1. 1 TFJ, Simulation of electrical signal path, part 1 MEDT8807 Scattering of sound Point spread function Medt8007 2015 Tonni Franke Johansen Hans Torp

2. 2 Outline Scattering of single sphere (Cobbold ch 5.1-5.3) Scattering from a distribution of scatterers ch 5.9 Point spread function ch 5.7 + «Notes on psf» (H.Torp) Simple 2D k-space simulator Anisotrophy in US imaging

3. 3 Scattering cross section

4. 4 Scattering by a sphere pipi psps p=p i +p s

5. 5

6. 6 The rigid, heavy sphere.

7. 7 From cobbold:

8. 8 Let the sphere be compressible with density  v and speed of sound c v. The surrounding medium has density  o and speed of sound c o.

9. 9 From Lars Hoff

10. 10 From Cobbold:

11. 11 Distribution of scatterers Common to use Rayleigh scatterers with distributed strength and/or posistion (blood, liver tissue) Distribution of scatterers presented in e.g.Angelsen ch.7.4-5 and Cobbold ch.5.9 Stochastic models (gaussion distributions, correlation)

12. 12 Human blood cell distribution

13. 13

14. 14 Pulse-echo response Field II Pulse-Echo response Rx transducer impulse response Rx spatial impulse response Excitation Tx transducer impulse response Tx spatial impulse response The Pulse-echo response is the “true” sensitivity map of our beam, where the echos most likely are originating from. Tore Bjåstad

15. 15

16. 16 Point spread function 1

17. 17 Point spread function 2

18. 18 Point spread function 3

19. 19 PSF in k-space

20. 20 Examining septum from different angles makes the bright line shift sideways Backscatter depends on fiber angle Torbjørn Hergum/Jonas Crosby

21. 21 Examining septum from different angles makes the bright line shift sideways Backscatter depends on fiber angle

22. 22 Examining septum from different angles makes the bright line shift sideways Backscatter depends on fiber angle Backscatter void not just attenuation: no shadow beneath