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Attenuation is linearly dependent on the medium length and attenuation coefficient, as well as – approximately – the frequency of the incident ultrasound beam for biological tissue (while for simpler media, such as air, the relationship is quadratic). Attenuation coefficients vary widely for different media.
In acoustics, acoustic attenuation is a measure of the energy loss of sound propagation through an acoustic transmission medium. ... such as soft tissue, polymers, ...
The Hounsfield unit (HU) scale is a linear transformation of the original linear attenuation coefficient measurement into one in which the radiodensity of distilled water at standard pressure and temperature is defined as 0 Hounsfield units (HU), while the radiodensity of air at STP is defined as −1000 HU.
Although absorption is rather low in this spectral range, it still contributes to the overall attenuation of tissue. Figure 3: The molar extinction coefficients of eumelanin and pheomelanin. [5] Other tissue components with less significant contributions to the total absorption spectrum of tissue are melanin and fat.
The attenuation coefficient of a volume, denoted μ, is defined as [6] =, where Φ e is the radiant flux;; z is the path length of the beam.; Note that for an attenuation coefficient which does not vary with z, this equation is solved along a line from =0 to as:
Soft tissue disorders are medical conditions affecting soft tissue. Soft tissue injuries are some of the most chronically painful and difficult conditions to treat because it is very difficult to see what is going on under the skin with the soft connective tissues, fascia, joints, muscles and tendons.
A single X-ray beam passing through the body is attenuated by both soft tissue and bone, and it is not possible to determine from a single beam how much attenuation is attributable to the bone. However, attenuation coefficients vary with the energy of the X-rays, and, crucially, the ratio of the attenuation coefficients also varies.
The attenuation due to scattering of energy in different tissues can be measured by a device called a transducer. Recorded information from transducers such as the relationship to the site of origin and intensity of the signal can then be put together to form images of what lies inside the target tissues.