Evaluation of the RUBY modular QA phantom for planar and non‐coplanar VMAT and stereotactic radiations

Abstract

Purpose This study evaluates the clinical use of the RUBY modular QA phantom for linac QA to validate the integrity of IGRT workflows including the congruence of machine isocenter, imaging isocenter, and room lasers. The results have been benchmarked against those obtained with widely used systems. Additionally, the RUBY phantom has been implemented to perform system QA (End‐to‐End testing) from imaging to radiation for IGRT‐based VMAT and stereotactic radiations at an Elekta Synergy linac. Material and Methods The daily check of IGRT workflow was performed using the RUBY phantom, the Penta‐Guide, and the STEEV phantom. Furthermore, Winston–Lutz tests was carried out with the RUBY phantom and a ball‐bearing phantom to determine the offsets and the diameters of the isospheres of gantry, collimator, and couch rotations, with respect to the room lasers and kV‐imaging isocenter. System QA was performed with the RUBY phantom and STEEV phantom for eight VMAT treatment plans. Additionally, the visibility of the embedded objects within these phantoms in the images and the results of CT and MR image fusions were evaluated. Results All systems used for daily QA of IGRT workflows show comparable results. Calculated shifts based on CBCT imaging agree within 1 mm to the expected values. The results of the Winston–Lutz test based on kV imaging (2D planar and CBCT) or room lasers are consistent regardless of the system tested. The point dose values in the RUBY phantom agree to the expected values calculated using algorithms in Masterplan and Monte Carlo engine in Monaco within 3% of the clinical acceptance criteria. Conclusion All the systems evaluated in this study yielded comparable results in terms of linac QA and system QA procedures. A system QA protocol has been derived using the RUBY phantom to check the IGRT‐based VMAT and stereotactic radiations workflow at an Elekta Synergy linac.

Systematic end-to-end testing of multiple target treatments using the modular RUBY phantom

“…Our results show discrepancies between the TPS calculations at off-axis positions, whereas better agreement was obtained between measurements and Monaco calculations. The same observation has been reported in a previous study by Poppinga et al [18] with point dose measurements. Kim et al [19] also compared ArcCheck measurements to both calculation algorithms by gamma index analysis, where higher gamma passing rates were achieved with Monaco calculations.…”

Historical Progress of Stereotactic Radiation Surgery

“…The Elekta’s RTsafe,[ 103 ] CIRS’s STEEV,[ 104 ] Standard Imaging’s Lucy 3D QA,[ 105 ] PTW’s Ruby[ 106 ] cranial phantoms, as well as high-resolution array detectors such as PTW’s OCTAVIUS Detector 1600 SRS,[ 107 ] Sun Nuclear’s SRS MapCHECK,[ 108 ] and IBA Dosimetry’s myQA SRS[ 109 ] are among the advanced equipment in this field. Some of these detector arrays also have an evaluation gamma index resolution of up to 2%/2 mm.…”