k-Wave

1. tiagodourado
   

   Member
   Joined: Oct '17
   Posts: 9

   Dear colleagues,

   I am trying to model the geometry and physical properties of the typical comet tail effect known in the medical ultrasound literature as 'comet tail' here at k-wave. However, I'm having difficulties, mainly to define the best sign of excitement. I've tried using phase-delayed transducers, but diffraction effects still show up in the B-images. Would anyone have any suggestions to guide me. Thanks in advance for the support.

   Observation: If anyone wants to better understand how such a comet tail occurs, please follow this link: https://www.researchgate.net/publication/273877750_The_Comet-tail_Artifact

   Posted 10 months ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,640

   Modelling tissue/air boundaries is generally tricky for models like k-Wave because of the large density mismatch. One trick is to artificially increase the density of air to ~100 (the transmission coefficient will still be small). What exactly are you struggling with? Is it you think k-Wave doesn’t capture the physics accurately, or that it doesn’t capture the image reconstruction artefact? If the latter, you could try simulating the RF data using k-Wave, but reconstructing the image using another tool, eg, https://www.ustb.no/.

   Posted 10 months ago #

3. tiagodourado
   

   Member
   Joined: Oct '17
   Posts: 9

   Really this physics question is where I'm having trouble reproducing the comet tail effect. Initially, I used point sources, as well as following a recommendation that you also mention in another post, where I placed several diffracting elements to represent impedance contrasts in the pleura. But the signals were not shown with the typical comet tail response, but with diffraction points (hyperbolas). In the sequence, I realized the possibility of using sources with a phase delay, but even so, the signal still appears with such hyperboles. Any suggestions on where I could fix it?

   Posted 10 months ago #

4. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,640

   If you're trying to mimic the image artefacts you see on a b-mode image, I guess you will need to simulate a linear array transducer (there are some examples in the documentation), as well as the image formation process. Many image features, including speckle, are strongly dependent on the transducer characteristics, processing, and image formation process. Similarly, the comet tails are a result of processing the waves reflected back to the transducer surface. I'm not sure what the corresponding transmitted field looks like.

   Posted 10 months ago #

5. tiagodourado
   

   Member
   Joined: Oct '17
   Posts: 9

   Many thanks for the good discussions and suggestions, Bradley. I'm really trying to walk through these linear array examples, but still without success. Regarding the processing stages, I know that in oil exploration geophysics a seismic migration stage is very common, which basically aims to collapse the diffractions, converging the energy to the top of the diffraction hyperbole. You or someone with knowledge of medical transducers and processing systems would be able to tell if this type of processing is involved. Thanks in advance for the help.

   Posted 10 months ago #

6. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,640

   Yes, a reverse-migration-like step is needed, usually via some kind of beamforming. There is a simple example in k-Wave, and some more sophisticated algorithms in the toolbox linked above (and also many others on GitHub).

   Posted 10 months ago #

7. tiagodourado
   

   Member
   Joined: Oct '17
   Posts: 9

   Thanks again for your contribution and always in a very constructive way to the development of activities using k-Wave. I'm very grateful for that. Congratulations to the entire team for the work they do for science.

   Posted 10 months ago #

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