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Keywords:
Tissue characterisation, Cirrhosis, Cancer, Experimental investigations, Equipment, Diagnostic procedure, Ultrasound, Experimental, Elastography, Ultrasound physics, Oncology
Authors:
H. E. Ting, C. H. Yeong, B. J. J. Abdullah, K. H. Ng; Kuala Lumpur/MY
DOI:
10.1594/ecr2014/C-1915
Aims and objectives
Introduction
Elasticity imaging,
otherwise known as elastography,
plays a significant role in the application of clinical diagnosis by providing useful structural and pathological information on the elastic properties of tissue in the body.
Many pathological processes such as inflammation and tumours can alter tissue elasticity significantly [Krouskop,
1998].
For example,
most cancers,
such as scirrhous carcinoma of the breast,
appear to be very stiff compared to normal tissue [Anderson,
1953].
One of the latest developments in elastography imaging is Shear Wave Elastography (SWE) (Refer to Fig.1) which uses ultrafast ultrasound to measure tissue elasticity in a selected area.
It is a real-time,
non-invasive and reproducible method to map tissue stiffness of the entire region of interest (ROI).
The process of SWE is demonstrated in Fig.2.
In SWE,
a transient pulse is sent out from the probe to push the underlying tissue,
causing the underlying tissue to deform or displace.
Human tissues,
which are elastic,
will oppose the push by a restoring force which subsequently generates transverse shear wave fronts propagating in opposite direction.
The propagation of shear wave is then captured using ultrafast technology in which a flat ultrasound wave is sent out to insonify the whole medium in one shot.
The propagation of shear wave in the medium is then captured just like a movie from which its velocity can be estimated.
From equation 1,
the elasticity of the tissue (Young’s modulus) can be computed [Bercoff,
2008].
E = 3ρc2 Equation (1)
where ρ is the local density (constant and equal to 1000 kg m-3 in soft tissue) and is the shear wave propagation velocity).
Objectives
This study aimed to verify the accuracy of SWE measurement in a gelatine-based elasticity phantom by comparing the elasticity measurements with a gold standard and investigate the effect of masses’ depth,
size and elasticity on the SWE measurements.