Abstract:A novel acquisition and processing method that enables realtime, single snapshot of optical properties (SSOP) and 3-dimensional (3D) profile measurements in the spatial frequency domain is described. This method makes use of a dual sinusoidal wave projection pattern permitting to extract the DC and AC components in the frequency domain to recover optical properties as well as the phase for measuring the 3D profile. In this method, the 3D profile is used to correct for the effect of sample's height and angle and directly obtain profile-corrected absorption and reduced scattering maps from a single acquired image. In this manuscript, the 3D-SSOP method is described and validated on tissue-mimicking phantoms as well as in vivo, in comparison with the standard profile-corrected SFDI (3D-SFDI) method. On average, in comparison with 3D-SFDI method, the 3D-SSOP method allows to recover the profile within 1.2mm and profilecorrected optical properties within 12% for absorption and 6% for reduced scattering over a large field-of-view and in real-time. 6498-6507 (2000).

Diffuse optical imaging probes deep living tissue enabling structural, functional, metabolic, and molecular imaging. Recently, due to the availability of spatial light modulators, wide-field quantitative diffuse optical techniques have been implemented, which benefit greatly from structured light methodologies. Such implementations facilitate the quantification and characterization of depth-resolved optical and physiological properties of thick and deep tissue at fast acquisition speeds. We summarize the current state of work and applications in the three main techniques leveraging structured light: spatial frequency-domain imaging, optical tomography, and single-pixel imaging. The theory, measurement, and analysis of spatial frequency-domain imaging are described. Then, advanced theories, processing, and imaging systems are summarized. Preclinical and clinical applications on physiological measurements for guidance and diagnosis are summarized. General theory and method development of tomographic approaches as well as applications including fluorescence molecular tomography are introduced. Lastly, recent developments of single-pixel imaging methodologies and applications are reviewed.

Imaging technologies working in the spatial frequency domain are becoming increasingly popular for generating wide-field maps of optical properties, enabling rapid analysis of tissue parameters. While acquisition methods have become faster and are now performing in real-time, processing methods remain slow, precluding real-time display of information. We present solutions that rapidly solve the inverse problem for extracting optical properties by use of advanced lookup tables (LUTs). We present methods and results based on a dense, linearly sampled lookup table and an analytical representation that generate maps of absorption and reduced scattering in ?10??ms, which is 100× faster than the standard method, with ?4% error compared to the Monte-Carlo simulation. Combined with real-time acquisition methods, the proposed techniques enable video-rate feedback of real-time property maps, enabling full video-rate guidance in the clinic.

Fluorescence imaging is well suited to provide image guidance during resections in oncologic and vascular surgery. However, the distorting effects of tissue optical properties on the emitted fluorescence are poorly compensated for on even the most advanced fluorescence image guidance systems, leading to subjective and inaccurate estimates of tissue fluorophore concentrations. Here we present a novel fluorescence imaging technique that performs real-time (i.e., video rate) optical property corrected fluorescence imaging. We perform full field of view simultaneous imaging of tissue optical properties using Single Snapshot of Optical Properties (SSOP) and fluorescence detection. The estimated optical properties are used to correct the emitted fluorescence with a quantitative fluorescence model to provide quantitative fluorescence-Single Snapshot of Optical Properties (qF-SSOP) images with less than 5% error. The technique is rigorous, fast, and quantitative, enabling ease of integration into the surgical workflow with the potential to improve molecular guidance intraoperatively.

Abstract:With almost 50% of all surgeries in the U.S. being performed as minimally invasive procedures, there is a need to develop quantitative endoscopic imaging techniques to aid surgical guidance. Recent developments in widefield optical imaging make endoscopic implementations of real-time measurement possible. In this work, we introduce a proof-ofconcept endoscopic implementation of a functional widefield imaging technique called 3D single snapshot of optical properties (3D-SSOP) that provides quantitative maps of absorption and reduced scattering optical properties as well as surface topography with simple instrumentation added to a commercial endoscope. The system's precision and accuracy is validated using tissue-mimicking phantoms, showing a max error of 0.004 mm −1 , 0.05 mm −1 , and 1.1 mm for absorption, reduced scattering, and sample topography, respectively. This study further demonstrates video acquisition of a moving phantom and an in vivo sample with a framerate of approximately 11 frames per second.

Significance: Spatial frequency domain imaging (SFDI) is a diffuse optical measurement technique that can quantify tissue optical absorption (μ a ) and reduced scattering (μ 0 s ) on a pixelby-pixel basis. Measurements of μ a at different wavelengths enable the extraction of molar concentrations of tissue chromophores over a wide field, providing a noncontact and label-free means to assess tissue viability, oxygenation, microarchitecture, and molecular content. We present here openSFDI: an open-source guide for building a low-cost, small-footprint, threewavelength SFDI system capable of quantifying μ a and μ 0 s as well as oxyhemoglobin and deoxyhemoglobin concentrations in biological tissue. The companion website provides a complete parts list along with detailed instructions for assembling the openSFDI system.Aim: We describe the design of openSFDI and report on the accuracy and precision of optical property extractions for three different systems fabricated according to the instructions on the openSFDI website.Approach: Accuracy was assessed by measuring nine tissue-simulating optical phantoms with a physiologically relevant range of μ a and μ 0 s with the openSFDI systems and a commercial SFDI device. Precision was assessed by repeatedly measuring the same phantom over 1 h. Results:The openSFDI systems had an error of 0 AE 6% in μ a and −2 AE 3% in μ 0 s , compared to a commercial SFDI system. Bland-Altman analysis revealed the limits of agreement between the two systems to be AE0.004 mm −1 for μ a and −0.06 to 0.1 mm −1 for μ 0 s . The openSFDI system had low drift with an average standard deviation of 0.0007 mm −1 and 0.05 mm −1 in μ a and μ 0 s , respectively. Conclusion:The openSFDI provides a customizable hardware platform for research groups seeking to utilize SFDI for quantitative diffuse optical imaging.

Summary: Lymphatic surgery has become an integral and flourishing component of the field of plastic surgery. The diversity of ongoing technological innovations in perioperative imaging, including intraoperative dyes and cameras, allows plastic surgeons to work at the supermicrosurgical level. This study aims to highlight innovations that have shaped and will continue to revolutionize the perioperative management of the lymphatic surgery patient in the future. As additional advances emerge, we need a systematic and objective way to evaluate the efficacy and clinical integration readiness of such technologies. Undoubtedly, these technologies will help lymphatic surgery trend toward increasing objectivity, which will be critical for continued evolution and advancement.

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