Electrophysical Agents - Ultrasound

The duty cycle is a measure of the amount of time a signal is on (active) compared to the total period (on + off) of the signal. It is calculated by dividing the duration of the pulse time (on) by the pulse period (on + off). This ratio indicates the percentage of time the signal is active during each cycle.

Athermal Acoustic streaming refers to the movement of fluids caused by a mechanical pressure wave. This means that when an ultrasound beam is applied, it creates a pressure wave that causes the fluid to move. It does not involve the vibration effect on gas bubbles, as mentioned in the other option.

The correct answer is the contraction and expansion of the crystal in response to an applied voltage. When a voltage is applied to a crystal, it causes the crystal to contract or expand. This contraction or expansion generates an electric voltage across the crystal. The voltage induced is of opposite polarity to the applied voltage.

With greater intensity, the temperature elevation will be higher. This means that as the intensity of a certain factor increases, the resulting temperature elevation will also increase.

Spatial Average Temporal Average Intensity refers to the average intensity of a signal over both the on and off cycles. This means that it takes into account the intensity of the signal during the entire duration, rather than just focusing on the peak intensity. By considering both the on and off cycles, a more comprehensive representation of the signal's intensity is obtained, providing a more accurate measure of its overall intensity.

The correct answer is "greatest intensity anywhere over the area of the transducer." Spatial peak intensity refers to the highest intensity level that can be achieved anywhere on the transducer's surface. It is not necessarily related to the total power output or the area of the applicator face.

Athermal cavitation refers to the phenomenon where gas bubbles are subjected to vibrations caused by an ultrasound beam. These vibrations can cause the bubbles to oscillate and collapse, leading to the release of energy. This process does not involve any significant increase in temperature, hence the term "athermal." The ultrasound beam induces mechanical pressure waves that create the vibrations, affecting the gas bubbles and causing them to undergo cavitation.

Ultrasound is a non-invasive imaging technique that uses high-frequency sound waves to produce images of the inside of the body. It can also be used for therapeutic purposes. In the context of clinical applications, ultrasound can be used for joint contractures and scar tissue to help improve mobility and reduce the tightness of the joints. It can also be used to reduce pain and muscle spasm by promoting blood flow and relaxation of the muscles. Additionally, ultrasound can be used for conditions like bursitis and tendinitis to reduce inflammation and promote healing. It can also aid in wound healing and the treatment of plantar warts by promoting tissue regeneration. However, ultrasound is not typically used for the treatment of cancer tumors.

The given statement is incorrect. It states that for dosage, a high output should always be used. However, this is not true. The appropriate dosage for any medication or treatment depends on various factors such as the individual's age, weight, medical condition, and the specific medication being used. It is important to follow the recommended dosage guidelines provided by healthcare professionals or stated on the medication packaging. Using a high output dosage without proper guidance can lead to adverse effects and potential harm to the individual.

The propagation of vibratory motion is known as sound wave(s). Sound waves are created when an object vibrates, causing the surrounding air particles to vibrate and transmit the energy in the form of waves. These waves then travel through the medium, such as air, water, or solids, and can be detected by our ears as sound. Sound waves are characterized by their frequency, wavelength, and amplitude, and they play a crucial role in communication and perception of the world around us.

The correct answer is "total power output of the applicator divided by the area of applicator face." Spatial average intensity refers to the average power output of the applicator distributed over the entire area of the applicator face. It is calculated by dividing the total power output by the area of the applicator. This measure provides an overall indication of the intensity of the energy being emitted by the applicator.

When there is an air pocket formed between the treatment head and the skin, it acts as a barrier for the energy to penetrate into the skin. Instead, the energy gets reflected back towards the treatment head. This reflection of energy reduces the amount of energy that actually reaches the skin, resulting in a large amount of energy being reflected.

This answer correctly states that direct means the generation of electric voltage across a crystal when the crystal is compressed. It explains that when the crystal is compressed, it will expand and induce a voltage of opposite polarity. This explanation accurately describes the process of direct generation of electric voltage in a crystal through compression and expansion.

The correct answer is higher because in sound velocity, the more rigid a material is, the faster sound waves can travel through it. Rigid materials have a higher stiffness, allowing sound waves to propagate more quickly compared to less rigid materials. Therefore, the sound velocity is higher in more rigid materials.

Longitudinal waves are supported in human body tissues. These waves travel by compressing and expanding the particles of the medium in the same direction as the wave is propagating. In the context of the human body, sound waves are an example of longitudinal waves that can travel through tissues. These waves are used in medical imaging techniques such as ultrasound, where they can penetrate the body and provide valuable information about internal structures.

The strength of an ultrasound beam is determined by its intensity. Intensity refers to the amount of energy carried by the ultrasound waves per unit area. Higher intensity means a greater concentration of energy in the beam, resulting in a stronger ultrasound signal. This is important in medical applications, where the intensity of the ultrasound beam can be adjusted to achieve the desired diagnostic or therapeutic effects.

In pulse mode, the sound beam will be at its maximum intensity during the "on" stage. This means that the sound wave will be at its highest peak, resulting in a stronger and more powerful sound beam.

The correct answer is the region of pregnant uterus, tumors/TB, and eye applications. Athermal US refers to the use of ultrasound without the production of heat. It is important to avoid using athermal US in the region of a pregnant uterus as it can potentially harm the developing fetus. Similarly, tumors or tuberculosis in the body should not be exposed to athermal US as it may worsen the condition or cause complications. Additionally, athermal US should not be applied to the eyes as it can cause damage to the delicate structures of the eye.

SATA stands for Standard Ambient Temperature and Pressure. It refers to the standard conditions of temperature and pressure at which a substance is measured or evaluated. The given statement suggests that the amount of heating depends on whether the substance is measured or evaluated under SATA or SATP conditions. However, without further context or information, it is not possible to provide a more specific explanation.

A coupling medium is required in ultrasound treatment because ultrasound energy is lost in air and reflected at the air-tissue interface. By using a coupling medium, such as gel, the energy can be transmitted efficiently from the transducer to the surface being treated. Additionally, eliminating as much air as possible ensures that the patient's skin surface is not scratched by the ultrasound head.

Spatial Average Temporal Peak Intensity refers to the highest level of intensity reached during a specific time period. It represents the maximum intensity experienced over a given duration. This measurement does not take into account the average intensity over both the on and off cycles, but rather focuses solely on the peak intensity.

Thermal ultrasound (US) is a therapeutic modality that uses sound waves to generate heat within the body tissues. However, there are certain dangers and contraindications associated with its use. Circulatory insufficiency refers to poor blood circulation, which can be worsened by the heat generated by thermal US. Inability to detect heat means that if a person cannot feel or sense the heat, they may be at risk of burns. Increased bleeding can occur due to the heat causing blood vessels to dilate. Acute infective disorders, such as active infections, can be aggravated by the heat. Thermal US should not be used in regions of the pregnant uterus, as it may harm the developing fetus. Tumors and tuberculosis (TB) are contraindications because the heat can potentially stimulate tumor growth or worsen TB symptoms. Eye applications are avoided due to the sensitivity of the eye tissues to heat. Lastly, thermal US should not be used on the spinal cord after laminectomy (surgical removal of the lamina of the vertebrae) to prevent damage to the spinal cord.

The reflection of ultrasound in tissue depends on the degree of mismatch of acoustic impedance. Acoustic impedance is a measure of how much resistance the tissue offers to the passage of sound waves. When there is a significant difference in the acoustic impedance between two tissues, such as between soft tissue and bone, a large portion of the ultrasound wave is reflected back at the interface. This reflection can be detected and used to create images of the internal structures of the body.

The question is asking for the two types of waves, and the correct answer is "longitudinal" and "transverse". Longitudinal waves are waves in which the particles of the medium vibrate parallel to the direction of wave propagation, while transverse waves are waves in which the particles of the medium vibrate perpendicular to the direction of wave propagation. These two types of waves have different characteristics and behaviors, making them distinct from each other.

The effects of ultrasound refer to the various outcomes or changes that occur when ultrasound waves interact with matter. These effects can include heating, mechanical vibrations, and the creation of microscopic bubbles. The intensity of the ultrasound waves determines the magnitude or strength of these effects. Higher intensity ultrasound waves will produce more significant effects, while lower intensity waves will have less impact. Therefore, the intensity of ultrasound is a crucial factor in determining the extent of its effects on the target material or organism.

The other athermal danger effects mentioned in the question are stasis of blood flow, endothelial damage, and platelet aggregation in blood vessels. Stasis of blood flow refers to the slowing down or cessation of blood circulation, which can lead to various health issues. Endothelial damage refers to the injury or dysfunction of the endothelial cells that line the blood vessels, which can disrupt normal blood flow and contribute to the development of cardiovascular diseases. Platelet aggregation in blood vessels refers to the clumping together of platelets, which can form blood clots and obstruct blood flow, potentially leading to serious complications such as heart attacks or strokes.

The absorption of sound increases as frequency increases because higher frequencies have shorter wavelengths, which allows them to be more easily absorbed by materials. The question is asking for the frequency most often used for therapeutic applications, and the answer is frequency 1. However, without knowing the specific frequencies mentioned in the question, it is not possible to provide a more detailed explanation.

The given answer provides the dosage guidelines for different conditions and treatment areas. For acute conditions, a dosage of 0.1-1.0 W/cm2 for 5 minutes is recommended, with no perceptible heat. For chronic conditions, the recommended dosage is 0.8-3.0 W/cm2 for 5-10 minutes, with mild to comfortable warmth. For PUS (Pulsed Ultrasound Stimulation), a dosage of 0.1-1.5 W/cm2 for 5-15 minutes is suggested, considering temporal average dosage. The treatment area is approximately 25 cm2.

The correct answer is "piezoelectricity" and "piezoelectric". Piezoelectricity is a property of certain crystals that allows them to generate an electric charge when subjected to mechanical stress or pressure. This property is utilized in ultrasound equipment, where the crystal is used to convert electrical energy into sound waves and vice versa. The term "piezoelectric" is used to describe materials that exhibit this property.

Ultrasound can elevate tissue temperature to a depth of 5 cm or more. This means that when ultrasound waves are applied to the body, they can penetrate up to 5 cm below the surface and increase the temperature of the underlying tissues. The depth of penetration depends on various factors such as the frequency of the ultrasound waves and the characteristics of the tissues being treated. However, it is important to note that excessive heating can cause damage to the tissues, so ultrasound therapy should always be administered by trained professionals.

Ultrasound can have negative effects on the body, including the retardation of growth in long bones. This is because the high-frequency sound waves generated by ultrasound can disrupt the normal growth and development of bones. Additionally, ultrasound can damage spinal cord tissue, as the waves can cause excessive heating or mechanical stress on the delicate spinal cord. Furthermore, ultrasound can destroy other tissues in the body, as the intense energy generated by the waves can lead to tissue damage or cell death.

A transducer is a device that converts one form of energy to another. This means that it takes input energy in one form, such as mechanical, electrical, or thermal energy, and transforms it into a different form of energy, such as electrical signals, sound waves, or light. Transducers are commonly used in various applications, such as sensors, microphones, speakers, and solar cells, where the conversion of energy from one form to another is necessary for the device to function properly.

The biophysical effect of ultrasound (US) can be either thermal or non-thermal. Thermal effects refer to the increase in tissue temperature due to the absorption of ultrasound energy, which can have various therapeutic benefits such as increased blood flow and tissue relaxation. On the other hand, non-thermal effects involve mechanical and acoustic phenomena that do not result in a significant rise in temperature. These effects include cavitation, microstreaming, and acoustic streaming, which can be utilized for applications like tissue healing and drug delivery.

Ultrasound therapy utilizes sound waves beyond the range of human hearing to penetrate deep into tissues. These sound waves cause vibrations within the tissues, generating heat and promoting a range of therapeutic effects. Ultrasound is commonly used to reduce pain, increase blood flow, and promote tissue healing in conditions such as muscle strains, tendonitis, and bursitis.

Ultrasound has been found to have various physiological effects on the body. It can increase collagen tissue extensibility, meaning that it can make connective tissues more flexible and pliable. Ultrasound can also cause alterations in blood flow, potentially improving circulation in the targeted area. It can change nerve conduction velocity, which affects the speed at which nerve signals are transmitted. Additionally, ultrasound can increase the pain threshold, making individuals less sensitive to pain. It can also increase enzymatic activity, which may have a positive impact on various metabolic processes. Lastly, ultrasound can change the contractile activity of skeletal muscles, potentially improving muscle function.

Sound waves can be produced in two ways: continuously or in pulses. Continuous sound waves are produced when a sound source vibrates continuously, creating a continuous stream of sound waves. On the other hand, pulsed sound waves are produced when a sound source vibrates intermittently, creating a series of sound waves with gaps in between. Therefore, the correct answer is "continuous pulsed" because sound waves can be produced in either of these two ways.

Thermal effects refer to the process of increasing the temperature of tissues. This can be achieved through various methods such as applying heat externally or using devices that generate heat. Elevating tissue temperature can have several beneficial effects, including increased blood flow, relaxation of muscles, and promotion of tissue healing. By raising the temperature of tissues, thermal effects can help improve circulation, reduce pain, and enhance the effectiveness of certain therapeutic interventions.

Cavitation refers to the formation and collapse of small gas bubbles in blood or tissue fluids. This process can lead to expansion and compression of these bubbles, causing intense changes in cellular activity and potential tissue damage.

The penetration of ultrasound is related to frequency, protein content, and mismatch in impedance. It is also directly/indirectly proportional to frequency in a homogeneous medium and expressed in half value depth.

Acoustic streaming refers to the movement of fluid induced by the propagation of sound waves. This phenomenon can lead to changes in ion fluxes and cellular activity. Specifically, it can cause an increase in the movement of ions across the cellular membrane and also increase the permeability of the membrane wall.

When two waves with the same frequency and amplitude travel in opposite directions and interfere with each other, they create a standing wave. In this case, the standing waves are formed when reflected waves are added to incoming waves. The result of this interference is that areas of constructive interference will produce higher amplitudes of sound, while areas of destructive interference will have lower amplitudes. Therefore, only some areas will receive the ultrasound, resulting in the production of reflected, new, heat, and sound waves.

The piezoelectric effect refers to the generation of an electric charge in certain materials when subjected to mechanical stress. The direct piezoelectric effect occurs when the mechanical stress directly produces an electric charge, while the indirect piezoelectric effect involves the mechanical stress inducing a change in the material's electric field, resulting in an electric charge. Therefore, the correct answer is "direct indirect" as it encompasses both forms of the piezoelectric effect.

Acoustic impedance is defined as the product of tissue density and velocity of sound in tissue.

The answer states that high frequency leads to greater attenuation of energy in superficial structures, while low frequency leads to lower attenuation in superficial structures but greater absorption in deep tissues. This means that at higher frequencies, energy is more likely to be absorbed or scattered by superficial structures, while at lower frequencies, energy can penetrate deeper into tissues before being absorbed.

The size of the transducer and the frequency of the sound waves will affect the spread of sound waves and the extent of the Fresnel zone. A larger transducer will emit sound waves over a wider area, resulting in a larger spread of the waves. Additionally, the frequency of the sound waves will determine the size of the Fresnel zone, with higher frequencies resulting in a smaller Fresnel zone and lower frequencies resulting in a larger Fresnel zone.

Frequency is the number of oscillations per second and is measured in hertz.

Continuous wave refers to a wave that maintains a constant amplitude and frequency over time. In this mode, the wave does not experience any interruptions or breaks. On the other hand, pulse mode refers to a wave that is intermittently interrupted, meaning that the intensity of the wave fluctuates between periods of high and low intensity. Therefore, the given answer correctly states that continuous wave means the wave is constant, while pulse mode means intensity is intermittently interrupted.

Ultrasound frequency refers to the number of sound waves per second. In this case, the given answer indicates that the ultrasound frequency is greater than 750 kHz, which means it is above 750,000 cycles per second. Therapeutic ultrasound, on the other hand, typically operates at a frequency between 0.75 and 3 MHz, which is between 750,000 and 3,000,000 cycles per second. This range is commonly used for medical treatments such as deep tissue heating and promoting tissue healing.

The wavelength is inversely related to the frequency of successive peaks in the pressure wave. This means that as the frequency increases, the wavelength decreases, and vice versa. In other words, when there are more peaks occurring within a given time period, the distance between these peaks is shorter, resulting in a shorter wavelength. Conversely, when there are fewer peaks occurring within a given time period, the distance between these peaks is longer, resulting in a longer wavelength.

Pulsing is a useful technique when the desired effect is either thermal or non-thermal. In the case of non-thermal acute soft tissue injuries, pulsing can be beneficial in promoting healing and reducing inflammation without the use of heat. This technique involves applying intermittent bursts of energy, which can stimulate cellular activity and improve blood flow to the injured area. By using pulsing, healthcare professionals can effectively treat non-thermal acute soft tissue injuries and facilitate the recovery process.