Diagnostic performance of swept-source optical coherence tomography in the detection of tooth cracks: a narrative review.

eview question / Objective What is the effectiveness of swept-source optical c o h e r e n c e t o m o g r a p h y ( S S -O C T ) compared to other diagnostic methods in detecting enamel, dentin, and root cracks in human teeth?Condition being studied Tooth cracks represent incomplete fractures that affect different layers of your teeth from shallow to deep.These fractures develop when teeth endure too much pressure plus age or when dental work and other stressors affect them.Tooth cracks grow to create discomfort while letting bacteria enter the tooth and lead to pulpitis, periodontal disease, and vertical root fractures.Finding tooth cracks at an early stage helps doctors improve treatment results and slow their growth.This review studies how SS-OCT helps find tooth cracks better than standard diagnostic tools without hurting patients.Healthcare professionals use dental imaging tools to find tooth cracks and improve treatment results for cracked teeth. METHODSSearch strategy Narrative description of included studies, focusing on methodology, outcomes, and limitations. Participant or population Human teeth.Intervention The systematic review focuses on Swept-Source Optical Coherence Tomography (SS-OCT), an imaging technique that uses nearinfrared light to detect tooth cracks in enamel, dentin, and root structures.SS-OCT is a noninvasive, radiation-free diagnostic tool that generates high-resolution, cross-sectional, and 3D images of dental structures.Comparator The effectiveness of SS-OCT will be compared against traditional and emerging diagnostic methods for tooth cracks.

PurposeThe aims of the present study were to compare the image quality and visibility of tooth cracks between conventional methods and swept-source optical coherence tomography (SS-OCT) and to develop an automatic detection technique for tooth cracks by SS-OCT imaging.MethodsWe evaluated SS-OCT with a near-infrared wavelength centered at 1,310 nm over a spectral bandwidth of 100 nm at a rate of 50 kHz as a new diagnostic tool for the detection of tooth cracks. The reliability of the SS-OCT images was verified by comparing the crack lines with those detected using conventional methods. After performing preprocessing of the obtained SS-OCT images to emphasize cracks, an algorithm was developed and verified to detect tooth cracks automatically.ResultsThe detection capability of SS-OCT was superior or comparable to that of trans-illumination, which did not discriminate among the cracks according to depth. Other conventional methods for the detection of tooth cracks did not sense initial cracks with a width of less than 100 μm. However, SS-OCT detected cracks of all sizes, ranging from craze lines to split teeth, and the crack lines were automatically detected in images using the Hough transform.ConclusionsWe were able to distinguish structural cracks, craze lines, and split lines in tooth cracks using SS-OCT images, and to automatically detect the position of various cracks in the OCT images. Therefore, the detection capability of SS-OCT images provides a useful diagnostic tool for cracked tooth syndrome.

Evaluation of dental caries, tooth crack, and age-related changes in tooth structure using optical coherence tomography

The aims of this study were to develop an automatic detection technique for tooth cracks and to suggest quantitative methods for measuring gingival sulcus depth using swept-source optical coherence tomography (SS-OCT). We evaluated SS-OCT with wavelength centered at 1310 nm over a spectral bandwidth of 100 nm at a rate of 50 kHz as a new diagnostic tool for the detection of tooth cracks and gingival sulcus depth. The reliability of the SS-OCT images was verified by imaging the crack in extracted human teeth and gingival sulcus of porcine sample. The SS-OCT could automatically detect the position of various cracks and visualize the deep periodontal pockets. Therefore, the detection capability of SS-OCT images could be useful diagnostic tool for dental cracks and periodontal pockets.

Purpose: To establish normative data for macular thickness in Chinese aged 30 to 80 years using the swept-source optical coherence tomography (SS-OCT) device. Methods: The study included 290 normal eyes, 430 NDR eyes and 150 DR eyes of community residents aged 30 to 80 years in Guangzhou, China. Mean macular thicknesses in Early Treatment Diabetic Retinopathy Study (ETDRS) subfields, central point thicknesses (CPT), and macular volume was measured by SS-OCT (Triton DRI OCT, Topcon, Tokyo, Japan) and Spectral-Domain OCT (SD-OCT; Heidelberg Engineering, Heidelberg, Germany). We assessed agreement between SS-OCT and SD-OCT measurements by intraclass correlation coefficients (ICC) and Bland-Altman plots. We established a conversion equation relating central subfield (CSF), CPT and macular volume between the two OCT devices. Results: Macular thickness measurements in SS-OCT were significantly thinner than in SD-OCT. The mean CSF thickness in normal eyes measured by SS-OCT and SD-OCT were 227.8 ± 19.4 μm and 260.0 ± 19.7 μm (p < .0001). CSF thickness was a significantly difference between genders (SS-OCT: male 237.2 ± 18.8 μm vs female 222.0 ± 17.5 μm, p < .0001). In all three groups, the agreement between SS-OCT and SD-OCT was excellent (all ICC > 0.9). The conversion equations for CSF, CPT and macular volume from SS-OCT to SD-OCT were derived, with over 95% of the predicted values fell within 10% of the actual measurements in DR and NDR eyes. Conclusion: We propose SS-OCT CSF thicknesses of 275 μm for males and 260 μm for females as the minimum criteria for macular edema in Chinese aged 30 to 80 years based on 2 SDs above the mean CSF. SS-OCT measurements were significantly thinner than SD-OCT. We derived equations from converting SS-OCT measurements to SD-OCT equivalents.

Advances in swept-source optical coherence tomography and optical coherence tomography angiography

Noninvasive Cross-sectional Visualization of Enamel Cracks by Optical Coherence Tomography In Vitro

Background: Parkinson’s Disease (PD) is the second-most common neurodegenerative disease affecting the elderly population. The eye has been referred to as a window to the brain due to its inseparable relationship with the central nervous system. The development of Swept-Source Optical Coherence Tomography (SS-OCT) and Optical Coherence Tomography Angiography (OCTA) technologies has offered us a better imaging modality to study the impact of PD on the retina. Method: Seventy-five eyes of 42 early-stage PD patients and 150 eyes of 75 matched healthy controls were enrolled in the current study. We performed SS-OCT and SS-OCTA to assess retinal nerve fiber layer (RNFL), ganglion cell layer (GCL) + inner plexiform layer (IPL), internal nuclear layer (INL) thickness, and retinal flow density and flow ratio. Results: Our study indicates decreasing superficial and deep flow density in most regions of the retina. Superficial and deep flow parameters were also associated with RNFL, GCL+IPL, and INL thickness. ROC analysis reveals superficial flow density demonstrated an Area Under Curve (AUC) of 0.688, which is greater than deep flow density and retinal thickness measurements. Conclusion: To the best of our knowledge, we are the first study using SS-OCT and SS-OCTA to study superficial and deep retinal flow changes in early-stage PD patients. Our study suggests decreasing retinal flow density provides greater diagnostic power than retinal thickness measurements in the early stage of PD. SS-OCTA parameters could potentially serve as imaging biomarkers in PD diagnosis and staging.

The purpose of the study was to evaluate the clinical efficacy of swept-source optical coherence tomography (SS-OCT), we compared the intradevice repeatability of thickness measurements obtained using SS-OCT to that of measurements obtained using spectral domain OCT (SD-OCT), and assessed the interdevice agreement of thickness measurements. This cross-sectional prospective study involved 3 consecutive measurements of peripapillary retinal nerve fiber layer (PP-RNFL) and ganglion cell-inner plexiform layer thickness in healthy subjects, using 2 different OCT systems. Intraclass correlation coefficients (ICCs) and coefficients of variability were calculated and compared for repeatability and agreement between study groups. Intradevice ICCs for each OCT system were compared, and Bland-Altman plots were used to evaluate their agreement. Fifty-eight eyes from 58 healthy subjects (25 men and 33 women) were analyzed. SS-OCT images yielded larger PP-RNFL thickness values than SD-OCT images in every sector examined. In contrast, SD-OCT images yielded larger macular ganglion cell-inner plexiform layer thickness values than SS-OCT images. For SS-OCT, intradevice ICCs were ≥0.9 for all sectors. However, for SD-OCT, the 3 PP-RNFL measurement sectors had correlation coefficients <0.9. Interdevice ICCs varied more and were lower than intradevice values, because thickness measurement values differed between the OCT devices. Measurements differed between systems even for the same subject. SS-OCT had an intradevice repeatability similar to that of SD-OCT. These findings support the clinical application of SS-OCT.

Clinical relevance Proper selection of phakic intraocular lens diameter is necessary to avoid complications related with excessive vaulting after its implantation. Background Horizontal corneal diameter, measured as white‐to‐white distance, is one of the parameters used for phakic intraocular lens diameter calculation. Agreement was assessed between three parameters: white‐to‐white distance obtained with swept source optical coherence tomography, and white‐to‐white distance obtained with Scheimpflug camera and angle‐to‐angle parameter obtained with anterior segment optical coherence tomography. Methods This study included 55 eyes of 43 patients. The white‐to‐white distance was measured with two biometry techniques: swept source optical coherence tomography and Scheimpflug camera. The angle‐to‐angle was measured with anterior segment optical coherence tomography. Analysis of agreement was performed by the Bland–Altman method. For every patient, simulation of Visian Implantable Collamer Lens (ICL) sizing was performed using the Online Calculation and Ordering System with different white‐to‐white distance or angle‐to‐angle. Results Statistically significant differences were found between swept source optical coherence tomography biometer and anterior segment optical coherence tomography (p = 0.001) and between swept source optical coherence tomography and Scheimpflug camera (p < 0.001). However, there was a good correlation between swept source optical coherence tomography and Scheimpflug camera (intraclass correlation co‐efficient = 0.623), with a shift toward higher white‐to‐white distance values on swept source optical coherence tomography. A relatively high correlation intraclass correlation co‐efficient (0.772) and lack of statistically significant differences (p = 0.068) between anterior segment optical coherence tomography and Scheimpflug camera results were observed. Simulation of phakic intraocular lens sizing showed that swept source optical coherence tomography white‐to‐white distance should not be used interchangeably with Scheimpflug camera white‐to‐white distance or angle‐to‐angle. Conclusion White‐to‐white distance measured with swept source optical coherence tomography was significantly different from values obtained with other methods. Angle‐to‐angle may support ICL sizing, helping in verification of white‐to‐white distance values obtained with other devices.

In this study, we included 28 patients with optic nerve head drusen (ONHD) seen at the University Eye Hospital of Cologne, Germany. The mean age was 40.9 ± 22.4 years. Sixteen patients were female, and twelve were male. The mean visual acuity was 0.18 ± 0.39 and 0.14 ± 0.23 LogMAR for the right and left eyes, respectively. A summary of baseline and morphological characteristics is given in Table 1. Three patients showed unilateral ONHD (patient no. 10, 26 and 28). The mean deviation in the perimetry was −6.74 ± 8.05 dB and −4.03 ± 5.04 dB for the right and the left eyes, respectively. A definite grid shown is used for the optical coherence tomography (OCT) quantification (Fig. 1). In this collective, optic head drusen are seen on the surface of the optic disc (superficial ONHD) in 45 eyes. This type of drusen is easily seen using funduscopy and fundus photography (Fig. 2). Drusen located on the surface of the optic disc also can be diagnosed using fundus autofluorescence, spectral domain OCT (SD-OCT), enhanced depth imaging OCT (EDI-OCT) and swept source OCT (SS-OCT). The fundus autofluorescence shows hyper-reflective materials, which are characteristics for drusen. In SD-OCT, hyporeflective materials can be easily seen in the depth of the optic nerve. Using EDI-OCT and SS-OCT, these drusen can be easily displayed. Drusen present in OCT as oval structures with hyporeflective filling and shadowing effect underneath the drusen. In all cases, hyper-reflective dots are seen around the drusen. In some cases, only some hyper-reflective dots without inner hyporeflective fillings are seen. Differentiating drusen to blood vessels can be challenging in some cases. Unlike drusen, vessels represent as oval structures with hyper- or hyporeflective fillings and shadowing effect underneath them. The outer linings of vessels are usually smooth without the aforementioned hyper-reflective dots (Fig. 3). In this study, the mean depth of ONHD was 205.45 ± 95.01 μm. Drusen and other retinal structure in the height of retinal nerve fibre layer (RNFL) through the retinal pigment epithelium (RPE) were best displayed using SD-OCT. Other structures underneath the RPE were best displayed using EDI-OCT. Swept source OCT (SS-OCT) displayed all structures from RNFL to the choroid sufficiently (Fig. 4). The outer boundaries of structures underneath optic nerve head drusen were however best shown using EDI-OCT. In eight eyes, optic disc drusen are buried in the depth of the optic disc. This type of drusen cannot easily be diagnosed using funduscopy. Also, in fundus autofluorescence, no hyper-reflective materials can be seen. Swept source optical coherence tomography, EDI-OCT and SS-OCT cannot penetrate into the depth to demonstrate the drusen either. In this case, only ultrasound is able to demonstrate the drusen in the depth of the optic nerve (Fig. 5). Optical imaging modalities showed similar sensitivity, that is 0.82, 0.77, 0.80 and 0.83 for SD-OCT, EDI-OCT, SS-OCT and FAF, respectively. The use of ultrasound showed the highest sensitivity of 1.0. The Youden's index for these imaging modalities was 0.82, 0.77, 0.80, 0.83 and 1.0 for SD-OCT, EDI-OCT, SS-OCT, FAF and ultrasound, respectively. The RNFL thickness around the optic nerve head was not significantly different comparing controls and ONHD patients (Table 2). Ganglion cell layer inner plexiform layer (GCLIPL) thickness was thicker in the superior and inferior part of the optic nerve head in ONHD patients (p = 0.002 and p = 0.019, respectively). Our findings encourage the use of different imaging modalities to diagnose and follow ONHD. We showed that non-buried ONHD are best displayed using optical imaging modalities, such as fundus photography, fundus autofluorescence and OCT. The non-buried ONHD can also be displayed using ultrasound as well; however, light-based imaging modalities offer mostly a more precise depiction of structures. This might be relevant, if one would like to follow and compare the structures in the future. We showed that SD-OCT depicts ONHD above the RPE best, while EDI-OCT the structure underneath the RPE level best. Swept source OCT (SS-OCT) displays all structures from RNFL to underneath the RPE level sufficiently. In conclusion, new imaging modalities based on OCT, that is EDI-OCT and SS-OCT, have their potential for diagnosing ONHD. They are however not suitable for imaging buried ONHD. We support the use of multiple imaging modalities in ONHD, as each of them has its pros and cons.

Wide-field (WF) swept-source (SS) optical coherence tomography angiography (SS-OCTA) was used to image diabetic tractional retinal detachments (TRDs) before and after pars plana vitrectomy. The clinical utility of SS-OCTA was assessed. Patients with diabetic TRDs were imaged prospectively with SS-OCTA. Ultrawide-field imaging was obtained when possible. Postoperative WF SS-OCTA imaging was performed. From January 2018 through December 2019, 31 eyes of 21 patients with diabetic TRDs were imaged. Wide-field SS-OCTA en-face images captured all areas of TRD and fibrovascular proliferation within the posterior pole that were visualized on ultrawide-field imaging. Optical coherence tomography angiography B-scans revealed the vascularity of preretinal membranes and identified areas of vitreoretinal traction and posterior vitreous detachment. Ten eyes underwent pars plana vitrectomy. Postoperative SS-OCTA imaging demonstrated removal of fibrovascular membranes, relief of traction, and resolution of TRDs. Retinal ischemia before and after surgical repair appeared similar. All clinically relevant features of diabetic TRDs were identified at baseline and assessed longitudinally after pars plana vitrectomy using WF SS-OCTA, which showed resolution of vitreoretinal traction and no apparent change in the status of retinal perfusion after surgery. If the media are clear and fixation is adequate, WF SS-OCTA is likely the only imaging modality needed for the diagnosis and longitudinal evaluation of diabetic TRDs.

In order to solve the problem of image real-time processing and correction for high-speed endoscopic swept-source optical coherence tomography (SS-OCT), we highly optimize a computer-unified device architecture-based platform and use a field-programmable gate array to summarize the application experience. We use the Half-Sync/Half-Asyn mode to optimize memory in order to build a high-throughput data thread pool for CPU. We use asynchronous streaming architecture to multiplex multiple threads at high speed to accelerate data processing. At the same time, we design a rotary scanning position information encoding feedback module to suppress image drift, which can realize 25ns logic-timing sequence synchronization control through FPGA 40MHz clock. The maximum complete attainable axial-scan-processing rate (including memory transfer and display of B-scan frames) is 3.52 MHz for a 16-bit pixel depth and A-scans/s of 1024 pixels. To our knowledge, this is the fastest processing rate reported to date with a single-chip graphical processing unit for SS-OCT. Finally, the established high-speed SS-OCT is used to image mouse esophagus and human fingers, and the output images are stable. When the image size is 1024 × 1024 pixels, the real-time imaging rate is 200 frames per second. This paper develops a real-time image processing and reconstruction technology suitable for high-throughput SS-OCT systems, which can have high-density operation and efficient parallelism, while suppressing high-speed image drift. It lays the foundation for the non-destructive, in vivo, non-staining, fast and convenient early tumor diagnosis of high-speed endoscopic SS-OCT.

ObjectiveTo elucidate the difference between choroidal thickness (CT) in primary open-angle glaucoma (POAG) and normal subjects and to compare the CT measured using spectral domain optical coherence tomography (SD-OCT) and...

Choroidal Analysis in Healthy Eyes Using Swept-Source Optical Coherence Tomography Compared to Spectral Domain Optical Coherence Tomography