Series Of Cross-sectional Images Research Articles

Comparative analysis of alignment algorithms for macular optical coherence tomography imaging

BackgroundOptical coherence tomography (OCT) is the most important and commonly utilized imaging modality in ophthalmology and is especially crucial for the diagnosis and management of macular diseases. Each OCT volume is typically only available as a series of cross-sectional images (B-scans) that are accessible through proprietary software programs which accompany the OCT machines. To maximize the potential of OCT imaging for machine learning purposes, each OCT image should be analyzed en bloc as a 3D volume, which requires aligning all the cross-sectional images within a particular volume.MethodsA dataset of OCT B-scans obtained from 48 age-related macular degeneration (AMD) patients and 50 normal controls was used to evaluate five registration algorithms. After alignment of B-scans from each patient, an en face surface map was created to measure the registration quality, based on an automatically generated Laplace difference of the surface map–the smoother the surface map, the smaller the average Laplace difference. To demonstrate the usefulness of B-scan alignment, we trained a 3D convolutional neural network (CNN) to detect age-related macular degeneration (AMD) on OCT images and compared the performance of the model with and without B-scan alignment.ResultsThe mean Laplace difference of the surface map before registration was 27 ± 4.2 pixels for the AMD group and 26.6 ± 4 pixels for the control group. After alignment, the smoothness of the surface map was improved, with a mean Laplace difference of 5.5 ± 2.7 pixels for Advanced Normalization Tools Symmetric image Normalization (ANTs-SyN) registration algorithm in the AMD group and a mean Laplace difference of 4.3 ± 1.4.2 pixels for ANTs in the control group. Our 3D CNN achieved superior performance in detecting AMD, when aligned OCT B-scans were used (AUC 0.95 aligned vs. 0.89 unaligned).ConclusionsWe introduced a novel metric to quantify OCT B-scan alignment and compared the effectiveness of five alignment algorithms. We confirmed that alignment could be improved in a statistically significant manner with readily available alignment algorithms that are available to the public, and the ANTs algorithm provided the most robust performance overall. We further demonstrated that alignment of OCT B-scans will likely be useful for training 3D CNN models.

Development and validation of an intuitive biomechanics-based method for intraocular pressure measurement: a modal analysis approach

BackgroundCurrent intraocular pressure (IOP) measurements based on non-contact tonometry are derived from statistics-driven equations and lack biomechanical significance, which often leads to under-estimation in post-refractive surgery cornea. This study aims to introduce and validate modal analysis-derived intraocular pressure (mIOP) as a novel method generated through Legendre-based modal decomposition of the anterior corneal contour; it provides an accurate and intuitive IOP measurement from an energy-based perspective.MethodsThis retrospective study included 680 patients. Healthy participants were divided into reference (n = 385) and validation (n = 142) datasets, and the others underwent either femtosecond-assisted laser in situ keratomileusis (FS-LASIK, n = 58) or transepithelial photorefractive keratectomy (TPRK, n = 55). Corneal curvature of the right eyes was extracted from raw serial cross-sectional images of the cornea generated by Corvis ST, a noncontact tonometer with a high-speed Scheimpflug-camera. Legendre expansion was then applied to the corneal curvature to obtain the modal profiles (i.e., temporal changes of the coefficient for each basis polynomial [modes]). Using the reference dataset, feature selection on the modal profiles generated a final mIOP model consisting of a single parameter: total area under curve (frames 1–140) divided by the area under curve of the rising phase (frames 24–40) in the fourth mode, i.e. the M4 ratio. Validation was performed in both the healthy validation and postoperative datasets. IOP-Corvis, pachymetry-corrected IOP, biomechanically corrected IOP, and mIOP values were compared. For the FS-LASIK and TPRK groups, pairwise postoperative IOP changes were analyzed through repeated measures analysis of variance, and agreement was examined through Bland–Altman analysis. Using a finite element analysis based three-dimensional model of the human cornea, we further compared the M4 ratio with the true intraocular pressure within the physiological range.ResultsThe M4 ratio-based mIOP demonstrated weak to negligible association with age, radius of corneal curvature, and central corneal thickness (CCT) in all validation analyses, and performed comparably with biomechanically corrected IOP (bIOP) in the refractive surgery groups. Both remained nearly constant postoperatively and were not influenced by CCT changes. Additionally, M4 ratio accurately represented true intraocular pressure in the in silico model.ConclusionsmIOP is a reliable IOP measurement in healthy and postrefractive surgery populations. This energy-based, ratio-derived approach effectively filters out pathological, rotational, misaligned movements and serves as an interpatient self-calibration index. Modal analysis of corneal deformation dynamics provides novel insights into regional corneal responses against pressure loading.

Modeling the musculoskeletal system of an insect thorax for flapping flight

Indirect actuation of the wings via thoracic deformation is a unique mechanism widely observed in flying insect species. The physical properties of the thorax have been intensively studied in terms of their ability to efficiently generate wingbeats. The basic mechanism of indirect wing actuation is generally explained as a lever model on a cross-sectional plane, where the dorsoventral movement of the mesonotum (dorsal exoskeleton of the mesothorax) generated by contractions of indirect muscles actuates the wing. However, the model considers the mesonotum as an ideal flat plane, whereas the mesonotum is hemispherical and becomes locally deformed during flight. Furthermore, the conventional model is two-dimensional; therefore, three-dimensional wing kinematics by indirect muscles have not been studied to date. In this study, we develop structural models of the mesonotum and mesothorax of the hawkmoth Agrius convolvuli, reconstructed from serial cross-sectional images. External forces are applied to the models to mimic muscle contraction, and mesonotum deformation and wing trajectories are analyzed using finite element analysis. We find that applying longitudinal strain to the mesonotum to mimic strain by depressor muscle contraction reproduces local deformation comparable to that of the thorax during flight. Furthermore, the phase difference of the forces applied to the depressor and elevator muscles changes the wing trajectory from a figure eight to a circle, which is qualitatively consistent with the tethered flight experiment. These results indicate that the local deformation of the mesonotum due to its morphology and the thoracic deformation via indirect power muscles can modulate three-dimensional wing trajectories.

Distance between the center of the FAZ measured automatically and the highest foveal bulge using OCT-angiography in elderly healthy eyes

The center of the fovea, termed the foveola, is the area of highest visual acuity, has the highest density of cone photoreceptors. We investigated the distance between the automatically-determined center of the foveal avascular zone (FAZ) and the manually-determined highest foveal bulge (FB) point using single swept-source optical coherence tomography angiography (OCTA) instrument. This cross-sectional study included 49 eyes of 49 individuals (34 women and 15 men; median age: 68 years) with no history of ocular disorders. The FAZ in the superficial capillary plexus was automatically determined using the Kanno–Saitama macro method, and the center of the FAZ was automatically determined using ellipse approximation. Another candidate foveal center, the highest FB point, was determined manually on the serial cross-sectional B-scan images. As a result, the foveal center was manually identified as the highest FB point on B-scan OCTA images. The center of the FAZ was more likely to be located inferior to the highest FB point (p = 0.031). In participants with a total (linear) distance of more than 50 μm between the center of the FAZ and the highest FB point, the displacement was significantly more in the horizontal direction than in the vertical direction (p = 0.017). These results can be applicable to further studies regarding the spatial relationships between the center of the FAZ and the highest FB point in various macular diseases or previously-treated eyes.

Sono-angiography for dialysis vascular access based on the freehand 2D ultrasound scanning.

Dialysis vascular access, preferably an autogenous arteriovenous fistula, remains an end stage renal disease (ESRD) patient's lifeline providing a means of connecting the patient to the dialysis machine. Once an access is created, the current gold standard of care for maintenance of vascular access is angiography and angioplasty to treat stenosis. While point of care 2D ultrasound has been used to detect access problems, we sought to reproduce angiographic results comparable to the gold standard angiogram (fistulogram) using ultrasound data acquired from a conventional 2D ultrasound scanner. A 2D ultrasound probe was used to acquire a series of cross sectional images of the vascular access including arteriovenous anastomosis of a subject with a radio-cephalic fistula. These 2D B-mode images were used for 3D vessel reconstruction by binary thresholding to categorize vascular versus non-vascular structures followed by standard image segmentation to select the structure representative of dialysis vascular access and morphologic filtering. Image processing was done using open source Python Software. The open source software was able to: (1) view the gold standard fistulogram images, (2) reconstruct 2D planar images of the fistula from ultrasound data as viewed from the top, analogous to computerized tomography images, and (3) construct a 2D representation of vascular access similar to the angiogram. We present a simple approach to obtain an angiogram-like representation of the vascular access from readily available, non-proprietary 2D ultrasound data in the point of care setting. While the sono-angiogram is not intended to replace angiography, it may be useful in providing 3D imaging at the point of care in the dialysis unit, outpatient clinic, or for pre-operative planning for interventional procedures. Future work will focus on improving the robustness and quality of the imaging data while preserving the straightforward freehand approach used for ultrasound data acquisition.

Serial cross-sectional images of the perilymphatic and endolymphatic spaces simulating delayed contrast-enhanced inner-ear MRI

Serial cross-sectional images of the perilymphatic and endolymphatic spaces simulating delayed contrast-enhanced inner-ear MRI

Effect of Manufacturing Process on Micro-Deformation Behavior of Sintered-Silver Die-Attach Material

Effects of pressurization and thermal-processing conditions on the deformation properties of sintered-silver sheets, excluding the contribution of the voids, (hereinafter, referred to as “micro-deformation properties”) were evaluated. Three types of thin-plate specimen sintered under the different conditions were prepared and these micro-deformation properties were compared. The first type was pressurized at 10 MPa for 10 min in the atmosphere at 573 K, the second type was annealed at 573 K for six hours before pressure processing and pressurized at 10 MPa for 10 min in the atmosphere at 573 K, and the third type was not pressurized and sintering in the atmosphere at 573 K for 10 min. The micro-deformation properties of these specimens were estimated by tensile testing and finite-element analysis (FEA) using a model that reproduces the microporous-structure. The microporous-structure models were made from serial cross-sectional images obtained by focused-ion-beam scanning electron microscope. These estimation results indicate that the micro-deformation properties of sintered-silver sheets do not depend on pressure, but on thermal-process conditions. The estimated micro-deformation properties were compared with those determined by nanoindentation tests and the validity of the estimated micro-deformation properties was confirmed. A deformation property of non-pressurized specimens was predicted by using the estimated micro-deformation properties and the microporous structures obtained from the pressurized specimens. The predicted deformation properties corresponded to experimental one. It is therefore concluded that if the deformation properties and microporous-structure of a sintered-silver specimen under a certain condition are determined, it is possible to predict the porosity dependency of deformation properties by FEA.

Investigation of characteristics and responses of insulating cement paste specimens with Aer solids using X-ray micro-computed tomography

Insulating concrete is a type of material designed to enhance energy efficiency by reducing thermal conductivity. It contains numerous voids induced by the use of air-entraining admixtures or aggregates, and these voids strongly affect the characteristics and responses of the material. Thus, appropriate methods to examine the void distribution of materials are needed. Here, X-ray micro-computed tomography (micro-CT) is adopted to investigate the spatial distribution of voids in a material without destroying the specimen. By using micro-CT, a series of cross-sectional images with the micrometer range pixel size can be obtained. Then, void density contour and probabilistic description methods, such as two-point correlation and lineal-path functions, are used to describe the void distribution inside the specimen. In this study, Aer solids, small prefabricated hollow air bubbles, are used for insulating cement paste specimens to increase the insulating effect. The cement paste specimens with different void ratios and Aer solids are generated, and their void distribution characteristics are investigated using the methods mentioned above. The thermal and mechanical responses of the insulating specimens are also evaluated by experiments and numerical methods. The effect of Aer solids on the material characteristics and the relationship between void distribution and material responses are confirmed from the obtained results.

Aggregate representation for mesostructure of stone based materials using a sphere growth model based on realistic aggregate shapes

The objectives of this study are: (1) to create aggregate representations based on their realistic shapes and establish an aggregate shape library by storing aggregate numerical representations of various shapes and angularities; and (2) to prepare mesostructure models for stone based materials using aggregate representations from the library. The numerical representations based on realistic shapes are created through three steps: (1) scan individual aggregate particles using an X-ray CT machine to obtain a series of cross sectional images at different heights; (2) process the sectional images and stack them to obtain the 3D aggregate boundary; and (3) apply a sphere growth model to fill the interior space of the boundary. The sphere growth includes a first growth in 26 divergent directions and a second growth in 8 divergent directions which start from each sphere in the first growth. Four aggregate particles were selected for the numerical representation construction using the sphere growth model. The modeling results showed that the four aggregates had filling ratios of 97.8, 95.3, 91.3 and 98.5 %, respectively. Afterward, the four numerical representations were stored as aggregate templates to establish a preliminary representation library, which can be invoked to generate numerical aggregate particles in the model reconstruction of stone based materials. A discrete element model and a finite element model of an asphalt concrete beam were reconstructed as examples of application of the numerical representation library. The study overall showed that: (1) the sphere growth model is an effective approach to construct aggregate numerical representations with a high accuracy; (2) the sphere growth model can significantly reduce the sphere amount of the numerical representations compared to previous related studies; and (3) these numerical representations can be successfully used to reconstruct the mesostructure models of stone based materials, which can potentially bring time and cost savings while keeping the model precision.

Carotid plaque morphometric assessment with three-dimensional ultrasound imaging

As investigations into nonsurgical treatment for atherosclerosis expand, the measurement of plaque regression and progression has become an important end point to evaluate. Measurements of three-dimensional (3D) plaque volume are more reliable and sensitive to change than are traditional estimates of stenosis severity or cross-sectional area. 3D ultrasound (3D US) imaging may allow monitoring of plaque volume changes but has not been used routinely due to the cumbersome motorized units required to drive transducers. We investigated the variability, reliability, and the least amount of change detectable by 1D plaque measures, as well as 2D and 3D measures of plaque morphometry, that can be applied in a clinical environment. 3D US imaging was obtained in 10 patients with carotid stenosis. The lumen and outer wall boundaries were outlined in serial cross-sectional images 1 mm apart. Three observers manually segmented vessel wall volumes (VWVs), and the segmentation was repeated again 4 weeks later. This allowed measurement of interobserver and intraobserver variability of 6 pairs of observations. We measured Bland-Altman statistics, intraclass correlation coefficients, coefficient of variability, and the minimum detectable plaque change for each morphometric measure. The mean VWV of carotid lesions in the study was 1276.8 mm(3) (range, 620.6-1956.3 mm(3)). Bland-Altman plots demonstrated low interobserver and intraobserver variability. The interobserver variability of volume measurements as a function of mean volume was 14.8% and interobserver variability was 8.9%. Reliability was 87% as quantified by the interclass correlation and was 95% by the intraclass correlation. The least detectable change in VWV was 12.9% for interobserver variability and 4.5% for intraobserver variability for the three observers. Carotid plaque diameter measurements from B-mode images have high variability. Plaque burden, as estimated by VWV, can be measured reliably with a 3D US technique using a clinical scanner. The volumetric change, with 95% confidence, that must be observed to establish that a plaque has undergone growth or regression is ∼12.9% for different observers and 4.5% for the same observer performing the follow-up study.

Composition and intramuscular fat estimation of Holstein bull and steer rib sections by using one or more computed tomography cross-sectional images

Predictions of the composition and intramuscular fat (IMF) of beef rib sections were estimated from 1 cross-sectional image taken at the 10th rib level, from one at the 11th rib level (IMF) or from a series of cross-sectional images taken between the 9th and 11th ribs with computed tomography (CT) scanner. Two hundred and twelve beef cuts from Holstein bulls and steers were scanned, with two thirds of the samples used for calibration and the rest for validation. The 9–11th rib section was CT scanned and manually dissected. In addition, the IMF was determined in minced loin. For each scan, the volume associated with each Hounsfield value was obtained for the whole rib section and for the Longissimus thoracis muscle as regions of interest. Volumes associated with a range of Hounsfield values were selected in a stepwise manner and used as predictors in the regression equation. With the exception of IMF prediction, the accuracy was higher when the entire rib section was scanned in comparison to a single cross-sectional image taken at the 10th rib level. However, as one single image is cheaper than scanning the entire rib section, a compromise between precision and cost must be considered to select an adequate prediction method using one cross-sectional image or a series of images comprising the whole rib section. The CT results from IMF content determinations of L. thoracis muscle improve when one cross-sectional image of all the cut (including other muscles and types of fat) is considered, probably because the high correlation between IMF content and fat content of the whole section. Moreover further studies are needed to improve CT scanning predictive accuracy.

Three-dimensional characterization of ODS ferritic steel using by FIB-SEM serial sectioning method.

Considerable attention has been paid to the research of the electron tomography due to determine the three-dimensional (3D) structure of materials [1]. One of the electron tomography techniques, focused ion beam/scanning electron microscopy (FIB-SEM) imaging has advantages of high resolutions (10 nm), large area observation (μm order) and simultaneous energy dispersive x- ray microanalysis (EDS)/ electron backscatter diffraction (EBSD) analysis. The purpose of this study, three-dimensional EBSD analysis of ODS ferritic steel which carried out cold work using FIB-SEM equipment was conducted, and it aimed at analyzing the microstructure obtained there. The zone annealing tests were conducted for ferritic steel [2,3], which were produced through mechanical alloying and hot-extrusion. After zone annealing, specimens were mechanically polished with #400∼4000 emery paper, 1 µm diamond paste and alumina colloidal silica. The serial sectioning and the 3D-electron backscattering diffraction (3D-EBSD) analysis were carried out. We made the micro pillar (30 x 30 x 15 µm). The EBSD measurements were carried out in each layer after serial sectioning at a step size and milling depth was 80 nm with 30 slices. After EBSD analysis, the series of cross-sectional images were aligned according to arbitrarily specified areas and then stacked up to form a volume. Consequently, we obtained the 3D-IPF maps for ODS ferritic steel. In this specimen, the {111} and {001} grains are layered by turns. In addition, the volume fraction value of both plane are similar. The aspect ratio increases with specimen depth. The 3D-EBSD mapping is useful to analysis of the bulk material since this method obtain many microstructure information, such a shape, volume and orientation of the crystal, grain boundary.

Freehand 3D Ultrasound to Measure Thrombus Volume in Patients with Acute Deep-Vein Thrombosis

Objective —Current imaging techniques are limited in their ability to quantify thrombus burden, progression, or resolution in patients with acute deep-vein thrombosis (DVT). These assessments are critical measures of therapeutic success when thrombolytic or thrombectomy treatment protocols are used for DVT. We have developed a novel freehand three-dimensional (3D) ultrasound method to measure thrombus volume. In this study, we evaluated the reliability of this new technology. Methods —We studied consecutive hospital inpatients with a first episode of acute DVT. Treatment decisions were not influenced by the study protocol. A combination of routine imaging in grayscale, color-flow, and power-Doppler modes along-with freehand 3D volumetric imaging with a linear transducer attached to an external tracking sensor was performed using a personal computer–based ultrasound scanner. Image-processing software loaded on the personal computer was used to process and reconstruct the serial cross-sectional images of the affected veins and outlined thrombus into a composite 3D image. Imaging and processing was performed twice by one sonographer, and repeated once by another sonographer. Results —The mean age of patients was 56.7 ± 15 years; 40% were women. A total of 70% of DVTs were in the lower extremity and 60% received anticoagulation. Thrombus volume was reliably determined by our protocol. The mean inter- and intraobserver differences in measurements were −0.09 ± 0.59 cm3 and 0.23 ± 0.43 cm3 (mean ± SD), which were well within 2 SD (Bland Altman statistics) of the mean volumes. Measurements of the second sonographer correlated well with those of the first (regression slope = 0.95 ± 0.07, p = 0.001) and those of the first observation correlated with the second observation performed by the same sonographer (regression slope = 0.91 ± 0.03, p = 0.001). Interrater agreement was good between the two sonographers (kappa = 0.71) and between two measurements by the same sonographer (kappa = 0.82). Conclusions —We have developed a novel freehand 3D-ultrasound imaging technique and protocol that reliably measures venous thrombus volume. There is good agreement in measurements between two observers and repeated measurements by one observer. The technique can be readily adapted for routine clinical practice. This protocol will be of increasing value as the appreciation for the deleterious effects of residual thrombus after DVT increases; and the use of aggressive thrombus removal treatments for acute DVT increases.

Predictive Value of Spectral-Domain Optical Coherence Tomography Features in Assessment of Visual Prognosis in Eyes With Neovascular Age-Related Macular Degeneration Treated With Ranibizumab

To determine whether pretreatment (baseline) optical coherence tomography (OCT) features can be used as predictors of visual acuity outcome at 12 months in eyes with neovascular age-related macular degeneration treated with intravitreal ranibizumab and to assess whether baseline OCT features can predict a change in visual acuity from baseline to 12 months. Retrospective, observational study. We retrospectively evaluated the serial cross-sectional images of the macula obtained using the Spectralis OCT (HRA+OCT; Heidelberg Engineering) in 100 eyes of 94 patients attending a single center and undergoing treatment with intravitreal ranibizumab for neovascular age-related macular degeneration. The baseline OCT characteristics and visual acuity were correlated to the final visual acuity (Early Treatment Diabetic Retinopathy Study letters) and change in visual acuity after 12 months of monitoring and treatment. Univariate and multivariate analyses were carried out to correlate these morphologic features with the final visual acuity and the change in visual acuity. Intact ellipsoid zone (P = .0001) and external limiting membrane in the subfoveal area (P < .0001) at baseline were the only 2 independent good prognostic indicators of final visual acuity at 12 months. However, none of the morphologic features at baseline could predict the change in visual acuity by 12 months. The results suggest that integrity of the outer retinal layers at baseline is crucial for determining final visual acuity at 12 months in eyes undergoing treatment with ranibizumab for neovascular age-related macular degeneration.

Assessment of Elbow Extensors Endurance in Young Athletes

The aim of this study was to compare different endurance parameters of elbow extensors between senior and junior athletes. A group of 23 junior (16.2 ± 0.8 years, BMI 21.8 ± 2.9 kg/m(2)) and 16 senior athletes (23.1 ± 6.2 y, BMI 23.6 ± 4.2 kg/m(2)) volunteered for the study. Strength measurements were performed on the isoacceleration dynamometer (5 sets of 10 maximal elbow extensions, 1 min resting period between each set). The following strength parameters were measured: maximal strength (MS), endurance strength (ES), fatigue rate (FR) and decrease in strength (DS). Both arms triceps brachii muscle mass (MM) was calculated using a series of cross-sectional images of upper arms obtained by the MRI. Triceps brachii muscle mass for both arms in senior athletes showed significantly higher values (1286.9 ± 323.7 g) compared to young athletes (948.9 ± 171.1 g, p<0.01). ES was 50% higher in seniors, while FR was 10% higher in juniors. MS was 35% higher in seniors, but no difference was discovered when this parameter was expressed in relation to muscle mass. DS was significantly different between juniors and seniors, except in absolute values. No significant correlation was found between triceps brachii muscle mass and FR or DS. Different values of strength decrease throughout multiple contractions could be attributed to different characteristics of various sports.

Accuracy of computer-aided geometric 3D reconstruction based on histological serial microgrinding preparation

Purpose: For our research on computer-optimised and automated cochlear implant surgery, we pursue a model-based approach to overcome the limitations of currently available clinical imaging modalities. A serial cross section preparation procedure has been developed and evaluated concerning accuracy to serve for modelling of a digital anatomic atlas to make delicate soft tissue structures available for pre-operative planning. Methods: A special grinding tool was developed allowing the setting of a specific amount of abrasion as equidistant slice thickness was considered a crucial step. Additionally, each actual abrasion was accurately measured and used during three-dimensional reconstruction of the serial cross-sectional images obtained via digital photo documentation after each microgrinding step. A well-known reference object was prepared using this procedure and evaluated in terms of accuracy. Results: Reconstruction of the whole sample was achieved with an error less than 0.4%, and the edge lengths in the direction of abrasion could be reconstructed with an average error of 0.6 ± 0.3 mm; both prove the realisation of equidistant abrasion. Using artificial registration fiducials and a custom-made algorithm for image alignment, parallelism and rectangularity could be preserved with average errors less than 0.4° ± 0.3°. Conclusion: We present a systematic, practicable and reliable method for the geometrically accurate reconstruction of anatomical structures, which is especially suitable for the middle and inner ear anatomy including soft tissue structures. For the first time, the quality of such a reconstruction process has been quantified and successfully proven for its usability.

Non-invasive quantification of resin–dentin interfacial gaps using optical coherence tomography: Validation against confocal microscopy

Objectives Regardless of the cause, gap formation at the tooth–restoration interface may result in treatment failure; non-destructive assessment and monitoring of these defects are important. The aim of this in vitro study is to assess the tooth–restoration interface using a non-invasive technique; swept source optical coherence tomography (SS-OCT) and to confirm the findings with confocal laser scanning microscope (CLSM). Methods Cylindrical class-I cavities (3 mm in diameter and 1.5 mm in depth) were prepared in the occlusal surface of human premolars. Each cavity was restored using an all-in-one adhesive system (Clearfil Tri-S Bond) and one of the three types of composites placed in bulk; Majesty Posterior, AP-X and Majesty LV (all by Kuraray Medical, Japan). Ten serial cross-sectional images of the whole restored cavity were obtained by SS-OCT at 1319 nm center wave length, to which locations the specimens were later trimmed, polished and observed under CLSM. An image analysis software was used to detect significant peaks in the signal intensity at the resin–dentin interface of the cavity floor. The presence and dimensions of gaps at the interface were also confirmed by CLSM. Results Increased SS-OCT signal intensity along the interface corresponded well to the interfacial gaps detected by CLSM. The actual gap size detected ranged from 26 μm to 1.9 mm in length, and the universal composite APX showed lowest interfacial gaps. Conclusion SS-OCT imaging technology can be used to non-invasively detect and quantify micrometer gaps at the bottom of composite restorations, and potentially become a monitoring tool for composite restorations both in the laboratory research, and in the clinics.

PVSS1. Ultrasonic Monitoring of Three-Dimensional Carotid Atherosclerotic Plaque Structure

Percent carotid stenosis is an imperfect determinant of asymptomatic disease severity. Plaques progress along the vessel faster than they thicken. Therefore, volume may be more sensitive than thickness measurements. Duplex ultrasound (DUS) imaging is optimal for plaque area and volume assessments provided operator and angle dependence can be overcome. We evaluated the accuracy and reproducibility of a novel 3D DUS protocol for plaque volume measurement. We used a 5-8 MHz linear transducer with an attached magnetic tracking system to acquire serial 2D images that were reformatted into 3D. The device was calibrated using a 1 mm spherical copper bead. Reproducibility of multiple anatomic fiducial landmarks were tested and an image of the optimal point established a landmark in 3D space that was used to register serial studies. 10 patients with carotid stenosis were examined. Serial cross sectional images were obtained with EKG gating. Images were stacked and reconstructed to obtain surface renderings of the lumen and adventitia to enable plaque volume measurements. The protocol was repeated by the same sonographer after the patient was moved and repositioned. Three trials achieved satisfactory calibration of the device to within 2mm. The philtrum and sternal notch were the most reproducible anatomical reference points. Correlation between the first and second measurements of cross sectional area and plaque volume was high (kappa=0.91 and 0.88) and intraobserver variability was low (difference of 0.1±2.5 mm2 and 0.09±3.9 mm3 for repeated scans). We report a novel approach of performing 3D DUS imaging using a standard scanner head. A reference point on the patient established a landmark in 3D space that enabled serial imaging. The reproducibility of cross sectional area and plaque volume measurements by this method was high, thereby providing a reliable method of serial follow-up of carotid plaques.

Correlation of fundus autofluorescence with photoreceptor morphology and functional changes in eyes with retinitis pigmentosa

To assess and correlate fundus autofluorescence (FAF) characteristics with photoreceptor morphology and functional features in eyes with retinitis pigmentosa (RP). Thirty-four eyes of 17 patients with RP were examined. We compared FAF images obtained by confocal scanning laser ophthalmoscopy with Spectral-domain optical coherence tomography (SD-OCT) and retinal function assessed by microperimetry. Normal FAF surrounded by a ring of increased FAF at the macular area was detected in 32 (94%) eyes. The diameter of the normal FAF was correlated significantly with the preserved area of the photoreceptor inner segment and outer segment (IS/OS) junction on SD-OCT (R=0.939, p<0.001). The area outside the ring was associated with loss of IS/OS junction and external limiting membrane (ELM). The ring of increased FAF demarcated the border between the central retina with preservation of the IS/OS junction and ELM, and the adjacent eccentric retina with loss of these bands. In two eyes of one patient, there was no preservation of normal FAF at the macula and the photoreceptor IS/OS junction was not detected on SD-OCT. The mean retinal sensitivity derived from microperimetry was correlated significantly with the area of normal FAF (R=0.929, p=0.007) and the preserved area of the IS/OS junction (R=0.851, p=0.032). Ten eyes had progressive reduction in size of the normal FAF inside the ring accompanied by decreased area of preserved IS/OS during 3.1 years. FAF appears to reflect the integrity of the photoreceptor layer. It may serve as a secondary outcome measure for novel therapeutic strategies for RP.

Spiral Computed Tomography Based Maxillary Sinus Imaging in Relation to Tooth Loss, Implant Placement and Potential Grafting Procedure

ABSTRACTObjectivesThe purpose of the present study was to explore the maxillary sinus anatomy, its variations and volume in patients with a need for maxillary implant placement.Material and MethodsMaxillary sinus data of 101 consecutive patients who underwent spiral computed tomography (CT) scans for preoperative implant planning in the maxilla at the Department of Periodontology, University Hospital, Catholic University of Leuven, Leuven, Belgium were retrospectively evaluated. The alveolar bone height was measured on serial cross-sectional images between alveolar crest and sinus floor, parallel to the tooth axis. In order to describe the size of the maxillary sinus anteroposterior (AP) and mediolateral (ML) diameters of the sinus were measured.ResultsThe results indicated that the alveolar bone height was significantly higher in the premolar regions in comparison to the molar region (n = 46, P < 0.01). The age showed negative relation to bone dimension (r = - 0.32, P = 0.04).Anterior and posterior border of the maxillary sinuses were mostly located in the first premolar (49%) and second molar (84%) regions, respectively. Maxillary sinus septa were indentified in 47% of the maxillary antra. Almost 2/3 (66%) of the patients showed major (> 4 mm) mucosal thickening mostly at the level of the sinus floor. The present sample did not allow revealing any significant difference (P > 0.05) in maxillary sinus dimensions for partially dentate and edentulous subjects.ConclusionsCross-sectional imaging can be used in order to obtain more accurate information on the morphology, variation, and the amount of maxillary bone adjacent to the maxillary sinus.