Gil-Sun Hong MD, Presenter: Nothing to Disclose

Choong Wook Lee MD, Abstract Co-Author: Nothing to Disclose

Mi-Hyun Kim, Abstract Co-Author: Nothing to Disclose

Cherry Kim MD, Abstract Co-Author: Nothing to Disclose

To assess the pattern of artifacts with high signal intensity in the brain stem on Diffusion Weighted Image (DWI) and determine if the artifacts in the brain stem could be corrected by DWI using two different phase encoding direction.

This retrospective study included 726 patients who visited emergency department (ED) with minor neurologic symptoms  and performed DWI to exclude central brain lesions. DWI protocol in ED included MRI scan with posteroanterior phase encoding direction (PA-PED) for whole brain and reversed phase encoding direction (anteroposterior direction, AP-PED) for brain stem. We defined the brain stem lesion showing high signal intensity on DWI as “artifact” if the corresponding lesion on follow up MRI disappeared or the patient’s symptom was improved on clinical follow up. Finally, we included 106 patients with 126 lesions in this study. Two emergency radiologists assessed the pattern of location, size and shape of artifacts in brain stem on DWI with PA-PED compared with those with AP-PED by consensus. Locations of artifacts were classified according to anatomy of brain stem and vascular territory: 7 levels of brain stem and 4 vascular territories (anteromedial, anterolateral, lateral and posterior group). Shapes of artifacts were classified into linear, dot and V-shape. It was assessed whether the artifacts in brain stem could be corrected by changing the phase encoding direction.

The artifacts in the brain stem on DWI with PA-PED significantly presented in the posterolateral territory and level 3-5, compared with those with AP-PED which significantly presented in the anterior portion and level 6 and 7 (P<.001). The shapes of artifact between two groups were significantly different: linear or dot shape (PA-PED) vs. V shape (AP-PED) (P<.001). All artifacts with high signal intensity in the brain stem on DWI with PA-PED or AP-PED were completely corrected on DWI with reversed phase encoding direction (n= 126/126, 100%).

The artifacts in the brain stem on DWI manifest different location pattern and shape. All artifacts with high signal intensity in the brain stem can be corrected by DWI with reversed phase encoding direction. 

DWI with reversed phase encoding direction is recommended in the intitial evaluation of suspected artifact mimicking infarction based on the knowledge of  the characteristic pattern of artifacts in the brain stem on DWI.

Hong, G, Lee, C, Kim, M, Kim, C, Pattern Analysis and Correction of Artifacts in the Brain Stem with DWI Using Two Different Phase Encoding Direction.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012883.html