Question from the MR Physics peanut gallery: How are you defining/measuring SNR for the anatomical sequences?

(Sticking to Siemens.) The way I think about this, if what you have are the dicoms from an mprage which was collected with a receiver array, acceleration and pre-scan normalization, then estimating anything about the electrical noise is impossible because (…. insert inappropriate vendor trashing here ….). Basically, the vendors have not designed their recon chains to produce images in SNR units. Or even images with a body coil intensity reference (i.e. pre-scan normalize) with a proper accounting of the noise so that you could make an image of the noise variance at each pixel to then feed into a smart segmentation.

Thoughts?

-Souheil

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Souheil Inati, PhD Staff Scientist FMRI Facility NIMH/NIH/DHHS souheil.inati@nih.govmailto:souheil.inati@nih.gov

On May 13, 2013, at 9:13 AM, Jordi Delgado <jordidem@pic.esmailto:jordidem@pic.es> wrote:

Hi Bruce,

Thank you for your fast answer. I'm focusing on SNR, Motion Correction and Intensity Inhomogeneities.

Regards,

2013/5/13 Bruce Fischl <fischl@nmr.mgh.harvard.edumailto:fischl@nmr.mgh.harvard.edu> Hi Jordi

this is definitely vendor specific. In Siemens you can for example turn on "prescan normalization" which will correct for intensity bias. You can have it generate two series - one with and one withour the correction. What other artifacts do you mean? There are lots of possibilities....

cheers Bruce

On Mon, 13 May 2013, Jordi Delgado wrote:

Dear FS experts,

I'm studying the most common artifacts on MRI scanning. I started with the SNR calculation (which is included in recent FS versions), but I'm afraid that these artifact is filtered/processed with the scanner control program, and I'm wasting time trying to calculate this ratio.

My qüestion is, any one of you know if the scanners control programs are correcting SNR, Inhomogeneties, motion, etc? Have any sense to detect these artifacts, as a quality assurance method before to accept/decline the adquired image with an external method of the scanner control program?

Thank you in advance,

-- Jordi Delgado Mengual PIC (Port d'Informació Científica) Campus UAB, Edifici D E-08193 Bellaterra, Barcelona Tel: +34 93 586 82 32tel:%2B34%2093%20586%2082%2032 Fax: +34 93 581 41 10tel:%2B34%2093%20581%2041%2010 http://www.pic.eshttp://www.pic.es/ Avis - Aviso - Legal Notice: http://www.ifae.es/legal.html

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-- Jordi Delgado Mengual PIC (Port d'Informació Científica) Campus UAB, Edifici D E-08193 Bellaterra, Barcelona Tel: +34 93 586 82 32 Fax: +34 93 581 41 10 http://www.pic.eshttp://www.pic.es/ Avis - Aviso - Legal Notice: http://www.ifae.es/legal.html _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edumailto:Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer

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