Assessment of open-field fluorescence guided surgery systems: implementing a standardized method for characterization and comparison

Abstract

Fluorescence guided surgery (FGS) has demonstrated improvements in decision making and patient outcomes for a wide range of surgical procedures. Not only can FGS systems provide a higher level of structural perfusion accuracy in tissue reconstruction cases but they can also serve for real-time functional characterization. Multiple FGS devices have been Food and Drug administration (FDA) cleared for use in open and laparoscopic surgery. Despite the rapid growth of the field, there has been a lack standardization methods.Aim: This work overviews commonalities inherent to optical imaging methods that can be exploited to produce such a standardization procedure. Furthermore, a system evaluation pipeline is proposed and executed through the use of photostable indocyanine green fluorescence phantoms. Five different FDA-approved open-field FGS systems are used and evaluated with the proposed method.Approach: The proposed pipeline encompasses the following characterization:(1) imaging spatial resolution and sharpness, (2) sensitivity and linearity, (3) imaging depth into tissue, (4) imaging system DOF, (5) uniformity of illumination, (6) spatial distortion, (7) signal to background ratio, (8) excitation bands, and (9) illumination wavelength and power. Results:The results highlight how such a standardization approach can be successfully implemented for inter-system comparisons as well as how to better understand essential features within each FGS setup.Conclusions: Despite clinical use being the end goal, a robust yet simple standardization pipeline before clinical trials, such as the one presented herein, should benefit regulatory agencies, manufacturers, and end-users to better assess basic performance and improvements to be made in next generation FGS systems.

Impact of signal-to-noise ratio and contrast definition on the sensitivity assessment and benchmarking of fluorescence molecular imaging systems

“…This is frequently adopted as a strategy for background definition in multiple studies. 9 , 28 The second ROI, b2, is located far from fluorescent wells and thus is not affected by fluorescence leakage. This is another frequently adopted definition of background, especially for studies where autofluorescence or diffusion is strong in the proximity of the target.…”

“…This is, also, very relevant to the fluorescent image-guided surgery (FIGS), given the FDA clearance of multiple FIGS devices for imaging with indocyanine green (ICG) and other contrast agents. 9 Addressing this need is essential for ensuring optimal impact and wider clinical acceptance of FMI and FIGS. 10 …”

“…Over the past few years, numerous studies on phantom development and standardization procedures, as well as attempts to achieve consensus in the community, have been reported. 1 , 2 , 9 , 11 – 19 Thus far, methods and reference targets for system evaluation and comparison have been developed on an individual basis, but a universal cross-platform metric for image fidelity evaluation has yet to be developed. 16 …”

“…Indeed, despite the fact that SNR and contrast are the most commonly used metrics for the sensitivity assessment of various systems, 1 , 26 there are only a few studies comparing different FIGS systems, most of which are optimized for ICG imaging. 9 , 19 , 27 In addition, the formulas used to calculate SNR and contrast and methods for evaluating background ROIs vary across different studies. In a recent study, LaRochelle et al.…”