Cumulative radiation dose during hospitalization for aneurysmal subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: Radiation exposure from neurointerventional procedures and diagnostic neuroimaging can be substantial, with many recommendations offered to guide the interventionalist in the conscientious use of ionizing radiation. Patients presenting with an aneurysmal subarachnoid hemorrhage can undergo multiple imaging procedures during a prolonged hospital course. Therefore, we reviewed a cohort of such patients to identify the sources and quantify the cumulative radiation exposure seen during their hospitalization. MATERIALS AND METHODS: We retrospectively reviewed a single-center experience with these patients to define the potential for short-term skin injury and long-term oncologic risk due to absorbed radiation dose and sources of ionizing radiation and their contribution to the cumulative absorbed dose to the cranial tissues. RESULTS: We demonstrated that substantial cumulative doses can be seen, with 87% of the cumulative absorbed dose occurring during neurointerventional procedures and 7% from CT. Mathematic modeling was performed identifying potential techniques to further reduce the cumulative radiation absorbed dose to these patients. CONCLUSIONS: We conclude that repetitive irradiation during the care of patients with aneurysmal subarachnoid hemorrhage can result in significant cumulative doses and a variety of techniques can be applied to reduce this absorbed dose. Use of radiation for diagnostic and therapeutic purposes during prolonged procedures of patients with subarachnoid hemorrhage demands diligence throughout the hospitalization.

Neuroform stent assisted aneurysm treatment: evolving treatment strategies, complications and results of long term follow-up.

INTRODUCTION: This report details experience with the Neuroform stent, with an emphasis on evolving treatment strategies, complication rates and treatment durability. METHODS: All patients undergoing Neuroform stent assisted aneurysm treatment were registered in prospectively maintained endovascular databases at two institutions. RESULTS: 284 patients with 302 aneurysms underwent aneurysm treatment with Neuroform during a 42-month study period. Imaging follow-up was available for 166 of 286 saccular aneurysms which were treated with stents and coils (average interval 12.9 months). 80 demonstrated progressive thrombosis (48.2%), 40 were unchanged (24.1%) and 46 (27.7%) demonstrated re-canalization, 25 (15.1%) of which were major recanalizations requiring retreatment. The vast majority of recanalizations and retreatments were observed in large or giant aneurysms. A cumulative total of 25 ischemic strokes (8.8%) and eight neurovascular deaths (2.8%) were recorded in these patients. Ten of these strokes were associated with transient deficits which went on to complete resolution by the time of discharge or at the initial clinical follow-up, yielding a significant stroke rate of 5.3%. Delayed (>48 h) complications, including four deaths-related to stroke (n=2, 6 days and 8 weeks post-procedure) and spontaneous parenchymal hemorrhages (n=2)-represent events which are a direct consequence of stenting and likely would not have been encountered in the context of standard non-stent supported embolization techniques. CONCLUSION: Neuroform facilitates the endovascular treatment of complex and wide necked cerebral aneurysms. However, complete occlusion at angiographic follow-up remains uncommon and is observed in only one-third of patients. Delayed complications (>48 h) represent an important component of the overall complications associated with Neuroform assisted aneurysm embolization.

Influence of patient age and stenosis location on wingspan in-stent restenosis.

BACKGROUND AND PURPOSE: Wingspan is a self-expanding, microcatheter-delivered microstent specifically designed for the treatment of symptomatic intracranial atherosclerotic disease. Our aim was to discuss the effect of patient age and lesion location on in-stent restenosis (ISR) rates after percutaneous transluminal angioplasty and stenting (PTAS) with the Wingspan system. MATERIALS AND METHODS: Clinical and angiographic follow-up results were recorded for all patients from 5 participating institutions. ISR was defined as >50% stenosis within or immediately adjacent (within 5 mm) to the implanted stent and >20% absolute luminal loss. For the present analysis, patients were stratified into younger (55 years) age groups. RESULTS: ISR occurred at a rate of 45.2% (14/31) in the younger group and 24.2% (15/62) in the older group (odds ratio, 2.6; 95% confidence interval, 1.03-6.5). In the younger group, ISR occurred after treatment of 13/26 (50%) anterior circulation lesions versus only 1/5 (20%) posterior circulation lesions. In the older group, ISR occurred in 9/29 (31.0%) anterior circulation lesions and 6/33 (18.2%) posterior circulation lesions. In young patients, internal carotid artery lesions (10/17 treated, 58.8%), especially those involving the supraclinoid segment (8/9, 88.9%), were very prone to ISR. When patients of all ages were considered, supraclinoid segment lesions had much higher rates of both ISR (66.6% versus 24.4%) and symptomatic ISR (40% versus 3.9%) in comparison with all other locations. CONCLUSION: Post-Wingspan ISR is more common in younger patients. This increased risk can be accounted for by a high prevalence of anterior circulation lesions in this population, specifically those affecting the supraclinoid segment, which are much more prone to ISR and symptomatic ISR than all other lesions.

Marginal sinus arteriovenous fistulas mimicking carotid cavernous fistulas: diagnostic and therapeutic considerations.

Marginal sinus fistulas (MSFs) are uncommon vascular anomalies. Occasionally, the dominant venous drainage is forced retrograde up the inferior petrosal sinus and into the cavernous sinus, causing chemosis, proptosis, and ocular hypertension, mimicking a carotid cavernous fistula. This atypical clinical presentation may lead to misdiagnosis and inappropriate hazardous treatment of an MSF. Identifying the site of the fistula and understanding the anatomy of the venous drainage are critical in providing appropriate, safe, and efficacious endovascular treatment.

Stent-assisted angioplasty of intracranial vertebrobasilar atherosclerosis: an initial experience.

OBJECT: Patients with intracranial vertebrobasilar artery (VBA) atherosclerotic occlusive disease have few therapeutic options. Unfortunately, VBA transient ischemic attacks (TIAs) herald a lethal or devastating event within 5 years in 25 to 30% of patients. The authors report their initial experience with eight patients in whom medically refractory TIAs secondary to intracranial posterior circulation atherosclerotic occlusive lesions were treated with stent-assisted angioplasty. METHODS: Eight patients (six men), ranging in age from 43 to 77 years, experienced signs and symptoms of VBA insufficiency despite combination therapy with warfarin and antiplatelet agents. Angiographic studies revealed severe distal vertebral (four patients), proximal basilar (one patient), or proximal and midbasilar stenoses (three patients). Aspirin and clopidogrel were administered for 3 days before primary angioplasty and stent placement, and this regimen was maintained by the patients on discharge. Patients underwent heparinization during the procedure and were given a bolus and 12-hour infusion of abciximab. A neurologist specializing in stroke evaluated all patients before and after the procedure. The VBAs in all patients were successfully revascularized with 7 to 28% residual stenosis. Six patients experienced no neurological complications. One patient died the evening of the procedure due to a massive subarachnoid hemorrhage. Two patients had groin hematomas, one developed congestive heart failure, and one had transient encephalopathy. All surviving patients are asymptomatic up to 8 months postoperatively. CONCLUSIONS: Although primary intracranial VBA angioplasty with stent insertion is technically feasible, complications associated with the procedure can be life threatening. As experience is gained with this procedure, it may be offered routinely as an alternative therapy to patients with medically refractory posterior circulation occlusive disease that may develop into catastrophic VBA insufficiency.

Hemorrhage detected using MR imaging in the setting of acute stroke: an in vivo model.

BACKGROUND AND PURPOSE: The treatment algorithm for acute cerebrovascular accidents has traditionally sorted these accidents as either hemorrhagic or nonhemorrhagic, and MR imaging, with its ability to allow expeditious assessment of vascular substrates and regional blood volume, is well suited for this purpose. Our purpose was to delineate the accuracy of MR imaging in acute, hemorrhagic forms of stroke during the time frame considered beneficial for intervention in an animal model. METHODS: Eighteen dogs with small, iatrogenic parenchymal, subarachnoid hemorrhage (SAH), or both were serially scanned over the initial 6-hour postictal period. Confirmatory pathologic specimens and 3-hour postictal CT scans were obtained in all animals. The MR and CT studies were then interpreted in a blinded fashion by two neuroradiologists for the presence of hemorrhage. The results were subjected to receiver operating characteristic analysis. RESULTS: MR imaging depicted acute parenchymal hemorrhage and SAH with a high degree of accuracy at 1.5 T. This finding was independent of each of the time points studied during the 6-hour window. For SAH, the MR accuracy for reader 1 was 0.86 (95% CI, 0.76-0.97); for reader 2, accuracy was 0.85 (95% CI, 0.71-0.99). The CT accuracy for the two readers was 0.42 (95% CI, 0.26-0.58) and 0.66 95% CI, 0.43-0.89), respectively. Fluid-attenuated inversion-recovery images improved the conspicuity of SAH on MR images and, along with spin-density-weighted spin-echo sequences, helped to establish the hemorrhagic nature. For parenchymal hemorrhage, the MR accuracy for reader 1 was 0.90 (95% CI, 0.81-0.99); for reader 2, accuracy was 0.93 (95% CI, 0.84-1.00). With CT, the accuracy of reader 1 was 0.91 (95% CI, 0.85-0.97) whereas for reader 2 accuracy was 0.76 (95% CI, 0.69-.83). Parenchymal hemorrhage detection and diagnosis was best with T2*-weighted gradient-echo images. CONCLUSION: MR imaging with appropriately selected sequences appears able to provide information regarding the presence (or absence) of hemorrhage in an acute stroke model requisite to the initiation of treatment.

Detachable balloon embolization: concomitant use of a second safety balloon.

We describe a relatively unusual case of carotid cavernous fistula in association with a persistent trigeminal artery, presumably related to aneurysm rupture near the carotid origin of the vessel. We emphasize the use of a second, nondetachable balloon solely for the purpose of stabilizing placement of the first device at the time of detachment.

Intra-arterial thrombolysis for perioperative stroke after open heart surgery.

Recent major surgery is an exclusion criterion for thrombolysis. Six patients with acute ischemic stroke underwent intra-arterial thrombolysis after recent open heart surgery without clinically significant bleeding complications, although one patient developed a small, asymptomatic cerebellar hemorrhage. Intra-arterial thrombolysis may be an option for patients with cerebral embolism in the perioperative period.

Endovascular occlusion of the carotid or vertebral artery with temporary proximal flow arrest and microcoils: clinical results.

PURPOSE: To determine the clinical effectiveness of parent artery occlusion of the carotid or vertebral artery by means of temporary proximal flow arrest and microcoils. METHODS: Nineteen parent artery occlusions (15 carotid, four vertebral) were performed in 19 patients who successfully passed a balloon test occlusion. In these patients, endovascular occlusion of the carotid or vertebral artery was accomplished with the use of temporary proximal flow arrest and microcoils. RESULTS: All 19 parent arteries were occluded. Eighteen patients (95%) had good outcomes and one (5%) had a poor outcome. Fourteen patients (74%) had no complications and five (26%) had complications, of whom only one was left with a permanent neurologic deficit. Three (60%) of the complications were the result of delayed ischemic events after parent artery occlusion and were not predicted by balloon test occlusion. CONCLUSION: Endovascular occlusion with temporary proximal flow arrest and microcoils can be done effectively and successfully. The predictive value of the balloon test occlusion is the major complicating factor, as it is with balloon occlusion. This technique offers an additional tool that can be used for endovascular occlusion of the carotid or vertebral artery and seems to be less difficult technically. It is our primary technique for parent artery occlusion.

Basilar artery rethrombosis: successful treatment with platelet glycoprotein IIB/IIIA receptor inhibitor.

We describe the use of abciximab to prevent rethrombosis of the basilar artery after transluminal angioplasty. A 60-year-old patient with vertebral basilar insufficiency and acute occlusion of the basilar artery underwent revascularization with urokinase and angioplasty. Despite the repeated use of urokinase and angioplasty under anticoagulation with heparin, the basilar artery immediately rethrombosed. In a final attempt to prevent rethrombosis, abciximab was administered before the final angioplasty, resulting in a widely patent basilar artery and no rethrombosis.

Segmented three-dimensional echo-planar flow imaging of the cervical carotid arteries.

PURPOSE: To implement and assess the application of segmented three-dimensional echo-planar MR imaging time-of-flight flow sequences for studying the anatomy of the cervical carotid arteries at 1.5 T. METHODS: The 3-D echo-planar sequences were segmented along the in-plane phase-encoding direction. Echo train lengths (ETLs) of 3 and 5 and signal bandwidths of +/-25, +/-33, and +/-50 KHz were tested along with a conventional (ETL = 1) 3-D MR flow study in six healthy volunteers and in five patients with known arteriosclerotic disease involving the carotid bifurcation as confirmed by conventional angiography. The volunteer data were used to rank the techniques with respect to vessel dimension, vessel/background contrast, and quality by four trained neuroradiologists. For the patient studies, the percentage of stenoses was measured for all MR studies and compared against the conventional angiographic data using the criteria of the North American Symptomatic Carotid Endarterectomy Trial. RESULTS: Using Wilcoxon's test statistic and a significance level of .05, we found that the conventional MR flow examination was better than the segmented techniques and that the segmented techniques with ETL of 3 were superior to their counterparts with ETL of 5. For the ETL of 3 techniques, the high-bandwidth studies were inferior to their lower bandwidth counterparts; however, there was no significant difference between the performance of the medium- and low-bandwidth sequences. The patient data revealed that the segmented techniques consistently overestimated the severity of stenosis; however, in no instance did any of the segmented examinations erroneously indicate the presence of disease. CONCLUSIONS: The reduction in acquisition time and the zero false-positive rate we obtained suggest that segmented 3-D echo-planar MR flow techniques may be used as a screening/locating study for cervical carotid artery disease.

Assessment of the efficacy of noninvasive screening for patients with asymptomatic neck bruits.

BACKGROUND AND PURPOSE: Several recent clinical trials have shown that endarterectomy is efficacious in patients with asymptomatic carotid artery stenosis. The purpose of this study was to evaluate the effectiveness of various test strategies for screening and diagnosing carotid artery disease. METHODS: We constructed a model of the natural history of carotid artery disease using literature-based estimates of the prevalence and incidence of carotid artery stenosis and associated morbidity and mortality. Markov cohort simulation was used to estimate the mean quality-adjusted life years and monetary costs associated with various management strategies. RESULTS: Screening is cost-effective in the baseline model. Key parameters affecting the efficacy of screening are prevalence of operable lesions, benefit of surgery, surgical complication rates, quality of life with stroke, rate of stenosis progression, and excess morbidity and mortality. CONCLUSIONS: Asymptomatic patients with carotid bruits may benefit from screening if the prevalence rate is > or = 20%, the benefits and risks associated with surgery are similar to those observed in the Asymptomatic Carotid Atherosclerosis Study, and the quality of life with stroke is considerably lower than the quality of life without stroke. Ultrasound followed by three-dimensional time-of-flight MR angiography, if indicated, is a promising test strategy.

Multiple myeloma involving the thyroid cartilage.

Extraosseous multiple myeloma involving the larynx is rare. We describe a patient with multiple myeloma and a plasmacytoma involving the thyroid cartilage. Ossification of the thyroid cartilage with formation of a marrow space could explain the occurrence of multiple myeloma in this unusual location.

High resolution, magnetization transfer saturation, variable flip angle, time-of-flight MRA in the detection of intracranial vascular stenoses.

OBJECTIVE: Factors that restrict 3D TOF MRA are limited resolution, saturation of flow, and degree of background suppression. We evaluated MRA for intracranial stenoses by using a 3D TOF technique that minimizes these factors. MATERIALS AND METHODS: Twenty-nine patients underwent MRA and intraarterial digital subtraction angiography (DSA). The MRA studies were performed on a 1.5 T Siemens SP 4000 system. Integrated techniques applied to the conventional 3D TOF acquisition included the following: (a) 256 x 256 matrix with a 140 mm FOV and 0.9 mm slice thickness, yielding a 0.54 x 0.54 x 0.9 mm3 voxel; (b) tilted optimized nonsaturating excitation (TONE); and (c) magnetization transfer saturation (MTS). The intraarterial DSA was performed on a Siemens Angiostar system with a 1,024 x 1,024 noninterpolated matrix. The MRAs were reviewed by two neuroradiologists. Two hundred seventy-seven vessels were evaluated for a total of 806 segments. Vessel segments were evaluated with a 5 point scale. RESULTS: The estimated accuracy of MRA for detecting stenosis over all intracranial vessel segments was 0.88 +/- 0.03 and 0.89 +/- 0.02 for the two readers, respectively. The estimated accuracy ranged from 0.94 +/- 0.02 and 0.93 +/- 0.02 for detecting internal carotid artery stenosis by the two readers, respectively, to 0.65 +/- 0.17 and 0.71 +/- 0.15 for detecting distal vertebral artery stenosis. In vessels determined by catheter angiography to be stenosis-free, reader confidence at the proximal versus distal segments was similar for the internal carotid, basilar, and posterior cerebral arteries. However, for the anterior and middle cerebral arteries, one or both readers were more confident in diagnosing the proximal segment. CONCLUSION: High resolution MTS TONE 3D TOF MRA is an accurate technique for the screening of medium and large vessel intracranial stenoses.

Hyperintense disks on T1-weighted MR images: correlation with calcification.

PURPOSE: To determine if calcification in the intervertebral disk is associated with hyperintensity on T1-weighted spin-echo magnetic resonance (MR) images. MATERIALS AND METHODS: Sagittal T1-weighted MR images that showed one or more hyperintense intervertebral disks and correlative computed tomographic (CT) scans, plain radiographs, or both, were obtained in 11 patients retrospectively and in 43 patients prospectively. Six patients underwent MR imaging with a fat-suppression technique. Histologic analysis of two disks was performed. RESULTS: Absence of calcification was associated with disks that were isointense relative to normal disks (P < .001), mild to moderate calcification was associated with hyperintense disks (P < .001 and P = .004 [two readers]), and both mild to moderate and marked calcifications were associated with hypointense disks (P < .001). Fat suppression resulted in a decrease in hyperintense signal in two patients. CONCLUSION: The results indicate that hyperintensity is associated with calcification. In the absence of clinical findings that suggest other causes, hyperintense disks are suggestive of degenerative disk disease.

Thoracolumbar burst fractures: evaluation with MR imaging.

PURPOSE: To determine the frequency of posterior ligamentous injury that occurs in patients with thoracolumbar burst fractures and to correlate ligamentous disruption with radiographic appearance. MATERIALS AND METHODS: Magnetic resonance (MR) imaging examinations of 21 patients with 25 thoracolumbar burst fractures were retrospectively evaluated to determine spinal ligament integrity. Radiographic and computed tomographic (CT) examinations were evaluated for interpediculate widening, midsagittal canal narrowing, posterior element fractures, and kyphosis; a radiographic assessment of posterior ligamentous integrity was made. These findings were then correlated with the status of the spinal ligaments. RESULTS: The patients were divided into two groups on the basis of the status of their supraspinous ligament (SSL). Six patients had disrupted SSLs, and 15 had intact SSLs. Radiographic and CT findings did not correlate with supraspinous ligament disruption. Radiographic indicators of posterior ligamentous disruption were present in only 33% of patients with SSL disruption. CONCLUSION: SSL disruption is a frequent occurrence in patients with burst fractures. No radiographic features of burst fractures correlate with SSL disruption, and radiographic signs of posterior ligamentous disruption are insensitive.

Time-of-flight intracranial MR venography: evaluation of the sequential oblique section technique.

PURPOSE: To implement a time-of-flight MR angiographic technique using the oblique acquisition of thin gradient-echo sections to evaluate the intracranial venous system, and to assess the feasibility of application of this technique in a routine clinical setting. METHODS: The MR angiographic technique consisted of a two-dimensional gradient-echo technique with sequential overlapped sections obtained with an oblique orientation, angled from the sagittal toward the coronal plane. Parameters were evaluated during 41 measurements in 21 healthy volunteers with the section orientation varying from direct sagittal to direct coronal, followed by 64 examinations in 53 patients with an angle of obliquity of 15 degrees to 20 degrees from the sagittal toward the coronal plane. Confirmation of MR venographic findings was through correlation with clinical data and imaging studies. RESULTS: The volunteer data demonstrated optimal visibility of the smaller midline structures with an angle of obliquity of 15 degrees or greater. Patient examinations with this angle demonstrated sinus obstruction or thrombosis (n = 11), sinus compression (n = 2), and apparent sinus stenosis (n = 1). CONCLUSIONS: Oblique-acquisition time-of-flight MR venography seems to provide a rapid, robust technique for intracranial venous examination and can be applied as a useful adjunct to parenchymal MR in the evaluation of suspected venoocclusive disease. This oblique technique demonstrated improved vessel contrast over direct sagittal acquisition, required significantly fewer sections and thus a shorter acquisition time than direct coronal acquisition, and was applied without difficulty in the vast majority of patients in the clinical setting.

Sequential three-dimensional time-of-flight MR angiography of the carotid arteries: value of variable excitation and postprocessing in reducing venetian blind artifact.

OBJECTIVE: Multiple overlapping three-dimensional (3D) time-of-flight carotid MR angiography potentially combines many of the desirable features of two-dimensional (2D) and single-volume 3D MR angiographic imaging techniques. Yet the maximum-intensity-projection images from such acquisitions are often degraded by artifact due to nonuniform signal intensity of contiguous imaging volumes and inadequate, yet arduous, postprocessing. The former has been termed venetian blind artifact. To date, the severity of the artifact has been minimized by the use of very thin slabs with a large percentage of overlap. However, the artifact typically is still appreciable, and the required acquisition and postprocessing times are increased. The purpose of this study was to examine the value of technical modifications of both the multislab acquisition and postprocessing procedures to reduce this artifact on images of healthy volunteers. SUBJECTS AND METHODS: Spatially variable RF pulses along the direction of flow were applied as excitation pulses in the multislab time-of-flight MR angiographic acquisitions to compensate for the nonuniform blood signal intensity caused by spin saturation. An automatic postprocessing technique was used to optimally combine the image data in overlapping slices by selecting the higher-intensity pixel of the two on a pixel-by-pixel basis. Ratios of the standard deviation of signal intensity to the mean signal intensity were computed as a function of RF profile and postprocessing method along the long axes of the arteries to measure the uniformity of the signal intensity of the blood. The spatially variable and sinc RF pulse acquisitions, combined with automatic and conventional manual postprocessing, were compared. RESULTS: Compared with the sinc pulse acquisition, the MR angiograms acquired with spatially variable excitation pulses improved the signal uniformity of the arteries with thicker volumes and less overlap, thereby reducing the acquisition time by 25% for similar spatial coverage. When used with the automatic postprocessing technique, the severity of the venetian blind artifact on maximum-intensity-projection images was minimized and the postprocessing time was reduced by roughly a factor of 5. CONCLUSION: The combined use of spatially variable excitation pulses and an automatic postprocessing technique can improve the uniformity of the signal from blood across the slab and allow thicker slabs to be acquired with less overlap. Data acquisition and postprocessing times can be reduced significantly. This work suggests it may be possible to easily produce overlapping 3D MR angiograms that should be superior to conventional 2D and 3D studies.