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CIC-methods / FID-A

Toolbox for simulation and processing of in-vivo magnetic resonance spectroscopy (MRS) data
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Basic Question - Input Parameters #88

Open Xoul26 opened 2 years ago

Xoul26 commented 2 years ago

Hey there! I'm new to spectroscopy, trying to create an LCModel RAW file to generate a Basis Set. However, I don't know what the following inputs are: number of points in FID/spectrum linewidth

How do I calculate those values and what do they mean?

I have a PDF file with all of the parameters of the spectroscopy sequences we run in a Siemens Prisma scanner, but I can't seem to find those specific parameters

Thanks!

jamienear commented 1 year ago

Hi,

The number of points in the spectrum is simply the number of discrete samples in both the time-domain signal (FID) and the MR spectrum. How to calculate this? I guess it depends on your needs in terms of spectral width and spectral resolution. The number of points is determined by the spectral width (in Hz) divided by the spectral resolution (in Hz). So if I wanted to have a spectral width of 2000 Hz, and I wanted to have a spectral resolution of 1 Hz, then I would need 2000 points in my spectrum. It is fairly common for the number of spectral points to be a power of 2 (i.e. 512, 1024, 2048, etc.), but this is not a requirement.

The linewidth refers to the width (in Hz) of a particular peak or resonance in the frequency domain spectrum. How to calculate this? It is related to the T2 relaxation constant as follows: lw [Hz] = 1/(pi T2* [s]). But when generating a basis set, this equation is nor particularly helpful. Generally a small linewidth such as 1 or 2 Hz is appropriate for a basis set.

Hope this helps.

Jamie

On Jun 20, 2022, at 8:54 AM, Xoul26 @.**@.>> wrote:

Hey there! I'm new to spectroscopy, trying to create an LCModel RAW file to generate a Basis Set. However, I don't know what the following inputs are: number of points in FID/spectrum linewidth

How do I calculate those values and what do they mean?

Thanks!

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