SU-E-T-557: A Planning Strategy of Volumetric Modulated Arc Therapy with Simultaneous Integrated Boost for Intracranial Stereotactic Radiotherapy.
PURPOSE
The purpose of this planning study was to evaluate the dosimetric effect of dose escalation for intracranial stereotactic radiotherapy by volumetric modulated arc therapy (RapidArc) with simultaneous integrated boost (SIB-VMAT).


METHODS
Dynamic conformal arc therapy (DCA), VMAT, and SIB-VMAT plans using Novalis Tx (Varian/BrainLAB) were performed for twenty target volumes in patients with intracranial metastases with median PTV of 16.0 cm3 (range 2.4-35.2 cm3 ). PTV was created with 2 mm expansion from GTV. All plans were generated with a prescribed dose of 35 Gy in 5 fractions to the PTV (D95 = 95%), and dose escalation up to 40 Gy (SIB-VMAT40) and 45 Gy (SIB-VMAT45) was performed only to the PTV-boost (PTV shrunk by 5 mm) for SIB-VMAT. Each plan was compared using conformity parameters.


RESULTS
The average Paddick conformity index (CI) was 0.78, 0.90, 0.91, and 0.89 for DCA, VMAT, SIB-VMAT40, and SIB-VMAT45, respectively. The average healthy tissue overdosage factor (HTOF), suggested by SALT was 0.118, 0.006, 0.007, and 0.011 for DCA, VMAT, SIB-VMAT40, and SIB-VMAT45, respectively. The average V30, V20, and V10 of normal brain for VMAT and SIB-VMAT decreased by 3.0 cm3 (range 0.1-8.2 cm3 ), 3.0 cm3 (range 0.1-8.7 cm@@@3@@), and 7.5 cm@@@3@@ (range 0.3-26.2 cm@@@3@@), respectively, compared to DCA depending on the target volume.


CONCLUSIONS
SIB-VMAT improved dose conformity to the PTV for intracranial stereotactic radiotherapy, and decreased high and low dose volume of normal brain compared to DCA. SIB-VMAT offers the ability of dose escalation due to high conformity of high dose regions inside the target volume.
['Ono|K|K|', 'Fujimoto|S|S|', 'Furukawa|K|K|', 'Kudo|T|T|', 'Akagi|Y|Y|', 'Hirokawa|Y|Y|']
Tissues Brain Dosimetry Radiosurgery