Implementation Of Fast Echo-planar Imaging (EPImix) MRI Sequence For Scan Time Reduction In Critical And Unco-operative Patients
To detail how a fast multi-contrast Echo planar Image mix (EPIMix) MRI sequence can lead to a successful reduction in scan time in critical and uncooperative patients compared to the routine clinical brain imaging without compromising the adequate image quality and diagnosis.
A prospective pilot study was conducted on 29 patients requiring emergent brain imaging for concerns of stroke(3), tremors(2), slurring of speech(3), headache(6), memory loss(4), imbalance(2), limb weakness(6), aphasia(1), dementia(1) and Parkinson's disease(1) using EPIMix brain imaging sequence on the Discovery 750w 3T, GE Healthcare MR system. EPIMix brain MRI consisting of six contrasts (T2*, T1/T2-FLAIR, T2, DWI, ADC) was acquired in 72-75 seconds. Routine T1w/T2w axial, coronal FLAIR and T2w sagittal images were also concurrently acquired and were correlated with EPIMix images for all the patients. Qualitative analysis of the EPIMix scans was performed by two experienced radiologists for assessment of diagnostic accuracy, artifacts, and image quality.
The image quality was diagnostic in all of these cases (100%) and the diagnostic performance was comparable between EPIMix and routine clinical MRI without much significant difference, indicating the preservation of adequate image quality on fast EPIMix scans (see Fig.1).
Fig 1. (i) 74-year-old male presented with a history of slurred speech. There is a chronic infarct with gliosis in the right parietal region. The internal content shows hyperintensity on T2WI (A) and T2-FLAIR (B), and hypointensity on T1-FLAIR (D)(arrows); no diffusion restriction on DWI (F) is seen (arrows). (ii) 71-year old male presented with a history of upper limb tremors. Hyperintensity in the right frontal periventricular white matter is seen on T2WI (G) and T2-FLAIR (H) and hypointensity on T1-FLAIR (J)(arrows) with reduced size of the frontal horn, possibly due to ependymitis granularis; no diffusion restriction on DWI is seen to suggest acute ischaemia (L) (arrows). (iii) 82-year-old male presented with a clinical profile of stroke. Cortical & subcortical gliosis is seen in the left middle frontal gyrus. The internal content shows hyperintensity on T2WI (M) and T2-FLAIR (N), and hypointensity on T1-FLAIR (P)(arrows); no diffusion restriction on DWI (R) is seen(arrows).
The pilot study reveals that the EPIMix sequence with rapid scanning can minimize motion artifacts and can be used in unstable patients to evaluate a wide range of brain pathologies without compromising diagnostic image quality.
EPIMix produces six weighted MRI contrasts in a short time, albeit some image artifacts such as geometric distortion at the skull base and susceptibility artifacts, which were noticed in almost all EPIMix scans. Image degradation with the above-mentioned artifacts is the result of an inherent trade-off between scan time reduction and image quality.