Dosimetric validation for an automatic brain metastases planning software using single‐isocenter dynamic conformal arcs

Abstract

An automatic brain‐metastases planning (ABMP) software has been installed in our institution. It is dedicated for treating multiple brain metastases with radiosurgery on linear accelerators (linacs) using a single‐setup isocenter with noncoplanar dynamic conformal arcs. This study is to validate the calculated absolute dose and dose distribution of ABMP. Three types of measurements were performed to validate the planning software: 1, dual micro ion chambers were used with an acrylic phantom to measure the absolute dose; 2, a 3D cylindrical phantom with dual diode array was used to evaluate 2D dose distribution and point dose for smaller targets; and 3, a 3D pseudo‐in vivo patient‐specific phantom filled with polymer gels was used to evaluate the accuracy of 3D dose distribution and radiation delivery. Micro chamber measurement of two targets (volumes of 1.2 cc and 0.9 cc, respectively) showed that the percentage differences of the absolute dose at both targets were less than 1%. Averaged GI passing rate of five different plans measured with the diode array phantom was above 98%, using criteria of 3% dose difference, 1 mm distance to agreement (DTA), and 10% low‐dose threshold. 3D gel phantom measurement results demonstrated a 3D displacement of nine targets of 0.7±0.4 mm (range 0.2 ~ 1.1 mm). The averaged two‐dimensional (2D) GI passing rate for several region of interests (ROI) on axial slices that encompass each one of the nine targets was above 98% (5% dose difference, 2 mm DTA, and 10% low‐dose threshold). Measured normalD95, the minimum dose that covers 95% of the target volume, of the nine targets was 0.7% less than the calculated normalD95. Three different types of dosimetric verification methods were used and proved the dose calculation of the new automatic brain metastases planning (ABMP) software was clinical acceptable. The 3D pseudo‐in vivo patient‐specific gel phantom test also served as an end‐to‐end test for validating not only the dose calculation, but the treatment delivery accuracy as well.PACS number(s): 87.53.Lv, 87.55.km, 87.55.Qr

GammaKnife versus VMAT radiosurgery plan quality for many brain metastases

“…With the recent introduction of commercial single‐isocenter planning algorithms for simultaneously treating multiple brain metastases, either using automated dynamic conformal arcs or automated VMAT, more dosimetric comparison to GK is required. These studies have already demonstrated a reduction in monitor units compared with conventional VMAT.…”

End to end comparison of surface‐guided imaging versus stereoscopic X‐rays for the SRS treatment of multiple metastases with a single isocenter using 3D anthropomorphic gel phantoms

“…This hollow phantom can be printed with bone‐mimicking materials based on anatomical structures of a past patient, based on CT data or scans, and it is filled with water and a 3D polymer gel dosimeter insert to simulate soft tissue equivalence 30 . Irradiation of this gel phantom provides the ability to evaluate 3D dose distributions for SRS 18,31,32 . The custom phantom is designed with a glossy white exterior, which is incompatible with the SGRT cameras.…”

“…30 Irradiation of this gel phantom provides the ability to evaluate 3D dose distributions for SRS. 18,31,32 The custom phantom is designed with a glossy white exterior, which is incompatible with the SGRT cameras. A nude makeup foundation (Stay Matte, Rimmel, London) was applied to the phantom's surface to simulate a skin tone visualizable by the scanner units.…”

“…35,36 More specifically, studies have evaluated the suitability of using 3Dprinted head phantoms with bone mimicking materials for patient-specific plan verification procedures, and they demonstrate excellent agreement with the actual patient. 18,37 Gel dosimetry permits evaluation of 3D dose distributions for SRS 18,31,32 and has been recommended for initial validation of a stereotactic program. However, it is important to note that the equipment…”

Characterization of a novel 3D printed patient specific phantom for quality assurance in cranial stereotactic radiosurgery applications

“…3D printing is being increasingly employed in radiotherapy for applications ranging from construction of treatment accessories (Canters et al 2016, Lindegaard et al 2016, Ricotti et al 2016, Jones et al 2017, Zhao et al 2017 to patient geometry and/or material reproduction (Ehler et al 2014, Liu et al 2016, Madamesila et al 2016, Kamomae et al 2017, Yea et al 2017. Regarding the latter, introducing material inhomogeneities in the phantoms has recently drawn considerable attention.…”