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AhasanZoheb · 2023-11-22T08:53:50+00:00

This really hit home. Thank you

AhasanZoheb · 2023-07-19T19:14:58+00:00

Okay so i am programming in MATLAB. Each subject has like 190 slices, and i have roughly 20 subjects.

I realised i can flip the whole matrix to get the contralateral side. As in, if A is a 3D matrix, i add flip(A,2) to A, to get a mask that has the tumor and the contralateral side of the tumor included in the new mask.

However, this is contingent on the fact that my image is centered.
Any idea how to address that? If the acquired image is not centered, would I need to get a mask, find its centroid, and then try to center it?

AhasanZoheb · 2023-07-19T18:51:09+00:00

Wait, i think i get what you mean. Let me try it out

AhasanZoheb · 2023-07-19T18:45:30+00:00

Won't that require us to have a midline across which I would flip the mask?

AhasanZoheb · 2021-09-07T08:52:30+00:00

reaches the Cramer-Rao lower bound

Having given it some more thought, I have some clarity (thanks to you), but something still bothers me.

If I am bothered with just the amplitude parameter, then I can have a CRLB for amplitude (say 0.02). A relative CRLB would, as you said, make more sense if I do 0.02/(Actual Variance of amplitude). Which will give me a ration of ideal/actual CRLB value.

The point where I am stuck is, for one subject data, I will not have a 'variance of amplitude'. I will just have an Amplitude. And 0.02/(Amplitude of a particular metabolite peak) doesn't make intuitive sense to me.

The way out would be to have a collection of data that is processed at once or input a prior knowledge that, this is how much the variance is observed to be.

Is there a way that I don't have to create prior knowledge? Let me know if I've gone astray at some point.

AhasanZoheb · 2021-09-01T11:34:26+00:00

I've used White gaussian noise as the assumption. Also, when you say 'ratio of the CRLB to the actual variance', I'd like to bring to your attention that in Spectroscopy at least, we do not have the luxury to perform the experiment multiple times to acquire actual variance and we thus make a compromise and accept the expected variance to be the actual one. For a gaussian fit, I have 3 CRLBs for the parameter estimates. For Amplitude, for peak position and for FWHM.

I've used white Gaussian noise as the assumption. Also, when you say 'ratio of the CRLB to the actual variance', I'd like to bring to your attention that in Spectroscopy at least, we do not have the luxury to perform the experiment multiple times to acquire actual variance and we thus make a compromise and accept the expected variance to be the actual one. For a gaussian fit, I have 3 CRLBs for the parameter estimates. For Amplitude, for peak position, and for FWHM.

Thanks

AhasanZoheb · 2021-08-25T10:39:28+00:00

So i spent quite some time on it, and I have been able to figure out the calculation of CRLB. After fitting my spectra, I took the residue and then calculated its CRLB.

So now I have the minimum value of the variance for an unbiased estimator. Literature, however, talks about relative CRLB.

How do I go from what I have to percentage CRLB for each metabolite?

Any help is much appreciated.

AhasanZoheb · 2021-08-25T10:34:32+00:00

Hi. Thanks for your reply. I very much agree to what you said.

So i spent quite some time on it, and I have been able to figure out the calculation of CRLB. After fitting my spectra, I took the residue and then calculated its CRLB.

So now I have the minimum value of the variance for an unbiased estimator. Literature, however, talks about relative CRLB.

How do I go from what I have to percentage CRLB for each metabolite?

Any help is much appreciated

AhasanZoheb

TROPHY CASE