FUNCTIONAL MRI OF REGIONAL CEREBRAL BLOOD CHANGES DURING BREATH HOLDING

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Introduction: Diffusion- and perfusion-weighted MRI (DWI and PWI) provides unique diagnostic information not available from neurological or CT assessments. To implement these new methodologies in the clinical setting, a 20-minute DWI/PWI protocol has been used to evaluate these new MR methodologies for the diagnostic advantages and predictive value they bring to the management of clinical stroke and to longitudinally monitor the progression of ischemia to infarction. Methods: Patients presenting with new neurologic symptoms within 6 hours of onset were studied over the past 8 months. These patients were imaged at presentation following neurological and CT exams and again at 3-6 hours, 9-12 hours, 36-48 hours and finally at 30 days. Cases were excluded if the time of onset was not clearly established. Because the time of ischemic onset within the first few hours is often difficult to determine accurately, eight patients were included in this study. An in-patient GE Signa Horizon (gradient strengths 22 mT/m) was used for all studies. Results: The ASE-EPI sequence was chosen over corresponding SE-EPI and the GRE-EPI options as the best balance between susceptibility sensitivity (FR2*) and background image artifacts at a single-dose injection. All patients showed regional DW hyperintensity in anatomic locations appropriate to the clinical symptoms. ADC values were lower than normal at acute timepoints and elevated above normal beyond 10 days, in agreement with earlier studies. Depiction of the acute ischemic lesions from normal brain or pre-exiting chronic lesions was significantly improved using the IR-ADC maps over the conventional ADC maps. The DW and IR-ADC maps were superior over the conventional and FLAIR T2-wt images in depiction of hyperacute lesions and the differentiation of acute from chronic lesions. Averaged ("trace") ADC maps were superior in lesion conspicuity to the anisotropic ADC maps for all lesions. The PWI exam was superior to the DWI and T2 exams in the depiction of hyperacute events. Conclusions: DWI/PWI protocols provide rapid identification of the extent, location, and circulation of the relevant lesion(s) and the underlying hemodynamic behaviors responsible for the clinical symptoms.