2077

Schulte, R.; Lee, T.S.; Schubert, Keith E.

doi:10.1016/j.ijrobp.2006.07.480

Cited by 1 publication

(1 citation statement)

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“…This is achieved in part through superior cranial immobilization now able to provide intratreatment motion of less than 200 m ͑Refs. 1 and 2͒ and superior localization using multiple imaging modalities such as 3 T magnetic resonance imagers providing greater spatial resolution of the order of 300 m. 3,4 Conformality of the dose distribution to the target volume is achieved by using a number of small radiation fields entering the brain from various angles and converging at the target volume focal point. There have been past attempts to reduce beam penumbra to achieve a more conformal and homogeneous dose distribution.…”

Section: Introductionmentioning

confidence: 99%

Intermediate energy photons to improve dose gradient, conformality, and homogeneity: Potential benefits for small field intracranial radiosurgery

et al. 2008

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A previously conceived and demonstrated principle of reducing penumbra for small radiosurgical dose fields is here now applied to a multiple beam arrangement in a stereotactic head phantom. In this work it is found that the fourfold reduction in radiological penumbra of small, single 1 MV x-ray fields translates to a more conformal, homogeneous dose distribution in the more complex beam arrangements. The film dosimetry is conducted with a high resolution digital microscope to quantify the sharp dose gradients. Further, the Gafchromic EBT film measurements in phantom are compared to calculations using the Xknife RT3 (Radionics, Burlington, MA) treatment planning software (TPS) with modeled 1 MV beam data. An orthogonal pair of coplanar beams and an 18-beam coplanar arc irradiation both yielded agreement between the modeling within the TPS and the film work. Conventional 6 MV modality is compared alongside 1 MV throughout. The 90%-50% and 90%-10% dose gradients at the intersection of the orthogonal beam pair were 1.7 and 4.7 mm for 6 MV versus 0.5 and 1.3 mm for 1 MV for an identical setup. The 18-beam coplanar arc plan yielded 90%-80% and 90%-50% dose gradients of 0.84 and 2.2 mm for 6 MV versus gradients of 0.29 and 1.36 mm for 1 MV for the midaxial slice coplanar with all beamlet axes. Uncertainties in gradient measurements were +/- 0.15 mm. The 18-beam coplanar beam arrangement represented a worst case scenario for penumbra overlap deteriorating the dose distribution. In brief, 1 MV x-rays provided superior homogeneity, conformality, and dose fall-off to 6 MV for the irradiations examined.

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Section: Introductionmentioning

confidence: 99%