Towards reliable handheld optical microcirculatory blood flow Imaging

Abstract

Background: Handheld laser speckle contrast imaging (LSCI) plays a vital role in clinical environments; however, motion artifacts (MA) can undermine the reliability of perfusion images. Existing methods for preventing and suppressing MA are often impractical or overly complex. While machine vision techniques show promise in enhancing medical imaging quality, their application in mitigating MA remains largely unexplored.
Objective: This study introduces an innovative linear regression-based method for motion artifact correction (MAC) in LSCI, validated through measurements on psoriasis patients [1].
Methods: We conducted paired handheld and mounted LSCI measurements on 14 psoriasis lesions using the handheld perfusion imager (HAPI), previously validated for eye safe and user friendly clinical investigation [2]. By delineating lesion boundaries for clinical assessment, the HAPI utilized a monochromatic camera for both speckle imaging and motion detection, thus simplifying hardware requirements [3]. We accurately estimated the relative displacements between the test object and the LSCI probe, enabling the application of MAC to the perfusion images by correlating the calculated speed with local perfusion.
Results: Linear regression of spatial perfusion and on-surface speed extrapolated the zero-speed point as the predicted motion artifact-corrected value for each location. Based on this correction, the discrepancy in mean perfusion between handheld and mounted modes significantly decreased (median error of 14.2 perfusion units (p.u.) on lesions before correction (p<0.0005), compared to 0.5 p.u. after correction (p=0.2)).
Conclusions: Our findings support the efficacy of handheld LSCI and validate our MAC approach in a psoriasis context. We address one of the two primary causes of MA—on-surface speeds—and successfully correct mean perfusion, assuming constant temporal perfusion at each site.
Significance: We present a practical, non-contact, marker-free technique for reliable handheld perfusion imaging, paving the way for enhanced clinical applications in dermatology, burn treatment, and plastic surgery [4].

References:
[1] A. Chizari, et al., “Mitigation of Motion Artifacts in Handheld Laser Speckle Contrast Imaging Illustrated on Psoriasis Lesions,” IEEE Trans Biomed Eng, pp. 1–9, 2024, doi: 10.1109/TBME.2024.3438375.
[2] M. J. Schaap et al., “Perfusion measured by laser speckle contrast imaging as a predictor for expansion of psoriasis lesions,” Skin Research and Technology, 2021, doi: 10.1111/srt.13098.
[3] A. Chizari, et al., “Handheld versus mounted laser speckle contrast perfusion imaging demonstrated in psoriasis lesions,” Sci Rep, vol. 11, no. 1, p. 16646, Aug. 2021, doi: 10.1038/s41598-021-96218-6.
[4] A. Rook, et al., “Handheld wireless laser speckle contrast imaging (LSCI) during DIEP flap breast reconstruction: a pilot study,” in Optical Diagnostics and Sensing XXIV: Toward Point-of-Care Diagnostics, J. S. Baba and G. L. Coté, Eds., SPIE, Mar. 2024, p. 18. doi: 10.1117/12.3001925.