Tissue mimicking phantoms play a crucial role in the development of Acoustic Radiation Force Impulse Imaging. This paper deals with the preparation and study of agar based tissue mimicking phantoms. Acoustic and elastic properties are studied for various concentration of agar samples (1.7%-10% by weight). Acoustic properties are measured using pulse echo transmit receive principle. Young's modulus of the samples are measured using compression test. Reproducible phantom preparation procedures are standardised for matching various properties of normal and abnormal human soft tissues. © 2012 IEEE.

M Ramasubba Reddy

Department of Applied Mechanics

ACOUSTIC RADIATION FORCE IMPULSE IMAGING

Compression tests

Elastic properties

MECHANICAL PROPERTY MEASUREMENTS

PREPARATION PROCEDURES

PULSE ECHOES

soft tissue

TISSUE MIMICKING PHANTOM

Young's Modulus

Acoustic properties

algae

Compression testing

Imaging systems

Mechanical properties

Polysaccharides

Tissue

biomechanics

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Characterization of tissue mimicking phantoms for acoustic radiation force impulse imaging

IST 2012 - 2012 IEEE International Conference on Imaging Systems and Techniques, Proceedings

A pilot study was carried out to investigate the performance of ultrasound stiffness imaging methods namely Ultrasound Elastography Imaging (UEI) and Acoustic Radiation Force Impulse (ARFI) Imaging. Specifically their potential for characterizing different classes of solid mass lesions was analyzed using agar based tissue mimicking phantoms. Composite tissue mimicking phantom was prepared with embedded inclusions of varying stiffness from 50 kPa to 450 kPa to represent different stages of cancer. Acoustic properties such as sound speed, attenuation coefficient and acoustic impedance were characterized by pulse echo ultrasound test at 5 MHz frequency and they are ranged from (1564 ± 88 to 1671 ± 124 m/s), (0.6915 ± 0.123 to 0.8268 ± 0.755 db cm-1 MHz-1) and (1.61×106 ± 0.127 to 1.76 × 106 ± 0.045 kg m-2 s-1) respectively. The elastic property Young's Modulus of the prepared samples was measured by conducting quasi static uni axial compression test under a strain rate of 0.5 mm/min upto 10 % strain, and the values are from 50 kPa to 450 kPa for a variation of agar concentration from 1.7% to 6.6% by weight. The composite phantoms were imaged by Siemens Acuson S2000 (Siemens, Erlangen, Germany) machine using linear array transducer 9L4 at 8 MHz frequency; strain and displacement images were collected by UEI and ARFI. Shear wave velocity 4.43 ± 0.35 m/s was also measured for high modulus contrast (18 dB) inclusion and X.XX m/s was found for all other inclusions. The images were pre processed and parameters such as Contrast Transfer Efficiency and lateral image profile were computed and reported. The results indicate that both ARFI and UEI represent the abnormalities better than conventional US B mode imaging whereas UEI enhances the underlying modulus contrast into improved strain contrast. The results are corroborated with literature and also with clinical patient images. © 2013 Elsevier B.V. All rights reserved.

Ultrasonics

Study of ultrasound stiffness imaging methods using tissue mimicking phantoms

Pathological changes of the body have been observed to change the mechanical properties of soft tissue types which can be imaged by ultrasound elastography. Though initial clinical results using ultrasound elastography in detection of tumors are promising, quantification of signal to noise ratio, resolution and strain image patterns are the best achieved under a controlled study using phantoms with similar biomechanical properties of normal and abnormal tissues. The purpose of this work is to characterize the biomechanical properties of agar based tissue mimicking phantoms by varying the agar concentration from 1.7 to 6.6% by weight and identify the optimum property to be used in classification of cancerous tissues. We performed quasi-static uniaxial compression test under a strain rate of 0.5. mm/min up to 15% strain and measured Young's modulus of phantom samples which are from 50. kPa to 450. kPa. Phantoms show nonlinear stress-strain characteristics at finite strain which were characterized using hyperelastic parameters by fitting Neo-Hookean, Mooney Rivlin, Ogden and Veronda Westmann models. We also investigated viscoelastic parameters of the samples by conducting oscillatory shear rheometry at various precompression levels (2-5%). Loss modulus values are always less than storage modulus which represents the behavior of soft tissues. The increase in agar concentration increases the shear modulus of the samples as well as decreases the linear viscoelastic region. The results suggest that dynamic shear modul are more promising than linear and nonlinear elastic modul in differentiation of various classes of abnormal tissues. © 2014 Elsevier Ltd.

Journal of the Mechanical Behavior of Biomedical Materials

Characterization of biomechanical properties of agar based tissue mimicking phantoms for ultrasound stiffness imaging techniques

Modelling of tissue mimicking phantoms play a crucial role in the development of Ultrasound Elastography. This paper deals with both computer modelling and physical design of agar based tissue mimicking phantoms with embedded inclusions of varying stiffness in uniform homogeneous background. The elastic properties of agar based phantom are imaged using Ultrasound Elastography. The computer modelling and linear strain analysis of the phantom are done using finite element method. The visual display of strain results are compared with the experimental results and they are in good agreement. This allows us to model many hypothetical structures of real life and will be useful while validating signal processing algorithms for new imaging modalities. © 2012 IEEE.

2012 IEEE-EMBS Conference on Biomedical Engineering and Sciences, IECBES 2012

Modelling, design and development of tissue mimicking phantoms for Ultrasound Elastography

Many ailments and/or malfunctions of the body have been observed to change the viscous behavior and elastic properties of biological soft tissues. The technique of elastography has evolved to image such properties. The clinical evidence gathered during studies involving elastography to identify cancerous lesions is very promising. However, the quantification of the resolution and specificity of elastography is best achieved under a controlled study using tissue-mimicking phantoms. One challenge is to reproduce viscoelastic behavior in phantoms as observed in biological tissues. In this paper, polyacrylamide gel based tissue-mimicking phantoms have been developed to experimentally study the role of viscoelastic properties in a controlled manner. To measure the Young's modulus, the phantoms were subjected to linear loading, and the stressstrain relationship is deduced therefrom. It is seen that the phantoms show hysteresis behavior. The viscoelastic properties of these phantoms were measured by subjecting the samples to cyclic loading. Normal forces during this process of loading were also measured as a measure of sample elasticity. To emulate the normal and pathological lesions, samples were prepared with varying concentration of monomer and studied. Three models, namely, Maxwell, KelvinVoigt (KV), and KelvinVoigt fractional derivative (KVFD), were chosen to fit the experimental data. Of these, the KVFD model was found to be best fitting for the experimental data obtained. Results indicate that stiffer samples exhibit large variations in the storage modulus when the precompression levels are altered. © 2006 IEEE.

IEEE Transactions on Instrumentation and Measurement

Measurement of viscoelastic properties of polyacrylamide-based tissue-mimicking phantoms for ultrasound elastography applications

Elastic and viscoelastic characterization of agar

Physical Principles of Medical Ultrasonics

Ultrasound in Medicine & Biology

Assessment of the acoustic properties of common tissue-mimicking test phantoms

Ultrasonic Imaging

Observations of Tissue Response to Acoustic Radiation Force: Opportunities for Imaging

Journal	IST 2012 - 2012 IEEE International Conference on Imaging Systems and Techniques, Proceedings
Open Access	No