Question about raw data recording

[schaeferjakob]

I have a question about your RF data interface. When I record raw data there, I get a package with several files for a recording. This contains one file with the extension env.tgc, which encodes the time gain compensation in the envelope files. There is no such file for the RF recordings; there are only two entries for a TGC in the rf.yml file. Is there no more precise TGC in the RF data or is it simply not specified so precisely?
I hope my question was formulated understandably, if not, please ask me.

Many thanks and best regards

[clariusk]

The RF data timestamps will correlate to the envelope image timestamps, therefore you can use the envelope TGC to correlate to the RF signal - note the TGC is identical for both data sets to keep consistency.

[schaeferjakob]

Ah ok thank you very much. It's just a bit confusing that you also specify a "timestamp_rf.tgc" file in the read-me. But thanks anyway.

[clariusk]

yes, looks like we don't generate the RF TGC file anymore, also note that the TGC file will only be generated when Auto Gain is ON, when it is OFF, then the TGC is fixed and will be embedded in the main YAML file.

[schaeferjakob]

Hi, I have another question about the TGC. In the YAML-file there are 2 Values for the tgc: one amplification value at 0mm and one at the end of the image (ca. at the imaging depth). But in the tgc-files are just the values between those 2 values given. Does this mean that you have to add the tgc-values from the YAML-file onto the values of the tgc-file or how is one supposed to use those values?
And secondly: For recordings without Auto-Gain, there are just the two tgc-values given in the YAML-file (at the beginning and at the end). How are those signals amplificated then?
Thank you and best regards
Jakob Schäfer

[clariusk]

1. No, they are not additive, the one in the YAML file is the base TGC used when auto gain is off.
2. The base TGC is used in the case of auto gain being off - when you are using the 3 sliders to alter the gain manually in this mode, this is a digital gain (DTGC) applied only to the grayscale image, as the RF data has a fixed DTGC, but will always use the same analog TGC as grayscale.

[schaeferjakob]

Ah ok thank you very much for your help. But what I still don't understand: What do the two tgc values in the YAML file mean? So on which length is the amplification how big in the following example?

[clariusk]

for your example, starting at the skinline, amplification is 15dB, and linearly interpolated until it reaches 35dB at 7cm, note if the imaging depth is greater than the last TGC value, then it stays constant at the last value set.

[schaeferjakob]

Ok. And is the amplification also linearly interpolated in the recordings with auto gain ON or is it stepwise in this case?

[clariusk]

yes, same thing, the points are linearly interpolated, but typically with more points

[schaeferjakob]

Ok. Thank you very much for your help and fast response :)

[schaeferjakob]

Hi, I have another question on this topic: With the following amplification values:

In the first step from 0 mm to 7.5 mm. Do we have a constant amplification of 19.78 dB or do we have a linear increase from 0 dB to 19.78 dB?

Thank you very much and best regards!

[clariusk]

yes, exactly, 0->7.5 would use 19.78dB