ACA-Pro: calibration protocol for quantitative diffuse reflectance spectroscopy. Validation on contact and noncontact probe- and CCD-based systems

Abstract

We have developed an adaptive calibration algorithm and protocol (ACA-Pro) that corrects from the instrumental response of various spatially resolved diffuse reflectance spectroscopy (DRSsr) systems to enable the quantification of absorption and scattering properties based on a Monte Carlo-based look-up-table approach. The protocol involves the use of a calibration reference base built with measurements of a range of different diffusive intralipid phantoms. Moreover, an advanced strategy was established to take into account the experimental variations with an additional measurement of a common solid material, allowing the use of a single calibration reference base for all experiments. The ACA-Pro is validated in contact and noncontact probe-based DRSsr systems. Furthermore, the first results of a setup replacing the probe with a CCD detector are shown to confirm the robustness of the approach.

Contact, high-resolution spatial diffuse reflectance imaging system for skin condition diagnosis

“…Because of the limitations listed before, the developed system might show inability to address a wider range of properties (currently from 0.31 to 2.30 cm −1 in absorption and 12.7 to 38.1 cm −1 in reduced scattering). In this case, use of multiple calibration phantoms, as investigated in previous studies, 29,40 could extend the accessible μ 0 s range. In future work, evaluation of the device's performance on an extended range of optical properties, notably toward lower levels of absorption, should be conducted.…”

“…In order to evaluate the potential of the developed system for the characterization of absorption and scattering properties of tissue, validation experiments were conducted on homogeneous liquid phantoms, following a methodology employed by other authors. 13,15,29 Phantoms consisted of solutions of 20% Intralipid fat and black India ink (Rotring Inc., Hamburg, Germany) at varying concentrations in distilled water. The absorbance A of solutions was measured by a spectrophotometer (CARY 300, Agilent) in a 1-cm tank, yielding the absorption coefficient μ a ¼ lnð10Þ × A.…”

Validation of optical properties quantification with a dual-step technique for biological tissue analysis

“…The Non-Contact DRS system that we use is detailed in a previous study 21 and its design preserves the same geometrical dimensions of the initial Contact DRS system described. Measurements performed with both systems inspect the same sample volume to allow their direct comparison: Contact DRS is considered as the reference measurement system to validate our Non-Contact DRS results.…”

“…1(a) (right). The specific treatment of these Non-Contact DRS measurements has been precisely described 21 and will not be detailed here.…”

“…Contrary to the techniques that suppose a single modeled scattering coefficient and hinder the absolute quantification of the absorption coefficient, [4][5][6][7] our system intends to quantitatively estimate both absolute optical properties over a wide FOV. To do so, we have developed the exhaustive adaptive calibration algorithm (ACA)-Pro that has been adapted both for punctual DRS measurements 21 and to wide field MSI images.…”