Evaluation of the peripheral dose in stereotactic radiotherapy and radiosurgery treatmentsa)

Abstract

PurposeThe 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.MethodsTreatment 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.ResultsMean 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.ConclusionsThe 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.

Report of AAPM TG 135: Quality assurance for robotic radiosurgery

“…35,36 During the treatment process, the ALARA principle should be considered, i.e., the treatment planning should be designed to achieve the clinically optimal results with as few beams and monitor units as feasible. The use of multiple collimators has been demonstrated 37 to reduce the number of MU needed for a treatment plan.…”

Static jaw collimation settings to minimize radiation dose to normal brain tissue during stereotactic radiosurgery

“…Because stereotactic radiosurgery has been used not only for primary tumors but also for benign diseases, such as AVMs, this result may be meaningful in regards to radiation late effects, 6,7 particularly with pediatric patients 8 -11 whose brains are still developing or when a critical organ, such as the brainstem or the optic chiasm, is near the PTV. 9 The idea of zero static jaw margins could be an extreme scenario, but it is important to emphasize a planner's awareness about the function of static jaw margins to reduce the normal brain tissue dose near the PTV.…”

Adaptive fractionated stereotactic Gamma Knife radiotherapy of meningioma using integrated stereotactic cone-beam-CT and adaptive re-planning (a-gkFSRT)

“…This report shows, for the first time, that fractionated stereotactic Gamma Knife radiotherapy is feasible, combining the accuracy, significantly steeper gradients, and lower total body dose of the stereotactic Gamma Knife system [9,10] with the flexibility of fractionated treatment from a linear accelerator with mask system and CBCT. Furthermore, the Icon system introduces adaptive planning and a new patient tracking system to the clinical routine.…”