<title>Highlights of laser-tissue interaction mechanism</title>

Real-time co-localized OCT surveillance of laser therapy using motion corrected speckle decorrelation

“…The quantitative analysis of the speckle fluctuations can be performed by determining the temporal correlation of the OCT signal. When relying on the intensity of the signal, the second-order autocorrelation function g (2) is generally used to quantify the correlation. In what follows, we describe how g (2) can be used to create a map of the OCT signal correlation across the field of view.…”

“…When relying on the intensity of the signal, the second-order autocorrelation function g (2) is generally used to quantify the correlation. In what follows, we describe how g (2) can be used to create a map of the OCT signal correlation across the field of view. We define a discrete coordinate system (z, x, y) defining the axes in depth, in-plane lateral location, and out-of-plane lateral location, respectively.…”

“…The second-order autocorrelation function g (2) is defined as the time-delayed correlation of the intensity of an ensemble at a time difference τ. Considering that an OCT system determines the intensity of backscattered light as a function of depth z (first index), lateral position x (second index) and time t (third index), the inter-B-scan autocorrelation function can be written as [51,52] g (2)…”

“…However, as explained above, during tissue coagulation the tissue transitions through different states and, therefore, the acquired signal corresponds to a dynamic process. In a dynamic process, g (2) depends not only on τ, but also on t. In order to adapt Eq. (1) for a dynamic process to detect the state of coagulation, we limit the temporal extent of the summation to allow us to calculate a time-dependent correlation -assuming the sample is in the same state inside a limited time interval.…”

“…Laser therapy allows for targeted removal or thermal coagulation of tissues through light absorption by various absorbers in the tissue, such as water, hemoglobin and other macromolecules [1][2][3]. It is used in the treatment of epithelial cancerous and pre-cancerous lesions such as Barrett's esophagus [4][5][6], in eye diseases such as diabetic retinopathy [7][8][9][10] and retinal vein occlusion [11,12] and in respiratory papillomatosis, a viral-induced disease in the upper airway [13,14].…”