High-Resolution Magnetic Resonance Imaging Using Compressed Sensing for Intracranial and Extracranial Arteries: Comparison with Conventional Parallel Imaging

OBJECTIVE: To compare conventional sensitivity encoding (SENSE) to compressed sensing plus SENSE (CS) for high-resolution magnetic resonance imaging (HR-MRI) of intracranial and extracranial arteries. MATERIALS AND METHODS: HR-MRI was performed in 14 healthy volunteers. Three-dimensional T1-weighted imaging (T1WI) and proton density-weighted imaging (PD) were acquired using CS or SENSE under the same total acceleration factors (AF(t))-5.5, 6.8, and 9.7 for T1WI and 3.2, 4.0, and 5.8 for PD-to achieve reduced scanning times in comparison with the original imaging sequence (SENSE T1WI, AF(t) 3.5; SENSE PD, AF(t) 2.0) using the 3-tesla system. Two neuroradiologists measured signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), and used visual scoring systems to assess image quality. Acceptable imaging was defined as a visual score ≥ 2. Repeated measures analysis of variance and Cochran's Q test were performed. RESULTS: CS yielded better image quality and vessel delineation than SENSE in T1WI with AF(t) of 5.5, 6.8, and 9.7, and in PD with AF(t) of 5.8 (p 0.05). SNR and CNR in CS were higher than they were in SENSE, but lower than they were in the original images (p < 0.05). CS yielded higher proportions of acceptable imaging than SENSE (CS T1WI with AF(t) of 6.8 and PD with AF(t) of 5.8; p < 0.0167). CONCLUSION: CS is superior to SENSE, and may be a reliable acceleration method for vessel HR-MRI using AF(t) of 5.5 for T1WI, and 3.2 and 4.0 for PD.

CENTRAL NERVOUS SYSTEM COMPLICATIONS OF CORONARY ARTERY BYPASS GRAFT SURGERY

BACKGROUND: Coronary artery bypass graft (CABG) surgery is performed more frequently than before in Korea. Central nervous system (CNS) complications are often the major prognostic determinants following the surgery. We carried out a prospective study to clarify the incidence and risk factors of neurologic complications after CABG surgery. METHODS: A consecutive series of 150 patients undergoing 152 CABG operations from March 1995 to July 1997 by one cardiac surgeon was evaluated by a team of neurologists before and after the surgery. The patients received extensive preoperative examinations including the evaluation of intracranial & extracranial cerebral artery disease. RESULTS: In 44 operations (28.9%), we detected various neurologic complications, including encephalopathy (36 operations, 23.7%), cerebral infarction (5 operations, 3.3%), and seizure (7 operations, 4.6%). Eight patients died postoperatively including one due to neurologic complication. On univariate analysis, age, degree of intracranial artery disease (ICAD), duration of bypass time, hypotension index, duration of ventricular assistant device (VAD), intraoperative event, intra- or postoperative arrhythmia, reoperation, and postoperative bleeding were statistically significant risk factors of CNS complications (p< 0.05). After multivariate analysis, however, age alone remained significant (p=0.02). The degree of ICAD showed marginal significance (p=0.06). CONCLUSIONS: The incidence of CNS complication in the patients undergoing CABG surgery was 28.9%. Our results showed that age was an independent risk factor of CNS complications. And the possibility of ICAD as a risk factor was suggested. Further study with a large number of patients would be necessary to prove the above suggestion.