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--- library:mri_brain [2025/03/04 15:44] – [Scan Coverage and Planning] scott
+++ library:mri_brain [2025/05/05 16:32] (current) – [Scan Coverage and Planning] scott
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-=====Brain=====
+=====Brain MRI=====
 ====Scan Coverage and Planning====
 ===Sagittal Plane===
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 ===Typical Scan Protocol===
-The protocol below represents a full brain exam. There is variation depending on the clinical question and clinician preference. The **minimum** recommended sequences are in bold text. Note that some sequences such as the DWI have specific use cases and should be considered required if their indication is present, ie if an ischemic stroke is the clinical question, don't skip the DWI.
+The protocol below represents a full brain exam. There is variation depending on the clinical question and clinician preference. The **minimum** recommended sequences are in bold text. Note that some sequences such as the DWI have specific use cases and should be considered required if their indication is present, ie if an ischemic stroke is the clinical question, don't skip the DWI. It is highly suggested to acquire at last one post contrast series with fat saturation.
 **Sagittal T2**\\
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 Dorsal T1\\
-===Tips and Tricks===
+====Tips and Tricks====
+===DWI in the Brain===
+Diffusion weighted imaging can be difficult in small animals, especially with older scanners and sequences. There are several steps to take to get the most out of the DWI sequence available on any scanner:
+  - **Minimize the TE as much as possible**; this can be done sometimes with reducing the Phase FOV, parallel imaging, or reducing the matrix
+  - **Set the Phase direction anterior/posterior**; DWI sequences tend to warp/smear in the phase direction, so this can help keep it at least symmetrical. The DWI sequence is based on an Echo Planar technique which does not include any refocusing pulses, so the longer the sampling time and TE, the more time phase errors have to accumulate and compound. This is especially true with older systems that do not have fast gradients. A/P phase
+  -** Shim around the brain**; animals typically have much larger sinuses than humans right next to the brain.
+==GE Specifics==
+  * Where possible disable dual spin echo, this reduces TE and the dual echo isn't particularly effective
+  * Where possible, choose the DWI setting 'TETRA'
+  * ADC MAP process for older scanners: Functool-->ADC--> Threshold until only brain is green --> Next ---> Compute --> Film/Save --> Multiple locations --> Save as processed images
+==Siemens Specifics==
+  * It can be difficult to acquire diagnostic DWI on small brains with older Siemens scanners, as the smallest FOV possible can be on the order of 180-200mm.
+  * Try to use a flex coil, or flex + spine coil; this will enable the use of grappa and help with SNR
+  * Use low resolution; <128, grappa set to 2, and increase averages to 4-8.  This may also allow for a smaller FOV.
+===Sequence Substitutions===
+With Brain MRI in particular, there are quite a few sequence variations that may be encountered or substituted. These different sequences may provide the same or similar image contrast, but have different SNR, be 3D vs 2D, or have additional special properties. As with all things in MRI, there are trade-offs and pros/cons with each sequence choice that will be noted below. The different sequences will be categorized by their image contrast. Please note that some sequences will be vendor or software level specific, so may not be available on every scanner.
+==T2* Contrast==
+{{:library:merge_profile.png?600|}} {{:library:swi_profile.png?600|}}{{:library:swi_artifact.png?600|}}
+==T1 Contrast==
+{{:library:t1_fse_profile.png?600|}}  {{:library:fspgrprofile.png?600|}}}}  {{:library:3d_fse_profile.png?600|}} {{:library:t1_flair_profile.png?600|}}  {{:library:mprage_profile.png?600|}}