k-Wave

1. theo7
   

   Member
   Joined: Apr '11
   Posts: 1

   I am working on a photoacoustic imaging project with two colleagues at the University of British Columbia. K-wave has been an invaluable tool.

   The phantoms which we're using for imaging are composed of overlapping hairs. Reconstructing the hairs which are parallel to the ultrasound transducer is not a problem, however, hairs which are perpendicular or nearly perpendicular do not show up at all. In simulated data, ie. arbitrary shapes forward projected to create sample data, the problem remains the same, with long shapes perpendicular to the sensor not showing up in the image reconstruction.

   We've come to the conclusion that it's necessary to rotate the transducer and take multiple measurements. But we were also wondering if anyone else had encountered this problem and had any suggestions with regards to the algorithm which might improve the appearance of vertical lines. Thanks!

   Posted 13 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi,

   Thanks for your post. This is a commonly encountered problem in PAT and is normally referred to as the limited view or limited angle problem. In your case, for a long shape perpendicular to the sensor, most of the acoustic energy will travel outwards and not be detected by the sensor. You can conceptualise this diagrammatically by drawing rays perpendicular to the object surface and seeing whether they intersect your sensor surface.

   Try searching for these papers for some more detailed information:

   # Xu et al., "Reconstructions in limited-view thermoacoustic tomography," Med. Phys. (2004).
   # Paltauf et al., "Weight factors for limited angle photoacoustic tomography," Phys. Med. Biol. (2009).

   Thanks,

   Brad.

   Posted 13 years ago #

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