Characteristics of a novel treatment system for linear accelerator–based stereotactic radiosurgery

Abstract

The purpose of this study is to characterize the dosimetric properties and accuracy of a novel treatment platform (Edge radiosurgery system) for localizing and treating patients with frameless, image‐guided stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). Initial measurements of various components of the system, such as a comprehensive assessment of the dosimetric properties of the flattening filter‐free (FFF) beams for both high definition (HD120) MLC and conical cone‐based treatment, positioning accuracy and beam attenuation of a six degree of freedom (6DoF) couch, treatment head leakage test, and integrated end‐to‐end accuracy tests, have been performed. The end‐to‐end test of the system was performed by CT imaging a phantom and registering hidden targets on the treatment couch to determine the localization accuracy of the optical surface monitoring system (OSMS), cone‐beam CT (CBCT), and MV imaging systems, as well as the radiation isocenter targeting accuracy. The deviations between the percent depth‐dose curves acquired on the new linac‐based system (Edge), and the previously published machine with FFF beams (TrueBeam) beyond Dmax were within 1.0% for both energies. The maximum deviation of output factors between the Edge and TrueBeam was 1.6%. The optimized dosimetric leaf gap values, which were fitted using Eclipse dose calculations and measurements based on representative spine radiosurgery plans, were 0.700 mm and 1.000 mm, respectively. For the conical cones, 6X FFF has sharper penumbra ranging from 1.2−1.8 mm (80%‐20%) and 1.9−3.8 mm (90%‐10%) relative to 10X FFF, which has 1.2−2.2 mm and 2.3−5.1 mm, respectively. The relative attenuation measurements of the couch for PA, PA (rails‐in), oblique, oblique (rails‐out), oblique (rails‐in) were: −2.0%, −2.5%, −15.6%, −2.5%, −5.0% for 6X FFF and −1.4%, −1.5%, −12.2%, −2.5%, −5.0% for 10X FFF, respectively, with a slight decrease in attenuation versus field size. The systematic deviation between the OSMS and CBCT was −0.4±0.2 mm, 0.1±0.3 mm, and 0.0±0.1 mm in the vertical, longitudinal, and lateral directions. The mean values and standard deviations of the average deviation and maximum deviation of the daily Winston‐Lutz tests over three months are 0.20±0.03 mm and 0.66±0.18 mm, respectively. Initial testing of this novel system demonstrates the technology to be highly accurate and suitable for frameless, linac‐based SRS and SBRT treatment.PACS number: 87.56.J‐

Optical surface guidance for submillimeter monitoring of patient position during frameless stereotactic radiotherapy

“…1,[15][16][17][18][19][20] To characterize the accuracy of our system prior to ACO and CIB, we wanted to determine which portion of the RTDs seen at non-zero couch angles were due to couch walkout. 1,[15][16][17][18][19][20] To characterize the accuracy of our system prior to ACO and CIB, we wanted to determine which portion of the RTDs seen at non-zero couch angles were due to couch walkout.…”

Evaluation of a magnetic resonance guided linear accelerator for stereotactic radiosurgery treatment

“…[1,11,25]. However, the technical obstacles in developing an MR-guided radiosurgery system are significant due to the interactions between the magnetic field of an MRI system and the linear accelerator (Linac) system.…”

Using weighted power mean for equivalent square estimation

“…Relative AIC values of the three ES formulae are computed based on some open field photon S cp measurements from the Varian dataset and the reference 10. In all cases, the WPM model performed the best, and Sterling the worst.…”

“…For S cp in the Varian dataset (method 2 above) and the published measurement data from a Varian TrueBeam Edge unit,10 the quality of an ES formula was visualized in the ${\mathrm{normalS}}_{\mathrm{normalcp}}\mathrm{normalvs}.\mathrm{normalES}$ plot. The reason for this was that if an ES formula correctly identified the underlying relationship between a rectangular field and its corresponding ES measured in S cp , then all data points, no matter whether they were from square field measurements or rectangular field measurements, should fall onto the same curve in a plot of ${\mathrm{normalS}}_{\mathrm{normalcp}}\mathrm{normalvs}.\mathrm{normalES}$.…”