Precision of measurement of tissue optical properties with optical coherence tomography

Abstract

Accurate and noninvasive measurement of tissue optical properties can be used for biomedical diagnostics and monitoring of tissue analytes. Noninvasive measurement of tissue optical properties (total attenuation and scattering coefficients, optical thickness, etc.) can be performed with the optical coherence tomography (OCT) technique. However, speckle noise substantially deteriorates the accuracy of the measurements with this technique. We studied suppression of speckle noise for accurate measurement of backscattering signal and scattering coefficient with the OCT technique. Our results demonstrate that the precision of measurement of backscattering signals with the OCT technique can be 0.2% for homogeneously scattering media and 0.7% for skin, if spatial averaging of speckle noise is applied. This averaging allows us to achieve the precision of tissue scattering coefficient measurements of approximately +/-0.8%. This precision can be further improved by a factor of 2-3, upon optimization of OCT operating parameters.

Quantitative measurement of attenuation coefficients of weakly scattering media using optical coherence tomography

“…Again arbitrary, W' > 0.8 and p-value of the runs test p runs > 0.05 are considered acceptable. The assumption of independent scatter of the weighted residuals is a priori violated due to low pass filtering (either in hardware or software) in the OCT data acquisition, or possible speckle averaging [6] prior to fitting. When necessary, this is dealt with by using each n'th point of the data set in the fitting, where n corresponds to the number of points in the duration of the averaging time of the filters.…”

“…Since imaging depths generally do not exceed ≈ 1 mm, this may well be justified for weakly scattering media (µ t < 6 mm -1 for the samples used in this paper). We first compare the single scattering model [4,5,6] to a multiple scattering model [7] using the same calibrated scattering samples with µ t ranging from 2 mm -1 to 6 mm -1 described in [15] and used in a similar analysis in [8]. The experiments are performed under the condition of dynamic focusing (i.e., the focal plane coincides with the probing location) such that the influence of the confocal properties during the depth scan is constant.…”

“…Currently, two models are available. Widely used [4,5,6] is the so-called single scattering model, which assumes that only light that has been backscattered once contributes to the OCT signal. A model taking into account multiple scattering was introduced by Thrane et al [7] and has recently been used to extract optical properties of atherosclerotic lesions [8] and human skin [9].…”

Quantitative assessment of hemodynamic and structural characteristics of in vivo brain tissue using total diffuse reflectance spectrum measured in a non-contact fashion

“…Such applications in an intraoperative setting has drawn tremendous attention since it is relatively economic to set up in the operating room and efficient enough to provide real-time feedbacks [1]. Many techniques have been developed to measure optical properties from in vivo biological tissues over the past two decades [2][3][4][5][6][7][8][9][10][11][12][13]. Some of these techniques, such as optical coherence tomography [6,7] and low-coherence enhanced backscattering spectroscopy [8,9], are limited to quantify scattering-related properties.…”

Estimation of the scattering coefficients of turbid media using angle-resolved optical frequency-domain imaging

“…The accuracy of scattering coefficient measurements with conventional OCT and OFDI is limited by speckle, however, which greatly reduces the signal-to-noise ratio. Although averaging over many spatial locations can reduce speckle and permit measurements of μ s with high accuracy [9], this type of averaging reduces the resolution with which differences in scattering coefficients can be resolved. Angle-resolved OFDI was recently demonstrated as a novel method of acquiring OFDI images that allows substantial speckle reduction by averaging the magnitudes of multiple interferometric scans (A-lines) obtained simultaneously from a broad range of backscattering angles [10].…”