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1. Dept. Elect. Eng. Technion – Israel Institute of Technology. Ultrasound Image Denoising by Spatially Varying Frequency Compounding. Yael Erez , Yoav Y. Schechner , and Dan Adam. Ultrasound Problems. 7. Transmitter Receiver. Speckle noise. Blurring. Radial axis. Attenuation.
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1 Dept. Elect. Eng. Technion – Israel Institute of Technology Ultrasound Image Denoising by Spatially Varying Frequency Compounding Yael Erez , Yoav Y. Schechner , and Dan Adam
Ultrasound Problems 7 Transmitter Receiver Speckle noise Blurring Radial axis Attenuation System noise Lateral axis Erez, Schechner & Adam, Proc. DAGM 2006
Previous Work 70s Wiener filter Space invariant Not using noise statistics 80s Compounding (frequency & spatial) Weighted median filter (Mcdicken et al.) 86 Local frequency diversity (Forsberg et al.) Smoothing Not handling attenuation 89 Anisotropic diffusion (Perona and Malik) 90 95 Non-linear Gaussian filters (Aurich) Low signal Late 90s Harmonic imaging Wavelets (Insana et al, Loi et al.) 01,04
8 Image Formation probe Received signal Velocity of acoustic wave in tissue Erez, Schechner & Adam, Proc. DAGM 2006
Image Formation 9 Sector Probe Radial axis Sweeping beam Lateral axis Erez, Schechner & Adam, Proc. DAGM 2006
10 Lateral PSF D D High freq. = better (?) Low acoustic freq High acoustic freq Erez, Schechner & Adam, Proc. DAGM 2006
Attenuation 11 r a object distance Low freq. = better (?) probe Erez, Schechner & Adam, Proc. DAGM 2006
15 Speckle Noise Low acoustic freq High acoustic freq Erez, Schechner & Adam, Proc. DAGM 2006
Wave phenomenon 16 Wave interference Object blur: as if no interference Object Speckle Noise Erez, Schechner & Adam, Proc. DAGM 2006
17 PSF D D Depends on: • Radial distance • Acoustic frequency Low acoustic freq High acoustic freq Erez, Schechner & Adam, Proc. DAGM 2006
18 r = 7cm r = 11cm 1 White noise r = 15cm 0.8 0.6 0.4 0.2 0 -2 -1 0 1 2 Radial lag (mm) Measuring Noise Statistics Erez, Schechner & Adam , Proc. DAGM 2006
Standard Pre-Processing 19 Time gain compensation Envelope detection Dynamic range compression RF line Sampling
Speckle Noise 20 = log operation Iinear noise Erez, Schechner & Adam, Proc. DAGM 2006
Model 21 … … … correlated noise !!! Erez, Schechner & Adam, Proc. DAGM 2006
22 y = Hx + n … … … Stochastic Reconstruction Erez, Schechner & Adam, Proc. DAGM 2006
Best Linear Unbiased Estimator 23 Considering noise statistics Erez, Schechner & Adam, Proc. DAGM 2006
Input: Dual Acoustic Frequency 24 Low acoustic freq High acoustic freq 5 6 7 Radial distance [cm] 8 9 10 11 Erez, Schechner & Adam, Proc. DAGM 2006
Stochastic Freq. Compounding 25 Arithmetic mean Stochastic reconstruction 5 6 7 Radial distance [cm] 8 9 10 11 Erez, Schechner & Adam, Proc. DAGM 2006