Effect of acetic acid on optical coherence tomography (OCT) images of cervical epithelium

Diffuse optical microscopy for quantification of depth-dependent epithelial backscattering in the cervix

A fiber optic imaging approach is presented using structured illumination for quantification of almost pure epithelial backscattering. We employ multiple spatially modulated projection patterns and camera-based reflectance capture to image depth-dependent epithelial scattering. The potential diagnostic value of our approach is investigated on cervical ex vivo tissue specimens. Our study indicates a strong backscattering increase in the upper part of the cervical epithelium caused by dysplastic microstructural changes. Quantization of relative depth-dependent backscattering is confirmed as a potentially useful diagnostic feature for detection of precancerous lesions in cervical squamous epithelium.

Backscattering intensity measurements in optical coherence tomography as a method to identify parathyroid glands

BACKGROUND AND OBJECTIVE

Previous studies have shown that the use of optical coherence tomography (OCT) permits the differentiation between parathyroid tissue, thyroid tissue, lymph nodes and adipose tissue. We investigated the backscattering intensity profiles of OCT images in order to determine whether significant differences between these tissue types exist.

METHODS

Mean backscattering intensity profiles were obtained from OCT images of parathyroid glands, thyroid tissue, lymph nodes and adipose tissue. The profiles were analyzed employing Fisher's Linear Discriminant Analysis (LDA). The results were cross validated employing improved parameter estimation techniques.

RESULTS

Mean backscattering intensity profiles from 300 OCT images of 34 patients undergoing thyroid or parathyroid surgery were analyzed. The overall rate of correct classifications was 96.15%. The cross validation employing improved parameter estimation techniques yielded results identical to those derived from Fisher's LDA.

CONCLUSION

Besides the individual assessment of OCT images by interpreting morphological criteria, backscattering intensity measurements can reliably distinguish between different tissue entities.

Effect of optical clearing agents on optical coherence tomography images of cervical epithelium

Optical coherence tomography (OCT) can be used as an adjunct to colposcopy in order to detect precancerous and cancerous cervical lesions. Optical clearing agents (OCAs) temporarily reduce the optical scattering of biological tissues. The purpose of this study was to investigate their influence on OCT imaging. OCT images were taken from unsuspicious and suspicious areas of fresh conization specimens immediately after resection and 5, 10, and 20 min after application of dimethyl sulfoxide (DMSO) or polyethylene glycol (PEG). Corresponding histologies were obtained from all sites. The images taken 5, 10, and 20 min after application of OCA were compared to the initial images with respect to changes in brightness, contrast, and scanning depth using a standard nonparametric test of differences of proportions. Further, mean intensity backscattering curves were calculated from all OCT images in the histological groups CIN2, CIN3, inflammation, and normal epithelium. Mean difference profiles within each of these groups were determined, reflecting the mean differences between the condition before the application of OCA and the exposure times 5, 10, and 20 min, respectively. The null hypothesis was tested employing the Dicky-Fuller-test, Hotelings-test and run test. The visual analysis of 434 OCT images from 109 different sites of 24 conization specimens showed a statistically significant increase in brightness and contrast for normal and dysplastic epithelium after application of DMSO or PEG. Further, the analysis of mean intensity profiles suggests the existence of an increased backscattering intensity after application of DMSO or PEG. DMSO and PEG contribute substantially to optical clearing in cervical squamous epithelium and therefore influence OCT imaging in a positive way. With further refinement of the OCT technology, the observed changes may be beneficial in interpreting the tissue microstructure and identifying cervical intraepithelial neoplasia.