a) Calculate the Acoustic impedance of subcutaneous tissue, muscle and bone. Assume subcutaneous tissue has a density of 1060kg/m3 (Hedrick 2003), muscle has a density of 1104kg/m3 (Madjor 2008) and bone has a density of 5065kg/m3 (Hedrick 2003). Give your answer in Mrayls. Please use speed of sound as 1540m/s for tissue, muscle and bone
In ultrasound, Acoustic impedance (Z) is the quantity of measurement of resistance to sound when passing through a medium (Hedrick,Hykes&Starchman 2005, p.10).
According to Gill (2012,p. 11) the equation for Acoustic impedance is Z=ρc, where (Z=Acoustic impedance, ρ =density of medium and c =velocity of beam). From this equation is understood that acoustic…show more content…
In addition, as a result of high attenuation in bones, absorption of sound occurs resulting in vibration and friction and hence, sound energy loss. For these reasons, one should scan a liver through the intercostal spaces where little or no reflection occurs or under the ribs but not through the ribs.
2. Including a definition of pre and post processing, explain whether you would use read zoom or write zoom to image a gallbladder.
Preprocessing refers to manipulation of scan information or data prior to storage in memory following scan conversion while post processing refers to manipulation of scan data after storage in the scan converter. Write zoom is associated with preprocessing while read zoom is associated with post processing (Schirber, 2013, pg. 110). In write zoom, the image is rewritten with more pixels than the initial image and thus the image is given more definition magnification. For read zoom, the image is magnified this is like enlarging a photo hence the image will only be bigger. Therefore, one should use write zoom to image a gall bladder since it gives more details and an image of high quality.
3. The most common type of transducer used for deep organ imaging such as the liver is a 6Mhz convex array. The most type of transducer for imaging a thyroid is a 15 Mhz linear array. Explain, with reference to both transducer shape (linear and convex) and frequency why this is so.
A 6 Mhz convex array transducer has a wide footprint