Tolerance dose in gamma knife surgery of lesions extending to the anterior visual pathway.
OBJECTIVE
The authors performed a retrospective analysis of the radiation dose to the anterior visual pathway (AVP) to assess its tolerance to gamma knife surgery.


METHODS
They examined five cases followed for more than 3 years. The AVP was treated with 10-Gy doses or higher. The mean maximum delivered dose to the AVP was 14 Gy. Ten gray or more was delivered to 25.5% of the ipsilateral AVP, 12 Gy or more to 12.5% of the ipsilateral AVP, and 14 Gy or more to 5.7% of the ipsilateral AVP. Although the mean follow-up period was 40.8 months (36-51 months), no cases of visual function deterioration developed.


CONCLUSIONS
The tolerance dose of the AVP is considered to be less than 8 to 10 Gy; however, although the delivered dose to the AVP definitely exceeded the tolerance dose in all five cases, no visual disturbance has been identified. Longer follow up is required before any final conclusions may be drawn. Nonetheless, it is suggested that a visual disturbance may be avoided by using careful accurate dose planning even if the dose delivered to the AVP is higher than currently believed to be acceptable.
Kenai
Hiroyuki
H
Department of Neurosurgery, Nagatomi Neurosurgical Hospital, Oita, Japan. ngkckenai@mb.neweb.ne.jp
Yamashita
Masanori
M
Nakamura
Takaharu
T
Asano
Tomoshige
T
Sainoh
Michifumi
M
Nagatomi
Hirofumi
H
D000236:Adenoma / Q000473:pathology / Q000601:surgery*; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006392:Hemangioma, Cavernous / Q000473:pathology / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008577:Meningeal Neoplasms / Q000473:pathology / Q000601:surgery*; D008579:Meningioma / Q000473:pathology / Q000601:surgery*; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000473:pathology / Q000601:surgery*; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000528:radiation effects*; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods; D047368:Tumor Burden / Q000528:radiation effects; D014795:Visual Pathways / Q000473:pathology