Videographic Assessment of the Embolic Characteristics of Three Polymeric Compounds: Ethylene Vinyl Alcohol, Cellulose Acetate, and Liquid Urethane
Alexander M. Norbash
,a and
Robert J. Singera
a From the Division of Interventional Neuroradiology, Brigham and Women's Hospital (A.M.N.), and the Division of Vascular Neurosurgery, Massachusetts General Hospital (R.J.S.), Harvard University, Boston, MA.
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FIG 1. An example of neck-up aneurysm positioning with flow arrest. The polymer, 8% VIN, enters as a continuous, gravitationally dependent layer that fills the aneurysm. This example highlights the significance of placing the aneurysm in a gravitationally dependent position for embolization when instilling heavier-than-blood polymers.FIG 2. A and B, After there is adequate aneurysm filling with polymer (A), gentle suction is applied to the introducing catheter to detach it from the polymer (B). Optimally, there is uncomplicated catheter retrieval without significant detachment tail formation or polymer mass retraction/displacement. In this example, a small residual aneurysm remains (arrow), and there is parent vessel luminal encroachment with partial pullout of the polymer mass during detachment.
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FIG 3. An example of an unfavorable, large outflow tail (arrow), which can potentially serve as a thrombotic nidus.FIG 4. An example of a small detachment tail (arrow), defined as a tail extending into the parent vessel for a distance less than half the aneurysm-neck diameter.FIG 5. An extreme case of catheter-polymer adhesion, showing displacement of the polymer mass into the parent vessel when catheter detachment is attempted. In this example, the entire parent-vessel transverse diameter has been blocked by the pullout embolic mass, with as yet unsuccessful detachment.FIG 6. An example of polymer solution instillation in a nondependent aneurysm performed with complete flow arrest, showing rapid and gravitationally dependent outpouring of the embolic solution. The solution is pouring into the more gravitationally dependent parent vessel. In a terminal aneurysm model, such as the easily pictured basilar tip model, the unfavorable consequences can be readily appreciated
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FIG 7. Distinct layering of the gravity-dependent DMSO (arrow). DMSO diffuses through biologic tissues at uncertain rates; layering is clearly seen in this aneurysm model, which is impermeable to DMSO, that may not be seen in biologic systems.FIG 8. A continuous embolic string, seen in only one case with an 8% UCO solution. The leading point of the embolic string was unfortunately carried out of the aneurysm by the outflow zone, although clear string compaction occurred even during the early phase of the string mass coiling.FIG 9. An unfavorable observation made with the UCO mixtures was a "smoky" fragment layer of polymer particles at the interface between the polymer mass and the parent-vessel fluid. These particles may ultimately embolize distally, with unknown fluid embolic complications.
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