Frequency Domain Optical Coherence Tomography Research Articles

Algorithm and software for field distortion correction in a commercial SD-OCT for corneal curvature assessment.

Accurate assessment of corneal curvatures using frequency domain optical coherence tomography (OCT) with galvanometer scanners remains challenging due to the well-known scan field distortion. This paper presents an algorithm and software for correcting the distortion using only two simple measurements in which a readily available standard sphere is positioned in different depths in front of the OCT scanner. This offers a highly accessible and easily reproducible method for the field distortion correction (FDC). The correction was validated by measuring different spherical phantoms and conducting corneal curvature measurements of ex vivo porcine corneas using a commercial spectral-domain OCT system and a clinically approved swept-source OCT as a reference instrument. Thus, the error in radius measurements of spherical phantoms was reduced by >90% and astigmatism by >80% using FDC. In explanted porcine eyes, the error in astigmatism measurements with the Telesto was reduced by 75% for power and 70% for angle. The best fitting sphere radius was determined up to a deviation of 0.4% from the Anterion. This paper describes a correction algorithm for OCT immanent distortion that is applicable to any scanning OCT setup and enables precise corneal curvature measurements. The MATLAB software for the FDC is publicly available on GitHub.

Assessing the efficacy of saline flush in frequency-domain optical coherence tomography for intracoronary imaging

BackgroundThe increased amount of contrast media in frequency-domain optical coherence tomography (FD-OCT) imaging during percutaneous coronary intervention (PCI) has raised potential concerns regarding impairment of renal function.ObjectivesThis study aimed to evaluate the effectiveness of heparinized saline flush in FD-OCT-guided PCI and identify clinical factors contributing to optimal image quality.MethodsWe retrospectively collected 100 lesions from 90 consecutive patients, and a total of 200 pullbacks were analyzed for the initial and final evaluation in which saline was used as the flushing medium.ResultsThe study population had a mean age of 73, with 52% having chronic kidney disease (CKD). The median amount of contrast used was 28 ml, and no complications were observed associated with saline flush OCT. Imaging quality was then categorized as excellent, good, or unacceptable. Among the total runs, 87% demonstrated clinically acceptable image quality, with 66.5% classified as excellent images and 20.5% classified as good images. Independent predictors of excellent images included lumen area stenosis ≥ 70% (adjusted odds ratio [OR] 2.37, 95% confidence interval [CI] 1.02–5.47, P = 0.044), and the use of intensive flushing (adjusted OR 2.06, 95% CI 1.11–3.86, P = 0.023) defined as a deep engagement of guiding catheter (GC) or a selective insertion of guide extension catheter (GE). Intensive flushing was performed in 60% of the total pullbacks, and it was particularly effective in improving image quality in the left coronary artery (LCA).ConclusionThe use of saline flush during FD-OCT imaging was safe and feasible, which had a benefit in renal protection with adequate imaging quality.

TCTAP A-059 Comparison of Contrast Media Versus Hydroxyethyl Starch for Frequency-Domain Optical Coherence Tomography Imaging in Coronary Artery Disease

TCTAP A-059 Comparison of Contrast Media Versus Hydroxyethyl Starch for Frequency-Domain Optical Coherence Tomography Imaging in Coronary Artery Disease

Characteristics and significance of outer retinal thickness changes in reticular macular disease

Objective: To study the characteristics and significance of changes in the thickness of the outer retinal layer (ORL) outside the macula in patients with reticular macular disease (RMD). Methods: A cross-sectional study was conducted. The clinical data of patients who visited the Department of Ophthalmology of the First Affiliated Hospital of Guangzhou Medical University from February to September 2019 were retrospectively collected. Thirty-one patients with at least one eye (54 eyes in total) diagnosed with early/mid-stage age-related macular degeneration (AMD) were consecutively included in the AMD group, and 33 patients with at least one eye (64 eyes in total) showing subretinal wart-like deposits on optical coherence tomography images were consecutively included in the RMD group. Thirty-two volunteers aged between 50 to 90 years with a normal fundus in both eyes (64 eyes in total) were consecutively included in the healthy control (HC) group. Frequency domain optical coherence tomography was applied to examine and analyze the thickness features of the ORL, inner retinal layer and choroid at the macular fovea (F), 2 mm of the temporal edge (T), the nasal edge (N), the superior edge (S) and inferior edge (I) of the macular fovea in each group. The correlations of the thickness of ORL with the choroidal thickness and the blood flow density of the choriocapillaris layer in patients with RMD were also analyzed. Results: The thickness of ORL at the F, T, S and I sites in the RMD group was significantly thinner than that in the AMD and HC groups. The difference was most obvious at the F site [(90.27±8.93), (98.04±11.7) and (97.19±7.02)μm] in the RMD, AMD and HC groups, respectively; all P<0.01). In the logistic regression model with independent variables of the ORL thickness at the macular F site, gender and age, there was a significant association between the thickness of ORL at the F site and the incidence of RMD (odds ratio=0.926, P<0.05). The ORL and choroid in the eyes of patients with RMD were significantly thinner at the F site [(90.27±8.93) and (163.21±72.43) μm, respectively; both P<0.01] compared with the AMD [(98.04±11.7) and (235.34±64.15) μm, respectively] and HC [(97.19±7.02) and (240.08±62.27) μm, respectively] groups. However, the ORL and choroidal thickness did not show significant and strong linear correlations at multiple sites. In contrast, there was a significant linear correlation between the blood flow density of the choriocapillaris layer and the thickness of ORL at the F, T and S sites in patients with RMD (r=0.487, 0.722, 0.467, respectively; all P<0.05). Conclusions: The thickness of ORL outside the macula of eyes with RMD is thinner than that of healthy eyes and eyes with early/mid-stage AMD. The thinning of ORL outside the macula is related to the decrease in the blood flow density of the choriocapillaris layer in patients with RMD.

The vascular response to ultrathin biodegradable polymer sirolimus-eluting stent at 2-weeks and 1-year follow up in patients with ST-elevation myocardial infarction

Abstract Background Recent clinical study suggests newer-generation drug-eluting stents (DES) that combine ultrathin strut and nano-coating with biodegradable polymers sirolimus-eluting stent (BP-SES) could improve long-term clinical outcomes in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI) over current generation DES. However, the details of vascular response in very early and chronic phase have not been systematically addressed. Objective and method We exploratory investigate early and chronic vascular response following BP-SES implantation in patients with STEMI to reveal mechanism of the favorable clinical outcomes in recent studies using frequency domain-optical coherence tomography (FD-OCT). Consecutive twenty-four patients with STEMI who underwent FD-OCT after primary PCI and were eligible for follow-up FD-OCT at 2 weeks and 1 year after implantation were enrolled between June 2018 and August 2020. OCT was performed immediately after PCI, at 2-weeks (2W) and 1-year (1Y) after the primary PCI. Struts were recorded as uncovered if any part was visibly exposed in the lumen or covered if a layer of tissue covered all reflecting surfaces. Struts of stents that are smaller than 3.0mm of diameter with more than 80μm between the center reflection and the adjacent vessel surface were recorded as malapposed. The reduction of atherothrombotic protrusion burden within the stent was also assessed. Results Twenty-four patients (age 64.9±11.4 years, male 83.3%) were enrolled. The percentage of uncovered struts significantly decreased from post-PCI to 2W follow-up and from 2W follow-up to 1Y follow-up (62±20% post-PCI versus 27±11% at 2W follow up, p&amp;lt;0.0001 and 2W follow-up versus 3.3±3.3% at 1Y follow up, p&amp;lt;0.0001). Malapposed struts also decreased from post-PCI to 2W follow-up (4.1±3.6% post-PCI versus 1.5±2.2% at 2W follow-up, p&amp;lt;0.0001), but no significant difference was shown between 2W follow-up and 1Y follow-up (2W follow-up versus 1.0±2.3 at 1Y follow up, p=0.12). The average protrusion area of athero-thrombotic burden decreased (0.57±0.32 at post-PCI versus 0.42±0.22 mm2 at 2W follow up, p&amp;lt;0.0001) and its volume showed similar tendency (16.6±10.7 at post-PCI versus 12.9±8.23 mm3 at 2W follow up, p=0.0011). Thrombus was shown in all patients at post-PCI, but two patients (8.0%) showed it at 1Y follow-up. Conclusion(s) This study elucidated very early and chronic vascular responses following ultrathin strut BP-SES implantation in STEMI patients by FD-OCT. It showed resolution of athero-thrombotic materials in very early phase and favorable progression of strut coverage in very early and chronic phase. Funding Acknowledgement Type of funding sources: None.

Comparison of Idiopathic Macular Hole Interventions Using Frequency Domain Optical Coherence Tomography and Optical Coherence Tomography Angiography.

Objective We aimed to determine the efficacy of different idiopathic macular hole treatment methods to improve recovery time and patient outcomes using Frequency Domain Optical Coherence Tomography (SD-OCT) and Optical Coherence Tomography Angiography (OCTA). Methods This retrospective study included patients with idiopathic macular hole who were admitted to our hospital between 1st January 2019 and 31st October 2021. The control group was treated with internal limiting membrane tamponade, and the study group was treated with clamshell therapy. Treatment conditions (internal limiting membrane treatment duration and hole closure rate), best corrected visual acuity (BCVA) before and after surgery, OCTA measurements, and SD-OCT were assessed. The retinal nerve fiber layer (RNFL), retinal ganglion cell layer (GCL), and retinal pigment epithelium (RPE) thicknesses were also analyzed. Results The treatment time and hole closure rate of the internal limiting membrane in the study group were higher than those in the control group. The curative effect of the study group was better than that of the control group. The postoperative DCP blood vessel density in both groups was higher than that before operation, and the study group was higher than the control group. The FAZ area and circumference were lower than those before surgery, and the study group was lower than the control group. At 3 months after operation, the thickness of DIOA, nasal temporal RNFL, and GCL were decreased in both groups, and the observed values in the study group were lower than those in the control group. At 3-month follow-up, there was no significant difference in RPE thickness between the two groups. Conclusion Flip and cover therapy is the most effective treatment. SD-OCT and OCTA provide an objective basis for clinical intervention by comparing the effects of different procedures on the retinal condition of patients.

Linewidth considerations for MEMS tunable VCSEL LiDAR.

The flexible membranes used in MEMS tunable VCSELs are so small and light that thermally induced vibrations can impact laser performance. We measure the thermal vibration spectrum of such a membrane showing peaks at the spatial vibration mode resonant frequencies of the membrane/plate. These vibrations result in a theoretical floor to the linewidth of the VCSEL. Frequency domain LiDAR and optical coherence tomography systems can get around this thermal linewidth limit with adequate clock measurement and processing. Essentially an OCT/LiDAR sweep with a concomitantly measured clock is a feed-forward linewidth reduction scheme. This can be achieved because the membrane resonances are relatively low frequency. LiDAR ranging out to 9 meters has been demonstrated with a resolution of 13 μm, close to the transform limit for the 70 nm sampling range.

Plaque microstructures during metformin therapy in type 2 diabetic subjects with coronary artery disease: optical coherence tomography analysis.

While metformin is recommended as a first-line cardioprotective therapy for type 2 diabetic patients, whether it exerts direct effects on atherosclerotic plaque remains uncertain. The current study characterized coronary plaque microstructures in type 2 diabetic patients who received metformin. We retrospectively analyzed 409 non-culprit lipid plaques in 313 type 2 diabetic patients with coronary artery disease (CAD) by using frequency-domain optical coherence tomography (FD-OCT) imaging. FD-OCT derived plaque microstructures were compared in patients stratified according to metformin use. A proportion of 38.6% of study subjects received metformin. Patients receiving metformin more likely exhibited a history of hypertension (79.3% vs. 67.1%, P=0.03) and metabolic syndrome (52.8% vs. 36.4%, P=0.01). On FD-OCT imaging, the prevalence of lipid plaque was lower in the metformin group (66.2% vs. 77.9%, P=0.03). Furthermore, the metformin group demonstrated plaques with a smaller lipid arc (median: 168.7° vs. 208.5°, P=0.008), shorter longitudinal length (media: 5.1 vs. 9.1 mm, P=0.04), and a lower frequency of cholesterol crystal (3.9% vs. 18.2%, P=0.01) and spotty calcification (3.9% vs. 34.8%, P=0.008). These differences remained significant after adjusting for clinical characteristics and glycemic control. However, in patients who received insulin, the favourable effect of metformin on lipid arc was not observed (insulin user: P=0.87; insulin non-user: P=0.009; P value for interaction between two groups, P=0.02). Metformin use was associated with a lower prevalence of vulnerable plaque features in type 2 diabetic patients with CAD, especially insulin non-user. These findings suggest the potential of metformin to exert direct plaque stabilization effects in type 2 diabetic subjects.

Air-Liquid Exchange by Free Hand and One Needle for Unhealed Macular Hole.

Aim To report the treatment of 7 cases of unsealed hole after macular hole surgery with air-fluid exchange. Methods Retrospective case series. We collected 7 eyes of 7 patients with unsealed hole an unsealed hole about 2 weeks after macular hole surgery (23G vitrectomy with internal limiting membrane peeling with sterilizing air tamponade) in our hospital from February 2018 to December 2018. All patients underwent “air-liquid exchange by free hand and one needle.” The prone position was taken one week after operation. The macular holes before and after operation were examined by frequency-domain optical coherence tomography (SD-OCT). Results The size of the macular hole before vitrectomy was 481 ± 156 μm (range: 281–609 μm). Two weeks after vitrectomy (before air and liquid exchange), the size of the macular hole was 295 ± 92 μm (range: 210–421 μm). All macular holes were closed within 7–14 days after air-liquid exchange. There was no complaint of discomfort among these patients. Conclusion From this preliminary study, air-liquid exchange by free hand and one needle seems to be safe and effective in the treatment for patients with unsealed and tiny macular hole after vitrectomy as the lack of long effective gas in China. However, the exact efficacy and safety need further large case studies.

Diagnostic Performance of Frequency-Domain Optical Coherence Tomography to Predict Functionally Significant Left Main Coronary Artery Stenosis.

Aims The aim of this study was to assess the safety and diagnostic efficacy of frequency-domain optical coherence tomography (FD-OCT) in identifying functional severity of the left main coronary artery (LM) stenosis determined by fractional flow reserve (FFR). Methods and Results 101 patients with LM lesion (20–70% diameter stenosis angiographically) underwent FFR measurement and FD-OCT imaging of the LM. The following parameters were measured by FD-OCT in the LM: reference lumen area (RLA), reference lumen diameter (RLD), minimum lumen area (MLA), minimum lumen diameter (MLD), % lumen area stenosis, and % diameter stenosis. The LM lesions were analyzable by FD-OCT in 88/101 (87.1%) patients. FFR at maximum hyperemia was ≤0.80 in 39/88 (44.3%) patients. FFR values were correlated significantly with FD-OCT-derived LM lumen parameters. An MLA cutoff value of 5.38 mm2 had the highest sensitivity and specificity of 82% and 81%, respectively, followed by an MLD of 2.43 mm (sensitivity 77%, specificity 72%) and AS of 60% (sensitivity 72%, specificity 72%) for predicting FFR <0.80. Conclusions FD-OCT is a safe and feasible imaging technique for the assessment of LM stenosis. An FD-OCT-derived MLA of ≤5.38 mm2 strongly predicts the functional severity of an LM lesion.

Prediction of the functional significance of the left main stenosis using frequency domain optical coherence tomography

Abstract Background Frequency domain optical coherence tomography (FD-OCT) has been used for the assessment of non-ostial left main coronary artery stenosis (LM). However, no study has evaluated the use of this imaging technique for the prediction of functional significance of LM lesions determined by the fractional flow reserve (FFR). Purpose The aim of this study was to assess the safety and diagnostic efficacy of FD-OCT in identifying functional severity of the LM stenosis determined by (FFR). Methods One hundred one patients with LM lesion (20–70% diameter stenosis angiographically) underwent FFR measurement and FD-OCT imaging of the LM. The following parameters were measured by FD-OCT in the LM: reference lumen area (RLA), reference lumen diameter (RLD), minimum lumen area (MLA), minimum lumen diameter (MLD), % lumen area stenosis, % diameter stenosis. Results The LM lesions were visible and measurable by FD-OCT in 88/101 (87.1%) patients. However lesions with ostial location were analyzable by FD-OCT only in 17/30 (56.4%) patients (Figure 1). FFR at maximum hyperemia was ≤0.80 in 39/88 (44.3%) patients. FFR values were correlated significantly with FD-OCT derived LM lumen parameters. Receiver operating characteristic curves showed that an MLA cutoff value of 5,38 mm2 had the highest sensitivity and specificity of 82% and 81% respectively (Figure 2A), followed by an MLD of 2.43 mm (sensitivity 77%, specificity 72%) (Figure 2B) and an %AS of 60% (sensitivity 72%, specificity 72%) (Figure 2C) for predicting FFR ≤0.80. Conclusions FD-OCT is safe and feasible imaging technique for the assessment of a LM stenosis except the ostial LM lesions which are analyzable in half of the cases. An FD-OCT derived MLA of ≤5.38 mm2 strongly predicts the functional severity of a LM lesion. Funding Acknowledgement Type of funding sources: None. Angiography and OCT image of LM stenosisROC curves of MLA, MLD and AS

Head-to-head comparison of quantitative measurements between intravascular imaging systems: An in vitro phantom study

IntroductionThe present study aimed to compare the accuracy of quantitative measurements by contemporary intravascular imaging systems including optical frequency domain imaging (OFDI), frequency domain optical coherence tomography (FD-OCT), and 6 intravascular ultrasound (IVUS) systems.MethodsWe imaged five cylindrical phantom models made from an acrylic resin with known lumen diameters (1.51, 2.03, 3.04, 4.04, and 5.04 mm, respectively) using OFDI (FastView and LUNAWAVE, Terumo), FD-OCT (Dragonfly JP and ILUMIEN OPTIS, Abbott Vascular), and 6 mechanically rotating IVUS systems including a system, two 40-MHz, one 45-MHz, two 60-Mhz and one broad-band frequency IVUS systems. The OFDI, FD-OCT, and IVUS images were obtained using automated motorized pullback in a tank filled with 37-degree Celsius saline and, in cases of OFDI and FD-OCT, contrast-saline mixture (1:1 ratio) and contrast under the system setting of the refractive index for the corresponding flush medium.ResultsAll the imaging systems showed good accuracy and excellent precision of lumen measurement with the relative differences between the measured diameter and actual phantom diameter being ranging from −2.9% to 8.0% and minimum standard deviations of the measured diameters (≤0.02 mm).ConclusionThe present study demonstrated that contemporary intravascular imaging systems including OFDI, FD-OCT, and IVUS provided clinically acceptable accuracy and excellent precision of quantitative lumen measurement in phantom models in vitro across a wide range of dimensions. Future research to confirm these findings in vivo are warranted.

Frequency-Domain Optical Coherence Tomography for Intracranial Atherosclerotic Stenosis: Feasibility, Safety, and Preliminary Experience.

Background: Despite advances in non-invasive imaging, the characterization of atherosclerotic plaque remains superior with frequency-domain optical coherence tomography (FD-OCT) in the clinical coronary and experimental cerebrovascular literature. An assessment of the feasibility and safety of FD-OCT for intracranial atherosclerotic stenosis (ICAS) is desirable.Methods: We analyzed a cohort of all consecutive FD-OCT evaluations for ICAS performed at our institution from April 2017 to August 2018 (16 months) in patients who suffered from transient ischemic attack (TIA) or non-disabling stroke despite optimal medical management within 90 days of admission attributable to angiographically verified 70–99% stenosis of an intracranial artery.Results: Thirty-three patients harboring 36 lesions with an average age of (57.6 ± 7.1) years (male sex 27 cases) comprising nine cases of lesions located within the anterior circulation and 24 cases within the posterior circulation were identified. Of the 33 patients with 36 lesions, the FD-OCT imaging catheter detected 35/36 (97%) lesions except in one case in which the FD-OCT catheter failed to navigate excessively tortuous vessels, and FD-OCT images in 27 patients (81.8%) were finally obtained successful, where the target lesion was fully visible, and image quality under at least one pullback was graded 2 or 3. There were no symptomatic complications. Blood flow was the most common artifact encountered (51.9%).Conclusion: FD-OCT is safe and feasible for the assessment of ICAS in the anterior and posterior circulation. The use of diagnostic interferometry will have to be weighed against its cost, and these preliminary findings should be verified by prospective large-scale studies.

Optical coherence tomography

During the past decade, noninvasive imaging has emerged as a valuable tool in clinical dermatology and dermatologic research. Optical coherence tomography (OCT) is one such type of noninvasive imaging. OCT uses the principle of interferometry to produce real-time images. A low-power diode laser shines infrared light onto tissues, which reflects back to an optical fiber interferometer. Using time delay and the backscattered light intensity, a two-dimensional image akin to an ultrasound is rendered. We review the history, types, and modalities of OCT, plus the many applications of frequency domain, high definition, and dynamic OCT in practice, including its utility in diagnosis, monitoring, and grading disease severity in a variety of cutaneous conditions.

Spectral fusing Gabor domain optical coherence microscopy based on FPGA processing

High-resolution imaging using high numerical aperture imaging optics is commonly known to cause a narrow depth of focus, which limits the depth of field in optical coherence tomography (OCT). To achieve semi-invariant high resolution in all directions, Gabor domain optical coherence microscopy (GD-OCM) combines the in-focus regions of multiple cross-sectional images that are acquired while shifting the focal plane of the objective lens. As a result, GD-OCM requires additional processes for in-focus extraction and fusion, leading to longer processing times, as compared with conventional frequency domain OCT (FD-OCT). We previously proposed a method of spectral domain Gabor fusion that has been proven to improve the processing speed of GD-OCM. To investigate the full potential of the spectral domain Gabor fusion technique, we present the implementation of the spectral domain Gabor fusion algorithm using field programmable gate arrays (FPGAs) in a spectral acquisition hardware device. All filtering processes are now performed in an acquisition device as opposed to the post-processing of the original GD-OCM, which reduces the amount of data transfer between the image acquisition device and the processing host. To clearly demonstrate the imaging performance of the implemented system, we performed GD-OCM imaging of a stack of polymeric tapes. GD-OCM imaging was performed over seven focus zones. The results showed that the processing time for linear wavenumber calibration and spectral Gabor filtering can be improved with FPGA implementation. The total processing time was improved by about 35%.

Early Vascular Response to Ultrathin Biodegradable Polymer Sirolimus-Eluting Stents for the Treatment of ST-Elevation Myocardial Infarction After Plaque Rupture.

Recent clinical studies suggest that newer-generation drug-eluting stents that combine ultrathin struts and nanocoating (biodegradable polymer sirolimus-eluting stents, BP-SES) could improve long-term clinical outcomes in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). However, the early vascular response to BP-SES in these patients has not been investigated so far.We examined this response in 20 patients with STEMI caused by plaque rupture using frequency-domain optical coherence tomography (OCT) to understand the underlying mechanisms. Plaque rupture was diagnosed by OCT before PCI with BP-SES implantation was performed. OCT was again performed before the final angiography (post-PCI) and after 2 weeks (2W-OCT).BP-SES placement caused protrusion of atherothrombotic material into the stent lumen and incomplete stent apposition in all patients. After 2 weeks, incomplete stent apposition was significantly reduced (% malapposed struts: post-PCI 4.7 ± 3.3%; 2W-OCT 0.9 ± 1.2%; P < 0.0001), and the percentage of uncovered struts also significantly decreased (% uncovered struts: post-PCI; 69.8 ± 18.3%: 2W-OCT; 29.6 ± 11.0%, P < 0.0001). The maximum protrusion area of the atherothrombotic burden was significantly reduced (post-PCI 1.36 ± 0.70 mm2; 2W-OCT 0.98 ± 0.55 mm2; P = 0.004).This study on the early vascular responses following BP-SES implantation showed rapid resolution of atherothrombotic material and progression of strut apposition and coverage. (UMIN000041324).

Saline as an Alternative to Radio-Contrast for Optical Coherence Tomography-Guided Percutaneous Coronary Intervention: A Prospective Comparison

ObjectivesTo do a quantitative comparison of saline and contrast Frequency domain optical coherence tomography (FD-OCT) during percutaneous coronary intervention (PCI) optimisation. Methods13 pairs of OCT runs were analysed, wherein each pair consisted of a contrast run and a heparinized saline run taken in the same coronary artery at the same position. Quantitative analysis was done comparing minimal lumen area (MLA), proximal reference diameter (PRD), distal reference diameter (DRD) and percentage area stenosis (AS) at the same anatomical location. Lesion morphologies, rendered stent view and 3D reconstruction were compared for image clarity. ResultThe saline OCT runs resulted in comparable MLA (3.88 ± 2.59 mm2 with saline run vs 3.88 ± 2.71 mm2 with contrast run; p = 0.650), PRD (3.66 ± 0.52 mm with saline vs 3.65 ± 0.52 mm with contrast; p = 0.463), DRD (2.97 ± 0.22 mm with saline vs 2.99 ± 0.88 mm with contrast; p = 0.433), and AS (59.60 ± 18.62% with saline vs 59.18 ± 19.11% with contrast; p = 0.753) with respect to the contrast runs. The Bland Altman plots of the measured parameters indicate good agreement between saline and contrast OCT. Linear regression analysis indicated the absence of proportional bias All lesion morphologies (calcified, fibrotic, thin cap fibroatheroma, macrophages, cholesterol crystals and edge dissection), 3D reconstruction and rendered stent view were clearly demonstrable in the saline OCT runs. ConclusionsUsing heparinized saline as flushing media in coronary FD-OCT may result in vessel dimensions that are comparable with contrast. Heparinized saline may be used as a contrast saving alternative for FD-OCT during PCI optimization.

Optical Coherence Tomography for Ophthalmology Imaging.

Optical coherence tomography (OCT) is a depth-resolved imaging modality, which is able to achieve micrometer-scale resolution within biological tissue noninvasively. In the past 30years, researchers all around the world had made several essential efforts on techniques relevant to OCT. OCT has become a routine process for eye diseases with different types. In this chapter, the three important stages in the development of OCT are briefly illustrated, including the time domain OCT (TD-OCT), the frequency domain OCT (FD-OCT) and the optical coherence tomography angiography (OCTA). Each of the technique has made great progress for use on living human eye imaging in clinical applications. TD-OCT was first proposed and commercialized, which is able to achieve acceptable 2D depth-resolved cross-sectional images of human retina in vivo. FD-OCT was the upgraded OCT technique compared with TD-OCT. By capturing the coherent signal within the Fourier space, the FD-OCT could improve the image sensitivity compared with TD-OCT, and achieve dozens of kilo hertz imaging speed. OCTA is the newest developments of OCT technique, which is able to visualize the micro vasculature networks of human retina in vivo. With OCTA technique, the newest ophthalmologic OCT system is able to achieve detailed diagnosis for both micro-structure and vasculature abnormalities for clinical applications. The further development of OCT technique on imaging speed, contrast, resolution, field of view, and so on will make OCT to be a more powerful tool for clinical usages.

Changes of retinal thickness in macular area of myopia children

Objective: To study the changes of macular retinal thickness in children with moderate and low myopia by frequency domain OCT. Methods: 108 school-age children aged 7-12 years were selected and enrolled into the group. Among them, 58 cases (116 eyes) with simple moderate and low myopia in the myopia group and 50 cases (100 eyes) with straight eyes in the emmetropia group. The retinal thickness in different parts of macular area was compared between the two groups, and the correlation between retinal thickness in different parts of macular area and diopter and axial length was analyzed by Pearson correlation analysis. Results: The length of eye axis in moderate and low myopia group was longer than that in emmetropia group, and the difference was statistically significant (P &lt; 0.05). There was no significant difference in CMT(Central Macular Thickness) and I-AMT(average macular thickness of inner circle) between the two groups (P &gt; 0.05). The AMT(Average Macular Thickness) and O-AMT(average macular thickness of outer circle) in moderate and low myopia group were lower than those in emmetropia group, and the differences were all statistically significant (P &lt; 0.05). The thickness of the retina below the macula and the nasal side was positively correlated with the refractive power in patients with moderate to low-grade myopia (r=0.201, 0.302, P＜0.05), and the thickness of the retina around the macula was negatively correlated with the refractive power (r=-0.326, P＜0.05). Conclusion: There is no significant difference in macular central retinal thickness between children with moderate and low myopia and normal children, and the thickness of paracentral retina tends to become thinner with the deepening of myopia.

Frequency-domain optical coherence tomography with undetected mid-infrared photons

Mid-infrared (mid-IR) light scatters much less than shorter wavelengths, allowing greatly enhanced penetration depths for optical imaging techniques such as optical coherence tomography (OCT). However, both detection and broadband sources in the mid-IR are technologically challenging. Interfering entangled photons in a nonlinear interferometer enables sensing with undetected photons, making mid-IR sources and detectors obsolete. Here we implement mid-IR frequency-domain OCT based on ultra-broadband entangled photon pairs spanning from 3.3 to 4.3 µm. We demonstrate 10 µm axial and 20 µm lateral resolution 2D and 3D imaging of strongly scattering ceramic and paint samples. By intrinsically being limited only by shot noise, we observe times more sensitivity per integration time and power of the probe light. Together with the vastly reduced footprint and technical complexity, our technique can outperform conventional approaches with classical mid-IR light sources.