Post-dilatation intravascular brachytherapy trials on hypercholesterolemic rabbits using 32P-phosphate solutions in angioplasty balloons.
OBJECTIVE
Response of peripheral arteries to post-dilatation intravascular brachytherapy (IVBT) using 32P liquid sources was studied in a rabbit model.


METHODS
The applied sources were angioplasty balloons filled with aqueous solutions of Na2H32PO4, NaCl and iodinated contrast. Dose distribution was calibrated by thermoluminescence dosimetry. The uncertainty of in vitro determinations of the activity-dose dependence was +/- 15-30%. The animal experiments were performed on rabbits with induced hypercholesterolemia. The 32P sources were introduced into a randomly chosen (left or right) iliac artery, immediately after balloon injury. Due to the low specific activity of the applied sources, the estimated 7-49 Gy doses on the internal artery surface required 30-100 min irradiations. A symmetric, balloon-occluded but non-irradiated artery of the same animal served as control. Radiation effects were evaluated by comparing the thicknesses of various components of irradiated versus untreated artery walls of each animal.


RESULTS
The treatment was well tolerated by the animals. The effects of various dose ranges could be distinguished although differences in individual biological reactions were large. Only the 49 Gy dose at "zero" distance (16 Gy at 1.0 mm from the balloon surface) reduced hypertrophy in every active layer of the artery wall. The cross-sectional intimal thicknesses after 7, 12, 38 and 49 Gy doses were 0.277, 0.219, 0.357 and 0.196 mm2 respectively, versus 0.114, 0.155, 0.421 and 0.256 mm2 in controls (p < 0.05). The lowest radiation dose on the intima induced the opposite effect. Edge intimal hyperplasia was not avoided, which agrees with other reports. The edge restenosis and the variability of individual response to identical treatment conditions must be considered as limitations of the post-dilatation IVBT method.


CONCLUSIONS
Only application of highest irradiation doses was effective. The irradiation dose should be planned and calculated for adventitia.
Walichiewicz
Piotr
P
Brachytherapy Unit, Institute of Oncology-Gliwice Division, 44-101 Gliwice, Poland. piotrw@io.gliwice.pl
Wilczek
Krzysztof
K
Petelenz
Barbara
B
Jacheć
Wojciech
W
Jochem
Jerzy
J
Tomasik
Andrzej
A
Bilski
Pawel
P
Gaca
Pawel
P
Banaszczuk
Joanna
J
Ihnatowicz
Jerzy
J
Wodniecki
Jan
J
D000800:Angioplasty, Balloon; D000818:Animals; D001918:Brachytherapy; D004195:Disease Models, Animal; D004307:Dose-Response Relationship, Radiation; D006083:Graft Occlusion, Vascular / Q000000981:diagnostic imaging / Q000532:radiotherapy; D006937:Hypercholesterolemia / Q000000981:diagnostic imaging / Q000628:therapy*; D006965:Hyperplasia / Q000000981:diagnostic imaging / Q000532:radiotherapy; D007083:Iliac Artery / Q000473:pathology / Q000528:radiation effects / Q000601:surgery; D008955:Models, Cardiovascular; D010761:Phosphorus Radioisotopes / Q000627:therapeutic use; D011817:Rabbits; D011829:Radiation Dosage; D011851:Radioactivity; D011859:Radiography; D011874:Radiometry; D017539:Tunica Intima / Q000473:pathology / Q000528:radiation effects / Q000601:surgery
D010761:Phosphorus Radioisotopes