Vol. 15, #2

Ultrasonic Visualization And Stimulation
Of Classical Oriental Acupuncture Points
Joie P. Jones, PhD
Young K. Bae, PhD

INTRODUCTION
cupuncture has long been a major component of Oriental medicine. In spite of considerable evidence that acupuncture is effective in the treatment of pain and various disorders, Western medicine has been slow in its acceptance of this modality since the basic nature of the acupuncture process remains largely unknown. The research reported herein provides insight into a fundamental understanding of this process. We discovered that the classical acupuncture points correspond to regions of enhanced elasticity (increased ultrasonic attenuation) and that these regions of altered acoustical properties can change in size, shape, and even location in short periods of time. Quantitative ultrasonic methods were used to image the acupoints, and ultrasonic pulses with higher energies than used for imaging were employed to stimulate the acupoints. Ultrasonic stimulation elicited a response identical to that produced by conventional acupuncture needles as confirmed by functional magnetic resonance imaging (fMRI). Our findings identify an integrative method for locating and stimulating acupuncture points with greater accuracy, and provide a possible explanation for the varying efficacy found in some clinical studies of acupuncture.1,2

Figure 1. Ultrasonic attenuation images of acupoint BL 67 in subject #1 taken (a) on day 1 of the study, and (b) on day 2 of the study. The points represent measured attenuation data while the solid curves are contours of the attenuation profile representing a best fit to the data. The images are in a C-scan format; i.e., parallel to the surface of the skin at positions detailed in Table 1. The images are cross-sections through the acupoints at their maximum diameter and show what the acupuncture needle would "see" as it approaches the acupoint. The background grid is 0.5 mm on each side.

Cho and his associates3 used functional MRI (fMRI) to demonstrate that stimulation of specific acupoints in the foot and leg, described in standard acupuncture texts4 as points related to vision, elicited increases in cortical blood flow in circumscribed regions of the visual cortex comparable in magnitude and brain location to those obtained by stimulation of the visual cortex by flashes of light. When the acupuncture needle was directed at a nearby but non-acupoint site, no activity in the visual cortex was seen. Although other researchers have used fMRI to investigate the effects of acupuncture,5,6 this study3 was the first to show a direct correlation between acupuncture stimulation and brain activity. A later study7 confirmed a similar relationship between auditory-related acupoints and the auditory cortex.

In addition to the conventional application of acupuncture needles to the acupoints, a variety of energetic stimuli have proven effective in creating similar responses.8 In the present study, we used pulses of highly focused ultrasonic energy to stimulate the acupoint. Functional MRI was used to confirm the activation of corresponding areas of the brain.

METHODS
Acupoint BL 67, known as the urinary bladder channel and located on the lateral side of the small toe about 3 mm proximal to the corner or the nail, is described in classical acupuncture texts4 as being related to vision. This point was stimulated using conventional acupuncture needling and fMRI was used to record the corresponding activation of the occipital lobes of the brain. In addition, conventional ultrasonic imaging was used to monitor the placement and application of the acupuncture needle. Subsequently, the acupuncture needle was replaced with an ultrasonic stimulation transducer assembly. The acupoint was targeted and stimulated by ultrasonic pulses, and corresponding brain activity recorded by fMRI. For a wide range of ultrasound parameters, the fMRI results were indistinguishable from those produced by conventional acupuncture needles. Further fMRI studies reconfirmed the close correlation between direct stimulation of the eye using light, and stimulation of a vision-related acupoint using either a needle or pulses of ultrasonic energy.

The transducer assembly used in these studies was a highly focused PZT ultrasonic transducer (Harisonics Corp) mounted in a flexible, water-filled chamber, which was placed on the skin overlying the acupoint of interest. Accurate positioning mechanisms allowed the focal point (a volume with a diameter of about 0.2 mm) to be moved in depth. The transducer, designed for high power applications, had a center frequency of 5 MHz, a diameter of 2 cm, and a focal length of 6 cm. Initial ultrasound parameters were chosen based on earlier research using this modality to modify electrically evoked responses in mammalian brain.9-11 A wide range of ultrasound parameters produced the desired stimulation of the acupoint and showed the process to be sound and vigorous. Spatial/peak/temporal/averaged intensities in the range of 5 to 8 W/cm2 were required to produce an effect. Although these intensities are above those used in diagnostic ultrasound (in the 100s of mW/cm2 range), they are well below the cavitation threshold and the range where irreversible effects occur. Focusing the pulse on the surface of the skin or in depth beyond the acupoint produced no stimulation. No stimulations were observed at intensities below 5 W/cm2.

Seeking to better understand the fundamental mechanisms of the acupuncture process, we used ultrasound to image the acupoint site. While conventional ultrasonic imaging (using an ATL ultrasound scanner operating at frequencies of 5 and 7.5 MHz) was effective at monitoring the placement of the acupuncture needle, it did not reveal any remarkable anatomical features associated with the acupoint. Since ultrasonic scanners operating at higher frequencies (and therefore with greater resolution) were not available, we implemented a simple pulse-echo data acquisition system using a 50 MHz hand-held transducer (Ultran Inc, Boalsburg, PA). Holding the small (1 mm diameter) transducer on the surface of the skin, a short (30 ns) ultrasound pulse was transmitted into the tissue (using a Panametrics pulser), and the reflected signal known as an A-mode trace was recorded (digitized at 200 MHz) and stored in a standard PC computer. Ultrasonic power levels were well below those required to produce a stimulation of the acupoint. Moving the transducer in one-fourth diameter steps along a 2-dimensional rectangular grid, a series of A-lines were recorded which intersected and surrounded a specific acupuncture point. For the acupoint BL 67 in each foot, a 20-point by 20-point grid yielded 400 A-lines distributed evenly over a 5.75 x 5.75 mm square on the surface of the skin. Each A-line was a record of the reflected pressure waveform vs depth along a given direction. Frequency-dependent attenuation limits the depth of measurable reflected signals to about 1 cm. Moving a short (one-third the length of the interrogating pulse) time window along each A-line, we calculated the mean frequency of the power spectrum in each window. Plotting this mean frequency value vs depth for a given A-line provides a measure of the attenuation of sound along the given A-line. Such methods are standard for estimating the attenuation of sound in tissue12-14 and are based on the theory of Gaussian pulse propagation in a medium with frequency-dependent attenuation.14,15

Figure 2. Ultrasonic attenuation images of acupoint BL 67 in subject #1 taken over a 12-day period. See Figure 1 and Table 1.



A-line attenuation data along a path that did not include an acupuncture point showed the typical down-slope expected for soft tissue (~0.5 db/cm/MHz). A-line attenuation data along a path that did include a portion of an acu- point showed an enhanced attenuation value at the acupoint superimposed on the general background attenuation of soft tissue. Thus, acupoints represent local regions of enhanced acoustical attenuation (and therefore, enhanced elasticity). This finding is consistent with previous observations that acupoints undergo changes in mechanical properties with needling,16 that the local mechanical properties along a meridian are different from surrounding tissue,17 and that acupoints represent regions of enhanced electrical conductivity18,19 given the fact that changes in electrical properties are almost always associated with changes in acoustical properties.20

Viewing the A-line attenuation data 3-dimensionally, we constructed a cross-section of the acupoint at its maximum diameter. Figure 1A shows such a cross-section for BL 67 on the 1st day of our study. The points represent attenuation data. The solid curve, a contour of the attenuation profile, represents a best fit to the data. The background grid is 0.5 mm on each side. The shaded region is a cross section through the acupoint at its maximum diameter and represents what the acupuncture needle would "see" as it contacts the acupoint. Using reflections from the underlying bone structures of the toe, we accurately determined (within 30 m) the depth and relative location of the acupoint. We arbitrarily assigned the coordinates of (0.00, 0.00, 0.00) to the center of this acupoint. Figure 1B shows a cross-section of BL 67 on the 2nd day of our study (same subject, same time). Note that the acupoint changed in shape as well as location over a 24-hour period. Figure 2 shows cross-sectional profiles of BL 67 over a 12-day period; Table 1 indicates the relative position of the center of the acupoint.

RESULTS
The acupoint BL 67 was found to change in size, shape, and even location throughout the 12-day period. Similar results were noted for other acupoints (BL 60, 65, 66) along the same meridian.21 The mechanism for these changes is currently under investigation and thought to be of fundamental importance. For example, changes in elasticity at an acupoint could be produced by changes in the blood flow to the surrounding capillary bed caused by a response from the sympathetic nerve.These results were not an anomaly limited to a single subject. The measurements were repeated on 10 additional subjects, imaging specific acupoints on 2 successive days. The results obtained were similar to those reported above, i.e., each acupoint imaged was found to change in size and location from day 1 to day 2, and similar changes occurred for each acupoint along the same meridian.

Table 1. Relative locations of the center of acupoint BL 67 over a 12-day period in subject #1.

Day Of Measurement

Relative Position (x,y, z) (mm 6 0.04 mm)

1

(0.00, 0.00, 0.00)

2

(0.21, -0.32, 0.08)

3

(0.33, -0.11, 0.19)

4

(0.14, 0.23, -0.36)

5

(0.06, 0.17, -0.48)

6

(-0.18, 0.27, -0.32)

7

(-0.09, 0.13, -0.15)

8

(0.17, 0.26, -0.41)

9

(0.54, 0.39, -0.95)

10

(1.26, 0.88, -1.37)

11

(1.45, 1.26, -1.62)

12

(1.30, 1.04, -1.55)

Position coordinates on day 1 were arbitrarily assigned with respect to the underlying bone structures. Position coordinates on days 2-12 were relative to day 1. Coordinates x and y are in a plane parallel to the surface of the skin; coordinate z is perpendicular to the x, y plane. 

The characteristics and precise location of acupoints is a matter of debate.22 The standard acupuncture texts4 indicate that an acupoint should be located precisely on the locus defined by proportional measurement based on anatomical landmarks. However, in clinical situations, the discerning practitioner typically searches for the acupoint around the standard text acupoint location, implicitly assuming that the acupoint location is different in each person and changes in time.23 Our findings support the practitioner's approach.

Comparing our acupoint location data with textbook anatomical cross-sections showed that all the acupoints imaged in this study were located within the connective tissue. This finding agrees with the observations of Langevin and Yandow.24

CONCLUSION
Our study showed that pulses of ultrasonic energy can stimulate an acupoint, eliciting a response similar to that produced by standard needling. Ultrasonic stimulation of the acupoints offers many advantages over conventional methods and provides an extremely useful tool for the scientific study and quantitative evaluation of acupuncture. Since the subject experiences no pain or other sensation during ultrasonic stimulation, and since no rise in temperature is observed, the method is well suited for sham experiments. In addition, quantitative ultrasound methods have shown that acupoints represent regions of enhanced ultrasonic attenuation, which change in size, shape, and location over short periods of time. Our study also suggests that an ultrasonic acupuncture system could be developed that would locate the acupoint (using quantitative ultrasound methods), and then stimulate the acupoint (using pulses of higher ultrasonic energy). "Ultrasonic Acupuncture" would seem to combine the best of Oriental medicine with the best of Western technology for the improvement of health care.

REFERENCES

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  3. Cho ZH, Chung SC, Jones JP, et al. New findings of the correlation between acupoints and corresponding brain cortices using functional MRI. Proc Natl Acad Sci U S A. 1998;95:2670-2673.
  4. Ellis A, Wiseman N,  Boss K. Fundamentals of Chinese Acupuncture. Brookline, Mass: Paradigm Publications; 1991.
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  21. In press. Ultrasound Med Biol and J Altern Complement Med.
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AUTHORS' INFORMATION
Joie P. Jones has a PhD in Physics, and is Professor of Radiological Sciences at the University of California Irvine. Dr Jones' professional interests include medical imaging and the development of ultrasound technology, as well as the critical evaluation of both diagnostic and therapeutic medicine modalities, particularly in the areas of complementary and alternative medicine and subtle energy medicine.

Joie P. Jones, PhD*
Dept of Radiological Sciences
University of California Irvine
Irvine, CA 92697-5000
Phone: 949-824-6147 • E-mail: jpjones@uci.edu

Young K. Bae has a PhD in Physics, and was formally trained in Eastern Medicine, including acupuncture and herbal therapy. Dr Bae is Chief Scientist at the Bae Institute, a private research, development, and clinical facility. His research interests include the integration of Western and Eastern medicine.

Young K. Bae, PhD, LAc
The Bae Institute of Immune Enhancement
1101 Bryan Avenue, Suite C
Tustin, CA 92780

*Correspondence and reprint requests

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