Re: [Freesurfer] Convert Scanner RAS to Vertex RAS

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Thanks, YuJing Tim

On Monday, December 18, 2023 at 07:38:14 AM CST, Huang, Yujing yhuang43@mgh.harvard.edu wrote:

<!--#yiv8856416734 filtered {}#yiv8856416734 filtered {}#yiv8856416734 filtered {}#yiv8856416734 filtered {}#yiv8856416734 filtered {}#yiv8856416734 p.yiv8856416734MsoNormal, #yiv8856416734 li.yiv8856416734MsoNormal, #yiv8856416734 div.yiv8856416734MsoNormal {margin:0in;font-size:11.0pt;font-family:"Calibri", sans-serif;}#yiv8856416734 span.yiv8856416734EmailStyle19 {font-family:"Calibri", sans-serif;color:windowtext;}#yiv8856416734 .yiv8856416734MsoChpDefault {font-size:10.0pt;}#yiv8856416734 filtered {}#yiv8856416734 div.yiv8856416734WordSection1 {}--> The conversions between  tkrRas and scannerRAS are as following in Freesurfer:

tkrRAS = tkrvox2ras * inv(vox2ras) * scannerRAS

scannerRAS = vox2ras * inv(tkrvox2ras) * tkrRAS

Best,

Yujing

From: freesurfer-bounces@nmr.mgh.harvard.edu freesurfer-bounces@nmr.mgh.harvard.eduOn Behalf Of Eric Tsang Sent: Thursday, December 14, 2023 5:51 PM To: freesurfer@nmr.mgh.harvard.edu Subject: [Freesurfer] Convert Scanner RAS to Vertex RAS

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Dear All,

I have great deal of trouble converting scanner RAS to vertex RAS. I have tried a couple of formula (in the following) which had failed to produce accurate coordinate.

[tkR tkA tkrS] = [ScannerRAS 1] / (vox2ras * inv(tkrvox2ras))

[tkR tkA tkrS] = [ScannerRAS 1] * inv(vox2ras0)

Both of these formula produced distorted coordinates. Please help!

Thanks,

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