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Global Health Technologies

Undergraduate Lightning Talks

Characterization of the color accuracy of a low-cost laparoscope designed for use in low-and middle-income countries

Saturday, October 26, 2024
1:05 PM – 1:10 PM EST
Location: Room 342

Introduction:  Laparoscopic surgery is the standard-of-care surgical approach for many procedures in the chest and abdomen (1). However, it is typically unavailable in low- and middle-income countries (LMICs) due to its excessive cost, lack of trained personnel, and lack of spare parts needed to fix broken equipment (1). To address this need, we developed the KeyScope laparoscope, a low-cost, durable laparoscope specifically designed for LMICs (1). However, certain characterization tests, such as color accuracy, are needed to test the KeyScope to ensure that it is up to regulation. Standard color targets (RezChecker Mini) are available, but the software used to analyze the targets (Imatest) is prohibitively expensive for testing in LMICs. Here we developed a custom Matlab Scripted App that can be substituted for Imatest, which will enable engineers in LMICs to more readily conduct color characterization of the KeyScope.

Materials and

Methods:  Our custom Matlab App uses the International Commission of Illumination L* a* b* (CIELAB) coordinates for computing color analysis, where L* represents the perceivable brightness of an image, and a* and b* represent the hues red/green and yellow/blue, respectively. The app uses the reference L*, a*, and b* coordinates and compares them to the coordinates measured from an image of the color target captured with our KeyScope. Specifically, the CIELAB 1976 equation (equation 1) calculates the absolute differences, ΔE*ab (including luminance), and equation 2 calculates the absolute chroma difference, ΔC*ab, which does not account for the luminance difference.

(1) ΔE*ab = [( L2* - L1*)^2 + ( a2* - a1*)^2 + ( b2* - b1*)^2 ]^1/2
(2) ΔC*ab = [ ( a2* - a1*)^2 + ( b2* - b1*)^2 ]^1/2 = [ ( ΔE*ab )^2 - ( L2* - L1*)^2 ]^1/2

Equation: (1) First Delta E, ΔE*ab aka CIE 1976 aka ΔE*76, to calculate the color error in which L*2, a*2, and b*2 are the reference coordinates and L*1, a*1, and b*1, input from the RezChecker Color Target. (2) This is the Delta C, ΔC*ab, which calculates the color error without considering luminance, L*.

Results, Conclusions, and Discussions: A representative image of the color target captured with our latest KeyScope prototype is shown in Figure 1A. The comparison of the KeyScope colors to the reference colors is shown in Figure 1B. As seen in Figure 1C, Matlab and Imatest had statistically similar results (p>0.05) in both color and chroma differences, indicating that our Matlab app accurately recapitulates the Imatest results. Moving forward, our app will be moved to Python, which is open source, and shared with our collaborators in Uganda who are manufacturing the KeyScope

Acknowledgements (Optional):  The NIH (R21CA249696, U01CA269190) funded this study and the NIH NIGMS MARC T34GM149472 to Wilhelm Smith

Reference:
1. Mueller, J.L., Rozman, N., Sunassee, E.D. et al. An Accessible Laparoscope for Surgery in Low- and Middle-Income Countries. Ann Biomed Eng 49, 1657–1669 (2021). https://doi.org/10.1007/s10439-020-02707-6