Statistical model for OCT image denoising

Abstract

Optical coherence tomography (OCT) is a non-invasive technique with a large array of applications in clinical imaging and biological tissue visualization. However, the presence of speckle noise affects the analysis of OCT images and their diagnostic utility. In this article, we introduce a new OCT denoising algorithm. The proposed method is founded on a numerical optimization framework based on maximum-a-posteriori estimate of the noise-free OCT image. It combines a novel speckle noise model, derived from local statistics of empirical spectral domain OCT (SD-OCT) data, with a Huber variant of total variation regularization for edge preservation. The proposed approach exhibits satisfying results in terms of speckle noise reduction as well as edge preservation, at reduced computational cost.

The hemodynamic changes during cupping therapy monitored by using an optical sensor embedded cup

“…To confirm this, it is necessary to monitor the tissue metabolic rate during cupping therapy by simultaneously measuring the blood flow and tissue oxygenation changes in a future study. From the results of the hemodynamic changes at the periphery site ( Figure 2B), the RHb responses are comparable to a previous study [18], but a difference appears in the OHb response. In our study, the OHb decreases immediately after the application of negative pressure and then recovers back to the baseline level in the middle of the cupping therapy.…”

“…The S-D was determined by considering the optical sensor size that can be placed inside the cup and the stable position of the LED and photodiode to maintain contact with the skin when the skin is sucked-up into the cup during treatment. To monitor the hemodynamic changes at the periphery site, another optical probe was fabricated with S-D of 3 cm which was decided to monitor hemodynamics globally because we expected that hemodynamics at the periphery site would not be specifically localized but would be more distributed, and it is same as the other group who monitored the periphery site [18]. The cup with the optical probe was then placed on the thoracolumbar fascia for the FIGURE 1 A, A cup with an optical probe that consists of a dual wavelength SMD type LED and a photodiode, B, placement of the suction cup and the NIRS probe cupping therapy.…”

“…Recently, one research group demonstrated NIRS as a promising tool to monitor the hemodynamics caused by the cupping procedure. Their results showed noticeable hemodynamic changes at the periphery site of cupping therapy [18]. However, their observation was limited to the peripheral area due to inaccessibility to the inside of the vacuum cup.…”

A novel algorithm to optimize generalized gamma distributed multiplicative noise with implications on speckle removal from OCT images

“…Nevertheless, additive denoising methods based on non-local means (NLM) [20]- [22], wavelet transformation [23]- [25] and constrained least square methods [26]- [28] have been used to remove speckle. In addition, NLM approaches require repeated similar patches in an image to perform well [29] which can be problematic because human brain tissue is highly spatially varying between 1 -20 µm resolution, wavelet methods can suffer from wavelet domain artifacts [29] and least squares fidelity is sub-optimal because it inherently and incorrectly assumes the speckle distribution to be log normal [9].…”

Improved wavelet hierarchical threshold filter method for optical coherence tomography image de-noising

“…7 For better understanding the speckle noise in OCT, many groups have done signi¯cant research on its statistics and properties. [8][9][10][11] Many methods have been proposed to attenuate the speckle noise in OCT images, these methods can be divided into two parts: hardware and software methods. Hardware methods are optical approaches that physically remove speckle noise, including frequency 12,13 and spatial compounding, [14][15][16][17][18] which can signi¯cantly improve signal-to-noise ratio of OCT images.…”