The safety of dedicated-team catheter-based diagnostic cerebral angiography in the era of advanced noninvasive imaging

BACKGROUND AND PURPOSE

Given the current high quality and usefulness of noninvasive cerebrovascular imaging, invasive angiographic evaluation of the cerebrovascular system is justified if the procedural risk for a neurologic complication is far below the anticipated benefit. The purpose of this study was to evaluate the safety of diagnostic cerebral angiography provided by a dedicated neurointerventional team in a high-volume university hospital.

MATERIALS AND METHODS

A consecutive cohort of 1715 patients undergoing diagnostic cerebral angiography at our institution from 2000 to 2008 was retrospectively assessed for incidence of stroke or TIA related to cerebral angiography. In the subgroup of patients (n = 40) who serendipitously underwent DWI within the first 30 days after cerebral angiography, the presence of new DWI hyperintensities found in territories explored during angiography was tabulated. Complications related to the catheter technique and sheath placement were also studied.

RESULTS

No stroke or permanent neurologic deficit was seen in any of the 1715 patients undergoing diagnostic neuroangiography. One patient experienced a TIA. Nonneurologic complications without long-term sequelae occurred in 9 patients. Two patients had punctate areas of restricted diffusion in territories that had been angiographically explored.

CONCLUSIONS

Within a high-volume neurointerventional practice, the risk for neurologic complications related to catheter-based diagnostic cerebral angiography can approach zero. As the absolute number of invasive diagnostic procedures diminishes with time, diagnostic cerebral angiography remains a useful tool while providing a foundation for neuroendovascular interventions, and should preferably be performed in institutions with high-volume operators also capable of managing unanticipated complicating adverse events.

Basilar artery stenosis: clinical and neuroradiographic features

INTRODUCTION

Although basilar artery stenosis (BAS) is an important cause of posterior circulation stroke, few reports detail the clinical and neuroradiological features of patients with BAS.

METHODS

A retrospective review of symptomatic BAS patients who were evaluated by our Stroke Center.

RESULTS

Twenty-eight patients were followed-up for a median of 16 months. Transient ischemic attacks (TIAs) specific for posterior circulation involvement were common (12/19 patients with TIA), were often multiple, and frequently preceded a posterior circulation stroke. The proximal (13/28) and mid (10/28) basilar arteries were the most common sites of stenosis. Brain infarction most often affected the pons, but also frequently involved the cerebellum and thalamus. Concomitant vertebral artery disease was prevalent (12/18 patients who underwent conventional cerebral angiography). Stroke mechanisms included artery to artery embolus, basilar branch disease, and hypoperfusion. The same-territory recurrent stroke rate was 8.2% per year. Most patients in the series were treated with warfarin. No patients suffered a recurrent stroke while on a therapeutic dose of warfarin (international normalized ratio [INR], 2.0 to 3.0). Angioplasty was performed in 6 patients.

CONCLUSIONS

The same-territory stroke recurrence rate was 8.2% per year. Warfarin (INR, 2.0 to 3.0) appeared to be effective in preventing recurrent strokes. Angioplasty of the basilar artery was technically feasible. Symptomatic BAS typically affected the proximal and mid-basilar artery and most often caused infarction in the pons. The mechanisms for stroke were heterogeneous. TIAs frequently preceded a posterior circulation stroke.

Preoperative selective internal carotid artery dural branch embolisation for petroclival meningiomas

We assessed the clinical value of preoperative embolisation of the dural branches of the internal carotid artery (ICA) in cases of petroclival meningioma was evaluated. We carried out preoperative selective embolisation on seven consecutive patients with large petroclival meningiomas, using nonbraided 2 F steam-shaped microcatheters and shapeable hydrophilic microguide-wires to enter the dural branches of the ICA. The embolisations were performed using digital subtraction fluoroscopy with 150-250 microm polyvinyl alcohol particles. The tumours were resected a few days after embolisation. We reviewed angiographic findings before and after endovascular devascularisation, blood loss during tumour resection and clinical outcome. All endovascular procedures were technically successful, and postembolisation angiography showed disappearance of or marked decrease in tumour stain in all cases. Intraoperative bleeding was easily controlled, and intraoperative blood loss was low.

Rheolytic thrombectomy of the occluded internal carotid artery in the setting of acute ischemic stroke

BACKGROUND AND PURPOSE

Acute thromboembolic stroke complicated by ipsilateral carotid occlusion may present both mechanical and inflow-related barriers to effective intracranial thrombolysis. We sought to review our experience with a novel method of mechanical thrombectomy, in such cases, using the Possis AngioJet system, a rheolytic thrombectomy device.

METHODS

A review of our interventional neuroradiology database revealed three patients in whom an occluded cervical internal carotid artery was encountered during endovascular treatment for acute stroke and in whom thrombectomy was attempted, using the 5F Possis AngioJet thrombectomy catheter. The medical records and radiographic studies of these patients were reviewed.

RESULTS

Three patients were identified (ages, 52--84 years). Two patients had isolated occlusion of the internal carotid artery; in one patient, thrombus extended down into the common carotid artery. Treatment was initiated within 190 to 360 minutes of stroke onset. Thrombectomy of the carotid artery was deemed necessary because of poor collateral flow to the affected hemisphere (chronic contralateral internal carotid artery occlusion [one patient] and thrombus extending to the carotid "T" [one patient]) or inability to pass a microcatheter through the occluded vessel (one patient). Adjunctive therapy included pharmacologic thrombolysis with tissue plasminogen activator (all patients), carotid angioplasty and stenting (two patients), and middle cerebral artery angioplasty (one patient). Patency of the carotid artery was reestablished in two patients, with some residual thrombus burden. In the third patient, the device was able to create a channel through the column of thrombus, allowing intracranial access.

CONCLUSION

Rheolytic thrombectomy shows potential for rapid, large-burden thrombus removal in cases of internal carotid artery thrombosis, allowing expedient access to the intracranial circulation for additional thrombolytic therapy.

Videographic assessment of the embolic characteristics of three polymeric compounds: ethylene vinyl alcohol, cellulose acetate, and liquid urethane

BACKGROUND AND PURPOSE

Aneurysms have been clinically and experimentally treated with various surgical and endovascular methods, including endovascular polymer instillation. Additional tools may help to identify advantages and disadvantages of polymeric aneurysm treatment. We assessed the value of high-resolution videography to compare in vitro embolization characteristics of ethylene vinyl alcohol copolymer (VIN), cellulose acetate polymer (ACE), and urethane copolymer (UCO).

METHODS

In a "neck-up" glass aneurysm model, solutions of 8% and 12% VIN, 8% and 12% ACE, and 8% UCO were introduced through a microcatheter into a xanthan gum solution at three flow rates: full physiological (62 cm/s), half physiological, and flow arrest. Each formulation was then introduced into a "neck-down" aneurysm model at flow arrest, for a total of 20 experiments. Results were tabulated for six different categories: outflow tail formation, inflow-zone polymer-mass deformation, inflow-zone migration, detachment tail formation, adherent mass pullout, and conjectural net effect.

RESULTS

Of the 20 experiments, nine had unacceptable results because of potential clinical complications. The results were unacceptable in four of eight VIN experiments, four of eight ACE experiments, and one of four UCO experiments. VIN performance was more dependent on flow arrest than the more viscous ACE. The growth of the ACE solutions was most circumferential, with balloonlike growth characteristics, little inflow-zone effects, and fewer outflow tails than seen with VIN. All compounds had the potential for partial catheter adhesion and catheter-adhesing tails. UCO had the highest percentage of favorable results and the lowest percentage of unfavorable results.

CONCLUSION

Videographic analysis allows detailed assessment of the dynamic embolization characteristics of polymers, revealing potential advantages of compounds such as UCO.

Silent thromboembolic events associated with the treatment of unruptured cerebral aneurysms by use of Guglielmi detachable coils: prospective study applying diffusion-weighted imaging

BACKGROUND AND PURPOSE

Aneurysm embolization using Guglielmi detachable coils (GDC) is gaining increasing acceptance as a viable alternative to surgery in the treatment of cerebral aneurysms. Although recent reports describe a significant rate of symptomatic thromboembolic complications with GDC use, many of the neurologic deficits are transient. We sought to determine the incidence of silent thromboembolic events with the use of diffusion-weighted imaging and to correlate radiologic findings with the results of neurologic examinations.

METHODS

Diffusion-weighted MR imaging was performed within 48 hours in 14 consecutive elective GDC aneurysm treatments. Embolizations were performed under systemic heparinization; all flush solutions were heparinized, and both guiding catheters and microcatheters were placed for continuous heparinized infusions. Neurologic examination, including the National Institutes of Health Stroke Scale determination, was performed by a stroke neurologist before the coiling procedures were performed, immediately after the procedures were performed, and before discharge. MR imaging examinations were reviewed by a stroke neurologist and an interventional neuroradiologist, with determination and characterization of diffusion-weighted imaging abnormalities.

RESULTS

Small areas of restricted diffusion, presumed to represent procedure-related embolic infarctions, were noted on the images of eight of 14 patients. All except one of the areas were located ipsilateral to the side of the catheterization. Six patients had evidence of multiple infarcts. Most lesions were small (<2 mm); one patient with coil stretch and herniation into the parent vessel had numerous infarcts with a dominant posterior frontal infarct. Pre- and posttreatment National Institutes of Health Stroke Scale scores were unchanged for 13 of 14 patients. Overall, the rate of asymptomatic emboli was 61% (eight of 13 treatments) in uncomplicated treatments. Strokes occurred independently of the number of coils used; the mean number of coils used for patients with strokes was 7.6 (range, two to 13) and for patients without evidence of infarcts was 10.2 (range, one to 30). This was not a significant difference (P > .5).

CONCLUSION

Silent thromboembolic events related to the use of the GDC system are a common occurrence, despite meticulous technique and systemic anticoagulation. Although clinical sequelae are rare, the high rate of occurrence suggests that alterations in the technique, such as the addition of antiplatelet agents, should be considered.

Advantages of adding diffusion-weighted magnetic resonance imaging to conventional magnetic resonance imaging for evaluating acute stroke

BACKGROUND

Accurate localization of acute ischemic lesions in patients with an acute stroke may aid in understanding the etiology of their stroke and may improve the management of these patients.

OBJECTIVE

To determine the yield of adding diffusion-weighted magnetic resonance imaging (DWI) to a conventional magnetic resonance imaging (MRI) protocol for acute stroke.

DESIGN

A prospective cohort study.

SETTING

A referral center.

PATIENTS AND METHODS

Fifty-two patients with a clinical diagnosis of acute stroke who presented within 48 hours after symptom onset were included. An MRI scan was obtained within 48 hours after symptom onset. A neuroradiologist (A.M.N.) and a stroke neurologist (G.W.A.) independently identified suspected acute ischemic lesions on MRI sequences in the following order: (1) T2-weighted and proton density-weighted images, (2) fluid-attenuated inversion recovery images, and (3) diffusion-weighted images and apparent diffusion coefficient maps.

MAIN OUTCOME MEASURES

Diagnostic yield and interrater reliability for the identification of acute lesions, and confidence and conspicuity ratings of acute lesions for different MRI sequences.

RESULTS

Conventional MRI correctly identified at least one acute lesion in 71% (34/48) to 80% (39/49) of patients who had an acute stroke; with the addition of DWI, this percentage increased to 94% (46/49) (P<.001). Conventional MRI showed only moderate sensitivity (50%-60%) and specificity (49%-69%) compared with a "criterion standard." Based on the diffusion-weighted sequence, interrater reliability for identifying acute lesions was moderate for conventional MRI (kappa = 0.5-0.6) and good for DWI (kappa = 0.8). The observers' confidence with which lesions were rated as acute and the lesion conspicuity was significantly (P<.01) higher for DWI than for conventional MRI.

CONCLUSION

During the first 48 hours after symptom onset, the addition of DWI to conventional MRI improves the accuracy of identifying acute ischemic brain lesions in patients who experienced a stroke.

Yield of diffusion-weighted MRI for detection of potentially relevant findings in stroke patients

OBJECTIVE

To determine whether diffusion-weighted imaging (DWI) could identify potentially clinically relevant findings in patients presenting more than 6 hours after stroke onset when compared with conventional MRI.

METHODS

MRI with both conventional (T2 and proton density images) and echoplanar imaging (DWI and apparent diffusion coefficient maps) was performed 6 to 48 hours after symptom onset (mean, 27 hours) in 40 consecutive patients with acute stroke. All acute lesions were identified first on conventional images, then on DWI, by a neuroradiologist who was provided with the suspected lesion location, based on a neurologist's examination before imaging. Abnormalities were rated as potentially clinically relevant if they were detected only on DWI and 1) confirmed the acute symptomatic lesion to be in a different vascular territory than suspected clinically, 2) revealed multiple lesions in different vascular territories suggestive of a proximal source of embolism, or 3) clarified that a lesion, thought to be acute on conventional imaging, was not acute.

RESULTS

The initial clinical impression of lesion localization was incorrect in 12 patients (30%). Clinically significant findings were detected by DWI alone in 19 patients (48%). DWI demonstrated the symptomatic lesion in a different vascular territory than suspected clinically or by conventional MRI in 7 patients (18%) and showed acute lesions in multiple vascular distributions in 5 patients (13%). In 8 patients (20%), DWI clarified that lesions thought to be acute on conventional MRI were actually old.

CONCLUSION

In patients imaged 6 to 48 hours after stroke onset, DWI frequently provided potentially clinically relevant findings that were not apparent on conventional MRI.

Sonography, CT, and MR imaging: a prospective comparison of neonates with suspected intracranial ischemia and hemorrhage

BACKGROUND AND PURPOSE

Sonography, CT, and MR imaging are commonly used to screen for neonatal intracranial ischemia and hemorrhage, yet few studies have attempted to determine which imaging technique is best suited for this purpose. The goals of this study were to compare sonography with CT and MR imaging prospectively for the detection of intracranial ischemia or hemorrhage and to determine the prognostic value(s) of neuroimaging in neonates suspected of having hypoxic-ischemic injury (HII).

METHODS

Forty-seven neonates underwent CT (n = 26) or MR imaging (n = 24) or both (n = 3) within the first month of life for suspected HII. Sonography was performed according to research protocol within an average of 14.4 +/- 9.6 hours of CT or MR imaging. A kappa analysis of interobserver agreement was conducted using three independent observers. Infants underwent neurodevelopmental assessment at ages 2 months (n = 47) and 2 years (n = 26).

RESULTS

CT and MR imaging had significantly higher interobserver agreement (P < .001) for cortical HII and germinal matrix hemorrhage (GMH) (Grades I and II) compared with sonography. MR imaging and CT revealed 25 instances of HII compared with 13 identified by sonography. MR imaging and CT also revealed 10 instances of intraparenchymal hemorrhage (>1 cm, including Grade IV GMH) compared with sonography, which depicted five. The negative predictive values of neuroimaging, irrespective of technique used, were 53.3% and 58.8% at the 2-month and 2-year follow-up examinations, respectively.

CONCLUSION

CT and MR imaging have significantly better interobserver agreement for cortical HII and GMH/intraventricular hemorrhage and can reveal more instances of intraparenchymal hemorrhage compared with sonography. The absence of neuroimaging findings on sonograms, CT scans, or MR images does not rule out later neurologic dysfunction.

False positive appearance of subarachnoid hemorrhage on CT with bilateral subdural hematomas

We describe a patient with bilateral traumatic subdural hematomas in whom CT findings of hyperattenuation in the basal cisterns and subarachnoid spaces falsely suggested superimposed acute subarachnoid hemorrhage.

Joint motion in an open MR unit using MR tracking

A system for active scan plane guidance during kinematic magnetic resonance (MR) examination of joint motion was developed utilizing an external tracking coil and MR tracking software. In a phantom study and during upright, weight-bearing, physiologic knee flexion, the external tracking coil maintained the scan plane through desired structures. Thus, MR tracking provides a robust method to guide the scan plane during MR imaging of active joint motion.

Intracystic hemorrhage of the middle fossa arachnoid cyst and subdural hematoma caused by ruptured middle cerebral artery aneurysm

We report a case of a cerebral aneurysm arising from the bifurcation of the left middle cerebral artery that ruptured into a left middle cranial fossa arachnoid cyst, associated with acute subdural hematoma. We discuss the relationships of aneurysm, arachnoid cyst, and subdural hematoma.

Percutaneous transfemoral embolization of an indirect carotid-cavernous fistula with cortical venous access to the cavernous sinus. Case report

The authors present the case of a 61-year-old man with an indirect carotid-cavernous fistula (CCF). Many now advocate a primary transvenous approach to deal with such lesions, with packing and thrombosis of the cavernous sinus leading to fistula obliteration. Transvenous access to the cavernous sinus via the inferior petrosal sinus is the usual route of access; both surgical and transfemoral superior ophthalmic vein approaches are also well described. In the case presented, the anatomy of the CCF was unfavorable for these approaches and its dominant venous egress was via a single enlarged arterialized cortical vein. The cavernous sinus was accessed with a transfemoral retrograde approach to the cortical draining vein. Successful CCF embolization was documented radiographically and clinically. To the authors' knowledge, this procedure has not been previously described in the English literature.

Embolization of basal ganglia and thalamic arteriovenous malformations

OBJECTIVE

Basal ganglia and thalamic arteriovenous malformations (AVMs) show a poor natural history and have proven difficult to treat. We report the safety and efficacy of presurgical and preradiosurgical embolization of these deep central lesions and describe the contribution of embolization to multimodality treatment.

METHODS

Thirty-eight patients with basal ganglia and/or thalamic AVMs underwent embolization in a total of 69 sessions. Seven of the 38 patients (18.4%) presented with hemorrhage, and 23 of 38 (60.5%) exhibited neurological deficits before therapy. Thirty patients (78.9%) underwent embolization with a liquid adhesive (cyanoacrylate), and five of these patients also underwent embolization with polyvinyl alcohol. Five patients (13.2%) were treated with polyvinyl alcohol or polyvinyl alcohol and silk. One patient (2.6%) underwent embolization alone, 19 (50.0%) underwent embolization followed by radiosurgery, 5 (13.2%) underwent embolization plus microsurgical resection, and 13 (34.2%) patients were treated using all three modalities.

RESULTS

Three patients did not undergo embolization because of the morphological features of the AVMs and poor endovascular access. The patients who underwent embolization achieved AVM volume reductions of 10 to 100% (mean, 49.7%). Fifteen patients (39.5%) achieved complete obliteration of their AVMs, one with embolization alone, three with embolization followed by radiosurgery, five with embolization plus microsurgical resection, and six with a combination of all three modalities. At the time of the last follow-up imaging session, embolization combined with radiosurgery (19 patients) yielded a mean volume reduction of 81.1%, and all three modalities (13 patients) yielded a mean reduction of 84.6%. Four permanent neurological deficits resulted from embolization (5.8% of procedures, 10.5% of patients). The embolization-related complication rate was higher in the earlier years (1984-1989) of this series.

CONCLUSION

Endovascular embolization plays an important role in multimodality treatment of AVMs involving the basal ganglia and/or thalamus. Embolization can result in obliteration of a significant volume of the AVM and may allow complete obliteration of the AVM when combined with microsurgical resection and/or stereotactic radiosurgery.

Outcome of angioplasty for atherosclerotic intracranial stenosis

BACKGROUND AND PURPOSE

We sought to assess the long-term outcome and efficacy of percutaneous transluminal angioplasty in the treatment of symptomatic intracranial atherosclerotic stenoses.

METHODS

Twenty-three patients with fixed symptomatic intracranial stenoses were treated over a 5-year period with percutaneous transluminal angioplasty. Patients who underwent successful angioplasty were followed up for 16 to 74 months (mean, 35.4 months).

RESULTS

An angioplasty that resulted in decreased stenosis was performed in 21 of 23 patients (91.3%). In 1 case a stenosis could not be safely crossed, and in another balloon dilatation resulted in vessel rupture. This vessel rupture resulted in the 1 periprocedural death in the series. In follow-up there was 1 stroke in the same vascular territory as the angioplasty and 2 strokes in the series overall. This yielded an annual stroke rate of 3.2% for strokes in the territory appropriate to the site of angioplasty.

CONCLUSIONS

Intracranial angioplasty can be performed with a high degree of technical success. The long-term clinical follow-up available in this series suggests that it may reduce the risk of future stroke in patients with symptomatic intracranial stenoses.

Management of biopsy needle artifacts: techniques for RF-refocused MRI

Several methods were investigated to improve the depiction of biopsy needles in radiofrequency (RF)-refocused magnetic resonance imaging. Distortion correction is performed by the use of view angle tilting (VAT): a gradient is employed on the slice-select axis during readout. Needle conspicuity is increased by offsetting the gradient echo from the spin echo and by inverting the 90 degrees RF pulse slice-select gradient. VAT effectively re-registers in-plane shifts. Since this method changes the projection angle through the slice, some structures appear blurred, while other structures appear sharper. VAT does not correct errors in slice selection. Offsetting the spin echo from the gradient echo increases needle conspicuity but can result in a shift in the apparent location of the needle. Inverting the 90 degrees slice-select gradient effectively increases the needle conspicuity with no shift in the needle location. These methods provide an easy and interactive means to manipulate needle artifacts but should be used cautiously.

MRI abnormalities associated with partial status epilepticus

OBJECTIVE

To report neuroimaging findings in patients with complex partial status epilepticus.

BACKGROUND

During status epilepticus, neuroimaging may be used to exclude other neurologic conditions. Therefore, it is important to identify the neuroimaging features that are associated with status epilepticus. In addition, MRI characteristics may provide insight into the pathophysiologic changes during status epilepticus.

METHODS

The history and neuroimaging examination results of three patients with complex partial status epilepticus were reviewed. Studies obtained during status epilepticus included diffusion-weighted MRI (DWI), MR angiography (MRA), postcontrast T1-weighted MRI, T2-weighted MRI, and CT. Follow-up MRI was obtained in two patients, and autopsy results were available for the third.

RESULTS

Some of the MRI and CT findings during partial status epilepticus mimicked those of acute ischemic stroke: DWI and T2-weighted MRI showed cortical hyperintensity with a corresponding low apparent diffusion coefficient, and CT showed an area of decreased attenuation with effacement of sulci and loss of gray-white differentiation. However, the lesions did not respect vascular territories, there was increased signal of the ipsilateral middle cerebral artery on MRA, and leptomeningeal enhancement appeared on postcontrast MRI. On follow-up imaging, the abnormalities had resolved, but some cerebral atrophy was present.

CONCLUSIONS

The radiologic characteristics of status epilepticus resemble those of ischemic stroke but can be differentiated based on lesion location and findings on MRA and postcontrast MRI. The MRI abnormalities indicated the presence of cytotoxic and vasogenic edema, hyperperfusion of the epileptic region, and alteration of the leptomeningeal blood-brain barrier. These changes reversed, but they resulted in some regional brain atrophy.

Embolization of rolandic cortex arteriovenous malformations

OBJECTIVES

To evaluate the safety and efficacy of preradiosurgical and presurgical embolization of arteriovenous malformations (AVMs) involving the rolandic cortex.

METHODS

Seventeen consecutive patients with rolandic AVMs seen during a 31-month period (December 1994-July 1997) were evaluated. All patients underwent superselective sodium amobarbital testing to determine any changes in the results of the neurological examinations before undergoing embolization. In 16 of 17 patients (94.1%), somatosensory evoked potentials augmented physical examinations. Patients were embolized with N-butyl cyanoacrylate (Histoacryl; B. Braun, Melsungen, Germany) and iophendylate (Ethiodol; Savage Labs, Melville, NY). Rigid control of the mean arterial pressure (65-75 mm Hg) was maintained in all patients for 24 to 48 hours after embolization.

RESULTS

Twenty-three embolization sessions were performed in 17 patients (mean, 1.5 sessions/patient), and a total of 40 feeding arteries were embolized. Two patients were unable to undergo embolization because of positive results of the amobarbital testing despite repeated attempts to reposition a microcatheter in the AVM circulation. In one case, somatosensory evoked potentials and the results of the physical examination were both positive; in the other case, only the somatosensory evoked potentials were used (in a pediatric patient under general anesthesia). All patients with AVMs that were embolized experienced a significant size reduction of their lesions (range, 20-95%; mean, 63%). There were no permanent complications. Four procedures (10% of the procedures, 23% of the patients) resulted in minor transient neurological deficits, with patients' conditions returning to baseline. Thirteen patients subsequently underwent radiosurgery, three underwent surgical resection, and one underwent combined surgery and radiosurgery. Complete obliteration of the lesions has been achieved in four patients to date (three who underwent surgery and one who underwent radiosurgery), with the remainder undergoing further follow-up.

CONCLUSION

When properly evaluated before treatment, rolandic AVMs can be embolized with a high success rate (measured by completed embolization and size reduction) and a low complication rate.

Intra-arterial rtPA treatment of stroke assessed by diffusion- and perfusion-weighted MRI

BACKGROUND

Diffusion-weighted MRI (DWI) and perfusion-weighted MRI (PWI) are new techniques that can be used for the evaluation of acute ischemic stroke. However, their potential role in the management of patients treated with recombinant tissue plasminogen activator (rtPA) has yet to be determined.

CASE DESCRIPTION

The authors present the case of a 73-year-old man who was treated with intra-arterial rtPA, and they compare findings on DWI and PWI scans with angiography. PWI revealed decreased cerebral perfusion corresponding to an area that was not successfully recanalized, but revealed no abnormality in regions in which blood flow was restored. DWI was unremarkable in the region that was reperfused early (3 hours) but revealed hyperintensity in an area that was reperfused 3. 5 hours after symptom onset and in the area that was not reperfused.

CONCLUSIONS

Findings on PWI correlated well with angiography, and DWI detected injured tissue in the hyperacute stage, whereas conventional MRI findings were negative. This suggests that these techniques may be useful to noninvasively evaluate the success of thrombolytic therapy.

Safety and biological efficacy of an adeno-associated virus vector-cystic fibrosis transmembrane regulator (AAV-CFTR) in the cystic fibrosis maxillary sinus

OBJECTIVE

The host immune response and low vector efficiency have been key impediments to effective cystic fibrosis transmembrane regulator (CFTR) gene transfer for cystic fibrosis (CF). An adeno-associated virus vector (AAV-CFTR) was used in a phase I dose-escalation study to transfer CFTR cDNA into respiratory epithelial cells of the maxillary sinus of 10 CF patients.

STUDY DESIGN

A prospective, randomized, unblinded, dose-escalation, within-subjects, phase I clinical trial of AAV-CFTR was conducted.

PATIENTS

Ten patients with previous bilateral maxillary antrostomies were treated.

MAIN OUTCOME MEASURES

Safety, gene transfer as measured by semiquantitative polymerase chain reaction (PCR), and sinus transepithelial potential difference (TEPD) were measured.

RESULTS

The highest level of gene transfer was observed in the range of 0.1-1 AAV-CFTR vector copy per cell in biopsy specimens obtained 2 weeks after treatment. When tested, persistence was observed in one patient for 41 days and in another for 10 weeks. Dose-dependent changes in TEPD responses to pharmacologic intervention were observed following treatments. Little or no inflammatory or immune responses were observed.

CONCLUSION

AAV-CFTR administration to the maxillary sinus results in successful, dose-dependent gene transfer to the maxillary sinus and alterations in sinus TEPD suggestive of a functional effect, with little or no cytopathic or host immune response. Further study is warranted for AAV vectors as they may prove useful for CFTR gene transfer and other in vivo gene transfer therapies. A prospective, randomized, double-blind, placebo-controlled, within-subjects, phase II clinical trial of the effect AAV-CFTR on clinical recurrence of sinusitis will determine the clinical efficacy of AAV gene therapy for CF.

Maxillary sinusitis as a surrogate model for CF gene therapy clinical trials in patients with antrostomies

BACKGROUND

Assessing the biological activity and clinical efficacy of gene therapy is critically important in cystic fibrosis (CF). It is widely accepted that clinical testing using surrogate markers including pulmonary function will be useful in assessing clinical efficacy. One problem with pulmonary surrogate markers of CF disease is the large number of patients and length of time required to demonstrate clinical efficacy. An alternative to pulmonary testing of new CF treatments is use of the maxillary sinuses as a surrogate model of CF lung disease. Using CF sinusitis as a surrogate model for testing clinical efficacy of new treatments is attractive because CF upper respiratory disease is similar to the lower respiratory disease with respect to electrophysiology and microbiology.

METHODS

Sinusitis recurrence in untreated sinuses was analyzed during a prospective, randomized, unblinded, dose-escalation, within-subjects, phase I clinical trial of the adeno-associated virus mediated cystic fibrosis transmembrane conductance regulator (AAV-CFTR) gene transfer.

RESULTS

Clinical symptoms combined with sinus endoscopy proved useful in the diagnosis of unilateral and bilateral sinusitis recurrence. Sinusitis recurred at a rate of 45% during one month of follow-up. IL-8 concentration rose in sinus fluids from affected sinuses. Bacterial cultures and increased sinus leukocytes corroborated recurrent sinusitis. Sinus CT scans were also useful in diagnosing recurrent sinusitis in this surrogate model of CF infectious exacerbations.

CONCLUSIONS

CF sinusitis as a surrogate for lung disease is particularly well-suited for phase II clinical trials of gene transfer agents, with the potential for measuring clinical efficacy in relatively small numbers of patients over relatively short periods of time.

Headache with neurological deficits and CSF lymphocytosis: A transient ischemic attack mimic

Headache with neurological deficits and cerebrospinal fluid (CSF) lymphocytosis (HaNDL) is a benign condition with a transient ischemic attack (TIA)-like presentation. It is a disease of young adults that is characterized by headache, transient focal neurological symptoms, and lymphocytic pleocytosis. The onset of neurological symptoms after cerebral angiography in patients with this disease has occasionally been reported. The authors present the case of a 28-year-old man with episodes of left-sided numbness and weakness associated with headache. He underwent cerebral angiography as part of his evaluation, after which he experienced an episode of right hemiplegia and aphasia. A subsequent magnetic resonance image (MRI) revealed two small new infarcts in the left parietal cortex. A diagnosis of HaNDL was made based mainly on clinical symptoms and CSF analysis. The symptoms resolved with conservative therapy. HaNDL is a benign condition that can present with symptoms similar to a TIA. Although HaNDL remains a diagnosis of exclusion, caution is required when considering cerebral angiography in the evaluation of patients with a HaNDL-like syndrome, because these patients seem prone to developing neurological symptoms after angiography.

The "over the core wire" technique for detachable coil retrieval

SUMMARY

We report four cases of malpositioned detachable coil retrieval. In all cases, the malpositioned coils were retrieved without additional neurological deficits. The stretched core wire was grasped with a fixed-loop snare (Gooseneck microsnare), and the detachable coil was retrieved using an over the core wire technique with a hydrophilic microcatheter.

Sphenoid pneumoceles cause episodic pressure-related blindness

Images

Japanese encephalitis

Japanese encephalitis (JE) is an acute encephalomyelitis which is a primary viral encephalitis accompanying a viral infection. Clinically, the patient who either resides in an endemic region or who has been exposed to the viral vector (mosquito) may have symptoms including high fever, headache, and impaired consciousness. JE involves many portions of the supratentorial and infratentorial compartments including the brain stem, hippocampus, thalamus, basal ganglia, and white matter. Classically MR imaging demonstrates the lesions of JE as hyperintense on T2-weighted images and hypointense on T1-weighted images. Hemorrhagic transformations have also been described in JE lesions, with corresponding expected T1 and T2 changes. Differential considerations based on the MRI appearance are somewhat broad, including but not limited to primary viral encephalitis, acute encephalopathy, limbic encephalitis, and acute disseminated encephalomyelitis. The therapy for JE is primarily conservative and supportive since there is no specific treatment for JE, and the disease has a high fatality rate. The prognosis depends on the extent of involvement at primary presentation, and on the autoimmune mechanisms of this disease.

Progressive facial hemiatrophy: abnormality of intracranial vasculature

Progressive facial hemiatrophy (PFH) or Parry-Romberg syndrome is associated with ipsilateral brain lesions and neurologic symptoms. We describe a 35-year-old man with PFH and frequent hemiplegic migraine. On cerebral angiography, reversible vessel caliber changes were seen within the symptomatic hemisphere. An abnormality of the intracranial vasculature may be present in some patients with PFH and neurologic manifestations.

Coexistence of occult vascular malformations and developmental venous anomalies in the central nervous system: MR evaluation

PURPOSE

We sought to determine the prevalence of coexistent occult vascular malformations (OVMs) and developmental venous anomalies (DVAs) and to investigate the relationship between them.

METHODS

One hundred two patients with OVMs were examined with precontrast and postcontrast T1-weighted MR imaging and with noncontrast T2-weighted MR imaging. Seventy-two patients had surgery, with subsequent pathologic confirmation of the final diagnosis.

RESULTS

Coexistent DVAs and OVMs were present in 23 (23%) of 102 patients. Seventy-nine patients had OVMs without DVAs, and in this population, multiple OVMs (from two to 10 or more) were seen in 13 patients (16%). In contrast, multiple OVMs were seen in 10 (43%) of 23 patients with coexisting OVMs and DVAs. Twenty-five (83%) of 30 OVMs coexisting with DVAs were infratentorial. In 72 patients with surgically resected OVMs, 49 (68%) had pathologically confirmed cavernous malformations. Among the patients with coexistent DVAs, seven (46%) had cavernous malformations, four (27%) had thrombosed arteriovenous malformations, and four (27%) had vascular malformations that were not classifiable.

CONCLUSION

Our study revealed a high prevalence of OVMs with coexistent DVAs, and a high percentage of these were in the posterior fossa. Contrast-enhanced MR imaging may increase the probability of finding these lesions, and therefore should be considered part of the preoperative evaluation, since the finding of unexpected coexistent lesions may affect surgical management.

Impaired cerebrovascular autoregulation after hypoxic-ischemic injury in extremely low-birth-weight neonates: detection with power and pulsed wave Doppler US

PURPOSE

To evaluate regional cerebral blood flow with power and pulsed wave Doppler ultrasound (US) in extremely low-birth-weight neonates with periventricular leukomalacia (PVL), germinal matrix hemorrhage (GMH), or both.

MATERIALS AND METHODS

The lenticulostriate arteries of 17 preterm neonates (birth weight < or = 1,100 g) were assessed daily with Doppler US during the first 5-6 days of life. The mean arterial pressure and bilateral peak velocity, resistive index, coronal vascular cross-sectional area, and product of the peak velocity and vascular cross-sectional area were measured.

RESULTS

Five neonates developed PVL, GMH, or both; results of follow-up examinations in 11 patients were normal. One neonate with severe intrauterine growth retardation and renal tubular acidosis was excluded. Neonates with PVL, GMH, or both showed significantly greater mean values and more variable values of vascular cross-sectional area and product of peak velocity and cross-sectional area than neonates without PVL or GMH (P < .025). Mean resistive index was significantly lower in neonates with PVL, GMH, or both than in neonates without (P < .01). There were no significant differences between mean arterial pressure in neonates with and those without PVL, GMH, or both.

CONCLUSION

By enabling the detection of autoregulatory fluctuations in cerebral blood flow associated with hypoxic-ischemic injury, power and pulsed wave Doppler US may enable identification of preterm neonates who are at risk of developing PVL, GMH, or both during the 1st week of life.

Diffusion-weighted MRI in transient global amnesia precipitated by cerebral angiography

BACKGROUND

Transient global amnesia is a well-described complication of cerebral angiography. Speculation about the pathophysiology exists but is as yet unsubstantiated. Diffusion-weighted MRI is a new imaging technique that is very sensitive in detecting acute ischemia. Its use in the evaluation of transient amnesia precipitated by cerebral angiography has not previously been reported.

CASE DESCRIPTION

A 44-year-old man underwent posterior circulation cerebral angiography for the investigation of episodic vertigo. Shortly after completion of the procedure, he was noted to have symptoms of transient global amnesia. Diffusion-weighted MRI at 6 and 44 hours after the procedure demonstrated increased signal in the right hippocampus and other areas within the posterior circulation bilaterally consistent with ischemia from emboli. Abnormalities on conventional MRI images performed at the same time points were noted only in retrospect. A follow-up MRI at 2 months was normal.

CONCLUSIONS

Ischemia from cerebral emboli may cause transient global amnesia precipitated by cerebral angiography. Diffusion-weighted MRI may be useful in defining the pathophysiology.

Intracavernous anterior cerebral artery origin with associated arteriovenous malformations: a developmental analysis: case report

OBJECTIVE AND IMPORTANCE

This case demonstrates an unusual association between arteriovenous malformations and an intracavernous anterior cerebral artery origin. To the best of our knowledge, this relationship has not been previously described. Identification and understanding of this relationship are important in pre-embolization and surgical planning and in offering some insight into neurovascular development.

CLINICAL PRESENTATION

The patient presented with severe recurring headaches and an otherwise nonfocal neurological examination. He maintained a stable neurological course throughout evaluation and therapy.

INTERVENTION

The patient underwent endovascular embolization of the arteriovenous malformations without consequence. He was then scheduled for radiosurgical treatment planning.

CONCLUSION

This case demonstrates an unusual neurovascular anomaly with associated arteriovenous malformations. To the best of our knowledge, this is the first reported case of such an association. An understanding of anomalous angioarchitecture and neurovascular development is essential for prudent endov ascular and surgical planning.

Virtual endoscopy of the paranasal sinuses using perspective volume rendered helical sinus computed tomography

Our goal was to use three-dimensional information obtained from helical computed tomographic (CT) data to explore and evaluate the nasal cavity, nasopharynx, and paranasal sinuses by simulated virtual endoscopy (VE). This was done by utilizing a new image reconstruction method known as perspective volume rendering (PVR). Thin-section helical CT of the nasal cavity, nasopharynx, and paranasal sinuses was performed on a conventional CT scanner. The data were transferred to a workstation to create views similar to those seen with endoscopy. Additional views not normally accessible by conventional endoscopy were generated. Key perspectives were selected, and a video "flight" model was choreographed and synthesized through the nasal cavity and sinuses based on the CT data. VE allows evaluation of the nasal cavity, nasopharynx, and paranasal sinuses with appreciation of the relationships of these spatially complex structures. In addition, this technique allows structural visualization with unconventional angles, perspectives, and locations not conventionally accessible. Although biopsies, cultures, and lavages routinely done with endoscopy cannot be performed with VE, this technique holds promise for improving the diagnostic evaluation of the nasal cavity, the nasopharynx, and the paranasal sinuses. The unconventional visual perspectives and very low morbidity may complement many applications of simple diagnostic endoscopy.

Perspective volume rendering of CT and MR images: applications for endoscopic imaging

PURPOSE

To use perspective volume rendering (PVR) of computed tomographic (CT) and magnetic resonance (MR) imaging data sets to simulate endoscopic views of human organ systems.

MATERIALS AND METHODS

Perspective views of helical CT and MR images were reconstructed from the data, and tissues were classified by assigning color and opacity based on their CT attenuation or MR signal intensity. "Flight paths" were constructed through anatomic regions by defining key views along a spline path. Twelve movies of the thoracic aorta (n=3), tracheobronchial tree (n=4), colon (n=3), paranasal sinuses (n=1), and shoulder joint (n=1) were generated to display images along the flight path. All abnormal results were confirmed at surgery.

RESULTS

PVR fly-through enabled evaluation of the full range of tissue densities, signal intensities, and their three-dimensional spatial relationships.

CONCLUSION

PVR is a novel way to present volumetric data and may enable noninvasive diagnostic endoscopy and provide an alternate method to analyze volumetric imaging data for primary diagnosis.

Vertebral artery stenting following percutaneous transluminal angioplasty. Technical note

The authors report initial results and follow up using stent placement to treat atherosclerotic stenosis in vertebral arteries. Three patients with severe atherosclerotic vascular disease underwent vertebral artery stent placement using a balloon expandable stent. Medical therapy (aspirin and warfarin) and conventional percutaneous angioplasty failed to resolve the disease and the patients developed symptomatic restenosis within 3 months of angioplasty. Two patients had symptoms of anterior circulation ischemia with carotid artery occlusions and reduced supply to the anterior circulation from the stenosed vertebral arteries. One patient had recurrent posterior circulation symptoms. Stents were successfully placed in all three, resulting in immediate reversal of stenosis and resolution of symptoms. Clinical follow-up study (mean 9 months) has shown no recurrent symptoms in the patient with posterior circulation symptoms, but the two patients with anterior circulation ischemia did develop recurrent symptoms. Angiographic follow up in these two patients at 3 months and 1 year, however, demonstrated continued patency of vertebral artery lumina. They underwent extracranial-intracranial bypass surgery to relieve their symptoms. This experience suggests stents can be placed without complication in the proximal vertebral arteries and may have an adjunctive role in the treatment of atherosclerotic cerebrovascular disease following unsuccessful angioplasty.

Neonatal intracranial ischemia and hemorrhage: diagnosis with US, CT, and MR imaging

PURPOSE

To assess the usefulness of ultrasound (US), computed tomography (CT), and magnetic resonance (MR) imaging in the detection of intracranial hemorrhage and ischemia in newborns.

MATERIALS AND METHODS

Seventy-six neonates who underwent US within 72 hours of CT or MR examination were studied. Four observers rated images for the presence of germinal matrix hemorrhage (GMH), intraventricular hemorrhage (IPH), extraaxial hemorrhage, and hypoxic-ischemic encephalopathy.

RESULTS

In 39% of neonates, CT and MR imaging provided greater confidence than US for the diagnosis or exlusion of neonatal ischemia or hemorrhage. Kappa analysis revealed significantly better interobserver agreement with CT than with US for the detection of GMH, IVH, IPH, and cortical infarction or ischemia (P <.005). Interobserver agreement was significantly better with MR imaging than with US for the detection of GMH, IVH, and cortical infarction or ischemia (P < .005).

CONCLUSION

Sensitivity and interobserver agreement are better with MR imaging and CT than with US for the detection of neonatal cortical ischemia or infarction.

Characterization of postoperative edema following laser-assisted uvulopalatoplasty using MRI and polysomnography: implications for the outpatient treatment of obstructive sleep apnea syndrome

Laser-assisted uvulopalatoplasty (LAUP) has been introduced as an alternative to uvuloplatopharyngoplasty for the treatment of snoring. Despite limited study, the use of this procedure has been expanded to include patients with obstructive sleep apnea syndrome. Although the potential cost-savings of performing sleep apnea surgery on an outpatient basis are self-evident, concern exists regarding the safety of this practice. In an effort to characterize the risk of performing LAUP on an outpatient basis, eight patients with mild or no sleep apnea were identified and intensively studied before and after the first stage of LAUP to cure snoring. Assessment included preoperative magnetic resonance imaging (MRI) scans, polysomnography, and videoendoscopy. Each of these diagnostic studies was then repeated between 48 and 72 hours after LAUP. Complete polysomnographic data were available for seven of the eight patients. The mean ( +/- SD) preoperative respiratory disturbance index (RDI) was 11.3 +/- 10.9, and the mean oxygen saturation nadir (LSAT) was 87.7 +/- 6.2% (n = 7). The mean airway cross-sectional area at the palate (by MRI) was 49.8 +/- 22.8 mm2 (n = 8). After LAUP, the mean RDI nearly doubled to 21.7 +/- 9.9 (P > .1). The apnea index increased fourfold from 3.3 +/- 3.5 to 14.8 +/- 10.9 (P < .03). The mean LSAT remained stable at 87.4 +/- 4.1% (P > .5). The cross-sectional area of the airway decreased to a mean of 47.9 +/- 22.4 mm2 (P > .5). These data suggest that LAUP may temporarily worsen obstructive sleep apnea. Although the clinical significance of this degree of worsening is uncertain, it would be prudent to consider perioperative use of nasal continuous positive airway pressure in patients with more than mild obstructive sleep apnea who undergo ambulatory LAUP.

Techniques for reducing interventional neuroradiologic skin dose: tube position rotation and supplemental beam filtration

PURPOSE

To limit the side effects of interventional neuroradiologic radiation, such as epilation, by applying a technique involving tube position rotation and by adding a supplemental inexpensive primary beam filter; and to show the dose effect of modifying technical factors.

METHODS

Combined skin dose from fluoroscopy and digital subtraction angiography was measured with an array of 16 thermoluminescent dosimeters during interventional neuroradiologic procedures in 12 control subjects, in 18 patients whose procedures included addition of an inexpensive primary beam filter (0.5 mm aluminum/0.076 mm copper), and in 10 patients in whom the tube position was rotated, additional primary beam filtration was used, and close attention was paid to technique.

RESULTS

Maximum thermoluminescent dosimetric measurements obtained with existing machine filtration ranged from 0.31 to 2.70 Gy in the control group (mean, 1.51 +/- 0.88); 0.25 to 2.42 Gy in the group with additional filtration alone (mean 0.96 + 0.64; average dose reduction, 36%); and 0.13 to 1.23 Gy in the group with additional filtration, tube position rotation, and close attention to technique (mean, 0.58 +/- 0.34; average dose reduction, 63%). Differences were statistically significant.

CONCLUSIONS

Greater than 50% skin dose reductions were documented during interventional neuroradiologic procedures by combining tube position rotation, supplemental primary beam filtration, and technical modifications.

Correction of scaphocephaly secondary to ventricular shunting procedures

Craniosynostosis following ventricular shunting procedures for hydrocephalus has become a recognized complication of shunting procedures. Secondary synostosis results from a decrease in intracranial volume leading to collapse of the cranial vault. Since this represents a distinct etiopathogenesis different from that typically involved, the surgical approach should be altered. Eight patients with secondary scaphocephaly underwent surgical reconstruction. The clinical data and radiographic studies were reviewed for these patients. The surgical approach consisted of sagittal or parasagittal strip craniectomies, lateral osteotomies with bone-flap expansion, occipital and frontal remodeling as needed, and the application of rigid fixation to maintain contour and prevent recurrent collapse of the cranial vault. Patient follow-up ranged from 3 to 37 months. Five of these patients were premature infants, an association not previously recognized in the literature. Satisfactory results were obtained in all patients. Keeping the craniectomy sites parent and achieving a more normal cranial contour through cranial remodeling have provided good results in this population.

Correlation of pressure measurements with angiographic characteristics predisposing to hemorrhage and steal in cerebral arteriovenous malformations

PURPOSE

To determine whether there is a physiologic explanation for the predisposition of patients with certain angiographic characteristics to symptoms of hemorrhage and steal.

METHODS

Superselective transcatheter feeding arterial pressure and mean arterial pressure measurements were obtained before embolotherapy in 32 patients with cerebral arteriovenous malformations. Pressures were correlated with previously described angioarchitectural characteristics predisposing to hemorrhage and steal. These included size of the arteriovenous malformation, feeding artery length, venous drainage pattern, and angiomatous change.

RESULTS

The feeding arterial pressure and feeding arterial pressure/mean arterial pressure ratios were significantly decreased in patients with angiomatous change. Feeding arterial pressure and feeding arterial pressure/mean arterial pressure ratios progressively decreased as lesions went from peripheral, to mixed, to central venous drainage. A trend for lower feeding arterial pressure was also demonstrated with greater feeding pedicle length. A statistically significant correlation could not be demonstrated between feeding arterial pressure or feeding arterial pressure/mean arterial pressure ratios and size of the arteriovenous malformation, hemorrhage, or symptoms of steal.

CONCLUSIONS

Feeding arterial pressure measurements help provide a physiologic basis for the relationship between certain angiographic characteristics and hemorrhage and steal symptoms in patients with arteriovenous malformation.

Stent placement for arterial and venous cerebrovascular disease: preliminary experience

PURPOSE

To report initial clinical experience with stent placement in the cerebrovascular circulation.

MATERIALS AND METHODS

Four patients underwent arterial or venous stent placement. Two patients had cervical internal carotid artery dissections, with aneurysms and stenoses of the distal cervical carotid artery. Two patients had venous occlusive disease involving the major dural sinuses, with substantial pressure gradients across the stenoses.

RESULTS

Immediately after stent placement, the true arterial lumina returned to normal diameter and both carotid aneurysms were more than 90% occluded. Follow-up angiography demonstrated continued improvement in the arterial aneurysms. Both patients with dural sinus venous occlusive disease showed substantial improvement of the sinus stenoses and substantial reversal of the pressure gradients after venous stent placement. At follow-up, these patients have done well.

CONCLUSION

This preliminary experience suggests there may be a role for stents in the management of arterial and venous cerebrovascular disease, including carotid artery dissection and venous occlusive disease.

Magnetic resonance imaging and measurement of blood flow

Blood flow can be shown as a negative image with magnetic resonance spin-echo techniques or as a positive image with gradient-echo techniques. Phase contrast refers to techniques where structures can be seen because of flow-induced phase shifts. These techniques can show the presence (slow flow) and also the direction of flow. Gradient-echo techniques--including phase-contrast versions--can be used with cardiac synchronization to obtain multiple images during the cardiac cycle. These images can be viewed in a movie or cine format to provide dynamic information about blood flow. Blood flow can be measured by using contrast media in boluses or even more elegantly with phase-contrast methods. Clinical applications of flow measurements are growing rapidly. Phase-contrast or gradient-echo techniques can be used to create magnetic resonance angiography, which was first used to study the carotid bifurcation and intracranial circulation and is now being used throughout the body.

Shunt flow measurement and evaluation of valve oscillation with a spin-echo phase-contrast MR sequence

PURPOSE

To present a spin-echo phase-contrast (SEPC) magnetic resonance pulse sequence designed to measure the very slow flow in ventricular shunt tubing.

MATERIALS AND METHODS

A flow phantom constructed of shunt tubing and incorporating no valve or a high-, medium-, or low-pressure valve was connected to a flow pump. Flow rates were 0.05-1.00 mL/min (72-1,440 mL/d). Flow measurement was performed with the thin-section SEPC sequence.

RESULTS

The flow rates measured with SEPC imaging correlated closely with the pump flow rate for the entire physiologic spectrum of shunt flow rates. This was true for all valves, resulting in overall R2s of .974 at 4 cm/sec and .980 at 2 cm/sec. Shunt flow was pulsatile with valves in place. There was a linear relationship between flow rate and the frequency of valve opening and closing.

CONCLUSION

The SEPC technique is an accurate and noninvasive method of measuring shunt flow.

Intracerebral lesion contrast with spin-echo and fast spin-echo pulse sequences

Fast spin-echo (FSE) magnetic resonance (MR) imaging was compared with conventional, peripherally gated T2-weighted spin-echo (SE) imaging in the detection of high- and low-signal-intensity lesions in the central nervous system. Lesion detectability was determined with percentage of contrast measurements and contrast-to-noise ratios with two different measurements for noise. All three measures of lesion detectability were similar. FSE and SE sequences were quantitatively equivalent in the detection of high-signal-intensity lesions. The SE sequence, however, was superior to the FSE sequence in the detection of small, low-signal-intensity lesions in the central nervous system caused by magnetic susceptibility effects.