phosphorus-radioisotopes and Carotid-Artery-Diseases

Recanalization after coil embolization can be prevented by radiation emitted from 32P coils. We wanted to determine the upper limits of 32P activities that could be implanted onto coils with respect to the potential injury to nearby nerves, delay in organization of the clot, and effects on neointima formation and recanalization.. We studied the effects of various 32P activities on recanalization and organization of thrombus after coil occlusion of canine arteries and on neointima formation at the neck of canine carotid bifurcation aneurysms. We also tested potential injury to nerves in the vicinity of radioactive or nonradioactive coils in 3 models: the brachial plexus (near proximal vertebral arteries) and the lingual nerve in a lingual artery bifurcation aneurysm model, both models being treated by radioactive or standard coil occlusion. Finally, we wrapped lingual nerves with nonradioactive or high-activity coils and studied their effects on lingual nerves and tongues. Results were assessed with a pathological scoring system and compared with Mann-Whitney and Kruskal-Wallis tests.. No deleterious effect of radiation on nerves could be detected. Neointima formation was not hampered, scores of aneurysms treated with 32P-coils being significantly better when compared with treatments with standard coils (P=0.002). Arteries treated with high-activity coils (>3.39 microCi) showed absent recanalization but delayed organization of the clot at 3 months compared with low-activity or nonradioactive coils (P<0.05).. beta-Radiation can prevent recanalization after coil occlusion. We could not demonstrate any deleterious effects of radioactivity on nervous structure or on neointima formation. Delayed organization of thrombus provides a rational basis to establish an upper limit for 32P activities to be implanted onto coils.

Topics: Animals; Blood Coagulation; Brachial Plexus; Carotid Artery Diseases; Dogs; Embolization, Therapeutic; Intracranial Aneurysm; Lingual Nerve; Phosphorus Radioisotopes; Tunica Intima

Beta radiation prevents recanalization after coil embolization. We sought to determine the effects of varying coil caliber, length, activity of 32P per centimeter of coil or per volume, and spatial distribution of coils on recanalization.. We studied the angiographic evolution of 81 canine maxillary, cervical, and vertebral arteries implanted with a variety of nonradioactive (n=29 arteries) or radioactive (n=52) devices. We compared 1- or 2-caliber 0.015 or 0.010 coils ion-implanted or not with 3 different activity levels (0.05 to 0.08, 0.06 to 0.12, 0.18 to 0.32 microCi/cm) of 32P and totaling 4, 8, and 16 cm in length for the same arterial volume. We also compared inhibition of recanalization by beta radiation delivered by stents, after coil occlusion proximal to or within the stent, with that delivered by coils placed within nonradioactive stents. We finally studied the angiographic evolution of canine lateral wall carotid aneurysms treated with 1 or 2 stents of various activity levels positioned inside the parent artery across the neck. Animals were killed at 4 and 12 weeks for macroscopic photography and pathological examination.. All arteries (29 of 29) occluded with nonradioactive devices were recanalized, while 49 of 52 arteries (94%) implanted with 32P devices were occluded at 4 weeks. All aneurysms treated with stents, radioactive or not, demonstrated residual filling of the sac or of channels leading to the aneurysms at follow-up angiography at 4 weeks.. The recanalization process found in the canine arterial occlusion model is minimally affected by coil caliber, number, and length or packing density. Beta radiation reliably inhibits this process, but thrombosis is an essential condition for the efficacy of a radioactive coil strategy.

Topics: Aneurysm; Animals; Arterial Occlusive Diseases; Arteries; Beta Particles; Carotid Artery Diseases; Carotid Artery Thrombosis; Carotid Artery, Common; Combined Modality Therapy; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Drug Implants; Embolization, Therapeutic; Endothelium, Vascular; Equipment Design; Maxillary Artery; Neck; Phosphorus Radioisotopes; Radiotherapy Dosage; Recurrence; Single-Blind Method; Stents; Vertebral Artery