biac:analysis:topup_correction
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biac:analysis:topup_correction [2019/02/22 14:03] – cmp12 | biac:analysis:topup_correction [2019/09/04 15:49] – cmp12 | ||
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There will be two series of single timepoint EPI images. | There will be two series of single timepoint EPI images. | ||
- | You need to calculate readout time in seconds ( the physical time it takes to get the acquisition matrix of a single slice ) and get the polarity direction ( phase encode direction ). | + | You need to calculate readout time in seconds |
the readout time in seconds for the parameter file will be: | the readout time in seconds for the parameter file will be: | ||
Line 14: | Line 14: | ||
echospacing in the BXH header is in microseconds | echospacing in the BXH header is in microseconds | ||
</ | </ | ||
+ | |||
+ | unfortunately at this point the polarity of the images will have to be determined from visual inspection. we aren't provided enough information in the metadata to give an entry into the BXH file ( yet ). | ||
+ | |||
+ | Here is a rough guide to help with inspection: | ||
+ | {{ : | ||
- | the polarity for the entry will have to be determined from the **seriesdescription**, | ||
reverse will be " | reverse will be " | ||
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there are 2 scenarios that typically apply here | there are 2 scenarios that typically apply here | ||
- | 1) a short acquisition with RPE B0s | + | 1) DWI and a short acquisition with RPE B0s |
- | 2) an entire | + | 2) 2 entire |
In both scenarios it is important to create your data with normal phase encoding direction first, followed by reversed. | In both scenarios it is important to create your data with normal phase encoding direction first, followed by reversed. | ||
Line 200: | Line 204: | ||
==== Prepare your input datasets ==== | ==== Prepare your input datasets ==== | ||
+ | |||
+ | Specify that a set of images (typically b=0 volumes) will be provided for use in inhomogeneity field estimation only | ||
For scenario 1, create your blip up / blip down B0 data the same way as above. | For scenario 1, create your blip up / blip down B0 data the same way as above. | ||
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< | < | ||
#concat the 2 series ( regular, reversed ) | #concat the 2 series ( regular, reversed ) | ||
- | bxh_concat | + | bxh_concat |
+ | 7_LAS.bxh bia6_00260_008_LAS.bxh both | ||
#extract the gradients | #extract the gradients | ||
- | extractdiffdirs --fsl both bvecs bvals | + | extractdiffdirs --fsl both.bxh bvecs bvals |
#convert to mif | #convert to mif | ||
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dwipreproc dwi.mif dwi_corr.mif -rpe_all -pe_dir AP -readout_time 0.10656 -debug | dwipreproc dwi.mif dwi_corr.mif -rpe_all -pe_dir AP -readout_time 0.10656 -debug | ||
- | -rpe_all signals that you've replicated | + | -rpe_all signals that you've replicated |
+ | A | ||
+ | LL the directions with a rpe acquisition | ||
-pe_dir is the phase encode direction of your regular acquisition | -pe_dir is the phase encode direction of your regular acquisition | ||
-readout_time from above | -readout_time from above | ||
</ | </ | ||
+ | |||
+ | {{ : | ||
biac/analysis/topup_correction.txt · Last modified: 2024/06/21 15:44 by 127.0.0.1