Photoacoustic imaging of microenvironmental changes in facial cupping therapy

Abstract

As a traditional medicine practice, cupping therapy has been widely used to relieve symptoms like fatigue, tension, and muscle pain. During the therapy, negative pressure is applied to the skin for a while with an intention to enhance blood circulation or induce micro-bleeding. The therapeutic effect, however, is not clear due to the lack of direct quantification. Aiming at a quantitative assessment of the treatment effect, we explore optical-resolution photoacoustic microscopy (OR-PAM) in monitoring the structural and functional changes after cupping. We find that, after 5-minutes of ∼ 20 kPa negative pressure cupping, more capillaries appear in the focus, and micro-blooding is observed from the capillaries. We quantify the images and find the blood vessel density is increased by 64%, and the total hemoglobin concentration in both the veins and the arteries exhibits 62% and 40% elevation, respectively. Oxygen saturation in the vein and artery decreased by 17% and 3% right after cupping, respectively. After two hours of recovery, the three blood-related parameters return to their original levels, indicating that the effects in the tissue last only a short period after cupping at the given pressure and time duration. Note that no significant cupping marks are induced with the treatment parameters in this study. This work proposes OR-PAM to quantitatively monitor and evaluate the effect of cupping therapy from the perspective of imaging. The method is also useful for accurate control of the therapeutic outcome.

Fig. 1.

Schematic of the photoacoustic-based microenviroment montioring system. HWP1-3, half-wave plate; MMF, multimode fiber; PBS1-2, polarizing beamsplitter; SF, single-mode fiber; UT, ultrasound transducer.

Fig. 2.

OR-PAM structural imaging of the same region of a mouse ear before (a) and right after (b) cupping. (c) Close-up of the dashed box in (a). (d) Close-up of the dashed box in (b).

Fig. 3.

Ear vessel photographs (a), OR-PAM images (b), total hemoglobin concentration (c), and vascular density (d) changes before and after the cupping treatment. In (c), changes of artery and vein within the white box in (b) are presented with the red (yellow) line and blue (green) dashed line, respectively. $\star$, p < 0.05 (tested by one way ANOVA). The error bars in (c) are standard deviations.

Fig. 4.

Dynamic changes in oxygen saturation before and after cupping. (a) $s{O}_2$ map of the mouse ear within the cupping process. (b) Averaged $s{O}_2$ changes of the artery (red/yellow line) and the vein (blue/green dashed line) for regions labeled with the rectangle in (a). $\star$, p < 0.05 (tested by One-way ANOVA). The error bars in (b) are standard deviations.