Rate of temperature increase in human muscle during 1 MHz and 3 MHz continuous ultrasound.

To achieve the thermal effects of ultrasound, the tissue temperature must be raised from 1 to > or = 4 degrees C, depending on the desired outcome of the treatment. In the past 25 years, there have been no in vivo studies that have measured rate of change in temperature during 1-MHz ultrasound treatments, and none have ever been performed with the 3-MHz frequency. Thus, we are left to pure speculation regarding how long to administer an ultrasound treatment. We performed this study to plot the rate of temperature increase during ultrasound treatments delivered at various intensities and frequencies. We inserted two 23-gauge thermistors into each subjects' medial triceps surae at the following depths: 1 MHz at depths of 2.5 and 5.0 cm (12 subjects) and 3 MHz at depths of .8 and 1.6 cm (12 subjects). Each subject received a total of four 10-minute treatments, one each at .5, 1.0, 1.5, and 2.0 W/cm2, and temperature was measured every 30 seconds. No significant difference was found in the rate of heating at the two depths (p = .987) within the same frequency and dose levels. The 3-MHz frequency heated significantly faster than the 1-MHz frequency at all doses tested (p < .001). On average, the rate of temperature increased per minute at the two depths of the 1-MHz frequency was: .04 degrees C at .5 W/cm2; .16 degrees C at 1.0 W/cm2; .33 degrees C at 1.5 W/cm2; and .38 degrees C at 2.0 W/cm2. The rate of temperature increase per minute at the two depths of the 3-MHz frequency was: .3 degrees C at .5 W/cm2; .58 degrees C at 1.0 W/cm2; .89 degrees C at 1.5 W/cm2; and 1.4 degrees C at 2.0 W/cm2. The results of this research should enable clinicians to choose the correct frequency, intensity, and treatment time when using thermal ultrasound.

[1]  Robert R. Young,et al.  Reversible Block of Nerve Conduction by Ultrasound: Ultrasonic Blocking of Nerve Fibers , 1961 .

[2]  Aldes Jh,et al.  Ultrasonic therapy in the treatment of hypertrophic arthritis in elderly patients. , 1952 .

[3]  Linda G. Monroe,et al.  Relative transmission of ultrasound by media customarily used for phonophoresis. , 1992, Physical therapy.

[4]  R. Gorkiewicz Ultrasound for Subacromial Bursitis , 1984 .

[5]  C G Warren,et al.  Heating produced by ultrasound in bone and soft tissue. , 1967, Archives of physical medicine and rehabilitation.

[6]  Justus F. Lehmann Therapeutic heat and cold , 1975 .

[7]  G. Forrest,et al.  Ultrasound: effectiveness of treatments given under water. , 1989, Archives of physical medicine and rehabilitation.

[8]  Kuitert Jh Ultrasonic energy as an adjunct in the management of radiculitis and similar referred pain. , 1954 .

[9]  Wood Mr,et al.  Ultrasound for Dupuytren's contracture. , 1980 .

[10]  R. Baker,et al.  The effect of therapeutic modalities on blood flow in the human calf. , 1991, The Journal of orthopaedic and sports physical therapy.

[11]  Oakley Em Application of continuous beam ultrasound at therapeutic levels. , 1978 .

[12]  G terHaar,et al.  Basic physics of therapeutic ultrasound. , 1978 .

[13]  Lehmann Jf The biophysical basis of biologic ultrasonic reactions with special reference to ultrasonic therapy. , 1953 .

[14]  W. Prentice Therapeutic Modalities in Sports Medicine , 1986 .

[15]  Gersten Jw Effect of ultrasound on tendon extensibility. , 1955 .

[16]  Patrick Mk Applications of therapeutic pulsed ultrasound. , 1978 .

[17]  Bearzy Hj Clinical applications of ultrasonic energy in treatment of acute and chronic subacromial bursitis. , 1953 .

[18]  F. B. Bundt Ultrasound therapy in supraspinatus bursitis. , 1958, Physical Therapy Reviews.

[19]  Kramer Jf Ultrasound: evaluation of its mechanical and thermal effects. , 1984, Archives of physical medicine and rehabilitation.

[20]  J. A. Kleinkort,et al.  Phonophoresis with 1 percent versus 10 percent hydrocortisone. , 1975, Physical therapy.

[21]  J. Lehmann,et al.  Therapeutic temperature distribution produced by ultrasound as modified by dosage and volume of tissue exposed. , 1967, Archives of physical medicine and rehabilitation.

[22]  M. Dyson,et al.  Stimulation of tissue repair by ultrasound: a survey of the mechanisms involved. , 1978, Physiotherapy.

[23]  N. Byl,et al.  Incisional wound healing: a controlled study of low and high dose ultrasound. , 1993, The Journal of orthopaedic and sports physical therapy.

[24]  W. Bierman Ultrasound in the treatment of scars. , 1954, Archives of physical medicine and rehabilitation.

[25]  Nwuga Vc Ultrasound in treatment of back pain resulting from prolapsed intervertebral disc. , 1983 .