Phase contrast and time-of-flight magnetic resonance angiography of the intracerebral arteries at 1.5, 3 and 7 T.

PURPOSE: Time-of-flight (ToF) and phase contrast (PC) magnetic resonance angiographies (MRAs) are noninvasive applications to depict the cerebral arteries. Both approaches can image the cerebral vasculature without the administration of intravenous contrast. Therefore, it is used in routine clinical evaluation of cerebrovascular diseases, e.g., aneurysm and arteriovenous malformations. However, subtle microvascular disease usually cannot be resolved with standard, clinical-field-strength MRA. The purpose of this study was to compare the ability of ToF and PC MRA to visualize the cerebral arteries at increasing field strengths. MATERIALS AND METHODS: The Institutional Review Board-approved study included eight healthy volunteers (age: 36 ± 10 years; three female, five male). All subjects provided written informed consent. ToF and PC MRAs were obtained at 1.5, 3 and 7T. Signal intensities of the large, primary vessels of the Circle of Willis were measured, and signal-to-noise ratios were calculated. Visualization of smaller first- and second-order branch arteries of the Circle of Willis was also evaluated. RESULTS: The results show that both ToF and PC MRAs allow the depiction of the large primary vessels of the Circle of Willis at all field strengths. Ultrahigh field (7T) provides only small increases in the signal-to-noise ratio in these primary vessels due to the smaller voxel size acquired. However, ultrahigh-field MRA provides better visualization of the first- and second-order branch arteries with both ToF and PC approaches. Therefore, ultrahigh-field MRA may become an important tool in future neuroradiology research and clinical care.

Combined treatment of subacute and acute synthetic and venous bypass-graft occlusions with percutaneous mechanical thrombectomy and thrombolysis.

INTRODUCTION: Percutaneous mechanical thrombectomy (PMT) is a third choice of treatment for acute arterial occlusions, in addition to thrombolysis and surgical thrombectomy. The aim of this retrospective study was to compare the combined treatment of PMT and local thrombolysis with thrombolysis therapy alone. MATERIALS AND METHODS: Sixty-nine patients with acute (<14 days [n = 35]) or subacute (14-42 days [n = 34]) femoropopliteal bypass occlusions were treated with PMT combined with thrombolysis. Seventy-two patients with acute [n=40] or subacute [n = 32] femoropopliteal bypass occlusions were treated with thrombolysis alone. The thrombolysis in myocardial infarction (TIMI) classification was used to assess the bypass occlusion. Local thrombolysis time and dosage, reopening time, time in the intensive care unit, necessary surgical re-interventions, and clinical outcome were compared between the 2 groups. RESULTS: The TIMI scores were significantly higher in the PMT plus thrombolysis group than in the thrombolysis group (acute occlusions 1188 versus 935, p<0.001; subacute occlusions 935 versus 605, p<0.001). The total urokinase dosage, the total hours of thrombolysis, time in the intensive care unit, and total hospital stay in the acute PMT plus thrombolysis group were significantly lesser than those in the thrombolysis group. After 24h of treatment, the ankle-brachial index improved in all groups (p<0.001): in the acute and subacute PMT plus thrombolysis group to 0.63 ± 0.14 and 0.43 ± 0.08, respectively; and in the acute and subacute thrombolysis group to 0.51 ± 0.11 and 0.41 ± 0.04, respectively. CONCLUSIONS: PMT combined with thrombolysis is a safe and very effective therapy for acute and subacute femoropopliteal bypass occlusions compared to treatment with thrombolysis alone.