Grading upper tract urothelial carcinoma with the attenuation coefficient of in-vivo optical coherence tomography

Theoretical and experimental determination of the confocal function of OCT systems for accurate calculation of sample optical properties

The attenuation coefficient of biological tissue could serve as an indicator of structural and functional changes related to the onset or progression of disease. Optical coherence tomography (OCT) provides cross sectional images of tissue up to a depth of a few millimeters, based on the local backscatter properties. The OCT intensity also depends on the confocal function, which needs to be characterised to determine correctly the exponential decay of the intensity based on Lambert-Beer. We present a model for the confocal function in scattering media based on the illumination with a Gaussian beam and the power transfer into a single mode fibre (SMF) of the backscattered light for an incoherently back scattered Gaussian beam using the Huygens-Fresnel principle and compare that model with the reflection from a mirror. We find that, contrary to previous literature, the confocal functions characterised by the Rayleigh range in the two models are identical. Extensive OCT focus series measurements on a mirror, Spectralon and Intralipid dilutions confirm our model, and show that for highly scattering samples the confocal function characterised by the Rayleigh range becomes depth dependent. From the diluted Intralipid measurements the attenuation coefficients are extracted using a singly scatter model that includes the previously established confocal function. The extracted attenuation coefficients were in good agreement for weakly scattering samples (μ s  < 2 mm-1).

Multiparameter interferometric polarization-enhanced imaging differentiates carcinoma in situ from inflammation of the bladder: an ex vivo study

Significance

Successful differentiation of carcinoma in situ (CIS) from inflammation in the bladder is key to preventing unnecessary biopsies and enabling accurate therapeutic decisions. Current standard-of-care diagnostic imaging techniques lack the specificity needed to differentiate these states, leading to false positives.

Aim

We introduce multiparameter interferometric polarization-enhanced (MultiPIPE) imaging as a promising technology to improve the specificity of detection for better biopsy guidance and clinical outcomes.

Approach

In this ex vivo study, we extract tissue attenuation-coefficient-based and birefringence-based parameters from MultiPIPE imaging data, collected with a bench-top system, to develop a classifier for the differentiation of benign and CIS tissues. We also analyze morphological features from second harmonic generation imaging and histology slides and perform imaging-to-morphology correlation analysis.

Results

MultiPIPE enhances specificity to differentiate CIS from benign tissues by nearly 20% and reduces the false-positive rate by more than four-fold over clinical standards. We also show that the MultiPIPE measurements correlate well with changes in morphological features in histological assessments.

Conclusions

The results of our study show the promise of MultiPIPE imaging to be used for better differentiation of bladder inflammation from flat tumors, leading to a fewer number of unnecessary procedures and shorter operating room (OR) time.

Intraoperative application of optical coherence tomography for lung tumor

On-site instant determination of benign or malignant tumors for deciding the types of resection is crucial during pulmonary surgery. We designed a portable spectral-domain optical coherence tomography (SD-OCT) system to do real-time scanning intraoperatively for the distinction of fresh tumor specimens in the lung. A total of 12 ex vivo lung specimens from six patients were enrolled. Three patients were diagnosed with invasive adenocarcinoma (IA), while the others were benign. After OCT-imaged reconstruction, we compared the qualitative morphology of OCT and histology among malignant, benign, and normal tissues. In addition, through analysis of the quantitative data, a discrete difference in optical attenuation coefficients around the junctional surface was shown by our data processing. This study demonstrated a feasible OCT-assisted resection guide by a rapid on-site tumor diagnosis. The results indicate that future deep learning of OCT-captured image systems able to improve diagnostic and therapeutic efficiency is warranted.

Multimodal Raman spectroscopy and optical coherence tomography for biomedical analysis

Optical techniques hold great potential to detect and monitor disease states as they are a fast, non-invasive toolkit. Raman spectroscopy (RS) in particular is a powerful label-free method capable of quantifying the biomolecular content of tissues. Still, spontaneous Raman scattering lacks information about tissue morphology due to its inability to rapidly assess a large field of view. Optical Coherence Tomography (OCT) is an interferometric optical method capable of fast, depth-resolved imaging of tissue morphology, but lacks detailed molecular contrast. In many cases, pairing label-free techniques into multimodal systems allows for a more diverse field of applications. Integrating RS and OCT into a single instrument allows for both structural imaging and biochemical interrogation of tissues and therefore offers a more comprehensive means for clinical diagnosis. This review summarizes the efforts made to date toward combining spontaneous RS-OCT instrumentation for biomedical analysis, including insights into primary design considerations and data interpretation.

Depth-resolved extraction of optical attenuation for glaucoma assessment in clinical settings: a pilot study

We assessed the ability of the optical attenuation coefficient (AC) to detect early-stage glaucoma with two AC estimation algorithms: retinal layer intensity ratio (LIR) and depth-resolved confocal (DRC). We also introduced new depth-dependent AC parameters for retinal nerve fiber layer assessment. Optical coherence tomography B-scans were collected from 44 eyes of age-similar participants with eye health ranging from healthy to severe glaucoma, including glaucoma suspect patients. Mean AC values estimated from the DRC method are comparable to ratio-extracted values (p > 0.5 for all study groups), and the depth-dependent AC_DRC parameters enhance the utility of the AC for detection of early-stage glaucoma.

Precision of attenuation coefficient measurements by optical coherence tomography

SIGNIFICANCE

Optical coherence tomography (OCT) is an interferometric imaging modality, which provides tomographic information on the microscopic scale. Furthermore, OCT signal analysis facilitates quantification of tissue optical properties (e.g., the attenuation coefficient), which provides information regarding the structure and organization of tissue. However, a rigorous and standardized measure of the precision of the OCT-derived optical properties, to date, is missing.

AIM

We present a robust theoretical framework, which provides the Cramér -Rao lower bound σμOCT for the precision of OCT-derived optical attenuation coefficients.

APPROACH

Using a maximum likelihood approach and Fisher information, we derive an analytical solution for σμOCT when the position and depth of focus are known. We validate this solution, using simulated OCT signals, for which attenuation coefficients are extracted using a least-squares fitting procedure.

RESULTS

Our analytical solution is in perfect agreement with simulated data without shot noise. When shot noise is present, we show that the analytical solution still holds for signal-to-noise ratios (SNRs) in the fitting window being above 20 dB. For other cases (SNR&lt;20 dB, focus position not precisely known), we show that the numerical calculation of the precision agrees with the σμOCT derived from simulated signals.

CONCLUSIONS

Our analytical solution provides a fast, rigorous, and easy-to-use measure for OCT-derived attenuation coefficients for signals above 20 dB. The effect of uncertainties in the focal point position on the precision in the attenuation coefficient, the second assumption underlying our analytical solution, is also investigated by numerical calculation of the lower bounds. This method can be straightforwardly extended to uncertainty in other system parameters.

The Diagnostic Yield and Concordance of Ureterorenoscopic Biopsies for Grading of Upper Tract Urothelial Carcinoma: A Dutch Nationwide Analysis

Objectives: To evaluate the diagnostic yield and concordance of upper tract urothelial carcinoma (UTUC) grading between ureterorenoscopic biopsies and surgical resections. Materials and Methods: The nationwide Dutch Pathology Registry (nationwide network and registry of histo- and cytopathology in the Netherlands [PALGA]) was searched for UTUC-positive renal units (RUs) with histopathology excerpts from ureterorenoscopic biopsies and surgical resections, matched for laterality and localization of the tumor, from 2011 until 2018. The positive predictive value (concordance) of the biopsy grade with regard to the final grade according to the World Health Organization (WHO) 2004 classification was calculated. Results: A total of 1002 UTUC-positive rental units were included, of which 776 UTUC-positive RUs were graded according to the WHO 2004 classification in the ureterorenoscopic biopsy, the localization-matched surgical resection, or in both. The diagnostic yield of biopsies for a classifying diagnosis was 89% with a sensitivity for UTUC of 84%. In case of UTUC, the diagnostic yield for biopsy-based grading and staging was 97% and 72%, respectively. The concordance of high-grade biopsies with regard to the final histopathology was 97% and 62% for low-grade biopsies. Upgrading to final high grade occurred in 33% of the low-grade biopsies. Downgrading to final low grade occurred in 2% of high-grade biopsies. Conclusions: This is the first study to portray the limitations of ureterorenoscopic biopsies for UTUC in a nationwide cohort. The diagnostic yield of ureterorenoscopic biopsies for a classifying diagnosis is suboptimal, but the diagnostic yield for grading according to the WHO 2004 classification is high. Yet, a worrisome amount of ureterorenoscopic biopsies are upgraded with regard to the surgical resection. Consequently, one-third of patients, who qualify for kidney-sparing treatment according to one of the criteria recommended for risk stratification, might be stratified incorrectly. These findings stress the importance of a timely and stringent ureterorenoscopic follow-up after kidney-sparing surgery and highlight the need for improvements in the diagnostic approach to optimize the risk stratification.

Parametric imaging of attenuation by optical coherence tomography: review of models, methods, and clinical translation

SIGNIFICANCE

Optical coherence tomography (OCT) provides cross-sectional and volumetric images of backscattering from biological tissue that reveal the tissue morphology. The strength of the scattering, characterized by an attenuation coefficient, represents an alternative and complementary tissue optical property, which can be characterized by parametric imaging of the OCT attenuation coefficient. Over the last 15 years, a multitude of studies have been reported seeking to advance methods to determine the OCT attenuation coefficient and developing them toward clinical applications.

AIM

Our review provides an overview of the main models and methods, their assumptions and applicability, together with a survey of preclinical and clinical demonstrations and their translation potential.

RESULTS

The use of the attenuation coefficient, particularly when presented in the form of parametric en face images, is shown to be applicable in various medical fields. Most studies show the promise of the OCT attenuation coefficient in differentiating between tissues of clinical interest but vary widely in approach.

CONCLUSIONS

As a future step, a consensus on the model and method used for the determination of the attenuation coefficient is an important precursor to large-scale studies. With our review, we hope to provide a basis for discussion toward establishing this consensus.

Real-time colorectal cancer diagnosis using PR-OCT with deep learning

Prior reports have shown optical coherence tomography (OCT) can differentiate normal colonic mucosa from neoplasia, potentially offering an alternative technique to endoscopic biopsy - the current gold-standard colorectal cancer screening and surveillance modality. To help clinical translation limited by processing the large volume of generated data, we designed a deep learning-based pattern recognition (PR) OCT system that automates image processing and provides accurate diagnosis potentially in real-time. Method: OCT is an emerging imaging technique to obtain 3-dimensional (3D) "optical biopsies" of biological samples with high resolution. We designed a convolutional neural network to capture the structure patterns in human colon OCT images. The network is trained and tested using around 26,000 OCT images acquired from 20 tumor areas, 16 benign areas, and 6 other abnormal areas. Results: The trained network successfully detected patterns that identify normal and neoplastic colorectal tissue. Experimental diagnoses predicted by the PR-OCT system were compared to the known histologic findings and quantitatively evaluated. A sensitivity of 100% and specificity of 99.7% can be reached. Further, the area under the receiver operating characteristic (ROC) curves (AUC) of 0.998 is achieved. Conclusions: Our results demonstrate that PR-OCT can be used to give an accurate real-time computer-aided diagnosis of colonic neoplastic mucosa. Future development of this system as an "optical biopsy" tool to assist doctors in real-time for early mucosal neoplasms screening and treatment evaluation following initial oncologic therapy is planned.

Management of Low-grade Upper Tract Urothelial Carcinoma: An Unmet Need

Upper tract urothelial cancers (UTUC) are frequently managed by radical nephroureterectomy (RNU), a major operative procedure that may entail short-term morbidity and long-term decline in renal function. Kidney-sparing procedures offer a less invasive alternative to RNU for low-risk, low-grade UTUC (LG-UTUC). They are associated with similar disease-specific survival rates and better long-term renal function, albeit with a potentially increased risk of recurrence. Strategies to decrease LG-UTUC recurrence include improved risk stratification and enhanced endoscopic instrumentation. Chemoablation may represent an alternative, innovative kidney-sparing approach for LG-UTUC.

Review of methods and applications of attenuation coefficient measurements with optical coherence tomography

The optical attenuation coefficient (AC), an important tissue parameter that measures how quickly incident light is attenuated when passing through a medium, has been shown to enable quantitative analysis of tissue properties from optical coherence tomography (OCT) signals. Successful extraction of this parameter would facilitate tissue differentiation and enhance the diagnostic value of OCT. In this review, we discuss the physical and mathematical basis of AC extraction from OCT data, including current approaches used in modeling light scattering in tissue and in AC estimation. We also report on demonstrated clinical applications of the AC, such as for atherosclerotic tissue characterization, malignant lesion detection, and brain injury visualization. With current studies showing AC analysis as a promising technique, further efforts in the development of methods to accurately extract the AC and to explore its potential use for more extensive clinical applications are desired.