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SU‐FF‐T‐525: The Study On the Effects of MLC Leakage‐Ray and Scattered‐Ray to Eyes and Lens in Whole Brain Radiotherapy
Author(s) -
Lin X,
Sun T,
Liu T
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3182023
Subject(s) - collimator , nuclear medicine , medicine , radiation therapy , x ray , lens (geology) , dose volume histogram , leakage (economics) , radiation treatment planning , optics , physics , radiology , macroeconomics , economics
Purpose : to study the effects of multi‐leaf collimator (MLC) leakage‐ray and scattered‐ray to eyes and lens in radiotherapy of patients with brain metastasis tumor. Methods and Materials: 10 patients treated by whole brain radiotherapy were selected, for each of which two model treatment plans were designed. Plan_1: Two fields in 90° (field_1) and 270° (field_2) were arranged to the brain, while the angle of collimators were fixed in 0°. Plan_2: The same angle of fields were arranged, but the angle of collimators were modified with rotation of 45° in field_1 and −45° in field_2, respectively. In this case, the lens and most of eyes were out of irradiated volume, so that most of leakage‐ray and scattered‐ray effecting to them were reduced. The whole brain was irradiated to the prescription dose. The dose of lens and eyes received were evaluated by dose‐volume histogram (DVH). Results: two plans both met the clinical demands with almost same dose distribution to whole brain. Compared to Plan_1, the maximum dose on left lens decreased on average 100.5cGy (t = 8.299, P <0.01), and the maximum dose on right lens decreased on average 109.5cGy (t = 7.567, P <0.01); the mean dose on left eyes decreased on average 151.6cGy (t = 3.252, P <0.01), and the mean dose of right eyes decreased on average 124.2cGy (t = 3.256, P <0.01). Conclusions: in the whole brain radiotherapy, the effects of leakage‐ray and scattered‐ray to lens and eyes were significant. Therefor, it is necessary and salutary to modify the angle of collimators in order to reduce the dose on lens and eyes remarkably.