Ability Of Optical Coherence Tomography Research Articles

The Relationship between Lumbar Puncture Opening Pressure and Retinal Nerve Fiber Layer Thickness in the Diagnosis of Idiopathic Intracranial Hypertension: Is a Lumbar Puncture Always Necessary?

Idiopathic intracranial hypertension (IIH), is characterized by elevated intracranial pressure (ICP) without an identified cause. Today, lumbar puncture (LP) is the most common method used for diagnosis by measuring cerebrospinal fluid (CSF) pressure to reflect intracranial pressure. This invasive examination has significant disadvantages, such as complications and negative experiences for patients. Therefore, noninvasive methods for ICP measurement are desired. Optical coherence tomography (OCT) is widely used for the diagnosis and follow-up of IIH patients as it reflects papilledema. The aim of this study is to investigate the relationship between CSF pressure and OCT parameters and the ability of OCT in the diagnostic approach. In our study, patients who were followed up with a diagnosis of IIH with complete neuro-ophthalmological examinations, including visual acuity (VA), visual field, and OCT imaging within 24 hours before lumbar puncture, were retrospectively evaluated. CSF pressure, visual acuity LogMAR, mean deviation of visual fields, retinal nerve fiber layer (RNFL) thickness measured by OCT, and treatment protocols were obtained from our hospital data system. A total of 42 eyes of 21 patients were enrolled in the study. A statistically significant positive and moderate correlation was found between CSF pressure values and average RNFL thickness (r=0.507; P=0.001). The same relationship was demonstrated in all 4 quadrants: inferior, superior, nasal, and temporal. Increased peripapillary RNFL thickness in optic nerve head OCT may be correlated with increased ICP in IIH patients. A larger number of patients are needed to better understand the correlation between OCT parameters and CSF pressure in patients with IIH.

Histology, OCT, and Micro-CT Evaluation of Coronary Calcification Treated With Intravascular Lithotripsy: Atherosclerotic Cadaver Study

BackgroundAlthough intravascular lithotripsy (IVL) has been an emerging novel option to treat vascular calcification, the specific effects on histology have not been systematically examined. ObjectivesThe authors examined the histologic effects of IVL on coronary calcified lesions from human autopsy hearts and evaluated the diagnostic ability of optical coherence tomography (OCT) and micro-computed tomography (CT) to detect calcium fracture as identified by the gold standard histology. MethodsEight coronary lesions were treated with IVL, and 7 lesions were treated with 10 atm inflation using an IVL catheter balloon without lithotripsy pulses (plain old balloon angioplasty [POBA]). OCT and micro-CT imaging were performed before and after treatment, and the presence of calcium fracture was assessed. The frequency and size of fractures were measured and compared with the corresponding histology. ResultsAll 15 treated lesions were diagnosed as sheet calcium by histology. Histological evidence of calcium fracture was significantly greater in the IVL group compared with the POBA group (62.5% vs 0.0%; P = 0.01). Calcified lesions with fracture had a larger maximum arc degree of calcification (median 145.6 [IQR: 134.4-300.4] degrees vs 107.0 [IQR: 88.9-129.1] degrees; P = 0.01). Micro-CT and histology showed an excellent correlation for fracture depth (R2 = 0.83; P < 0.0001), whereas OCT showed less correlation (R2 = 0.37; P = 0.11). The depth of fractures measured by OCT were significantly shorter than with those measured by histology (0.49 [IQR: 0.29-0.77] mm vs 0.88 [IQR: 0.64-1.07] mm; P = 0.008). ConclusionsIVL demonstrated a histologically superior fracturing effect on coronary calcified lesions compared with POBA. OCT failed to identify the presence of some calcium fractures and underestimated the depth of fracture when compared with micro-CT.

The early diagnostic value of optical coherence tomography (OCT) and OCT angiography in thyroid-associated ophthalmopathy.

The retinal microvascular density changes have been identified in thyroid-associated ophthalmopathy (TAO) patients. Whereas a lack of research has been done on the diagnostic ability of optical coherence tomography (OCT) combined with optical coherence tomography angiography (OCTA) parameters. This study aims to evaluate the retina perfusion variations in eyes with active and stable TAO and its diagnostic abilities using OCT and OCTA. This is cohort longitudinal retrospective study. A total of 51 patients with TAO and 39 healthy controls (HCs) were recruited. The TAO eyes were divided into active and stable stage groups. The foveal avascular zone (FAZ), macular perfusion density (mPD), and peripapillary PD were measured by OCTA. The peripapillary retinal nerve fiber layer (RNFL), central retinal thickness (CRT), and whole macular volume (wMV) were measured by OCT. Visual evoked potential (VEP) and visual field (VF) were also assessed. The mPD of the superficial retinal capillary plexus (SRCP) was significantly different in all subfields among active, stable, and HC groups (p < 0.05) except for the temporal inner (p = 0.137), and the active group achieved the lowest PD. The FAZ size increased significantly in the active and stable groups compared with the HC group (p < 0.001). Significant difference was observed in mPD of deep retinal capillary plexus (DRCP) in all quadrants among three groups (p < 0.05). Moreover, PD parameters of optic nerve head (ONH) and radial peripapillary capillary plexus (RPCP) showed a different trend among three groups (p < 0.05). The r-value of visual field-mean deviation (VF-MD) of TAO with DRCP-whole PD (wPD) and RPCP-wPD was 0.421 and 0.299, respectively (p < 0.05). The DRCP-wPD in OCTA and RNFL in OCT were significantly higher in area under the receiver operating characteristic curve (AUC) than that of HC eyes. OCT and OCTA can noninvasively detect the peripapillary and macular changes in various stages of TAO patients, and it might be a high diagnostic value tool to monitor the TAO progression.

Visualization and Validation of The Microstructures in The Airway Wall in vivo Using Diffractive Optical Coherence Tomography

At present, there is no available method to study the in vivo microstructures of the airway wall (epithelium, smooth muscle, adventitia, basement membrane, glands, cartilage). Currently, we rely on ex vivo histologic evaluation of airway biopsies. To overcome this obstacle, we have developed an endoscopic ultrahigh-resolution diffractive optical coherence tomography (OCT) system, operating at a wavelength of 800 nm, to non-invasively study the in vivo microstructures of the airway wall. Prior to human study, validation of diffractive OCT's ability to quantitate airway microstructural components is required. To validate and demonstrate the accuracy of this OCT system, we used an ovine model to image small airways (∼ 2 mm in diameter). Histologic samples and correlated OCT images were matched. The cross-sectional area of the airway wall, lumen, and other microstructures were measured and compared. A total of 27 sheep were studied from which we identified 39 paired OCT-histology airway images. We found strong correlations between the OCT and the histology measurements of the airway wall area and the microstructural area measurements of the epithelium, basement membrane, airway smooth muscle, glands, cartilage, and adventitia. The correlations ranged from r=0.61 (p<0.001) for the epithelium to r=0.86 (p<0.001) for the adventitia with the correlation between the OCT and the histology measurements for the entire airway wall of r=0.76 (p<0.001). Given the high degree of correlation, these data validate the ability to acquire and quantify in vivo microscopic level imaging with this newly developed 800nm ultra-high resolution diffractive OCT system.

Differentiation Between Benign and Malignant Pigmented Skin Tumours Using Bedside Diagnostic Imaging Technologies: A Pilot Study.

Rapid diagnosis of suspicious pigmented skin lesions is imperative; however, current bedside skin imaging technologies are either limited in penetration depth or resolution. Combining imaging methods is therefore highly relevant for skin cancer diagnostics. This pilot study evaluated the ability of optical coherence tomography, reflectance confocal microscopy, photo-acoustic imaging and high-frequency ultrasound to differentiate malignant from benign pigmented skin lesions. A total of 41 pigmented skin tumours were scanned prior to excision. Morphological features and blood vessel characteristics were analysed with reflectance confocal microscopy, optical coherence tomography, high-frequency ultrasound and photoacoustic imaging images, and the diagnostic accuracy was assessed. Three novel photoacoustic imaging features, 7 reflectance confocal microscopy features, and 2 optical coherence tomography features were detected that had a high correlation with malignancy; diagnostic accuracy > 71%. No significant features were found in high-frequency ultrasound. In conclusion, optical coherence tomography, reflectance confocal microscopy and photoacoustic imaging in combination enable image-guided bedside evaluation of suspicious pigmented skin tumours. Combining these advanced techniques may enable more efficient diagnosis of skin cancer.

Noninvasive Estimation of Pulsatile and Static Intracranial Pressure by Optical Coherence Tomography.

PurposeTo explore the ability of optical coherence tomography (OCT) to noninvasively estimate pulsatile and static intracranial pressure (ICP).MethodsAn OCT examination was performed in patients who underwent continuous overnight monitoring of the pulsatile and static ICP for diagnostic purpose. We included two patient groups, patients with idiopathic intracranial hypertension (IIH; n = 20) and patients with no verified cerebrospinal fluid disturbances (reference; n = 12). Several OCT parameters were acquired using spectral-domain OCT (RS-3000 Advance; NIDEK, Singapore). The ICP measurements were obtained using a parenchymal sensor (Codman ICP MicroSensor; Johnson & Johnson, Raynham, MA, USA). The pulsatile ICP was determined as the mean ICP wave amplitude (MWA), and the static ICP was determined as the mean ICP.ResultsThe peripapillary Bruch's membrane angle (pBA) and the optic nerve head height (ONHH) differed between the IIH and reference groups and correlated with both MWA and mean ICP. Both OCT parameters predicted elevated MWA. Area under the curve and cutoffs were 0.82 (95% confidence interval [CI], 0.66–0.98) and -0.65° (sensitivity/specificity; 0.75/0.92) for pBA and 0.84 (95% CI, 0.70–0.99) and 405 µm (0.88/0.67) for ONHH. Adjusting for age and body mass index resulted in nonsignificant predictive values for mean ICP, whereas the predictive value for MWA remained significant.ConclusionsThis study provides evidence that the OCT parameters pBA and ONHH noninvasively can predict elevated pulsatile ICP, represented by the MWA.Translational RelevanceOCT shows promise as a method for noninvasive estimation of ICP.

Relationship betweeen the amount and location of macrophages and clinical outcome: subanalysis of the CLIMA-study

BackgroundThe ability of optical coherence tomography (OCT) to recognize intraplaque macrophage infiltration is now well acknowledged. This post-hoc analysis of the CLIMA study aimed to address the clinical impact of the circumferential extension of OCT-defined macrophages and their location at one year follow-up. MethodsThe multicentre CLIMA study enrolled 1003 patients undergoing OCT evaluation of the untreated proximal left anterior descending (LAD) coronary artery. Measurements of circumferential extension of macrophages and measurements of the distance from intima-lumen contour to macrophages string were performed at the plaque cross-section judged as containing the greatest amount of macrophages. The main study endpoint was a composite of cardiac death, myocardial infarction (MI) and/or target vessel revascularization (TVR). ResultsPatients with large macrophage arc (p = 0.001) and superficial macrophage arc (p < 0.001) showed a higher one-year incidence of the main one-year composite endpoint. Consistently hypertension (p = 0.018), family history of CAD (p = 0.046), diabetes mellitus (p = 0.036), lower ejection fraction (p = 0.009) and chronic kidney disease (p = 0.019) were more frequently found in patients experiencing the main composite endpoint. At multivariate Cox regression analysis, fibrous cap thickness < 75 μm (HR 2.51, 95% 1.46–4.32), presence of large (HR 1.97, 95%CI 1.16–3.35, p = 0.012) and superficial (HR 1.72, 95%CI 1.02–2.90; p = 0.040) macrophage arc remained independent predictors of the main composite endpoint. Large macrophage arc was associated with target LAD related MI. ConclusionThe present post-hoc analysis of the CLIMA showed that the circumferential extension of macrophages and their location are related to a composite endpoint of cardiac death, MI and/or TVR.

Identification of the type of stent with three-dimensional optical coherence tomography: the SPQR study.

The ability of optical coherence tomography (OCT) to identify specific types of stent has never been systematically studied. The aim of this study was to test the accuracy of OCT imaging to identify patterns of stent platform and subsequently identify the type of stent implanted. Consecutive patients from six international centres were retrospectively screened, searching for OCT studies with metallic stents or scaffolds. The sample was analysed by two blinded operators, applying a dedicated protocol in four steps to identify the type of stent: 1) 3D and automatic strut detection (ASD), 2) 3D tissue view, 3) longitudinal view with ASD, 4) mode "stent only" and ASD. A series of 212 patients underwent OCT in the study centres, finding 294 metallic stents or scaffolds in 146 patients. The protocol correctly identified 285 stents (96.9%, kappa 0.965), with excellent interobserver agreement (kappa 0.988). The performance tended to be better in recently implanted stents (kappa 0.993) than in stents implanted ≥3 months before (kappa 0.915), and in pullback speed 18 mm/s as compared with 36 mm/s (kappa 0.969 vs 0.940, respectively). The type of stent platform can be accurately identified in OCT by trained analysts following a dedicated protocol, combining 3D-OCT, ASD and longitudinal view. This might be clinically helpful in scenarios of device failure and for the quantification of apposition. The blinding of analysts in OCT studies should be revisited.

The Paediatric Glaucoma Diagnostic Ability of Optical Coherence Tomography: A Comparison of Macular Segmentation and Peripapillary Retinal Nerve Fibre Layer Thickness.

Simple SummaryOptical coherence tomography (OCT) is an established ophthalmologic diagnostic tool to visualise vital retinal structures. In glaucoma, it is used to quantify the thickness decrease in the peripapillary retinal nerve fibre layer (pRNFL) and in the macula. While glaucoma management in adults incorporates traditional clinical parameters as well as instrumental methods such as OCT, guidelines for paediatric glaucoma focus on conventional methods. Even though some reports encouraging a broader use of OCT in children are present, its diagnostic potential in this particular population has still not been sufficiently analysed. To address this, the present study compares the glaucoma discriminative ability of OCT measurements of the pRNFL and macular layers in a paediatric population. The results indicate a reduction of the pRNFL and of inner macular layer thickness in glaucoma eyes, as well as a high correlation with the presence of glaucoma. The glaucoma discriminative ability can be maximised combining either all pRNFL sectors or the thickness results of the three innermost macular layers, even though sensitivity remains moderate. In conclusion, the OCT measurements of the pRNFL and macular thickness have a strong ability to diagnose paediatric glaucoma. However, OCT should be used in addition to conventional diagnostic tools rather than as a standalone method.Paediatric glaucoma leads to a decreased thickness of the peripapillary retinal nerve fibre layer (pRNFL) and of the macula. These changes can be precisely quantified using spectral domain-optical coherence tomography (SD-OCT). Despite abundant reports in adults, studies on the diagnostic capacity of macular SD-OCT in paediatric glaucoma are rare. The aim of this study was to compare the glaucoma discriminative ability of pRNFL and macular segment thickness in paediatric glaucoma patients and healthy children. Data of 72 children aged 5–17 years (glaucoma: 19 (26.4%), healthy: 53 (73.6%)) examined with SD-OCT (SPECTRALIS®, Heidelberg Engineering) were analysed retrospectively. The thickness of pRNFL sectors and of macular segment subfields were compared between diseased and healthy participants. Areas under the receiver-operating characteristic curves (AUC), sensitivity, and specificity from logistic regression were used to evaluate the glaucoma discriminative capacity of single and combined pRNFL and macular segments’ thickness. The results revealed a reduced thickness of the pRNFL and of the three inner macular layers in glaucoma patients, which correlates highly with the presence of glaucoma. The highest glaucoma discriminative ability was observed for the combination of pRNFL sectors or inner macular segments (AUC: 0.83 and 0.85, respectively), although sensitivity remained moderate (both 63% at 95% specificity). In conclusion, while confirmation from investigations in larger cohorts is required, SD-OCT-derived pRNFL and macular thickness measurements seem highly valuable for the diagnosis of paediatric glaucoma.

Application of optical coherence tomography to study the structural features of oral mucosa in biopsy tissues of oral dysplasia and carcinomas

This study aims to examine the ability of optical coherence tomography (OCT) to differentiate ex vivo epithelial structure of benign disorders, dysplastic, and oral squamous cell carcinoma (OSCC) in comparison with the structure of normal marginal mucosa of oral biopsies. As a secondary objective, we examined the inter- and intra-observer variations of OCT measurements of two calibrated assessors. Oral biopsies (n = 44) were scanned using the swept source OCT (SSOCT) and grouped by pathology diagnosis to benign, dysplasia or carcinoma. Two trained and calibrated assessors scored on the five OCT variables: thickness of keratin layer (KL), epithelial layer (EL), homogeneity of lamina propria (LP), basement membrane integrity (BMI), and the degree of reflection of the epithelial layer (Ep Re). Chi-square tests and Fischer's exact method were used to compare the data. The OCT images showed breached BM status in all the OSCC samples (100%). Epithelial reflection was noted to be hyper-reflective in all the OSCC and oral dysplasia samples (100%). An increase in KL in 66.67% of the OSCC and 100% of the oral dysplasia samples was found. EL was increased in all the OSCC samples (100%) and 85.72% of the oral dysplasias. Kappa values showed that there was very good agreement (over 0.7) when scoring individual parameters between the two assessors. The study showed that the BM status was a key parameter in the detection of SCC and for differentiating SCC from oral dysplasia or benign disorders. OCT is a non-invasive and non-radioactive adjunct diagnostic tool that can provide immediate results on the structure of oral mucosa. The BM status measured ex vivo was a key parameter in the detection of SCC and for differentiating SCC from oral dysplasia or benign disorders.

Optical coherence tomography detection of vulnerable plaques at high risk of developing acute coronary syndrome.

The ability of optical coherence tomography (OCT) to detect plaques at high risk of developing acute coronary syndrome (ACS) remains unclear. The aim of this study was to evaluate the association between non-culprit plaques characterized as both lipid-rich plaque (LRP) and thin-cap fibroatheroma (TCFA) by OCT and the risk of subsequent ACS events at the lesion level. In 1378 patients who underwent OCT, 3533 non-culprit plaques were analysed for the presence of LRP (maximum lipid arc > 180°) and TCFA (minimum fibrous cap thickness < 65 μm). The median follow-up period was 6 years [interquartile range (IQR): 5-9 years]. Seventy-two ACS arose from non-culprit plaques imaged by baseline OCT. ACS was more often associated with lipidic plaques that were characterized as both LRP and TCFA vs. lipidic plaques that did not have these characteristics [33% vs. 2%, hazard ratio 19.14 (95% confidence interval: 11.74-31.20), P < 0.001]. The sensitivity and specificity of the presence of both LRP and TCFA for predicting ACS was 38% and 97%, respectively. A larger maximum lipid arc [1.01° (IQR: 1.01-1.01°)], thinner minimum fibrous cap thickness [0.99 μm (IQR: 0.98-0.99 μm)], and smaller minimum lumen area [0.78 mm2 (IQR: 0.67-0.90 mm2), P < 0.001] were independently associated with ACS. Non-culprit plaques characterized by OCT as both LRP and TCFA were associated with an increased risk of subsequent ACS at the lesion level. Therefore, OCT might be able to detect vulnerable plaques.

Ability of Optical Coherence Tomography in Early Detection of Primary Open Angle Glaucoma

Introduction: As glaucoma is one of the leading causes of blindness, its early diagnosis is crucial. Standard Visual Field (VF) examinations are used in the diagnosis and follow-up of glaucoma, but the major drawback is that the abnormalities do not appear until 20-40% of ganglion cells are lost. Defects in the Retinal Nerve Fiber Layer (RNFL), measured by Optical Coherence Tomography (OCT), is an excellent objective and quantitative method in the diagnosis and management of glaucoma at earlier stages. Aim: To assess the ability of OCT in diagnosing early glaucomatous changes using RNFL, Optic Nerve Head (ONH) and macular thickness parameters. Materials and Methods: A hospital-based case control study was done for 18 months at Department of Ophthalmology, Sawai Man Singh (SMS) Hospital and Medical College, Jaipur, Rajasthan, India. Fifty patients meeting the inclusion criteria were evaluated in the study as case group. To compare the results with those of a normal population 50 age and sex matched subjects were included. Each subject underwent detailed ocular examination and RNFL, ONH and macular thickness parameters were measured using Spectral Domain (SD) OCT. The unpaired t-test was used to compare continuous variables and Chi-square test was used to compare categorical variables. The Area Under the Curve (AUC) with its 95% Confidence Interval (CI) was calculated. The p-value &lt;0.05 was considered significant. Results: A total of 50 glaucoma or glaucoma suspect cases and 50 controls partcipated in the present study, i.e., 100 eyes in each group were studied. Mean RNFL thickness, superior thickness, inferior thickness and temporal thickness were significantly (p&lt;0.05) lower among cases than controls. Cup area, cup/disc (C/D) area ratio, horizontal and vertical cup to disc ratio (CDR) were significantly (p=0.0001) higher among cases than controls. Vertically Integrated Rim Area (VIRA) was significantly (p&lt;0.05) lower among cases (0.19±0.13) than controls (0.28±0.05). There was no significant (p&gt;0.05) difference in disc area between cases and controls. All the macular thickness parameters were significantly (p&lt;0.05) lower among cases than controls except fovea. Overall, ONH and macular thickness parameters had high sensitivity and specificity than RNFL parameters in glaucoma patients. Conclusion: The present study found that a combination of RNFL, ONH and macular thickness parameters improved the diagnostic accuracy of OCT in early detection of Primary Open Angle Glaucoma (POAG).

Feasibility and Clinical Significance of In Vivo Cholesterol Crystal Detection Using Optical Coherence Tomography.

Cholesterol crystals (CCs) are frequently found at the site of acute myocardial infarctions (AMIs), but the role of CCs in the onset of AMI remains unclear due to the lack of validated in vivo imaging tools. The aim of this study was to validate the ability of optical coherence tomography (OCT) to detect CCs and to compare the prevalence and distribution of CCs in patients with AMIs and stable angina pectoris. Approach and Results: CC assessment using OCT were compared with histopathology results in 45 coronary samples. We investigated 152 consecutive patients with AMIs and 41 patients with single vessel-diseased stable angina pectoris. Based on the presence of plaque ruptures (PR), AMI patients were divided into 2 groups: those with PR (n=112) and those without PR (n=40). CCs invading fibrous caps were defined as superficial-type CCs. A multivariable logistic regression analysis was performed to determine PR predictors. The sensitivity and specificity of OCT for detecting CCs were 68% and 92%, respectively. The prevalence of plaques with CCs was higher in the AMI with PR group (AMI with PR 81%, AMI without PR 48%, stable angina pectoris 39%, P<0.01). A multivariable logistic model showed that superficial-type CCs and thin-cap fibroatheromas were positive predictors for PR. OCT has a high specificity and modest sensitivity for the detection of CCs. The combination of CCs invading fibrous cap and thin-cap fibroatheromas detected by OCT may better identify rupture-prone plaques.

Epithelial tissue thickness improves optical coherence tomography's ability in detecting oral cancer.

OCT is a non-invasive imaging technique that enables the measurement of epithelial thickness and architectural changes, which can help in the diagnosis of pre-cancerous and cancerous lesions. The purpose of the study was to assess whether epithelial tissue thickness improves optical coherence tomography's ability in detecting oral cancer. Surgically resected oral margins from 60 patients diagnosed with oral squamous cell carcinoma were subjected to OCT. Three OCT measurements (immediate, 1 h and 24 h post-resection) were conducted per resected tissue specimen to look at the effect of saline and formalin on the specimen and its effect on the reproducibility of the OCT. OCT was, then, used to measure the epithelial tissue thickness in cancer-free and cancer-involved margins in eight oral anatomical locations. This data was, then, combined with architectural changes data to calculate the sensitivity and specificity. An overall of 189 cancer-free margins and 51 cancer-involved margins had their epithelial thickness measured using OCT and compared to histopathology. With regards to the validity of the OCT and histopathological measurements, epithelial thickness showed good correlation between different readings at all oral sites. With regards to the reproducibility of the OCT measurements, the mean epithelial thickness for all measurements at first (immediate) and second (1 h post-resection - saline preserved) measurements was not significantly different. Underestimation of the epithelial depth in cancer-free margins was 20 μm, while in the cancer-involved margins was 10 μm. Combining data from architectural changes and epithelial thickness, a sensitivity of 92% and a specificity of 94% was achieved. Oral epithelium measurements using OCT were valid compared to those made with gold standard pathology. Measurements made using OCT was also reproducible with minor underestimation. Epithelial thickness, combined with architectural changes, led to high accuracy in differentiating between cancer-free and cancer-involved margins.

Evaluation of calculus imaging on root surfaces by spectral-domain optical coherence tomography.

The aim of this in vitro study was to evaluate the ability of optical coherence tomography (OCT) to display calculus on root surfaces. Ten teeth with calculus on the root surface were embedded in resin, omitting the root surface. A region of interest (ROI) was marked by small drill holes coronally and apically of the calculus and imaged by spectral-domain optical coherence tomography ([SD OCT], Telesto SP5, centre wavelength 1310 nm) and light microscopy (LM). To evaluate the impact of different fluids on calculus visualisation, using OCT, root surfaces were covered by a layer of NaCl and blood and displayed by OCT. Subsequently, teeth were completely covered with resin and sectioned for histological evaluation. Within the ROI, lengths of root surface and calculus were measured by LM and OCT, and the ratio [%] was calculated. In addition, at three sites of each ROI, agreement of presence and length of calculus was evaluated. Both methods were compared using Pearson's correlation. Regarding the presence of calculus, agreement between LM and OCT was strong (κi = 0.783, p = 0.033), and measurements regarding the length of the calculus were strongly correlated (ri >0.906; pi <0.001). However, the values differed for dry (p = 0.023) and NaCl-covered root surfaces (p = 0.035). Calculus on the root surface can be displayed by SD-OCT, which therefore may be suited as imaging technology for subgingival calculus in periodontal pockets.

Revealing structural modifications in thermomechanical reshaping of collagenous tissues using optical coherence elastography.

Moderate heating of such collagenous tissues as cornea and cartilages by infra-red laser (IR laser) irradiation is an emerging technology for nondestructive modification of the tissue shape and microstructure for a variety of applications in ophthalmology, otolaryngology and so on. Postirradiation high-resolution microscopic examination indicates the appearance of microscopic either spheroidal or crack-like narrow pores depending on the tissue type and irradiation regime. Such examinations usually require special tissue preparation (eg, staining, drying that affect microstructure themselves) and are mostly suitable for studying individual pores, whereas evaluation of their averaged parameters, especially in situ, is challenging. Here, we demonstrate the ability of optical coherence tomography (OCT) to visualize areas of pore initiation and evaluate their averaged properties by combining visualization of residual irradiation-induced tissue dilatation and evaluation of the accompanying Young-modulus reduction by OCT-based compressional elastography. We show that the averaged OCT-based data obtained in situ fairly well agree with the microscopic examination results. The results obtained develop the basis for effective and safe applications of novel nondestructive laser technologies of tissue modification in clinical practice. PICTURE: Elastographic OCT-based images of an excised rabbit eye cornea subjected to thermomechanical laser-assisted reshaping. Central panel shows resultant cumulative dilatation in cornea after moderate (~45-50°C) pulse-periodic heating by an IR laser together with distribution of the inverse Young modulus 1/E before (left) and after (right) IR irradiation. Significant modulus decrease in the center of irradiated region is caused by initiated micropores. Their parameters can be extracted by analyzing the elastographic images.

Quantitative analysis of retinal and choroidal microvascular changes in patients with diabetes

The relationship between choroidal and retinal microvascular changes has not yet been well described, and there were limited data on diagnostic ability of optical coherence tomography (OCT)-derived vascular parameters for determining diabetic retinopathy (DR) progression. We quantitatively analyzed OCT-derived vascular parameters at superficial (SCP) and deep retinal capillary plexus (DCP), and choroid. We assessed foveal avascular zone (FAZ), vessel density, vessel length density, and choroidal vascularity index in conjunction with DR stage. In this study, patients with diabetes and healthy controls were retrospectively analyzed. One-hundred seventy-four eyes were divided into six groups as follows: Healthy controls, no DR, mild non-proliferative DR (NPDR), moderate NPDR, severe NPDR, and proliferative DR. There were significant quantitative changes in retinal and choroidal vascular parameters with DR progression. The FAZ area and perimeter correlated positively with worsening DR severity; the FAZ circularity index, retinal vessel density, retinal vessel length density, and choroidal vascularity index correlated negatively with worsening severity. Among these, FAZ circulatory index demonstrated good diagnostic performance for DR. Our results cautiously suggest that functional circulatory disturbances in retinal and choroidal vasculatures occur before DR presents. As DR progresses, DCP retinal microvasculature changes precede SCP changes.

Macrophagic enhancement in optical coherence tomography imaging by means of superparamagnetic iron oxide nanoparticles.

The ability of optical coherence tomography (OCT) to visualise macrophages in vivo in coronary arteries is still controversial. We hypothesise that imaging of macrophages in OCT could be enhanced by means of superparamagnetic nanoparticles. We compared the optical backscattering and attenuation of cell pellets containing RAW 264.7 macrophages with those of macrophagic cell pellets labelled with very small superparamagnetic oxydised nanoparticles (VSOP) by means of light intensity analysis in OCT. The labelled macrophages were incubated with VSOP at a concentration of 1 mM Fe, corresponding to intracellular iron concentrations of 8.8 pg/cell. To study the effect of intracellular accumulation on the backscattering, VSOP dilutions without cells were also compared. OCT pullbacks of the PCR tubes containing the cell pellets were obtained and light intensity analysis was performed on raw OCT images in polar view, after normalisation by the backscattering of the PCR tube. The backscattering was estimated by the peak normalised intensity, whilst the attenuation was estimated by the number of pixels between the peak and the normalised intensity 1 (peak-to-one). VSOP-loaded macrophages have higher backscattering than the corresponding unlabelled macrophages (peak normalised intensity 6.30 vs. 3.15) with also slightly higher attenuation (peak-toone 61 vs. 66 pixels). The backscattering of the nanoparticles in suspension was negligible in the light intensity analysis. VSOP increase significantly the optical backscattering of macrophages in the nearinfrared region, with minimal increase in signal attenuation. This finding enables the enhancement of macrophages in conventional OCT imaging with an easily implementable methodology.

Optical coherence tomography and visual evoked potentials in pediatric MS.

Objective:To determine the relative ability of optical coherence tomography (OCT) and pattern-reversal visual evoked potentials (pVEPs) to detect visual pathway involvement in pediatric-onset MS.Methods:Pediatric-onset MS participants (onset <18 years) and healthy controls (HCs) underwent OCT (Cirrus HD-OCT) and pVEPs. Retinal nerve fiber layer (RNFL), ganglion cell layer to inner plexiform layer (GCL-IPL), and P100 pVEP latency were measured. Generalized estimating equation models were used to compare the groups, adjusting for age and intereye correlations.Results:Twenty-four pediatric MS participants, 14 with a history of remote (>6 months) optic neuritis (ON) in one eye (8 participants) or both the eyes (6 participants), and 24 HCs were enrolled. RNFL thinning (<83 μm, 2 SDs below HC eyes) occurred in 50% of ON eyes vs 5% of non-ON eyes. Prolonged VEP latency (>109 msec) occurred in 58% of ON eyes and 55% of non-ON eyes. A clinical history of ON predicted RNFL (p < 0.001) and GCL-IPL thinning (p = 0.011), whereas prolonged pVEP latency in children with MS occurred independent of ON history.Conclusions:OCT and pVEPs provide complementary but distinct insights. OCT is sensitive to retinal changes in the context of clinical ON, whereas pVEPs are useful to detect disseminated lesions of the visual pathway in children with MS.

Optical coherence elastography for strain dynamics measurements in laser correction of cornea shape.

We describe the use of elastographic processing in phase-sensitive optical coherence tomography (OCT) for visualizing dynamics of strain and tissue-shape changes during laser-induced photothermal corneal reshaping, for applications in the emerging field of non-destructive and non-ablative (non-LASIK) laser vision correction. The proposed phase-processing approach based on fairly sparse data acquisition enabled rapid data processing and near-real-time visualization of dynamic strains. The approach avoids conventional phase unwrapping, yet allows for mapping strains even for significantly supra-wavelength inter-frame displacements of scatterers accompanied by multiple phase-wrapping. These developments bode well for real-time feedback systems for controlling the dynamics of corneal deformation with 10-100 ms temporal resolution, and for suitably long-term monitoring of resultant reshaping of the cornea. In ex-vivo experiments with excised rabbit eyes, we demonstrate temporal plastification of cornea that allows shape changes relevant for vision-correction applications without affecting its transparency. We demonstrate OCT's ability to detect achieving of threshold temperatures required for tissue plastification and simultaneously characterize transient and cumulative strain distributions, surface displacements, and scattering tissue properties. Comparison with previously used methods for studying laser-induced reshaping of cartilaginous tissues and numerical simulations is performed.