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clariusdev / raw

Programs to Read and Process Raw Data from Clarius Devices
https://www.clarius.com
BSD 3-Clause "New" or "Revised" License
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Depth and Width Calculations #15

Open vanessahoang13 opened 1 year ago

vanessahoang13 commented 1 year ago

Hello,

I am currently scanning images using the C3 HD3 scanner in B-mode and had a few questions.

  1. What is the width of the image that the scanner captures?
  2. When setting the imaging depth, what calculations are used to determine that depth? I know that the sampling frequency is stated in the .yml file, however the calculation of depth = speed of sound x number of samples / sampling frequency does not equal the exact imaging depth in the .yml file (a few cm off). I am wondering if the sampling frequency applied varies with depth.

Thanks!

clariusk commented 1 year ago
  1. For the width, are you referring to field of view, scanlines, pixels, etc?
  2. Can you document the exact discrepancy seen?
vanessahoang13 commented 1 year ago
  1. Yes, I am wondering about the field of view. Is there a width of the image (eg. cm) that the transducer scans?
  2. I apologize, I believe I have calculated depth incorrectly. However, I am still curious as to how the data (like sampling frequency) is used to calculate imaging depth.
clariusk commented 1 year ago

The radius is 40 degrees across a surface of 57.6mm, so you should be able to calculate FOV from that Yes the formula you presented is correct, don't forget to include return time

vanessahoang13 commented 1 year ago

Hi Kris,

Thank you! I just wanted to clarify my calculations to make sure I am interpreting the data correctly.

  1. Did you mean radius in terms of mm? My C3 HD3 scanner has a radius of 45 mm listed, so using that value and the provided surface length: FOV = (Arc length 360) / (2 pi * r) = 73 degrees.

From that, I am wondering if using this equation for image width is correct: Image Width = 2 Image Depth (tan(FOV/2))

For example, assuming my image depth is set to 15cm and the previously calculated FOV, is the resulting image width = 22.2 cm?

  1. My calculations of image depth matches the set image depth for the B-mode data, however I am still unsure how to calculate image depth based on the raw rf data.
image

If depth = (speed of sound / 2) * (number of samples / sampling frequency) In the above screenshot of my _rf.yml file, the number of samples = 1632 and sampling frequency = 15 MHz. Using this information and the above equation, the depth = 8.37cm which does not match the set image depth of 15cm.

I noticed this line in the README file under the Data Type Formats section for RF data: At depths < 2cm, 60MHz sampling is applied; at 2 - 4cm, 30MHz sampling is applied; at depths > 4cm, 15 MHz sampling is applied.

If the sampling frequencies applied are different at varying depths, what is the formula used to calculate this depth?