81253894 Ultrasound Physics Essay

Sound waves are nothing more than an energy transfer through a medium be it through a liquid, solid, or a gas. Sound pressure or intensity is measured on logarithmic scale in decibels dB which increases on an order of magnitude. For instance a quiet conversation would be around 30 dB and whereas the human pain threshold would be just over 100 dB. While the pitch or frequency of the sound is measured in hertz or Hz, the higher the hertz the higher the pitch of the sound and vice versa (Hildebrand, 2004).

Although ultrasound QA guidelines exist for over 35 years, the implementation of QA has been inconsistent.25 One of the reasons for that may be a general opinion that formal QA in ultrasound is unnecessary because it is based on non-ionizing radiation. For imaging modalities where ionizing radiation is used, as mammography, QA is obligatory. The other reasons could be the lack of medical physicists and medical physics departments in hospitals and sonographers workload which limits the access to equipment. Although there are no legislation

One factor is dose, in other words, the output frequency of the probe; in general, it is thought that higher frequency output carries more risk of causing thermal and mechanical effects (1, 166). It follows then, that ultrasound modes that require a higher output would also be considered a greater risk; for instance, Doppler requires a much higher output than the more traditional B-mode ultrasound (5, 625). A longer duration of the exam has also been shown in animal models to have negative biological effects on the fetus (5, 625) and cumulative effects of multiple ultrasounds over the course of gestation may be an important component as well (1, 169). Finally, gestational age must also be considered; it could be theorized that if any damaging effects from ultrasound are possible, they could be incurred during the vulnerable first trimester (5,

In today’s world, our technology use and advancement is increasing rapidly. Staying up to date on all the latest improvements is essential especially when working in the medical field. Ultrasound has improved greatly over the years and is an important part of many diagnostic findings. One of the newer advancements added to ultrasound to help with findings is elastography.

There have been many technological advancements in the health care field. Ultrasounds have played a major role in these advancements. Many people have heard of an ultrasound or even undergone an exam themselves. Medical ultrasound imaging uses high-frequency sound waves to produce images of the inner body. Ultrasounds give health care professionals a visual of tissues. Sonographers are the skilled medical technicians trained to conduct ultrasounds. “A technician (sonographer) trained in ultrasound imaging will spread a clear, warm gel on the skin of the abdomen” (Shannon 205). Next the sonographer will rub the transducer over the gel. (Shannon 205). “The transducer converts electrical pulses into mechanical (sound) waves that are transmitted

The sound waves that we encounter in our daily lives exist as pressure vibrations in the air, water, and solid mediums that they travel through - dissipating and becoming weaker as the displacement from the initial source increases. As sound is transmitted in the form of a travelling wave, the pressure varies and is dependent on both the displacement and time passed from its emission, according to the following equation:

In diagnostic ultrasound examinations, very high frequency (1 to 5 megahertz) sound waves are directed at the body’s internal structures from a probe placed in contact with the skin (Ultrasound scan,

Ultrasounds can work because they're made from sound waves. The sound waves produce an image. Sound waves go through your skin and focus on a certain part of your your body. There’s a scanning device that helps you focus on the body part, its called a “Transducer”. A transducer is a hand held small device that sends and receives signals from ultrasounds. A transducer changes impulses into sound waves.

Sound is a mechanical wave, propagating through a medium in order for it to travel (Venables 2011a). Ultrasound is defined as high frequency sound waves, above the audible range i.e. >20 kHz (Zidan et al. 2011). These waves are formed using the pulse-echo principle (Venables 2011a). This principle refers to the piezoelectric crystals which are situated in the transducer. When an alternating electrical voltage is applied across the transducer element (Lieu 2010), the element undergoes a series of compressions and rarefactions, resulting in electrical energy being converted into mechanical waves (ultrasound). These ultrasound waves propagate through tissues until they reach an acoustic interface. It is here “where there is a change in impedance (an acoustic boundary)” (Venables 2011a, that ultrasound waves will be reflected back to the transducer as echoes. These reflected echoes are then turned into an electrical signal and displayed on the ultrasound image as shades of grey, ranging from black to white.

Frequency refers to the number of cycles of compressions and rarefactions in a sound wave per second, with one cycle per second being 1 hertz. While the term ultrasound generally refers to sound waves with frequencies above 20,000 Hz (the frequency range of audible sound is 20 to 20,000 Hz), diagnostic ultrasound uses frequencies in the range of 1-10 million (mega)

Acoustic mismatch, by definition, is the discrepancy between the acoustic impedances of two or more mediums (MacLennan, 2006). This occurs when a propagated soundwave, passing through one medium, travels into another medium of unequal impedance. In the context of ultrasounds, the soundwaves emitted by the transducer are affected by changes in acoustic impedance, this is acoustic mismatch. Much like any other forms of mechanical waves, a reflection of these waves occurs at interfaces and boundaries between mediums (most likely skin/muscle or organ/fluid in this case). In cases of high acoustic mismatch, reflections are so severe that a readable ultrasound is improbable.

the information on the propagating shear wave including the velocity of the shear wave could be measured by obtaining radiofrequency images with a high frame rate , which can be used to generate a tissue displacement map. then ,the elastic property for quantitative estimation is calculated by the propagating velocity of shear wave .ARFI, acoustic radiation force impulse, Woo Kyoung Jeong 2014) (104).

Echocardiography makes use of the properties of sound waves to identify tissues based on their densities. It differentiates tissue due to the fact that the speed of sound waves is dependent on the elastic properties and density of the medium it is travelling in, also known as the acoustic density of the tissue. The test uses ultrasound which have frequencies >20 KHz. Sound waves are generated by electrically stimulated piezoelectric crystal medium which then travels through an interface between tissues such as myocardium and blood. A

3D ultrasound also called sonograph, is often used in obstetrics during pregnancy, ultrasound uses high frequency sound waves to confirm and the date of a pregnancy and to provide images of the fetus, the placenta and the amniotic fluid (Griffin,2014). A high frequency transducer is used to record the sound waves to determine the size and shape of soft tissue (Ratini,2015). It is also used to create real time visual images of the embryo or fetus in the mother’s womb (Griffin,2014).

During MIRS an ultrasound imaging probe is inserted into the body through the small incision and it produces high-frequency sound wave continuously. After hitting muscle, some waves penetrate through muscles and some are reflected. Muscle thickness will be calculated only after analyzing the reflected echoes. The sonographic machine works with a high-frequency sound pulses of 1 to 5 megahertz. By analyzing this echoes, the machine calculates the distance in-between probe and tissue using the speed of sound waves in tissue(1540m/s) the reaching time, and information about muscle layer changes with the variation of the frequency. Results are shown in the monitor (Fig.2.) in video format. Video is collected and saved in image format and tissue