Customized Tool for the Validation of Optical Coherence Tomography in Differentiation of Prostate Cancer.

OBJECTIVE: To design and demonstrate a customized tool to generate histologic sections of the prostate that directly correlate with needle-based optical coherence tomography pullback measurements. MATERIALS AND METHODS: A customized tool was created to hold the prostatectomy specimens during optical coherence tomography measurements and formalin fixation. Using the tool, the prostate could be sliced into slices of 4 mm thickness through the optical coherence tomography measurement trajectory. In this way, whole-mount pathology slides were produced in exactly the same location as the optical coherence tomography measurements were performed. Full 3-dimensional optical coherence tomography pullbacks were fused with the histopathology slides using the 3-dimensional imaging software AMIRA, and images were compared. RESULTS: A radical prostatectomy was performed in a patient (age: 68 years, prostate-specific antigen: 6.0 ng/mL) with Gleason score 3 + 4 = 7 in 2/5 biopsy cores on the left side (15%) and Gleason score 3 + 4 = 7 in 1/5 biopsy cores on the right side (5%). Histopathology after radical prostatectomy showed an anterior located pT2cNx adenocarcinoma (Gleason score 3 + 4 = 7). Histopathological prostate slides were produced using the customized tool for optical coherence tomography measurements, fixation, and slicing of the prostate specimens. These slides correlated exactly with the optical coherence tomography images. Various structures, for example, Gleason 3 + 4 prostate cancer, stroma, healthy glands, and cystic atrophy with septae, could be identified both on optical coherence tomography and on the histopathological prostate slides. CONCLUSION: We successfully designed and applied a customized tool to process radical prostatectomy specimens to improve the coregistration of whole mount histology sections to fresh tissue optical coherence tomography pullback measurements. This technique will be crucial in validating the results of optical coherence tomography imaging studies with histology and can easily be applied in other solid tissues as well, for example, lung, kidney, breast, and liver. This will help improve the efficacy of optical coherence tomography in cancer detection and staging in solid organs.

Optical Coherence Tomography as a Tool for In Vivo Staging and Grading of Upper Urinary Tract Urothelial Carcinoma: A Study of Diagnostic Accuracy.

PURPOSE: Biopsies and cytology are cornerstones in the diagnosis of upper urinary tract urothelial carcinoma. However, a high rate of nondiagnostic biopsies, tumor upgrading and tumor up staging after nephroureterectomy has been observed. In this prospective in vivo study we evaluated the diagnostic accuracy of optical coherence tomography for the grading and staging of upper tract urothelial carcinoma. MATERIALS AND METHODS: A total of 26 patients underwent diagnostic ureterorenoscopy including biopsies and optical coherence tomography, followed by nephroureterectomy or segmental ureter resection. The sensitivity, specificity, negative predictive value and positive predictive value of upper tract urothelial carcinoma grading and staging by optical coherence tomography were evaluated according to the STARD (Standards for Reporting of Diagnostic Accuracy) initiative and the second stage (2a and 2b) of the IDEAL model. For tumor staging a 2×2 table for sensitivity and specificity was calculated. For tumor grading the Wilcoxon rank sum test was used to test µoct in low and high grade lesions followed by ROC analysis for sensitivity and specificity. RESULTS: In 83% the staging of lesions was in accordance with final histopathology. Sensitivity and specificity analysis for tumor invasion was 100% and 92%, respectively. Tumor size greater than 2 mm and inflammation were risks for false-positives. For low and high grade lesions median µoct was 2.1 and 3.0 mm-1, respectively (p <0.01). ROC analysis showed a sensitivity of 87% and a specificity of 90% using a µoct cutoff of 2.4 mm-1. CONCLUSIONS: This report describes optical coherence tomography as a real-time, intraoperatively diagnostic modality in the diagnostic evaluation of upper tract urothelial carcinoma. We confirmed the ability of optical coherence tomography to visualize, grade and stage urothelial carcinoma in the upper urinary tract.

Prostate cancer diagnosis by optical coherence tomography: First results from a needle based optical platform for tissue sampling.

The diagnostic accuracy of Optical Coherence Tomography (OCT) based optical attenuation coefficient analysis is assessed for the detection of prostate cancer. Needle-based OCT-measurements were performed on the prostate specimens. Attenuation coefficients were determined by an earlier described in-house developed software package. The mean attenuation coefficients (benign OCT data; malignant OCT data; p-value Mann-Whitney U test) were: (3.56 mm(-1) ; 3.85 mm(-1) ; p < 0.0001) for all patients combined. The area under the ROC curve was 0.64. In order to circumvent the effect of histopathology mismatching, we performed a sub-analysis on only OCT data in which tumor was visible in two subsequent histopathological prostate slices. This analysis could be performed in 3 patients. The mean attenuation coefficients (benign OCT data; malignant OCT data; p-value Mann-Whitney U test) were: (3.23 mm(-1) ; 4.11 mm(-1) ; p < 0.0001) for all patients grouped together. The area under the ROC curve was 0.89. Functional OCT of the prostate has shown to differentiate between cancer and healthy prostate tissue. The optical attenuation coefficient in malignant tissue was significantly higher in malignant tissue compared to benign prostate tissue. Further studies are required to validate these initial results in a larger group of patients with a more tailored histopathology matching protocol.

Volumetric laser endomicroscopy in Barrett's esophagus: a feasibility study on histological correlation.

Volumetric laser endomicroscopy (VLE) is a novel balloon-based optical coherence tomography (OCT) imaging technique that may improve detection of early neoplasia in Barrett's esophagus (BE). Most OCT studies lack a direct correlation between histology and OCT images. The aim is to investigate the optimal approach for achieving one-to-one correlation of ex-vivo VLE images of endoscopic resection (ER) specimens with histology. BE patients with and without early neoplasia underwent ER after delineating areas with electrocoagulation markers (ECM). After ER, specimens underwent additional ex-vivo marking with several different markers (ink, pin, Gold Probe) followed by ex-vivo VLE scanning. ER specimens were carefully sectioned into tissue blocks guided by the markers. Histology and VLE slides were considered a match if ≥ 2 markers were visible on both modalities and mucosal patterns aside from these markers matched on both histology and VLE. From 16 ER specimens 120 tissue blocks were sectioned of which 23 contained multiple markers. Fourteen histology-VLE matches were identified. ECMs and ink markers proved to be the most effective combination for matching. The last 6/16 ER specimens yielded 9/14 matches, demonstrating a learning curve due to methodological improvements in marker placement and tissue block sectioning. One-to-one correlation of VLE and histology is complex but feasible. The groundwork laid in this study will provide high-quality histology-VLE correlations that will allow further research on VLE features of early neoplasia in BE.

Functional optical coherence tomography of pigmented lesions.

BACKGROUND: Cutaneous melanomas are diagnosed worldwide in 231,130 patients per year. The sensitivity and specificity of melanoma diagnosis expresses the need for an additional diagnostic method. Optical coherence tomography (OCT) has shown that it allows morphological (qualitative) description of image features and quantitative analysis of pathology related light scattering by means of the attenuation coefficient (µoct ). OBJECTIVE: We hypothesize that OCT images of nevi will differ qualitatively and quantitatively from melanomas. METHODS: Forty lesions from 33 consecutive patients were imaged with OCT. After data acquisition, excision was performed. Epidermal layer thickness was measured and values of µoct were extracted from 200 OCT images of pigmented lesions. RESULTS: Morphologically, absence of the lower border of the lesion was characteristic for melanoma (P = 0.02). Also, the µoct was different between benign and malignant lesions (P = 0.02). There were no differences in epidermal layer thickness of benign lesions and melanoma. CONCLUSION: Although this preliminary study comprised a small number of patients, quantitative analysis of OCT images in pigmented skin lesions give valuable additional information about lesions characteristics. When using the attenuation coefficient, it might be possible to distinguish between benign lesions and melanomas.

Optical biopsy of epithelial cancers by optical coherence tomography (OCT).

Optical coherence tomography (OCT) is an optical technique that measures the backscattering of near-infrared light by tissue. OCT yields in 2D and 3D images at micrometer-scale resolution, thus providing optical biopsies, approaching the resolution of histopathological imaging. The technique has shown to allow in vivo differentiation between benign and malignant epithelial tissue, through qualitative assessment of OCT images, as well as by quantitative evaluation, e.g., functional OCT. This study aims to summarize the principles of OCT and to discuss the current literature on the diagnostic value of OCT in the diagnosis of epithelial (pre)malignant lesions. The authors did a systematic search of the electronic databases PubMed and Embase on OCT in the diagnostic process of (pre)malignant epithelial lesions. OCT is able to differentiate between benign and (pre)malignant lesions of epithelial origin in a wide variety of tissues. In this way, OCT can detect skin cancers, oral, laryngeal, and esophageal cancer as well as genital and bladder cancer. OCT is an innovative technique which enables an optical biopsy of epithelial lesions. The incorporation of OCT in specific tools, like handheld and catheter-based probes, will further improve the implementation of this technology in daily clinical practice.

Dependent and multiple scattering in transmission and backscattering optical coherence tomography.

We use transmission and backscattering optical coherence tomography (OCT) to distinguish and quantify dependent and multiple scattering effects in turbid media. With transmission OCT the dependent scattering coefficients for a range of monodisperse silica particle suspensions are determined. An excellent agreement is observed between the measured dependent scattering coefficients and calculations based on Mie calculations, the Percus-Yevick radial distribution function, and coherent light scattering theory. Backscattering OCT measurements are fitted using the extended Huygens-Fresnel (EHF) model with the dependent scattering coefficients obtained from the transmission OCT measurements as input parameters. Good agreement between the EHF model and the backscattering OCT measurements is observed. For large particles, the rms scattering angle θrms obtained from the EHF fit is in fair agreement with θrms calculated from the transmission OCT data.

New optical diagnostic tools in renal cell cancer.

In modern medicine the profound use of abdominal imaging has led to a dramatic change of presentation of renal tumors. Smaller tumors and therefore more benign masses are being discovered, and as systemic use of renal mass biopsies is not recommended by the general guidelines, an appropriate tool to assess the biology of renal tumors is highly desirable. Apart from new developments of currently applied diagnostic modalities, several research groups focus on the potential of optical diagnostic techniques to contribute to the diagnostic process of renal tumors. They use the interaction of light with biological tissue to gather information on the optical properties of a tissue sample and therefore providing information on the histological composition of this tissue in a non-invasive manner and in real-time. In this review we provide an overview of novel diagnostic techniques starting with the future of conventional diagnostics like Contrast-enhanced ultrasonography (CEUS) and positron emission tomography-computed tomography (PET-CT) followed by optical technologies that are potentially employed in the nearby future to improve the diagnostic process of renal tumors with a focus on optical diagnostic techniques.

Determination of the scattering anisotropy with optical coherence tomography.

In this work we demonstrate measurements with optical coherence tomography (OCT) of the scattering phase function in the backward direction and the scattering anisotropy parameter g. Measurements of the OCT attenuation coefficient and the backscattering amplitude are performed on calibrated polystyrene microspheres with a time-domain OCT system. From these measurements the phase function in the backward direction is determined. The measurements are described by the single scattering model and match Mie calculations very well. Measurements on Intralipid demonstrate the ability to determine the g of polydisperse samples and, for Intralipid, g = 0.35 ± 0.03 is measured, which is well in agreement with g from literature. These measurements are validated using the Intralipid particle size distribution determined from TEM measurements. Measurements of g and the scattering phase function in the backward direction can be used to monitor changes in backscattering, which can indicate morphological changes of the sample or act as contrast enhancement mechanism.

Macular pigment optical density measurements: evaluation of a device using heterochromatic flicker photometry.

PURPOSE: Accurate assessment of the amount of macular pigment (MPOD) is necessary to investigate the role of carotenoids and their assumed protective functions. High repeatability and reliability are important to monitor patients in studies investigating the influence of diet and supplements on MPOD. We evaluated the Macuscope (Macuvision Europe Ltd., Lapworth, Solihull, UK), a recently introduced device for measuring MPOD using the technique of heterochromatic flicker photometry (HFP). We determined agreement with another HFP device (QuantifEye; MPS 9000 series: Tinsley Precision Instruments Ltd., Croydon, Essex, UK) and a fundus reflectance method. METHODS: The right eyes of 23 healthy subjects (mean age 33.9 ± 15.1 years) were measured. We determined agreement with QuantifEye and correlation with a fundus reflectance method. Repeatability of QuantifEye was assessed in 20 other healthy subjects (mean age 32.1 ± 7.3 years). Repeatability was also compared with measurements by a fundus reflectance method in 10 subjects. RESULTS: We found low agreement between test and retest measurements with Macuscope. The average difference and the limits of agreement were -0.041 ± 0.32. We found high agreement between test and retest measurements of QuantifEye (-0.02 ± 0.18) and the fundus reflectance method (-0.04 ± 0.18). MPOD data obtained by Macuscope and QuantifEye showed poor agreement: -0.017 ± 0.44. For Macuscope and the fundus reflectance method, the correlation coefficient was r = 0.05 (P = 0.83). A significant correlation of r = 0.87 (P<0.001) was found between QuantifEye and the fundus reflectance method. CONCLUSIONS: Because repeatability of Macuscope measurements was low (ie, wide limits of agreement) and MPOD values correlated poorly with the fundus reflectance method, and agreed poorly with QuantifEye, the tested Macuscope protocol seems less suitable for studying MPOD.

Multiple and dependent scattering effects in Doppler optical coherence tomography.

Doppler optical coherence tomography (OCT) is a technique to image tissue morphology and to measure flow in turbid media. In its most basic form, it is based on single (Mie) scattering. However, for highly scattering and dense media multiple and concentration dependent scattering can occur. For Intralipid solutions with varying scattering strength, the effect of multiple and dependent scattering on the OCT signal attenuation and Doppler flow is investigated. We observe a non-linear increase in the OCT signal attenuation rate and an increasingly more distorted Doppler OCT flow profile with increasing Intralipid concentration. The Doppler OCT attenuation and flow measurements are compared to Monte Carlo simulations and good agreement is observed. Based on this comparison, we determine that the single scattering attenuation coefficient micros is 15% higher than the measured OCT signal attenuation rate. This effect and the distortion of the measured flow profile are caused by multiple scattering. The non-linear behavior of the single scattering attenuation coefficient with Intralipid concentration is attributed to concentration dependent scattering.

Quantitative comparison of the OCT imaging depth at 1300 nm and 1600 nm.

One of the present challenges in optical coherence tomography (OCT) is the visualization of deeper structural morphology in biological tissues. Owing to a reduced scattering, a larger imaging depth can be achieved by using longer wavelengths. In this work, we analyze the OCT imaging depth at wavelengths around 1300 nm and 1600 nm by comparing the scattering coefficient and OCT imaging depth for a range of Intralipid concentrations at constant water content. We observe an enhanced OCT imaging depth for 1600 nm compared to 1300 nm for Intralipid concentrations larger than 4 vol.%. For higher Intralipid concentrations, the imaging depth enhancement reaches 30%. The ratio of scattering coefficients at the two wavelengths is constant over a large range of scattering coefficients and corresponds to a scattering power of 2.8 ± 0.1. Based on our results we expect for biological tissues an increase of the OCT imaging depth at 1600 nm compared to 1300 nm for samples with high scattering power and low water content.

Influence of cataract on optical coherence tomography image quality and retinal thickness.

BACKGROUND: As optical coherence tomography (OCT) is widely used for diagnosis and monitoring of ocular pathology, especially in the elderly people, the influence of cataract on image quality and macular retinal thickness was studied. METHODS: In 29 patients scheduled for cataract surgery, preoperative and postoperative OCT scans were obtained. Cataracts were categorised as nuclear, posterior or cortical. Parameters for image quality (signal-to-noise ratio (SNR)) and signal strength and macular thickness were compared. A three-level expert grading scale was used to evaluate the discriminative abilities of SNR and signal strength. RESULTS: Nuclear cataracts (n = 12) provided better preoperative scans (higher SNR/signal strength) than posterior (n = 7) and cortical (n = 10) cataracts (p<0.004). Postoperatively SNR and signal strength increased significantly in all patients (p<0.001). The SNR was better at discriminating poor from acceptable and good scans than signal strength (area under the receiver operating curve: 0.879 and 0.810, respectively). Postoperative macular thickness overall showed a significant increase (p = 0.005), most evident in patients with posterior cataracts (p = 0.028). CONCLUSIONS: OCT imaging is influenced by cataract; image quality is reduced preoperatively and macular thickness measurements are slightly increased postoperatively. In individual patients, OCT scans remain reliable for gross clinical interpretation, even in the presence of cataract.

Colour oscillations in arterioarterial anastomoses reflect natural differences in donor and recipient oxygenation and hematocrit.

Our aim was to show that the colour difference between brighter and darker red, occasionally observed as an oscillating boundary in the recipient and donor parts of an arterioarterial anastomosis in severe twin-twin transfusion syndrome (TTTS), is a consequence of natural differences in blood oxygenation and hematocrit developing between donor and recipient twins. As method we defined a theoretical model of the placenta with dimensions from pathology examination. From literature we determined the optical absorption and scattering properties of all tissue components, and hematocrit and oxygen saturation values for donor and recipient twins. From our placental model we simulated the spectrum of back-scattered light by standard Monte Carlo photon propagation computations and calculated the colour of chorionic arterial and venous blood vessels by applying the physics theory of colour perception. Our computations demonstrate that recipient arterial blood is somewhat brighter red than donor arterial blood. The strong colour differences seen after laser coagulation of all anastomoses but the arterioarterial were explained from an angiotensin II cut-off in the recipient due to obliteration of arteriovenous anastomoses, causing a temporary increase in recipient placental perfusion and hence in blood oxygenation. In conclusion, natural differences in recipient versus donor blood oxygen saturation and hematocrit in severe TTTS explain the observed colour differences between brighter and darker red observed in the recipient and donor parts of arterioarterial anastomoses.

Quantitative optical coherence tomography of arterial wall components.

Optical coherence tomography (OCT) can be used to visualize the arterial wall and atherosclerotic plaques with high resolution. In this study, we verified the application of OCT to the quantitative analysis of plaque structural dimensions and optical attenuation coefficients of the components. We assessed the effect of balloon dilation on the OCT signal from the medial layer of porcine carotid artery ex vivo. Imaging of human autopsy samples was performed from the luminal side with a high (3.5 microm axial and 7 microm lateral) resolution OCT system (approximately 800 nm) or a regular (15-20 microm axial and 20 microm lateral resolution) OCT system (approximately 1,300 nm). For each sample, dimensions were measured by histomorphometry and OCT, and the optical attenuation was measured. In a tissue culture set-up, porcine carotid arteries were dilated and the attenuation coefficients of the dilated segments were compared to a control segment for 4 h. Quantitative analysis showed a strong and significant correlation between OCT and histology cap thickness measurements for both OCT systems. For both systems, the measured attenuation coefficients for diffuse intimal thickening and lipid-rich regions differed significantly from that of calcified tissue. Balloon dilation induced a time-dependent increase in the attenuation coefficient, which may be attributed to the induction of apoptosis. In conclusion both the high and regular resolution OCT systems can image the atherosclerotic plaques precisely. Quantitative analysis of the OCT signals allowed in situ determination of the intrinsic optical attenuation coefficient for atherosclerotic tissue components within regions of interest, which can help to discriminate between plaque and arterial wall components.

Optical coherence tomography of the Ex-PRESS miniature glaucoma implant.

PURPOSE: To describe the localisation of the Ex-PRESS miniature glaucoma implant with an experimental setup for optical coherence tomography (OCT) of the anterior segment of the eye. METHODS: An OCT scanner, central wavelength 1,280 nm, bandwidth 60 nm, resolution of 12 microm, was built onto a slitlamp to scan the anterior segment of the eye. Five ex-vivo porcine eyes received an Ex-PRESS miniature glaucoma implant and were used as a model to visualise the position of the implant in the anterior segment. RESULTS: In the ex-vivo porcine eyes, the OCT images showed the anatomy of the anterior segment in great detail. The anterior segment OCT was able to visualise the whole outline and position of the implant. The abrupt change in reflectivity going from tissue to the implant resulted in a clear border along the circumference of the whole device. CONCLUSION: In this paper, we have shown that we were able to outline the Ex-PRESS miniature glaucoma implant in the anterior segment of the ex-vivo porcine eye by using an experimental OCT setup built onto a slitlamp. The acquisition time of 0.8 s is short enough to allow for the scanning of patients, and anterior segment OCT is expected to aid in providing answers to the question regarding which parameters will determine the success or failure of such a device.