Effects of a holmium-166 incorporated covered stent placement in normal canine common bile ducts.
OBJECTIVE
A specially designed self-expandable covered metallic stent incorporated with beta-emitting radioisotope, Holmium-166 (Ho-166), was developed for delivering intraluminal brachytherapy as well as for internal bile drainage in malignant biliary stricture. The purpose of the study was to demonstrate the safety and tissue response of the radioactive metallic stent on the normal canine common bile duct (CBD) prior to the clinical application.


METHODS
Nitinol self-expandable stents (diameter; 4 mm, length; 20 mm) were covered with polyurethane membrane (50 microm thick) containing 21 to 135 muCi of Ho-166 (mean, 77.9 microCi). To prevent migration of stent, the membrane covered only the middle 1 cm of the stent and the ends of the stent were left uncovered. The stents were placed in the CBD of 20 healthy beagle dogs. For control, non-radioactive covered stents were placed in another three dogs. The dogs were killed 3 to 6 months after stent insertion and histopathologic examination of CBD was performed.


RESULTS
There was no stent migration in all cases. Varying degrees of papillary mucosal hyperplasia leading to significant narrowing of the lumen was observed within the lumen of the bare portion and under the mucosal surface of the non-radioactive covered stents. However, fibrosis was noted in Ho-166 coated area, instead of mucosal hyperplasia. Severity of fibrosis was correlated with estimated radiation dose. Despite high dose, there was no perforation of CBD wall. The membrane of Ho-166 coat was disrupted in some cases of 6 months follow-up.


CONCLUSIONS
Holmium-166 incorporated covered stents demonstrated fibrosis of CBD wall and inhibition of ingrowth of mucosal hyperplasia without serious complication such as perforation, while control group showed severe mucosal hyperplasia.
Won
Je Hwan
JH
Department of Diagnostic Radiology, Hospital of the University of Pennsylvania, Philadelphia, USA.
Lee
Jong Doo
JD
Wang
Hee Jung
HJ
Han
Jae Ho
JH
Kim
Jae Hyung
JH
Kim
Kyung-Hwa
KH
Park
Kyung Bae
KB
Itkin
Maxim
M
D000497:Alloys; D000818:Animals; D003135:Common Bile Duct / Q000000981:diagnostic imaging / Q000528:radiation effects*; D004285:Dogs; D006695:Holmium / Q000627:therapeutic use*; D011140:Polyurethanes; D011859:Radiography; D011868:Radioisotopes / Q000627:therapeutic use*; D015607:Stents
D000497:Alloys; D011140:Polyurethanes; D011868:Radioisotopes; C013616:nitinol; D006695:Holmium