Eric C. Bourekas

High resolution MRI of the deep brain vascular anatomy at 8 Tesla: susceptibility-based enhancement of the venous structures.

PURPOSE The purpose of this work was to describe the deep vascular anatomy of the human brain using high resolution MR gradient echo imaging at 8 T. METHOD Gradient echo images were acquired from the human head using a transverse electromagnetic resonator operating in quadrature and tuned to 340 MHz. Typical acquisition parameters were as follows: matrix = 1,024 x 1,024, flip angle = 45 degrees, TR = 750 ms, TE = 17 ms, FOV = 20 cm, slice thickness = 2 mm. This resulted in an in-plane resolution of approximately 200 microm. Images were analyzed, and vascular structures were identified on the basis of location and course. RESULTS High resolution ultra high field magnetic resonance imaging (UHFMRI) enabled the visualization of many small vessels deep within the brain. These vessels were typically detected as signal voids, and the majority represented veins. The prevalence of the venous vasculature was attributed largely to the magnetic susceptibility of deoxyhemoglobin. It was possible to identify venous structures expected to measure below 100 microm in size. Perforating venous drainage within the deep gray structures was identified along with their parent vessels. The course of arterial perforators was more difficult to follow and not as readily identified as their venous counterparts. CONCLUSION The application of high resolution gradient echo methods in UHFMRI provides a unique detailed view of particularly the deep venous vasculature of the human brain.

Time-of-Flight Magnetic Resonance Angiography at 7 Tesla

Objectives:Magnetic resonance angiography (MRA) is noninvasive and does not require the application of high doses of contrast agents, and thus is used in the clinical routine for evaluation of cerebrovascular diseases, eg, aneurysm and arteriovenous malformations. However, more subtle microvascular disease usually cannot be seen with the resolution capabilities of standard field strength MRA. The purpose of this study was to evaluate the ability of 7-T time-of-flight (ToF) MRA to depict the arterial brain vasculature and to compare the results to data from 1.5 T and 3 T. Materials and Methods:The study was IRB approved and complied with The Health Insurance Portability and Accountability Act. All subjects gave written informed consent. Eight healthy volunteers (age: 36 ± 10 years; 3 female, 5 male) were investigated using ToF MRA at 7 T, 3 T, and 1.5 T. Signal intensities of the large, primary vessels of the Circle of Willis were measured and signal-to-noise ratios were calculated. Visibility of smaller arteries was evaluated. Results:The results show that ultrahigh field allows depiction of the large vessels of the Circle of Willis. Although it provides only small increases in signal-to-noise ratios for these vessels, compared with 1.5 T and 3 T, it additionally demonstrates considerably more first- and second-order branches. Conclusions:Because of its considerably enhanced potential to depict vessels of the Circle of Willis and its first- and second-order branches, ToF MRA at 7 T may become an important tool in future neuroradiology research and clinical care.

High resolution MRI of the deep gray nuclei at 8 Tesla.

PURPOSE High resolution MR images obtained from a normal human volunteer at 8 T are utilized to describe the appearance of iron-containing deep gray nuclei at this field strength. METHOD High resolution (1,024 x 1,024 matrix) near-axial gradient echo images of the deep gray nuclei were acquired on a human volunteer by using an 8 T scanner. The images were acquired using a transverse electromagnetic resonator operating in quadrature. The following parameters were utilized: TR = 750 ms, TE = 17 ms, flip angle = 45 degrees, receiver bandwidth = 50 kHz, slice thickness = 2 mm, FOV = 20 cm. The 8 T images were reviewed and correlated to the known anatomy of the deep nuclei by comparing them with images observed at lower field strength, published diagrams, and histologic sections. In addition, the appearance of the nuclei was related to the known imaging characteristics of brain iron at lower fields. RESULTS The caudate, globus pallidus, putamen, thalami, substantia nigra, and red nuclei were clearly identified. The structures with the highest levels of iron, the globus pallidus, substantia nigra, and red nuclei, demonstrated significantly decreased signal, providing a map of iron distribution in the human brain. CONCLUSION Preliminary imaging at 8 T demonstrates the ability to acquire ultra high resolution images of the deep nuclei, with signal characteristics believed to represent the distribution of brain iron. This may prove to be important in the early diagnosis of several neurodegenerative disorders.

Human leptomeningeal and cortical vascular anatomy of the cerebral cortex at 8 Tesla.

PURPOSE The purpose of this work was to describe the human leptomeningeal and cortical vascular anatomy as seen at high resolution on an 8 T UHFMRI system. METHOD With a 1024 x 1024 matrix, axial gradient echo images of the cerebral cortex were acquired on a human volunteer at 8 T with TR 500 ms, TE 16 ms, flip angle 22.5 degrees, bandwidth 53 kHz, and slice thickness 2.84 mm. The same subject was evaluated at 1.5 T using similar parameters. The images were then reviewed in detail and compared with known cortical and leptomeningeal vascular anatomy. RESULTS Two hundred forty micron in-plane resolution images of the human brain were acquired at 8 T without evident artifact from susceptibility distortions, RF penetration, or dielectric resonances. The CSF, gray matter, and white matter structures were well discerned. The microscopic leptomeningeal vascular anatomy was well visualized, and the course of small perforating cortical vessels could be followed from the cortical surface to the white matter junction. CONCLUSION Initial 8 T images of the brain demonstrate detailed leptomeningeal and cortical vascular anatomy.

Intra-arterial carboplatin and intravenous etoposide for the treatment of metastatic brain tumors.

Metastatic brain tumors (MBT) are the most frequent complication of systemic cancer and often respond poorly to treatment. Median survival is only 16–24 weeks after conventional radiation therapy. Regional intra-arterial (IA) administration of chemotherapy results in increased tumor uptake of drug and may improve response rates and survival. Twenty-seven patients with MBT who had received prior irradiation were treated with IA carboplatin (200 mg/m2/d) and intravenous (IV) etoposide (100 mg/m2/d) for 2 days every 3–4 weeks. Eighteen patients (67%) had received prior systemic chemotherapy for their primary tumor. Patients ranged in age from 19 to 68 years (mean 48.1). Thirteen of 24 evaluable patients had objective responses (54.2%). There were 6 complete responses (25%), 6 partial responses (25%), 1 minor response (4.2%), 7 stable disease (32%), and 5 progressive disease (20.8%). Some patients with multifocal tumors had a mixture of responses. The median time to progression was 16.0 weeks overall and 30.0 weeks in responders (range 6–118 weeks). Overall median survival from the time of protocol initiation was 20.0 weeks. In six responders, death occurred due to systemic illness unrelated to MBT progression. Therapy was well tolerated, with predominantly hematologic toxicity. Angiographic complications were rare. Although these are preliminary results, IA carboplatin and IV etoposide is safe and well tolerated, appears to be active against brain metastases, and warrants further study.

Qureshi grading scheme for angiographic occlusions strongly correlates with the initial severity and in-hospital outcome of acute ischemic stroke.

Background. The thrombolysis in myocardial infarction (TIMI) grading scheme and other classification systems have limitations in evaluating patients with ischemic stroke because they do not account for occlusion location or collateral circulation. The Qureshi grading scheme has been recently proposed to evaluate the severity of arterial occlusion in acute ischemic stroke because of limitations in existing grading systems. Methods. The Qureshi grading scheme assigns a score from 0 to 5 on the basis of occlusion site and collateral supply. The authors determined the relationship between initial severity of stroke and outcome at discharge measured by the National Institutes of Health Stroke Scale (NIHSS) and the Qureshi grading scale assessed from initial angiography (by a neuroradiologist blinded to the clinical examination) in 57 patients who underwent intra arterial therapy for acute ischemic stroke within 6 hours of symptom onset. Results. A strong association was observed between the initial severity of neurological deficits and Qureshi scheme on angiography (F ratio = 2.6, P = .03). The initial NIHSS for grade 1 was 11 ± 4 and progressively increased to 23 ± 6 for grade 5. In the multivariate analysis, initial NIHSS was significantly associated with Qureshi scheme on angiography (R2 = 358, P = .03). The mean discharge NIHSS was 12 ± 10 (range, 0–40). There was also a direct relationship between the Qureshi scheme and discharge NIHSS (F ratio = 2.8, P = .02).Conclusion. The Qureshi grading scheme can be effectively used to determine the severity of ischemic stroke (brain at risk) from the initial angiography.

Intraarterial thrombolytic therapy within 3 hours of the onset of stroke.

OBJECTIVEThe National Institute of Neurological Disorders and Stroke (NINDS) Recombinant Tissue Plasminogen Activator Stroke Study Group showed that recombinant tissue plasminogen activator (rt-PA) administered intravenously within 3 hours of the onset of ischemic stroke can improve clinical outcome. Intraarterial (IA) thrombolysis has been shown to offer advantages over intravenous (IV) thrombolysis, but experience with this type of therapy within 3 hours of the onset of symptoms has not been reported previously. This study is the first retrospective analysis of a two-institution experience with IA thrombolysis within 3 hours of stroke onset. METHODSA total of 36 patients with angiographically demonstrated occlusions were treated with urokinase or rt-PA within 3 hours of stroke onset. Outcome measures included the percentage of patients with no or minimal neurological disability at 30 to 90 days as measured by the modified Rankin Scale, percentage recanalization, incidence of symptomatic intracranial hemorrhage, and mortality rate. The results were compared with those of the NINDS rt-PA study. RESULTSThe median admission National Institutes of Health Stroke Scale score was 14. Fifty percent of treated patients had a modified Rankin Scale score of 0 or 1 indicating no or little disability at 1 to 3 months compared with 39% of treated patients in the NINDS trial. Recanalization was 75%, symptomatic intracranial hemorrhage was 11% (versus 6.4% with IV rt-PA in the NINDS trial), and the mortality rate was 22% (versus 17% with IV rt-PA in the NINDS trial). CONCLUSIONThe results suggest that IA thrombolysis administered within 3 hours of stroke onset is a feasible and viable alternative to IV rt-PA on the basis of improved clinical outcomes, high recanalization percentage, and comparable mortality rate and despite increased symptomatic intracranial hemorrhage. Whether IA thrombolysis is superior to IV therapy awaits further study.

Qureshi Grading Scheme Predicts Subsequent Volume of Brain Infarction Following Intra-Arterial Thrombolysis in Patients with Acute Anterior Circulation Ischemic Stroke

The importance of the site of occlusion and the presence or absence of collaterals on initial angiography in patients with acute ischemic stroke has been recognized. Qureshi recently proposed a scheme that categorizes patients with ischemic stroke based on findings observed on initial angiography.

Intracranial ossifications and microangiopathy at 8 Tesla MRI

UNLABELLED Clinical evaluation and MR imaging of microangiopathy associated with hypertension is limited. We describe a case that illustrates sensitivity of MRI at 8 Tesla for imaging of microvasculature, iron, calcium deposits and silent white matter lesions (WML). A 60-year-old black hypertensive woman was evaluated for numbness in the face and extremities. MRI at 1.5 Tesla was unrevealing.MRI at 8 Tesla: Axial and sagittal Gradient Echo images were obtained with an 8T/80 cm human scanner and showed: 1) Large areas of signal voids due to ossifications and fat deposits within the falx. 2) Obstructed small vessels in the periventricular regions and distended cortical veins. 3) Numerous small WML, suggestive of mini-infarcts (<1 cm) and microhemorrhages. 4) Intracranial calcifications in the falx, tentorium, basal ganglia and chorioid plexus that were confirmed by CT scan. Atherosclerotic plaque in right carotid artery and reduced vasomotor reserve in middle cerebral arteries, documented by ultrasound, indicated large and small vessel disease. CONCLUSIONS MRI at 8 Tesla improves visualization of microangiopathy, ossifications and iron deposits due to enhanced magnetic susceptibility at ultra high magnetic field.

Intra-arterial Carboplatin and Intravenous Etoposide for the Treatment of Recurrent and Progressive Non-GBM Gliomas

Recurrent and progressive non-GBM gliomas are a diverse group of brain tumors that often respond poorly to adjuvant chemotherapy treatment. Regional intra-arterial (IA) administration of chemotherapy may result in increased tumor uptake of drug, with improvement in response rates and time to progression (TTP). Twenty-five patients with recurrent or progressive non-GBM gliomas were treated with IA carboplatin (200 mg/m2/d) and intravenous (IV) etoposide (100 mg/m2/d) for 2 days every 4 weeks. Patients ranged in age from 22 to 68 years (mean 37.8). All but one patient had received standard irradiation, and eight patients had attempted prior chemotherapy. Five of 25 patients had objective responses (20%), while another 15 patients had stable disease (60%), receiving a total of 318 IA treatment procedures. There was one complete response (4.0%), three partial responses (12.0%), one minor response (4.0%), 15 stable diseases (60.0%), and five progressive diseases (20.0%). The median TTP was 24.2 weeks overall and 32 weeks in responders. Overall median survival was 34.2 weeks. Therapy was well tolerated, with mainly hematologic toxicity. Two patients had embolic complications. Although these are preliminary results, IA carboplatin and IV etoposide have modest activity against recurrent and progressive non-GBM gliomas and warrants further study.