Tolerance of arteries to microplanar X-ray beams.
OBJECTIVE
The purpose is to evaluate effects of a new radiotherapy protocol, microbeam radiation therapy, on the artery wall. In previous studies on animal models, it was shown that capillaries recover well from hectogray doses of X-rays delivered in arrays of narrow (< or = 50 microm) beams with a minimum spacing of 200 microm. Here, short- and long-term effects of comparable microplanar beam configurations on the saphenous artery of the mouse hind leg were analyzed in situ by use of nonlinear optics and compared with histopathologic findings.


METHODS
The left hind leg of normal mice including the saphenous artery was irradiated by an array of 26 microbeams of synchrotron X-rays (50 microm wide, spaced 400 microm on center) with peak entrance doses of 312 Gy and 2,000 Gy.


RESULTS
The artery remained patent, but narrow arterial smooth muscle cell layer segments that were in the microplanar beam paths became atrophic and fibrotic in a dose-dependent pattern. The wide tunica media segments between those paths hypertrophied, as observed in situ by two-photon microscopy and histopathologically.


CONCLUSIONS
Clinical risks of long-delayed disruption or occlusion of nontargeted arteries from microbeam radiation therapy will prove less than corresponding risks from broad-beam radiosurgery, especially if peak doses are kept below 3 hectograys.
van der Sanden
Boudewijn
B
INSERM U836, Institute of Neuroscience Grenoble, France. Boudewijn.vandersanden@ujf-grenoble.fr
Bräuer-Krisch
Elke
E
Siegbahn
Erik Albert
EA
Ricard
Clément
C
Vial
Jean-Claude
JC
Laissue
Jean
J
D000818:Animals; D001158:Arteries / Q000473:pathology / Q000528:radiation effects; D005355:Fibrosis; D006614:Hindlimb / Q000098:blood supply*; D051379:Mice; D008807:Mice, Inbred BALB C; D008853:Microscopy / Q000379:methods; D009131:Muscle, Smooth, Vascular / Q000473:pathology / Q000528:radiation effects*; D009133:Muscular Atrophy / Q000209:etiology / Q000473:pathology; D011829:Radiation Dosage; D011833:Radiation Injuries, Experimental / Q000473:pathology; D011836:Radiation Tolerance / Q000502:physiology*; D011878:Radiotherapy / Q000379:methods; D017540:Tunica Media / Q000473:pathology / Q000528:radiation effects*