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 1

2. Blurring Speckle noise Attenuatio n System noise Transmitter Receiver Lateral axis Radial axis 7 Ultrasound Problems Erez, Schechner & Adam, Proc. DAGM 2006

3. 86 Wiener filter Weighted median filter (Mcdicken et al.) Local frequency diversity (Forsberg et al.) Anisotropic diffusion (Perona and Malik) Non-linear Gaussian filters (Aurich) Wavelets (Insana et al, Loi et al.) 89 90 95 01,04 Smoothing Not handling attenuation 70s Compounding (frequency & spatial)80s Harmonic imagingLate 90s Space invariant Not using noise statistics Low signal Previous Work

4. Image Formation Velocity of acoustic wave in tissue Received signal probe Erez, Schechner & Adam, Proc. DAGM 2006 8

5. Sector Image Formation Sweeping beam Lateral axis Radial axis Probe Erez, Schechner & Adam, Proc. DAGM 2006 9

6. Lateral PSF 10 Low acoustic freq DD High acoustic freq High freq. = better (?) Erez, Schechner & Adam, Proc. DAGM 2006

7. Attenuation probe Low freq. = better (?) r a object distance Erez, Schechner & Adam, Proc. DAGM 2006 11

8. Speckle Noise Low acoustic freqHigh acoustic freq 15 Erez, Schechner & Adam, Proc. DAGM 2006

9. Object Wave interference Object blur: as if no interference Speckle Noise Wave phenomenon Erez, Schechner & Adam, Proc. DAGM 2006 16

10. PSF 17 Low acoustic freq DD High acoustic freq Radial distance Depends on: Acoustic frequency Erez, Schechner & Adam, Proc. DAGM 2006

11. Measuring Noise Statistics -2012 0 0.2 0.4 0.6 0.8 1 Radial lag (mm) r = 7cm r = 11cm r = 15cm White noise Erez, Schechner & Adam, Proc. DAGM 2006 18

12. Standard Pre-Processing Sampling RF line Time gain compensation Envelope detection Dynamic range compression 19

13. Speckle Noise = Iinear noise log operation Erez, Schechner & Adam, Proc. DAGM 2006 20

14. Model …… … correlated noise !!! Erez, Schechner & Adam, Proc. DAGM 2006 21

15. …… … y = H x + n Stochastic Reconstruction Erez, Schechner & Adam, Proc. DAGM 2006 22

16. Considering noise statistics Best Linear Unbiased Estimator Erez, Schechner & Adam, Proc. DAGM 2006 23

17. 5 6 7 8 9 10 11 Radial distance [cm] High acoustic freqLow acoustic freq Input: Dual Acoustic Frequency 24 Erez, Schechner & Adam, Proc. DAGM 2006

18. Arithmetic meanStochastic reconstruction Stochastic Freq. Compounding 25 5 6 7 8 9 10 11 Radial distance [cm] Erez, Schechner & Adam, Proc. DAGM 2006