.003 and P = 0.001, respectively). Vascular density of choriocapillaris was correlated with vascular density of superficial capillary plexus and deep capillary plexus (P < 0.001 and P = 0.001, respectively). Conclusion: Vascular density of choriocapillaris varies with retinal vascular density rather than the structure of choroid using optical coherence tomography angiography. In contrast, retinal vascular density changes as the retinal structure. Our results provide more information about the relationship between retina and choroid.
关键词： choroidal vessels,optical coherence tomography,optical coherence tomography angiography,Retinal vessels,normal eye
更新于2025-09-04 15:30:14
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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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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow, Poland (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Medical applications of electrical tomography
摘要： While electrical capacitance tomography (ECT) and electrical impedance tomography (EIT) have found many successful industrial applications, only recently, research into medical applications of ECT and EIT were carried out at University of Manchester and Chiba University, including (1) Visualization of tooth surface by ECT for tooth canal treatment, (2) Visualization by ECT and EIT for revision hip replacement surgery, (3) Microfluidics for cell sensing and manipulation, (4) Imaging clots in blood flows and (5) Non-intrusive diagnosis of lymph problems. This paper will review the above medical applications of electrical tomography, from necessity of the work or problems to be addressed, sensing principles, experiment arrangement to some initial results. In addition, other research related to medical application of electrical tomography will also be briefly reviewed, such as by Swisstom AG in Switzerland, Dartmouth College in USA and some universities in China.
关键词： medical application,electrical capacitance tomography,electrical impedance tomography
更新于2025-09-04 15:30:14
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Ability of Swept-Source Optical Coherence Tomography to Detect Retinal and Choroidal Changes in Patients with Multiple Sclerosis
摘要： Purpose. To evaluate the ability of new swept-source (SS) optical coherence tomography (OCT) technology to detect changes in retinal and choroidal thickness in patients with multiple sclerosis (MS). Methods. A total of 101 healthy and 97 MS eyes underwent retinal and choroidal assessment using SS Triton OCT (Topcon). Macular thickness and peripapillary data (retinal, ganglion cell layer (GCL+, GCL++) and retinal nerve fiber layer (RNFL) thickness) were analyzed, including choroidal thickness evaluation. Results. Significant macular thinning was observed in all ETDRS areas (p < 0.001) in MS patients. Peripapillary retinal, RNFL, and GCL ++ thickness showed a significant reduction in patients in all sectors (p < 0.001) except in the nasal quadrant/sector (p > 0.05). GCL+ measurements were found to be reduced in the nasal (p = 0.003), inferonasal (p = 0.045), and temporal (p = 0.001) sectors and total thickness (p < 0.001). Choroidal thickness was reduced in the outer macular ring in MS patients compared with controls (p = 0.038). Conclusion. New swept-source technology for OCT devices detects retinal thinning in MS patients, providing increased depth analysis of the choroid in these patients. MS patients present reduced retinal and choroidal thickness in the macular area and reduced peripapillary retinal, RNFL, and GCL thickness.
关键词： ganglion cell layer,choroidal thickness,retinal thickness,retinal nerve fiber layer,swept-source optical coherence tomography,multiple sclerosis
更新于2025-09-04 15:30:14
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Multifractal and Lacunarity Analyses of Microvascular Morphology in Eyes with Diabetic Retinopathy: A Projection Artifact Resolved Optical Coherence Tomography Angiography Study
摘要： Objective: To evaluate the degree of microvascular impairment in diabetic retinopathy using multifractal and lacunarity analyses and to compare the diagnostic ability between traditional Euclidean measures (fovea avascular zone area and vessel density) and fractal geometric features. Methods: This retrospective cross-sectional study included a total of 143 eyes of 94 patients with different stages of diabetic retinopathy. The retinal microvasculature was imaged by projection removed optical coherence tomography angiography. We examined the degree of association between fractal metrics of the retinal microvasculature and diabetic retinopathy severity. The area under the receiver operating characteristic curve was used to estimate the diagnostic performance. Results: With increasing diabetic retinopathy severity, the multifractal spectrum shifted towards the left bottom and exhibited less left skewness and asymmetry. The vessel density, multifractal features and lacunarity measured from the deep capillary plexus were strongly associated with diabetic retinopathy severity. The multifractal feature D5 showed the highest diagnostic ability. The combination of multifractal features further improved the discriminating power. Conclusions: Multifractal and lacunarity analyses can be potentially valuable tools for assessment of microvascular impairments in diabetic retinopathy. Multifractal geometric parameters exhibit a better discriminatory performance than Euclidean measures, particularly for detection of the early stages of diabetic retinopathy.
关键词： diabetic retinopathy,optical coherence tomography angiography,microvascular network,lacunarity,multifractal
更新于2025-09-04 15:30:14
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Quantitative Fundus Autofluorescence and Optical Coherence Tomography in <i>ABCA4</i> Carriers
摘要： PURPOSE. To assess whether carriers of ABCA4 mutations have increased RPE lipofuscin levels based on quantitative fundus auto?uorescence (qAF) and whether spectral-domain optical coherence tomography (SD-OCT) reveals structural abnormalities in this cohort. METHODS. Seventy-?ve individuals who are heterozygous for ABCA4 mutations (mean age, 47.3 years; range, 9–82 years) were recruited as family members of affected patients from 46 unrelated families. For comparison, 57 affected family members with biallelic ABCA4 mutations (mean age, 23.4 years; range, 6–67 years) and two noncarrier siblings were also enrolled. Auto?uorescence images (308, 488-nm excitation) were acquired with a confocal scanning laser ophthalmoscope equipped with an internal ?uorescent reference. The gray levels (GLs) of each image were calibrated to the reference, zero GL, magni?cation, and normative optical media density to yield qAF. Horizontal SD-OCT scans through the fovea were obtained and the thicknesses of the outer retinal layers were measured. RESULTS. In 60 of 65 carriers of ABCA4 mutations (age range, 9–60), qAF levels were within normal limits (95% con?dence level) observed for healthy noncarrier subjects, while qAF levels of affected family members were signi?cantly increased. Perifoveal ?eck-like abnormalities were observed in fundus AF images in four carriers, and corresponding changes were detected in the outer retinal layers in SD-OCT scans. Thicknesses of the outer retinal layers were within the normal range. CONCLUSIONS. With few exceptions, individuals heterozygous for ABCA4 mutations and between the ages of 9 and 60 years do not present with elevated qAF. In a small number of carriers, perifoveal ?eck-like changes were visible.
关键词： heterozygous carrier,retinal pigment epithelium,lipofuscin,recessive Stargardt disease,optical coherence tomography,quantitative fundus auto?uorescence,Abca4,scanning laser ophthalmoscope
更新于2025-09-04 15:30:14
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Longitudinal Associations Between Microstructural Changes and Microperimetry in the Early Stages of Age-Related Macular Degeneration
摘要： PURPOSE. To determine whether longitudinal changes in mesopic visual function on microperimetry occurred independent of its associations with microstructural parameters on spectral-domain optical coherence tomography (SD-OCT) in the early stages of AMD. METHODS. Forty-one AMD eyes underwent microperimetry testing and SD-OCT scans over a 12-month period at 6-month intervals. Microstructural parameters analyzed include the retinal pigment epithelium-drusen complex (RPEDC) layer thickness, number of hyperre?ective foci (HF) and their inner retinal migration (represented by a weighted axial distribution score; AxD), and the number of atrophic areas. RESULTS. Microperimetric sensitivity was 0.29 dB (95% con?dence interval [CI] ? (cid:2)0.38 to (cid:2)0.20 dB, P < 0.001) and 0.13 dB (95% CI ? (cid:2)0.22 to (cid:2)0.03 dB, P ? 0.008) lower in each sector for every 10-lm higher RPEDC layer thickness and 1-HF present, but was not associated with the AxD score or the number of atrophic areas present (P (cid:3) 0.464). However, each 10- lm greater RPEDC layer thickness and 1-HF present was not independently associated with a further decline in sensitivity ((cid:2)0.08 dB/year, 95% CI ? (cid:2)0.24 to 0.07 dB/year, P ? 0.288 and 0.09 dB/year, 95% CI ? (cid:2)0.06 to 0.24 dB/year, P ? 0.242, respectively) over time when accounting for the association between RPEDC layer thickness and number of HF with microperimetric sensitivity. CONCLUSIONS. Longitudinal changes in mesopic visual function measured on microperimetry paralleled changes in the microstructural changes over a 12-month time frame, without any changes occurring independent of the associations between structure and function alone.
关键词： age-related macular degeneration,optical coherence tomography,microperimetry,longitudinal
更新于2025-09-04 15:30:14