Double-shot magnetic resonance imaging of cerebral lesions: fast spin-echo versus echo planar sequences

The authors compared two new rapid MRI techniques: double-shot echo-planar imaging (DS-EPI) versus double-shot fast spin-echo (DS-FSE) in the evaluation of cerebral lesions. The authors examined 35 patients with 37 lesions, which were hyperintense on long TR images. Patients were scanned with both DS-EPI and DS-FSE with a time of repetition (TR) of 10,000 milliseconds and an echo time (TE) of 80 milliseconds. Conspicuity was determined from region of interest measurements to calculate contrast to noise ratio (C/N). Visual comparisons between DS-EPI and DS-FSE, and between DS-EPI and T2-weighted conventional spin-echo (CSE) were also performed to evaluate the sequences' ability to depict hemorrhage. The mean C/N for both sequences was comparable: 36.7 for DS-FSE and 35.6 for DS-EPI, with no statistically significant difference (p = 0.77). With regards to depicting blood products, DS-EPI proved far more effective than DS-FSE and comparable to CSE. Also, DS-EPI proved to be more time-efficient, requiring 1.67 seconds per section, while DS-FSE required 3.33 seconds per section. Whereas DS-FSE and DS-EPI are comparable in their ability to depict hyperintense cerebral pathology, DS-EPI is more time-efficient, and therefore appears preferable. Because of the high magnetic susceptibility of DS-EPI, geometric distortion degrades visualization of lesions in the posterior fossa or near the sinuses. On the other hand, the high magnetic susceptibility results in high conspicuity of blood products.