Hi,
Was wondering if anyone could shed some light on this issue.
I have written code that simulates a couple wire targets and an anechoic spherical lesion in a medium with heterogeneous background scatterers.
The code is based on the "Simulating B-mode Ultrasound Images Example" from the k-wave.org website. Just like in the example code the active "window" for each scan-line is a subset of the complete phantom map (of speed-of-sound and density).
For some reason, there is a sharp discontinuity in the harmonic image starting exactly at the scan-line whose window contains the wire targets. Essentially, all the harmonic scan lines after this point have nearly double the amplitude than those before. Also, the data for the scan line when the wire target lies exactly at the edge of the window is completely incorrect (the original scan line before any processing is null).
I tried increasing the thickness of the PML layers...didn't seem to fix the issue.
The link below should have the fundamental image, the harmonic image and then a plot of a harmonic scan-line that is "before the discontinuity" and "after the discontinuity" after log-compression.
https://drive.google.com/file/d/1xNd_6g3EnVcORE3dtinUDMWSeLUspNp0/view?usp=sharing
I'm wondering if this is just an unavoidable result of changing the window for each scan line or if it some simulation error.
Thanks for any ideas.