Angle correction for small animal tumor imaging with spatial frequency domain imaging (SFDI)

Abstract

Spatial frequency domain imaging (SFDI) is a widefield imaging technique that allows for the quantitative extraction of tissue optical properties. SFDI is currently being explored for small animal tumor imaging, but severe imaging artifacts occur for highly curved surfaces (e.g. the tumor edge). We propose a modified Lambertian angle correction, adapted from the Minnaert correction method for satellite imagery, to account for tissue surface angles up to 75°. The method was tested in a hemisphere phantom study as well as a small animal tumor model. The proposed method reduced µ a and µ s` extraction errors by an average of 64% and 16% respectively compared to performing no angle correction, and provided more physiologically agreeable optical property and chromophore values on tumors. W. Pogue, " High spatial frequency structured light imaging for intraoperative breast tumor margin assessment, " vol. 9313, pp. 931304-931308, 2015.

Real-time endoscopic optical properties imaging

“…Because the single snapshot collects phase information as well, there is no additional acquisition time necessary to measure the sample's phase, though calibration steps are added to create distance-dependent correction factors. Profilometry corrections are therefore necessary for quantitative imaging of samples with variations in height and also help reduce imaging artifacts [16,17]. These previous studies have also demonstrated an upper limit of 75° for correcting the reflection angle of the sample surface, though further validation is needed for this endoscopic implementation.…”

“…Profile corrections are absolutely crucial for both SFDI [16,17] and SSOP [20] as varying sample height causes uncorrected measurements of absorption and reduced scattering properties. Hence, this work also implements and demonstrates the need for a height-based correction.…”

“…SFDI offers a widefield, noncontact approach for acquiring optical property maps that can be analyzed over several wavelengths to produce chromophore concentrations of endogenous tissue constituents [13][14][15]. Several steps have been made to improve the technique's robustness and processing schemes, including a fast 2-D look-up Table [15], a 3-D height correction method [16,17], and an optimization of wavelengths for spectroscopic fitting of tissue constituent concentrations [18]. These developments led to a first-in-human pilot study that measured skin flap oxygenation during reconstructive breast surgery [19].…”

Calibration and analysis of a multimodal micro-CT and structured light imaging system for the evaluation of excised breast tissue

“…Imaging of the breast specimen demonstrated co-localization of scattering information with a volumetric micro-CT scan. Imaging irregular specimen surfaces may pose a challenge in the future studies aimed at whole specimen imaging; however, if flattening the tissue surface with the custom acrylic holder does not suffice, a recently published modified Lambertian model has shown to effectively mitigate surface curative artifacts in spatial frequency domain imaging applications (Zhao et al 2016). …”

Monochromatic subdiffusive spatial frequency domain imaging provides in‐situ sensitivity to intratumoral morphological heterogeneity in a murine model

“…The basic setup of the camera and projector is shown in Figure 1, where imaging is done in an inverted geometry through a glass slide in order to mitigate surface curvature artifacts of the sample, arising when the sample is non-normal to the optical axis. Although these artifacts pose a challenge for in-vivo translation, recent work aims to mitigate their affects [15]. The digital micromirror based projection device is coupled to multiple LEDs as light sources.…”