Optical diagnostics of mercury jet for an intense proton target.

An optical diagnostic system is designed and constructed for imaging a free mercury jet interacting with a high intensity proton beam in a pulsed high-field solenoid magnet. The optical imaging system employs a backilluminated, laser shadow photography technique. Object illumination and image capture are transmitted through radiation-hard multimode optical fibers and flexible coherent imaging fibers. A retroreflected illumination design allows the entire passive imaging system to fit inside the bore of the solenoid magnet. A sequence of synchronized short laser light pulses are used to freeze the transient events, and the images are recorded by several high speed charge coupled devices. Quantitative and qualitative data analysis using image processing based on probability approach is described. The characteristics of free mercury jet as a high power target for beam-jet interaction at various levels of the magnetic induction field is reported in this paper.

Contrast-enhanced 3D MR DSA of the carotid artery bifurcation: preliminary study of comparison with unenhanced 2D and 3D time-of-flight MR angiography.

PURPOSE: To compare the delineation of stenosis at the carotid artery bifurcation on three-dimensional (3D) magnetic resonance (MR) digital subtraction angiographic (DSA) images with that on two-dimensional (2D) and 3D time-of-flight (TOF) MR angiographic images. MATERIALS AND METHODS: Twenty-six patients with 29 carotid artery bifurcations and symptoms of cerebral ischemia underwent 3D MR DSA. A time-resolved series was generated with 3D MR DSA after the bolus injection of gadodiamide. The resolution for a carotid artery examination was 0.4 x 0.4 x 1.0 mm, with volumes reconstructed at 4.5-second intervals. The 3D MR DSA images were compared with contemporaneously acquired unenhanced 2D and 3D TOF images. Two observers ranked the 2D and 3D TOF MR angiographic and 3D MR DSA images according to the following: (a) stenosis delineation, (b) internal carotid artery delineation, (c) intravascular signal intensity, and (d) diagnostic confidence. RESULTS: The mean ranking for diagnostic confidence was 1.10 (1 = best technique, 3 = worst technique) for 3D MR DSA. Compared with the pooled 2D TOF and 3D TOF ranks, the 3D MR DSA rank was significantly better (P < .01). Similar levels of statistical significance were found for the other criteria. CONCLUSION: Three-dimensional MR DSA improves the delineation of carotid arterial stenosis by virtually eliminating saturation effects and reducing intravoxel dephasing. Surface morphology and nearly occluded vessels ("string sign") were easily identified. Confidence in identifying carotid arterial occlusions was also very high with this technique.

Advancing loop technique for endovascular access to the anterior cerebral artery.

Direct endovascular access to the anterior cerebral artery (ACA) with a guidewire and catheter is not always possible. A C-shaped guidewire advanced as a loop into the middle cerebral artery and then withdrawn to advance the guidewire into the ACA is a way to gain endovascular access to the ACA when the direct approach is unsuccessful.

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.

Collagen-coated acrylic microspheres for embolotherapy: in vivo and in vitro characteristics.

PURPOSE: To evaluate the in vivo and in vitro properties of collagen-coated acrylic microspheres and to compare them with polyvinyl alcohol (PVA) particles. METHODS: Samples of 100- to 300-microns, 300- to 500-microns, 500- to 700-microns, and 700- to 900-microns collagen-coated acrylic microspheres and 200- to 300-microns PVA particles were suspended in solutions of 50% saline and 50% contrast material. The samples were evaluated for quantitative and qualitative microscopic characteristics (shape, size, deformability); injectability via standardized microcatheters; degree of particulate penetration in the pig rete mirabile; and reaction of tissue to the particles in 48-hour- and 4-week-old specimens. RESULTS: The acrylic microspheres were spherical and deformable. The sample of 100- to 300-microns microspheres (n = 202) had a mean diameter of 210 microns (standard deviation, 43 microns). Hub accumulation, particle aggregation, and catheter occlusion were not observed with the microspheres (all sizes) but were noted with the PVA particles. The 200- to 300-microns PVA particles formed aggregates in the proximal rete. The 100- to 300-microns microspheres were found throughout the rete and beyond. Chronic transmural and perivascular inflammation was observed with the microspheres and the PVA particles. CONCLUSIONS: Particle aggregation and catheter occlusion do not complicate the transcatheter delivery of collagen-coated acrylic microspheres as they do with PVA particles. For a given particle and vessel size, acrylic microspheres penetrate to a much greater extent than the PVA particles. Tissue reaction to acrylic microspheres and PVA particles is similar.

MR angiography of saccular aneurysms after treatment with Guglielmi detachable coils: preliminary experience.

PURPOSE: To review our experience using MR angiography to assess the cerebral vasculature after aneurysmal treatment with Guglielmi detachable coils (GDCs). METHODS: Forty three-dimensional time-of-flight MR angiographic studies were performed in 23 patients after endovascular aneurysmal therapy with GDCs. Digital subtraction angiographic (DSA) studies were evaluated retrospectively for the following findings: parent artery patency, branch vessel patency, residual flow within the aneurysm, and residual aneurysmal neck. The MR angiographic examinations were inspected for the same findings, as well as for the degree of signal loss surrounding the coil mass. Clinical histories were reviewed to determine the impact of MR angiographic findings on therapy. RESULTS: Patency status of the parent artery was correctly identified on 25 of 26 MR angiographic examinations with DSA confirmation. Thirty-four of 37 patent branch vessels were identified by MR angiography. Residual neck was correctly identified in seven studies of six aneurysms, with no false-negative or false-positive results. Intraaneurysmal flow was correctly identified in five of eight studies of six aneurysms with residual flow shown by DSA. Artifact and hemorrhage mimicked residual flow in two of 18 MR angiographic studies of aneurysms with no residual flow shown by DSA. In eight patients, MR angiography provided clinically useful information that affected therapy. CONCLUSIONS: MR angiography can identify flow within an aneurysm after treatment with GDCs as well as in the adjacent parent and branch vessels. This technique may be a useful adjunct to DSA in some clinical situations.

The effect of flow arrest on distal embolic events during arterial occlusion with detachable coils: a canine study.

PURPOSE: To determine the effect of proximal flow arrest on the frequency and timing of distal embolic events during occlusion of the common femoral artery with detachable coils. METHODS: Twenty-three complex fibered platinum coils were delivered into 10 common femoral arteries without proximal flow arrest. The arteries were continuously monitored for flow and embolic events by Doppler sonography during delivery and for at least 10 minutes after delivery of each coil. Thirty-four coils were delivered into 6 arteries after proximal flow arrest by inflation of a nondetachable balloon. After balloon deflation, each artery was monitored by Doppler sonography for 10 minutes. RESULTS: In the 10 arteries occluded without flow arrest, 87 events (8.7 per artery) occurred, of which 47 were embolic and 40 were indeterminate. In the 6 arteries with flow arrest, the number of emboli detected was 3 (0.5 per artery). Embolic events occurred only if there was residual flow. In those arteries that were occluded when the flow-arrest balloon was deflated, no emboli were detected. CONCLUSIONS: Proximal flow arrest virtually eliminates the risk of distal emboli during arterial occlusion with detachable fibered coils. The use of fibered coils, in conjunction with proximal flow arrest, allows for safe arterial occlusion when detachable balloons are not available or their use is not feasible.

Vertebrobasilar junction aneurysms associated with fenestration: treatment with Guglielmi detachable coils.

Three patients with vertebrobasilar junction aneurysms and associated fenestration were treated with Guglielmi detachable coils. The structure and hemodynamics of fenestrations may account for their frequent association with aneurysms. The complex hemodynamics of these aneurysms requires evaluation of both vertebral arteries. One treatment complication occurred but resulted in no deficit. All patients have returned to normal activity and remain healthy at 14 to 46 months.

Early treatment of ruptured aneurysms with Guglielmi detachable coils: effect on subsequent bleeding.

The major causes of mortality and morbidity in patients surviving the rupture of a saccular aneurysm are subsequent bleeding and vasospasm. The purpose of this study was to evaluate the influence of early treatment of ruptured aneurysms with Guglielmi detachable coils on the incidence of subsequent bleeding. Thirteen patients were treated within 72 hours of initial aneurysm rupture with Guglielmi detachable coils. Excluding three patients who died 2, 4, and 12 weeks after initial hemorrhage, all others have been followed up for intervals between 6 and 36 months (mean, 16 mo). None of these have had either clinical or radiographic evidence of subsequent bleeding. Assuming that there is a 30% incidence of subsequent bleeding in conservatively (nonsurgically) treated patients, the 0% subsequent bleed rate observed in this subgroup was significant at a P value of 0.01. Only one procedure-related complication occurred in this series, and 9 of 13 (69%) aneurysms were 100% occluded at the time of initial treatment. All aneurysms were at least 90% occluded at the end of initial treatment. In addition to reducing the risk of subsequent bleeding, early treatment facilitated the institution of an aggressive approach for management of both vasospasm and increased intracranial pressure. Patient outcome, as measured by the Glasgow Outcome Scale, was good in 9 of 13 (69%), poor in 1 of 13 (8%), and death in 3 of 13 (23%) patients. The results of this study suggest that early Guglielmi detachable coil treatment of ruptured aneurysms may be effective in reducing the incidence of subsequent bleeding and can be performed with a low incidence of complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of experimental canine carotid aneurysms with platinum coils.

PURPOSE: To evaluate and compare the deliverability, positioning, stability, and effectiveness of aneurysm occlusion and the incidence of parent-artery thrombosis of two different types of platinum coils, using a canine carotid aneurysm model. METHODS: 29 experimental canine carotid aneurysms (19 lateral, 6 bifurcation, and 4 terminal) were constructed and treated with complex-shaped fibered platinum coils and simple curved nonfibered platinum Guglielmi detachable coils (GDCs). RESULTS: Fibered complex coils were stable, producing 38% complete aneurysm occlusion and 61% average reduction in aneurysm lumen size but resulting in 19% parent artery occlusions. GDC coils were stable, producing 31% complete aneurysm occlusion and 95% average reduction in aneurysm lumen size with no parent-artery occlusions. CONCLUSIONS: GDC coils produced an average reduction in aneurysm lumen size of 95% without any associated parent-artery occlusions. There were no delayed migrations of GDC coils. The ability to remove, reposition, and detach a coil was the most significant feature of the GDC coil.

Platinum coil coatings to increase thrombogenicity: a preliminary study in rabbits.

The authors investigate a modification of the Gugliemi detachable coil. They have developed a rabbit model and coating technique to test differences in thrombogenicity of platinum coils with a variety of polyurethanes.

Canine model of terminal arterial aneurysm.

A canine model of terminal aneurysms using a venous pouch surgical technique is described. This model mimics the anatomy and hemodynamics of some types of carotid and basilar tip aneurysms. This technique produces aneurysms 15 x 21 mm in size. The aneurysms have been used to investigate the hemodynamics and treatment of terminal aneurysms.

An endovascular retrieving device for use in small vessels.

A new retrieval device for use in small vessels was evaluated in a canine model. Retrieval was attempted on 25 coils, three silicone balloons, and five catheter and guide wire fragments placed in the renal, pulmonary, hepatic, brachiocephalic, subclavian, carotid, and maxillary arteries. This was successful in 91% (30/33). The snare could also be selectively placed in the vertebral and proximal basilar arteries.

Microcatheter retrieval device for intravascular foreign body removal.

A microcatheter foreign body retrieval device is described and its first two clinical applications are presented. The device functions identically to larger loop snare retrievers. It permits access to small vessels and was successful in its first clinical applications.

Anomalous origin of the posterior inferior cerebellar artery from the internal carotid artery.

A rare anomalous origin of the posterior inferior cerebellar artery arising from the internal carotid artery is described. The embryologic explanation postulated is the persistence of a primitive communicating vessel (presegmental artery) between the anterior and posterior circulation.

Aneurysm hemodynamics: an experimental study.

PURPOSE: To study the flow of blood in aneurysms. METHODS: A canine model was used to study the hemodynamics of lateral, bifurcation, and terminal aneurysms with angiography and color Doppler techniques. FINDINGS: Flow within experimental aneurysms, although not laminar, is seldom if ever turbulent, but rather is highly predictable, varying primarily according to the relationship of the aneurysm to its parent artery. CONCLUSIONS: These studies support earlier in vitro work and provide further evidence that not all aneurysms share similar stresses. A more complete understanding of these hemodynamic features will be useful in the establishment of criteria that allow recognition of those aneurysms that are more or less likely to rupture, to grow, or to thrombose.

Flow dynamics of lateral carotid artery aneurysms and their effects on coils and balloons: an experimental study in dogs.

PURPOSE: To investigate the hemodynamic characteristics of lateral carotid artery aneurysms in a canine model and to determine their influence on coils and balloons. MATERIALS AND METHODS: Forty aneurysms were created in fourteen dogs and their hemodynamic characteristics and influence on coils and balloons were evaluated with angiography and color Doppler pre- and postplacement. Twenty aneurysms were treated with coils, eight with balloons, and 12 aneurysms served as controls. RESULTS: The aneurysms demonstrated three distinct zones of flow: 1) an inflow zone entering at the distal aspect of the aneurysm ostium, 2) an outflow zone exiting at the proximal ostium, and 3) a central slow flow vortex. The inflow zone is a determining factor in the placement and stability of coils and balloons placed within the aneurysm and in the thrombosis of an aneurysm. The force of the inflow is considerable and can alter the shape of coils and displace both coils and balloons positioned within the aneurysm. CONCLUSIONS: Coils and balloons need to be of shapes and sizes that do not conform to the inflow and outflow zones. Filling the aneurysm and blocking or displacing the inflow zone can produce thrombosis of an aneurysm with preservation of the parent artery.

Delayed visual loss due to trauma of the internal carotid artery.

The group of six patients in this study experienced delayed visual loss following head trauma. Visual loss occurred from 1 day to 13 years after the initial injury. All patients suffered indirect trauma to the internal carotid artery resulting in formation of either an aneurysm or pseudoaneurysm or a carotid-cavernous fistula. Review of the radiologic and clinical findings was performed in six patients. The diagnosis was established by computed tomography, magnetic resonance imaging, and angiography. All patients had follow-up clinical evaluation and imaging studies. Treatment by neurosurgical or interventional neuroradiologic procedures resulted in significant visual improvement in five patients. Different pathophysiologic mechanisms could be correlated with the delayed visual loss produced by the two types of lesions. The pathologic changes associated with the aneurysms/pseudoaneurysms included direct compression of optic nerves and/or chiasm and intracranial hematoma. A carotid-cavernous fistula caused delayed visual loss by either hematoma at the orbital apex or compression of the chiasm and/or optic nerves by saccular dilatation of the cavernous sinus. The delayed onset of decreased vision following head trauma should alert the physician to the possibility of a traumatic aneurysm/pseudoaneurysm or a carotid-cavernous fistula. Different neuro-ophthalmologic symptoms can usually be correlated with the pathologic changes demonstrated by neuroimaging procedures.