An Initial Study on Multi-Point Laser Acupuncture Based on 2-D Galvo Mirror

Abstract

Currently, the majority of commercially available laser acupuncture instruments are still hand-held and only support single-point stimulation. Simultaneous multi-point stimulation improves the therapeutic efficacy of laser acupuncture by stimulating multiple acupoints at the same time. A “2-dimensional (2-D) galvo mirror” was utilized as a positioning laser acupuncture device for multi-acupoints stimulation. Due to its ability to perform 2-D fast scanning, a single laser beam was reflected by the mirror and stimulated multiple acupuncture points simultaneously. This introduction to the new system, presents its architecture, and shows some initial results. This initial stage of development was focused on the acupoints of the human forearm. This proposed system is the first low-cost, noncontact laser acupuncture system that enables continuous multi-acupoint stimulation with a single laser beam. Notably, it is technically feasible to develop this technique into a whole-body laser acupuncture stimulation system.

INTRODUCTION

Acupoint-combination (multi-point stimulation) is an important method in acupuncture.¹ Considering various diseases and syndromes, stimulations at multiple acupuncture points can play a synergistic effect and enhance treatment efficiency. Most of the commercially available laser acupuncture devices are still hand-held single-point operating devices, which have the advantages of being easy to use and being flexible to operate. But one needs to do operate these devices in sequence to stimulate multiple acupoints. This is a time-consuming and labor-intensive process for both the acupuncture practitioner and the patient. To resolve this problem, researchers, during the very first years of this century, had already developed different systems for simultaneous and continuous laser stimulation of different acupoints.¹ In addition, a robotic system for performing laser acupuncture has also been a good choice to consolidate this process.^2–5 However, given that the so- called “laser needle” system does not work without optical fibers and that the robotic arm has a limited range of movement, there are restrictions on selections of acupoints.

In this study, an automatic 2-dimensional (2-D) galvo mirror was used to reflect a single laser beam to multiple acupoints in a very short time, creating a condition in which each acupoint was stimulated effectively by laser light almost at the same time, thereby using optical-fiber–less transmission to achieve multiple-point stimulation. By utilizing a camera to localize marked acupoints on the human body, through artificial intelligence (AI) deep-learning techniques, we can control the 2-D galvo mirror to guide the reflected laser light to stimulate the acupoints. Furthermore, the ability of the mirror to perform 2-D fast scanning enables us to switch quickly between acupoints to stimulate multiple acupoints.

The upper limbs of the human body were the main objects in the initial development of this system. Compared to the automatic laser acupuncture system with the robotic arm, the newer instrument is not limited by the size and movements of a robotic arm, which makes the new device more cost-effective for developing a whole-body acupuncture system. We hope that this will be a scientific breakthrough for research on automatic laser acupuncture systems.

PREVIOUS RELATED WORKS

In previous work, an emulated laser acupuncture device with lift–thrust and reinforcement–reduction functions was developed to emulate traditional acupuncture methods.^6,7 We stimulated the Neiguan point (PC-6) of subjects with an emulated laser acupuncture device, and measured the temperature change of their fingertips with a thermal imager. Laser acupuncture with a lift–thrust operation caused a more-rapid, stable, and lasting temperature rise at the fingertips than without a lift–thrust operation.⁸

In terms of acupoint visualization, Lan and colleagues conducted research on visualization of facial acupoints. By integrating various technologies, including feature-point detection, deformation, and a 3-D morphable model, a high-precision acupoint localization system was designed and implemented.⁹ For mild symptoms (e.g., headaches, sleep disorders), patients can find the affected acupoints quickly for to perform massage with this system. In fact, by combining the acupoint-finding function with the current device architecture, it is possible to develop an automatic laser acupuncture device. In the future, we will work toward this goal and construct an AI-based multi-point laser acupunctures system.

SYSTEM ARCHITECTURE

The system is divided into three parts: (1) a laser light source; (2) a 2-D laser galvo mirror; and (3) a depth camera. The laser light source was a 5 mW red light laser (wavelength 650 nm). The 2-D galvo mirror (Optotune Inc.) is a dual-axis mirror with a mechanical tilt angle of ±25°, and an optical deflection of ±50°. This device has a built-in position feedback system, with a standard proportional–integral-derivative controller, which can control the deflection angle precisely within ±5 μrad. The depth camera was used to measure the distance between the “object” and the 2-D galvo mirror to adjust the deflection angle of the mirror.

RESULTS

Figure 1 shows the architecture of the new proposed multi-point laser acupuncture system. Here we used a 5 mW red laser (wavelength 650 nm) as the light source for the laser acupuncture. The shutter in front of the laser beam determined when the laser light acted on the object. The laser beam is reflected by a mirror. A human forearm with marked acupoints was used as the “object” to be treated. The image coordinates of the acupoints were obtained using an image- processing technique. These coordinates were the targets for adjusting the rotation angle of the galvo mirror and guiding the laser beam to the acupoints. Furthermore, the target position was changed quickly and flexibly for multi-point acupuncture by changing the angle of the galvo mirror. The desired angles to the target acupoints were computed through a deep neural network. (It is also worth pointing out here that the rotation of the galvo mirror enables multiple points to be treated quickly and sequentially without having to reposition patients or their extremities.)

FIG. 1.

Architecture diagram of the proposed multi-point laser acupuncture system. The laser beam, with controllable energy, is reflected by the galvo mirror and irradiates the “object.” A camera is used to localize human acupuncture points, and by controlling the rotation angle of the galvo mirror, the laser beam is guided to stimulate acupoints. Rotation of the galvo mirror enables multiple points to be treated in a rapid and sequential manner, without the need to reposition a patient or an extremity.

Figure 2 shows the performance of the proposed system for acupoint localizations. After marking the acupoints on the human forearm (PC-7 Daling and LU6 Kongzui), the galvo mirror was rotated quickly and accurately to reflect the light spot onto these predetermined acupoints. Note that the difference between the center of the light spot and the center of the marked acupoint is <1 mm, which is generally less than the diameter of an acupoint (∼5 mm).

FIG. 2.

The rotation angle of the galvo mirror was adjusted to guide the laser spot irradiating on the acupoints (PC-7 Daling [left] and LU-6 Kongzui [right]) accurately.

DISCUSSION

At the end of the last century, there were attempts to manage laser acupuncture stimulation in such a way that one did not have to stimulate 1 point after the other; instead there was the possibility of stimulating numerous acupuncture points simultaneously and continuously. In fact, at the beginning of this century, such systems were developed successfully and, in practice, they have proven to be extremely reliable and important.¹⁰ The next step—a touch-sensitive laser acupuncture stimulation—is still a challenge to this day. Individual attempts have been made to implement the power supply for the lasers directly into the applicator at the acupoint, but the results have not been applicable in practice; the dimensions were too large.

To avoid a large amount of so-called optical fibers, the first attempts were made to use a robotic arm for laser stimulation. Good results were obtained, but the speed quality of the stimulation was very slow. For this reason, the system described herein uses a mirror to achieve a continuous, noncontact simultaneous stimulation of several acupoints. A caveat might be that, depending on the Traditional Chinese Medicine diagnosis of a patient and that patient's vascular autonomic signal, some acupoints may need to be stimulated for a longer duration than others in 1 session. However, a solution to this problem can also be integrated easily into a program design with the help of AI. We believe that the new method presented herein could be another important step in the practical and safe use of laser acupuncture.

CONCLUSIONS

For this research, we proposed a multi-point laser acupuncture system utilizing a 2-D galvo mirror, as a laser spot-positioning device, and a depth camera to determine the spatial coordinates of the acupoints. The proposed system, as far as we know, could be a low-cost laser acupuncture system that enables multi-acupoint stimulation with a single laser beam. In this initial stage, we focused on the acupoints of the human forearm, but it is technically feasible to develop this technique into a whole-body acupoint stimulation system.

AUTHORS' CONTRIBUTIONS

Drs. Lan, Lee, Chang, Wu, and Wang wrote the original draft of this article. Drs. Lan, Litscher, and Wang reviewed and edited it. All of the authors read and approved the article for publication.

AUTHOR DISCLOSURE STATEMENT

No financial conflicts of interest exist.

FUNDING INFORMATION

This study was financially supported by the Ministry of Science and Technology in Taiwan (MOST 110-2221-E-214-008).