Abstract
A more precise radiation therapy technique to treat unilateral optic nerve sheath meningioma is presented. It uses an immobilization device to align the ipsilateral optic nerve with a vertical axis and employs three small half-beam blocked fields to deliver radiation to a small conformal volume, thereby reducing the dose to the optic chiasm and the contralateral optic nerve. Three patients were successfully treated with this technique, and a fourth patient with optic nerve glioma was also treated in a similar fashion and was included in this study. The new technique irradiates a much smaller volume of tissue to high dose levels: 58 cm3 is irradiated to the 80% isodose level and only 18 cm3 to the 95% level. In contrast, the opposed lateral technique irradiates 171 and 73 cm3 to these levels, respectively. Thus, a considerable reduction in the volume of normal tissue irradiated was accomplished. Doses to the pituitary and contralateral optic nerve were 4% of the treatment dose for the new technique, whereas these doses were 40% and 100% for opposed laterals and 10% and 3% for wedged pair, respectively. The average setup error for this technique was very small, 50% of the setups measured were less than 1 mm off, and 92.5% were less than 3 mm off. However, for the conventional setups without a mask, only 21 % of the setups were less than 1 mm off and 55% less than 3 mm off. We recommend this technique for localized unilateral optic nerve sheath meningioma and other optic nerve lesions that may require radiation therapy.
Original language | English (US) |
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Pages (from-to) | 1093-1098 |
Number of pages | 6 |
Journal | International Journal of Radiation Oncology, Biology, Physics |
Volume | 22 |
Issue number | 5 |
DOIs | |
State | Published - 1992 |
Keywords
- Dose-volume histogram
- Meningioma
- Optic nerve
- Optic nerve sheath
- Radiation therapy
- Technique
ASJC Scopus subject areas
- Radiation
- Oncology
- Radiology Nuclear Medicine and imaging
- Cancer Research