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talk in 500-520 words about (shear wave elastography)

Use your own words, don't copy and paste

Use your own words, don't copy and paste

Answer 1

Shear Wave Elastography

This is a medical technique for diagnosis of various diseases in various organs in our body. It falls under the Ultrasound Elastography technique; by that I mean we send waves via a transducer into our body and then we read change in behaviour of waves such as it's frequency on computer screen which in turn tells us about the kind of disease the organ or tissue have. In fact Elastography means medical imaging that provides us graphs to read the elastic properties and stiffness of soft tissue. The measure of softness of a tissue revels the status of disease tissue is carrying, for example: tissues are harder than it's surrounding tissues when they have tumours, a diseased liver tissue is more stiffer than the tissue of a healthy liver.

In Shear Wave Elastography we send acoustic radiation push to a targeted tissue, these waves travel sideways to the tissue and thus called shear waves. The rate of travelling of these waves when moving through lateral positions of the tissue is read through either ultrasound or MRI (Magnetic Resonance Imaging). These readings gives us the idea of stiffness of the tissue. Shear waves travel faster in stiffer tissue than normal one. Additionally, under simple conditions we can estimate the elastic properties such as E, Young's Modulus and G, Shear Modulus. Systems either display a point measure(estimate speed in small box i.e. withing the range of few millimeter squares) or multiple point measures (push pulses at multiple locations). Point measures have higher precision than multiple point measures because it doesn't have any spacial variations in speeds and stiffness; that is as the range is so small that the spacial variations can be neglected.

While making these measurements one needs to be careful of the region in which he/she is performing this diagnosis, we have to select the homogeneous region around the tissue which is far from the boundaries and the structures which may disrupt the wave propagation for example: blood vessels.

Note: One should always have to calculate the Doppler Effect while taking these measurements. Here, two Doppler Effects can be witness if closely observed. Let's understand this by first considering the transducer as source of sound waves which travels through our flesh and reach to the tissue. The tissue may be not still, in fact it either has a motion towards the transducer or away from the transducer, for the sake of explanation let's say it is moving away from the transducer. Hence, due to Doppler Effect it must receive the sound wave at different frequency, in fact at higher frequency. Then the waves at the interface of tissue gets reflected back to the transducer. This time tissue will act as a source of sound wave which is now propagating at higher frequency than the one it had released from the transducer. So here, tissue will act as the moving source and transducer as the stationary receiver. As tissue is moving away from the transducer hence, the frequency of sound wave received by the transducer is again higher than by which it gets reflected. Therefore, one can witness these two Doppler effect during this diagnosis method.

Shear Wave Elastography relies on the displacement of the tissue due to the acoustic ration force, here it is primarily push. This force can either be generated by pressure force or radiation or focused ultrasound beam. The displacement of tissue induces elastic shear waves, which propagate laterally around the tissue and detected by ultrasound transducer. The velocity of shear waves tells the elasticity of the tissue, the stiffer the tissue, the faster the shear waves propagates.