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DOI http://dx.doi.org/10.1016/S0360-3016(97)80740-7
Title Optic nerve tolerance to single and fractionated radiation simulating radiosurgery: a rabbit model using visual evoked potentials, fundoscopy and histology
Creator/Author Bastin, Kenneth ; Mehta, Minesh
Publication Date1997 Jul 01
OSTI IdentifierOSTI ID: 20423220
Other Number(s)ISSN 0360-3016; IOBPD3 ; TRN: US03R3777006893
Resource TypeJournal Article
Resource RelationInternational Journal of Radiation Oncology, Biology and Physics ; VOL. 39 ; ISSUE: 2,suppl.1 ; PII: S0360301697807407; Copyright (c) 1997 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); PBD: 1997
Subject62 RADIOLOGY AND NUCLEAR MEDICINE ; FRACTIONATED IRRADIATION; LATENCY PERIOD; NERVES; RABBITS; RADIATION INJURIES; RADIOSENSITIVITY
Description/Abstract Purpose/Objective: To develop a rabbit model enabling single or fractionated optic nerve irradiation, measure post-irradiation visual evoked potentials (VEP), fundoscopic and histopathologic changes, and relate different radiation dosing fractions to these measurable physiologic changes. Materials and Methods: Forty male New Zealand white rabbits underwent surgical right orbital prolapse with template-guided optic nerve irradiation using an iridium-192 high dose rate afterloader. Rabbits were randomized into single fraction groups (0 (control), 10, 12.5, 15, 20, and 30 Gy (3 per group); or two fraction groups of 0 (control) 5, 7.5, 10, 15, and 20 Gy (3 per group); or three fractions groups of 10 and 15 Gy (2 per group)). Bilateral fundoscopy and pattern-reversal VEPs (0.5 and 1 c/deg, 1 hertz) were performed at 6 and 12 months (mos) following scheduled irradiation. VEP peaks (P1) were measured. Sacrifice and necropsy followed 12 month evaluation, allowing for histological changes. Results: Excluding deaths from anesthesia (2), CNS mite infection (2), sepsis, pyothorax, 'undetermined' and technically non-analyzable VEP recordings, 24 complete rabbit data sets were evaluated. Fundoscopy demonstrated no gross changes at any dose. Histopathology demonstrated generalized optic nerve atrophy without radiation dose correlation. Among single fraction groups, VEP showed a 6 mos post-irradiation P1 prolongation only in the 20 and 30 Gy groups (maximum 67%). At 12 mos lower dose single fraction groups had a prolonged P1 peak. All fractionated groups above 5 Gy x 2 had P1 prolongation times at 6 mos (maximum 46% in the 15 Gy x 3 data set) but by 12 mos these groups had non-measurable, deteriorated VEPs. Correlating VEP P1 latency with the calculated linear quadratic formula (LQM) biologically equivalent dose (BED,{alpha}/{beta}=3) for each group demonstrated a general correlation (t-Test P<.001) as shown: Conclusion: Using a rabbit model for selective optic nerve irradiation we conclude that (a) VEP P1 latency correlates with radiation dose (b) fractionated radiation correlates to VEP P1 prolongation as predicted by the LQM formula (c) higher radiation doses produce earlier P1 latency, followed by signal deterioration (d) fundoscopy and histopathology are not sensitive outcome variables in this rabbit model. Further studies correlating VEP and optic nerve radiation may influence the design of future radiosurgery trials.
Country of PublicationUnited States
LanguageEnglish
Formatpage(s) 226
System Entry Date2004 Feb 23

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