Ultrasound stimulation of musculo-skeletal tissue structures
A method for ultrasound stimulation of musculo-skeletal tissue structures includes generating a plurality of acoustic spatial-temporal modes comprised of a sinusoidal-complex, wherein the sinusoidal-complex has a modulation envelope that enhances spatial-temporal measurement accuracy at a site of a multi-layered biological tissue structure, and a pulse repetition frequency and duty cycle that are osteogenic at the site of the multi-layered biological tissue structure, beam steering the acoustic spatial-temporal modes to the site of the multi-layered biological tissue structure to promote tissue healing, and producing bi-modal stress levels in the multi-layered biological tissue structure that are sufficient to generate bone fracture healing.
1 . A method for ultrasound stimulation of musculo-skeletal tissue structures, the method comprising the steps of:
generating a sinusoidal-complex in an acoustic spatial-temporal shear mode, wherein the sinusoidal-complex in the acoustic spatial-temporal shear mode is represented as
s
(
t
)
AM
=
(
1
+
m
sin
ω
m
t
)
sin
ω
c
t
=
sin
ω
c
t
-
(
m
/
2
)
cos
(
ω
c
+
ω
m
)
t
+
(
m
/
2
)
cos
(
ω
c
-
ω
m
)
t,
wherein s(t) AM is a transmitting signal, t is time, ω c is a carrier frequency, m is a modulation index that controls a degree of amplitude modulation, and ω m is a modulation frequency; and
beam-steering the sinusoidal-complex along a bone axis of a musculo-bone fracture tissue in a multi-layered biological tissue structure;
wherein the beam-steered sinusoidal complex in the acoustic spatial-temporal shear mode activates an integrin response of a bone tissue extracellular matrix through shear-wave stimulation;
wherein the beam-steered sinusoidal complex in the acoustic spatial-temporal shear mode produces an effective amount of shear stress levels in the multi-layered biological tissue structure that biophysically stimulates bone tissue repair and bone fracture healing in the musculo-bone fracture tissue, beginning with periosteal healing in the musculo-bone fracture tissue,
wherein a transmitting signal amplitude modulation envelope of the sinusoidal-complex in the acoustic spatial-temporal shear mode is constant, an osteogenic acoustic intensity shear stress level per beam of the sinusoidal-complex in the acoustic spatial-temporal shear mode is 50 milliwatts/cm 2 , a pulse repetition frequency (PRF) of the sinusoidal-complex in the acoustic spatial-temporal shear mode for bone tissue repair is 1 kilohertz (kHz), a duty cycle of the sinusoidal-complex in the acoustic spatial-temporal shear mode is about 20%, a frequency of the sinusoidal-complex in the acoustic spatial-temporal shear mode for long bone healing is 1.0 megahertz (MHz) and a frequency of the sinusoidal-complex in the acoustic spatial-temporal shear mode for spinal fusion healing is 0.5 megahertz MHz, and a dosage time of the sinusoidal-complex in the acoustic spatial-temporal shear mode is equal to or less than 20 minutes, and
wherein the osteogenic acoustic intensity shear stress level, PRF, the duty cycle, the frequency for the long bone healing, the frequency for the spinal fusion healing, and the dosage time have been simultaneously optimized to produce the amount of the shear stress levels in the multi-layered biological tissue structure that biophysically stimulates the bone tissue repair and the bone fracture healing in the musculo-bone fracture tissue.
2 . The method of claim 1 , wherein the carrier frequency of the sinusoidal-complex that promotes the bone fracture healing is between 0.5 megahertz MHz and 1.5 MHz.
3 . The method of claim 1 , wherein 1/PRF is matched to a relaxation time of the stimulated bone tissue repair by the sinusoidal-complex.
4 . The method of claim 1 , wherein the sinusoidal-complex in the acoustic spatial-temporal shear mode is generated by an ultrasonic transducer or transmitter system that includes a power supply, a microcontroller, a signal generator, a beamformer, one or more power amplifiers, a single transducer or a phased array, and a display.
5 . The method of claim 4 , further comprising beam-steering the sinusoidal complex to the fracture site using the phased array.
6 . The method of claim 4 , further comprising beam-steering the sinusoidal-complex to the musculo-bone fracture tissue by the single transducer, wherein the single transducer is an acoustic modal converter (AMC) in a form of a wedge block,
wherein the wedge block forms an angle that is substantially equal to or less than a second critical angle of the sinusoidal-complex, includes one or more of a thermoplastic, a thermoset, an elastomer, or a mixture thereof, is nontoxic in humans, and is impermeable to human blood.
7 . The method of claim 6 , wherein the wedge block has an attenuation of less than 7 decibel (dB) per centimeter at 1.5 MHz.