1、Busting the ghost in coherent plane-wave imaging,Alfonso Rodriguez-Molares, Lasse Lvstakken, Bastien Denarie, and Hans Torp,Centre for Innovative Ultrasound Solutions,Contents,Background Contrast ratio in CPWC Results In-vitro data of the contrast ratio in CPWC In-silico data of the contrast ratio i

2、n CPWC A picture of a ghost Theory What we know about ghost? Understanding the ghost Busting the ghost? Results (again) Busting the ghost in CPWC images Discussion,Background,Resolution Contrast Ratio, 1 2 ,Increases with the number of plane-waves,Results Experimental apparatus,Verasonics 256 Vantag

3、e scanner L12-3v probe: 192-element, 9 MHz, 0.2 mm pitch STAI dataset: 1.5 cycles CPWC dataset: 1.5 cycles, F =1.2, Boxcar, =23.87,Results - Anechoic cyst optimally focused,=20 log (,) (,),Optimally focused beams,CR=30.41 dB,Results - Anechoic cyst CPWC,Montaldo et al. 2009,Rodriguez-Molares et al.

4、now,Results - Anechoic cyst CPWC,=20 log (,) (,),Optimally focused beams,CR=67.99 dB,1 J.A. Jensen: Field: A Program for Simulating Ultrasound Systems, Paper presented at the 10th Nordic-Baltic Conference on Biomedical Imaging Published in Medical & Biological Engineering & Computing, pp. 351-353, V

5、olume 34, Supplement 1, Part 1, 1996. 2 J.A. Jensen and N. B. Svendsen: Calculation of pressure fields from arbitrarily shaped, apodized, and excited ultrasound transducers, IEEE Trans. Ultrason., Ferroelec., Freq. Contr., 39, pp. 262-267, 1992.,Results Simulated PSF optimally focused,Results Simula

6、ted PSF CPWC,Point Spread Function Field II,Anechoic cyst - Experiment,Results Experimental and Simulation,PSF tail Edge waves Range lobes,Results The ghost,Theory what we know about the ghost, related to the edges of the aperture as its influence can be reduced with a 25% tukey apodization,Point Sp

7、read Function Field II,Anechoic cyst - Experiment,Theory understanding the ghost,Theory understanding the ghost,Theory understanding the ghost,Theory understanding the ghost,Theory understanding the ghost,Theory busting the ghost,Theory busting the ghost,angle dependent transmit apodization (ADTA),T

8、heory busting the ghost,Results Simulated PSF ADTA,Results Anechoic cyst ADTA,Results - Comparison,Point Spread Function Field II,Anechoic cyst - Experiment,Discussion,Advantages: Higher contrast ratio than any other transmit apodization scheme Faster convergence to the theoretical maximum CR Ghost

9、free images! Drawbacks:,Discussion,Transmit apodization optimised for a specific point,Discussion the catch,N=63,N=63,Discussion the catch,Discussion compromise between CR and coverage,Broad ADTA,Discussion,Advantages: Higher contrast ratio than any other Transmit Apodization Faster convergence to theoretical maximum Ghost free! Drawbacks: Reduced coverage Optimal CR in close-ups Suboptimal CR in full frames,Or optimal CR with multiple transmitions full frame,Needle Detection by Image Sour