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PA: Ultrasound
| Question | Answer |
|---|---|
| Does US have more proof with human or animal studies? | Animal |
| What frequency is US? | Anything above 20,000 Hz |
| Definition of frequency | Number of oscillations a molecule undergoes during one second |
| Definition of hertz | measurement of sound waves |
| What is 1 Hz? | 1 cycle/second |
| What is the wavelength? | Distance between two successive peaks in the pressure wave |
| What is US? | Form of acoustic energy requiring a medium when treating human tissue |
| How does US work? | Sound waves "bump" into adjacent molecules, transfer energy and continues |
| What is the positive pressure phase of US considered? | Compression |
| What is the negative pressure phase of US considered? | Dispersion |
| What is the piezoelectricity? | Crystals generate electric voltage when mechanically compressed or expanded |
| What is the reverse piezoelectric effect? | Voltage is applied and the crystal can compress and expand |
| What type of wave are US waves? | Chemical pressure waves |
| How deep does 1 MHz go? | >2cm below skin |
| How deep does 3 MHz go? | 1-2cm |
| What is the duty cycle? | Fraction of time during a single pulse period that the beam of sound is present |
| What is the intensity? | Strength of power or quantity of energy produced by US transducer |
| What is power measured in? | Watts |
| Is power uniform across an US transducer? | No |
| Wat is the effective radiating area? | Actual cross-sectional area of the US beam exiting metal end plate |
| What is the beam non-uniformity ratio? | Ratio between spatial peak intensity and spatial average intensity |
| What is the lowest acceptable beam non-uniformity ratio? | 6:1 |
| What types of waves do gases and liquids have? | Longitudinal waves |
| What direction are gases and liquids to the direction of energy flow? | Parallel |
| What types of waves do solids have? | Longitudinal and transverse waves |
| What direction are solids to the direction of the energy flow? | Perpendicular |
| What are the majority of tissues in the body? | Gases and liquids |
| What is the only tissue to get a transverse wave? | Bone |
| What is acoustic impedence? | Materials ability to transmit sound and density of structure of material |
| If a AI is low, what is the transmission, what does this mean, and what is an example? | Low AI = High transmission = material absorbs little sound Ex: Blood |
| If a AI is high, what is the transmission, what does this mean, and what is an example? | High AI = Low transmission = material absorbs more, not letting things through Ex: Bone |
| When does reflection and refraction occur? | When energy is transmitted through materials of differing impedances |
| What happens with sound waves from subcutaneous tissue to muscle? | Some reflection back to subcutaneous tissue |
| What happens with sound waves from muscle to bone? | Way more reflected back to muscle |
| Which heats up faster, tendons and ligaments or muscle? | Tendons and ligaments |
| Why do tendons and ligaments heat up faster? | High collagen content Avascularity |
| What do animal studies show about wound healing with US? | Increased wound healing |
| When energy strikes at a perpendicular angle the reflection is directly ____ to the tissue | Perpendicular |
| When energy strikes a boundary at a non-perpendicular angle the reflection angle is the ______ as the strike angle | Same |
| What is a standing wave and when does it occur? | When reflected wave interacts with waves traveling away from the energy source Occurs when you don't move the head |
| Definition of attenuation | Measure of the decrease in sound energy as the US travels, either by absorption, reflection, or refraction |
| Which types of tissues absorb US energy the best? | Denser tissues with high protein content |
| How do thermal effects occur during US? | Occur due to friction between molecules |
| Temp increase for metabolic rate | 1 degree C |
| Temp increase to reduce spasm and pain and increase blood flow | 2-3 degrees C |
| Temp increase to increase collagen extensibility | 4 degrees C |
| What is cavitation? | Small gas bubbles present in tissue |
| What part of the body actually have studies that show improvement due to US? | Calcific tendonitis of the shoulder |
| What are deep heat indications for US? | Joint contracture Scar tissue Pain Muscle spasm Subacute or chronic soft tissue inflammation |
| What are indications for US to facilitate healing? | Acute injury/inflammation of soft tissue or peripheral nerve Open wounds Fracture |
| Contraindications of US | Region of pacemaker During pregnancy (over area) Over eyes and testes Region of active bleeding or infection Region of a tumor or malignancy Region of DVT Over heart, stellate or cervical ganglia Over epiphyseal plates or growing bones Over spina |
| Precautions of US | Sensation of area being treated Communication or cognitive deficits Poor circulation or vascularity Treatment over plastic or metal implants |
| What is direct contact coupling? | Coupling medium required |
| What is indirect coupling? | Water immersion (1-2cm away) |
| What is phonophoresis? | Use of US to enhance delivery of medication through the skin |
| Mechanisms of phonophoresis | Dilating points of entry (hair follicles, sweat glands) Increasing local circulation Increasing kinetic energy of local cells and the medication itself Increasing cell membrane permeability |
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