Evaluation of the peripheral dose in stereotactic radiotherapy and radiosurgery treatments.
OBJECTIVE
The main purpose of this work was to compare peripheral doses absorbed during stereotactic treatment of a brain lesion delivered using different devices. These data were used to estimate the risk of stochastic effects.


METHODS
Treatment plans were created for an anthropomorphic phantom and delivered using a LINAC with stereotactic cones and a multileaf collimator, a CyberKnife system (before and after a supplemental shielding was applied), a TomoTherapy system, and a Gamma Knife unit. For each treatment, 5 Gy were prescribed to the target. Measurements were performed with thermoluminescent dosimeters inserted roughly in the position of the thyroid, sternum, upper lung, lower lung, and gonads.


RESULTS
Mean doses ranged from of 4.1 (Gamma Knife) to 62.8 mGy (LINAC with cones) in the thyroid, from 2.3 (TomoTherapy) to 30 mGy (preshielding CyberKnife) in the sternum, from 1.7 (TomoTherapy) to 20 mGy (preshielding CyberKnife) in the upper part of the lungs, from 0.98 (Gamma Knife) to 15 mGy (preshielding CyberKnife) in the lower part of the lungs, and between 0.3 (Gamma Knife) and 10 mGy (preshielding CyberKnife) in the gonads.


CONCLUSIONS
The peripheral dose absorbed in the sites of interest with a 5 Gy fraction is low. Although the risk of adverse side effects calculated for 20 Gy delivered in 5 Gy fractions is negligible, in the interest of optimum patient radioprotection, further studies are needed to determine the weight of each contributor to the peripheral dose.
Di Betta
Erika
E
Department of Neurosurgery, Division of Medical Physics, Fondazione IRCCS, Istituto Neurologico C. Besta, 20133 Milano, Italy.
Fariselli
Laura
L
Bergantin
Achille
A
Locatelli
Federica
F
Del Vecchio
Antonella
A
Broggi
Sara
S
Fumagalli
Maria Luisa
ML
D001932:Brain Neoplasms / Q000532:radiotherapy / Q000601:surgery; D006801:Humans; D008297:Male; D009900:Optic Nerve / Q000528:radiation effects; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry; D016634:Radiosurgery / Q000009:adverse effects*; D011879:Radiotherapy Dosage; D013269:Stochastic Processes