Journal of Pure and Applied Ultrasonics

Narendra D. Londhe ¹, R. S. Anand ¹

Affiliations
1 Electrical Engineering Department, IIT Roorkee, Roorkee-247667, IN

Abstract

In this paper, two theoretical methods for the description of nonlinear ultrasound wave generated from axis symmetric circular source and propagation in soft human tissues is described. Burgers’ equation has been used to model the nonlinear propagation of single sinusoidal wave of finite amplitude. In the first method, the analytical solution of Burgers’ equation was achieved by using Fubini method in preshock region while weak shock theory applied in postshock region for lossless medium. In case of lossy medium, the analytical solution of Burgers’ equation is achieved by using linear diffusion equation via Hopf-Cole transformation in preshock region and Fay’s equation in postshock region. In the second method the operator splitting methodology is implemented in which absorption term is solved using Crank Nicholson Finite Difference (CNFD) method in time and nonlinear term by using analytical method at each step for both lossless and lossy medium. Both the methods are solved in MATLAB. The results have been shown for waveform distortion and shock formation radiated by circular piston source for lossless and lossy tissue mediums. The analytical study of fundamental, second and third harmonic components variation along the distance of propagation has been done using both proposed methods and has been compared.

Keywords

Nonlinear Wave, Ultrasonic Imaging, Burgers’ Equation, Shock Formation, Soft Tissues.

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K. S. Aprameya ¹, R. S. Anand ², B. K. Mishra ³, S. Ahmed ⁴

Affiliations
1 Department of Electrical Engg, University BDT College of Engg, Davangere, IN
2 Department of Electrical Engg, Indian Institute of Technology, Roorkee, IN
3 Department of Mechanical and Industrial Engg, Indian Institute of Technology, Roorkee, IN
4 Naval Surface Warfare Center, Maryland, US

Abstract

The aim of this paper is to perform a comparative study of flaw response with the grain noise signal in an ultrasonic pulse echo simulation. This is one of the analytical methods to determine the flaw response. The flaw response is predicted using the approximation techniques like Kirchoff approximation, Born approximation and modified Born approximation. The grain noise signal generated in addition to flaw response is modelled analytically. By comparing the results of predicted flaw response and grain noise signal, the possibility of flaw detection can be estimated. Here the flaw considered for study is a spherical void and the material selected for study is a polycrystalline metal. Firstly, the comparison is made for 1 MHz circular transducer and secondly the study is performed for different center frequencies of transducer.

Keywords

Spherical Void, Pulse Echo Simulation, Scattering Amplitude, Grain Noise Signal, Predicted Flaw Response.

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Deep Gupta ¹, R. S. Anand ¹, Barjeev Tyagi ¹

Affiliations
1 Department of Electrical Engineering, Indian Institute of Technology Roorkee, Roorkee-247667, U.P., IN

Abstract

Edge preserved enhancement is of great interest in ultrasound medical images. Speckle is a main factor which affects the quality; contrast resolution and most importantly texture information present in ultrasound images and can make the post-processing difficult. In this paper, a new algorithm based on discrete ripplet transform (DRT) and overlapping group shrinkage (OGS)/thresholding scheme using bilateral filter (BLF) is presented. The DRT, a new efficient multiscale geometric representation with the different features of anisotropy, localization, directionality and multiscale, is employed to provide effective representation of the noisy coefficients. Bilateral filtering and OGS thresholding scheme are applied to DRT coefficients to improve the despeckling efficiency with this consideration that blurring associated with the speckle reduction should be less and fine details are enhanced properly for the enhancement of ultrasound images. The proposed algorithm helps also to improve the visual quality of ultrasound medical images by reducing the speckle significantly while preserving the edge features. Experimental results show that the performance of proposed algorithm for noise suppression, feature and edge preservation in terms of different performance measures.

Keywords

Ultrasound, Discrete Ripplet Transform (DRT), Bilateral Filter (BLF), Overlapping Group Shrinkage (OGS), Thresholding, Speckle.

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