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brachial_plexus [2026/04/27 16:39] – [Scan Coverage and Planning] scottbrachial_plexus [2026/06/29 16:18] (current) – scott
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 =====Positioning===== =====Positioning=====
  
-Positioning for the brachial plexus exam is especially important. To ensure the nerves and forelimbs can be well assessed, both limbs should be positioned as __symmetrical__ as possible, and pulled __rostrally__ and well secured. Proper limb positioning will ensure that the peripheral brachial plexus nerves can be imaged closest to isocenter, compared slice-to-slice, and without excessive slice coverage. +Positioning for the brachial plexus exam is especially important. To ensure the nerves and forelimbs can be well assessed, both limbs should be positioned as __symmetrical__ as possible, and pulled __rostrally__ and well secured. Proper limb positioning will ensure that the peripheral brachial plexus nerves can be imaged closest to isocenter, compared slice-to-slice, and without excessive slice coverage. Typically dorsal recumbency is preferred, and any compatible coils that can be positioned over the elbows or sternum will help with SNR.
-Typically dorsal recumbency is preferred, and any compatible coils that can be positioned over the elbows or sternum will help with SNR.+
  
-=====Anatomy=====+=====Scan Coverage and Planning=====
  
-The brachial plexus exam can be more difficult than a standard brain or spine exam, as there is more complex anatomy, different positioning requirements, and different scanning challenges.  A good sense of the anatomy is crucial to proper coverage and slice orientation.+==== A note on Localizers====
  
-The brachial plexuses are bundles of nerves that originate from about C4/5 to T2/3 and extends into the forelimbs on both sides. When there is an injury or lesion in the brachial plexus, a patient may present with muscle atrophy or forelimb lameness without an orthopedic cause. Below are MIPs of the brachial plexus nerves in 3 planes. Keep in mind that the nerves extend deeper into the forelimb than visualized on these sequences, so the required coverage will be larger.+When planning out your localizer images, be sure to use a LARGE FOV so that the forelimbs and shoulders are well demonstrated, positioning can be checked, and coil extents can be seen. Use a LOT of slices to cover all the anatomy; you want to be able to find the shoulder joints, elbows,  and sternum on all three planes.
  
-{{::nervestir_sag_mip.gif?}}  {{::nerve_stir_ax_mip.gif?}}  {{::nerve_stir_dor_mip.gif?}} 
  
-=====Scan Coverage and Planning=====+====Sagittal Plane====
  
-==== A note on Localizers==== 
  
-When planning out your localizer images, be sure to use a LARGE FOV so that the forelimbs are well demonstrated, positioning can be checked, and coil extents can be seen. Use a LOT of slices to cover all the anatomy; you want to be able to find the shoulder joints, elbows,  and sternum on all three planes. 
-====Sagittal Plane==== 
 For brachial plexus scout images, add more slices on all planes to cover sternum to spine dorsally, shoulder to shoulder sagittal, and C3 to T3 axially. On the axial and dorsal scout imaging, plan the slices parallel to the center of the spinal cord. On the sagittal scout image, center the FOV on C6/7. For brachial plexus scout images, add more slices on all planes to cover sternum to spine dorsally, shoulder to shoulder sagittal, and C3 to T3 axially. On the axial and dorsal scout imaging, plan the slices parallel to the center of the spinal cord. On the sagittal scout image, center the FOV on C6/7.
 For each patient, the FOV should be re-sized to include at least C4/5 to include the T3/4. On the dorsal scout image, add enough slices to cover out to the humeral head on both sides unless specifically doing a unilateral study. **Be sure to use an ODD number of slices. This will ensure that the center slice is in true midline through the spinal cord.** For each patient, the FOV should be re-sized to include at least C4/5 to include the T3/4. On the dorsal scout image, add enough slices to cover out to the humeral head on both sides unless specifically doing a unilateral study. **Be sure to use an ODD number of slices. This will ensure that the center slice is in true midline through the spinal cord.**
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 ====Dorsal Plane==== ====Dorsal Plane====
-The dorsal plane is particularly useful when scanning for brachial plexus pathology, as it provides a good overview of both forelimbs symmetrically. As a first screening sequence, the dorsal should cover from the sternum to just past the vertebral bodies, with the FOV large enough to demonstrate both forelimbs. The __Brachial Plexus__ nerves exit ventrocaudally  from C4/5 to T1/2 and extend into the forelimbs and dorsal to the humeral head. Incidental findings are also frequently located on the dorsal plane (Right image, red arrow)+ 
 + 
 +The dorsal plane is particularly useful when scanning for brachial plexus pathology, as it provides a good overview of both forelimbs symmetrically. As a first screening sequence, the dorsal should cover from the sternum to just past the vertebral bodies, with the FOV large enough to demonstrate both forelimbs and shoulders. The __Brachial Plexus__ nerves exit ventrocaudally  from C4/5 to T1/2 and extend into the forelimbs and dorsal to the humeral head. Some plexus pathology may lead to changes in the signal intensity of muscles (Right image, red arrow)
  
 {{::bplexusdorplan.png?500|}}{{:dorincidental.png?500|}} {{::bplexusdorplan.png?500|}}{{:dorincidental.png?500|}}
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   * Square matrix; ie 256x256 select a slightly lower resolution to save time and keep it square    * Square matrix; ie 256x256 select a slightly lower resolution to save time and keep it square 
   * Utilize higher bandwidth   * Utilize higher bandwidth
-  * If applicable to your system, try PROPELLER/BLADE+  * If applicable to your system, try PROPELLER/BLADE; pretty good for motion and also reduces flow artifact
  
 To reduce the effect of flow artifact: To reduce the effect of flow artifact:
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   * Run a dorsal early in the exam, preferably a STIR   * Run a dorsal early in the exam, preferably a STIR
-  * Check for symmetry; denervation changes are more easily spotted as fluid like intensity in muscles+  * Check for symmetry; denervation changes can lead to T2 hyperintensity or muscle atrophy
   * Good fat saturation; use Dixon techniques whenever possible. If no Dixon is available, be sure to manually shim the area of interest   * Good fat saturation; use Dixon techniques whenever possible. If no Dixon is available, be sure to manually shim the area of interest
 +  * Run high resolution NON-fat saturated sequences; the nerves are fairly dark and will be more apparent when surrounded by bright fat
 +
 +===Fat Saturation===
 +
 +Fat saturation can be tricky in the cervical/plexus area due the uneven anatomy, presence of microchips, and large FOV's required. 
 +
 +{{::poorfatsat.png?400|}}
 +
 +  * Use Dixon techniques for fat saturation (Dixon, FLEX, IDEAL)
 +  * SPAIR/SPECIAL techniques may be a bit more homogenous if available
 +  * Manually shim to the area of interest
 +  * Position and scan close the isocenter
 +  * Use the smallest appropriate FOV