Determination of Blood Flow Velocity and Transit Time in Cerebral Arteriovenous Malformation using Microdroplet Angiography A. A. DIVANI, 1 B. B. LIEBER, 1,2 A. K. WAKHLOO, 3 M. J. GOUNIS, 1 and L. N. HOPKINS 2 1 Department of Mechanical and Aerospace Engineering, State University of New York at Buffalo, Buffalo, NY, 2 Department of Neurosurgery, State University of New York at Buffalo, Buffalo, NY, and 3 Department of Radiology and Neurological Surgery, University of Miami School of Medicine, Miami, FL (Received 1 May 2000; accepted 1 December 2000) Abstract—Advancement in imaging and biomedical technol- ogy has improved the use of catheter-based transarterial embo- lization occlusive therapy of cerebral arteriovenous malforma- tions AVMs. Among a variety of embolic agents, liquid adhesives acrylates have proven to be more successful in permanent obliteration of AVMs. The use of liquid adhesives requires the experience and skill of the operator. However, acquiring accurate information on blood flow and transit times through the AVM prior to embolization can optimize the treat- ment. In addition, knowledge of the polymerization time and behavior of the acrylate enables a complete and safe occlusion of the arteriovenous transition within the AVM nidus. Standard commercially available iodine-based contrast agents seem to be insufficient to determine AVM transit times from angiograms. For a more accurate assessment of AVM transit times, the use of a nonsoluble contrast agent Ethiodol and a high-speed digital subtraction angiography DSA is suggested. Small amounts 20 l of Ethiodol were infused to create micro- droplets and traced using DSA at 15 fps. Transit time, defined as the time interval required for a droplet to reach the venous part of the AVM after being flushed from the tip of the cath- eter, could be accurately calculated. Postprocessing was used to calculate trajectories and velocities of microdroplets. © 2001 Biomedical Engineering Society. DOI: 10.1114/1.1349696 Keywords—Arteriovenous malformation, Angiography, Embo- lization, Microdroplets, Ethiodol. BACKGROUND Arteriovenous malformations AVMs are uncommon congenital vascular lesions that may arise at an early fetal stage. An AVM is a direct arteriovenous shunt without an intervening capillary bed. 1 Though such shunts can occur throughout the entire body, AVMs have a higher incidence in the cerebral circulation and receive more attention due to their impact on brain function. It is believed that the prevalence of cerebrovascular arterio- venous malformations is between 0.8% and 1.4% in the population. 2,17 In an AVM, blood bypasses normal brain tissue and flows directly into the vein and back to the heart. The morphology of an AVM is highly variable. It can be composed of one feeding artery and one draining vein, or have multiple of each. The connection between the artery and the vein A–V can be direct fistulous or through an interposed vascular network plexiform. Current treatments for AVMs include microsurgery, radiosurgery, embolization, or a combination thereof. 8 The goal is to obtain a complete obliteration of the AVM while avoiding the risk of hemorrhage or stroke. Com- plete excision of an AVM prevents subsequent hemor- rhage. However, the size of the AVM, its location, and the medical condition of the patient are limiting factors in choosing surgery as treatment. Surgical resection of some lesions can be associated with a totally disabling deficit or death. 31 Radiosurgery refers to the use of stereotactically fo- cused beams to deliver a large single dose of radiation to an intracranial target. Radiosurgery is gaining popularity in treatment of AVMs. It has shown to obliterate AVMs by creating smooth muscle cell proliferation and finally exclusion of the diseased vascular structure from the circulation. A complete obliteration is usually obtained within 2–3 years after the treatment. During this period, however, patients are unprotected against hemorrhage, which is considered a major drawback for this treatment. 6 Radiosurgery appears to be more effective for small and medium size AVMs and for low and medium- flow plexiform AVMs. 6 The third option currently available is endovascular embolization occlusion of the AVM. After the first published report of an embolization in 1960 by Luessen- hop and Spence, 16 various embolic agents have been used such as silicon spheres, detachable silicon balloons, coils, surgical silk, ethanol, polyvinyl alcohol particles, ethylene vinyl alcohol copolymer mixtures, and alkyl- cyanoacrylate IBCA and NBCA. 3,5,9,18,23,24,34 Emboliza- tion is either a curative procedure or an adjunct to ra- diosurgery or microsurgery to achieve a size reduction. 3,13 Gruber et al. 14 reported a 15% and Address correspondence to B. Barry Lieber, State University of New York at Buffalo, Center for Biomedical Engineering, 337 Jarvis Hall, Buffalo, NY 14260. Electronic mail: lieber@eng.buffalo.edu Annals of Biomedical Engineering, Vol. 29, pp. 135–144, 2001 0090-6964/2001/292/135/10/$15.00 Printed in the USA. All rights reserved. Copyright © 2001 Biomedical Engineering Society 135