The commissioning and validation of Monaco treatment planning system on an Elekta VersaHD linear accelerator

Abstract

Accurate beam modeling is essential to help ensure overall accuracy in the radiotherapy process. This study describes our experience with beam model validation of a Monaco treatment planning system on a Versa HD linear accelerator. Data were collected such that Monaco beam models could be generated using three algorithms: collapsed cone (CC) and photon Monte Carlo (MC) for photon beams, and electron Monte Carlo (eMC) for electron beams. Validations are performed on measured percent depth doses (PDDs) and profiles, for open‐field point‐doses in homogenous and heterogeneous media, and for obliquely incident electron beams. Gamma analysis is used to assess the agreement between calculation and measurement for intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans, including volumetric modulated arc therapy for stereotactic body radiation therapy (VMAT SBRT). For all relevant conditions, gamma index values below 1 are obtained when comparing Monaco calculated PDDs and profiles with measured data. Point‐doses in a water medium are found to be within 2% agreement of commissioning data in 99.5% and 98.6% of the points computed by MC and CC, respectively. All point‐dose calculations for the eMC algorithm in water are within 4% agreement of measurement, and 92% of measurements are within 3%. In heterogeneous media of air and cortical bone, both CC and MC yielded better than 3% agreement with ion chamber measurements. eMC yielded 3% agreement to measurement downstream of air with oblique beams of up to 27°, 5% agreement distal to bone, and within 4% agreement at extended source to surface distance (SSD) for all electron energies except 6 MeV. The 6‐MeV point of measurement is on a steep dose gradient which may impact the magnitude of discrepancy measured. The average gamma passing rate for IMRT/VMAT plans is 96.9% (±2.1%) and 98.0% (±1.9%) for VMAT SBRT when evaluated using 3%/2 mm criteria. Monaco beam models for the Versa HD linac were successfully commissioned for clinical use.

Commissioning of a 1.5T Elekta Unity MR‐linac: A single institution experience

“…Setting the electron density of the ArcCheck for use with the Monaco TPS has been previously reported. 35 36 The pretreatment image was a 2-minute 3D T1-weighted sequence and the ATS option was used for adaptive plan calculation.…”

Analysis of patient‐specific quality assurance for Elekta Unity adaptive plans using statistical process control methodology

“…Due to the design of the Unity MR-linac, the ArcCheck phantom is first placed on the QA platform and translated into the bore. A CT scan of the ArcCheck was imported into the Monaco treatment planning system(TPS) and the relative electron densities were determined as described by Snyder et al14,15 The alignment of the ArcCheck phantom utilizes a custom QA platform since the Unity MR-linac only has a sagittal laser, which is insufficient to properly align the phantom by itself. As a result, the alignment reproducibility is dependent on the consistency of how the ArcCheck phantom and platform are setup on the treatment couch.…”

Maintaining dosimetric quality when switching to a Monte Carlo dose engine for head and neck volumetric‐modulated arc therapy planning

“…A standard set of RS verification tests has been published, 36 demonstrating agreement with measurements in both homogeneous and heterogeneous phantoms on par with similar commercial algorithms. 5,37,38 Both Pinnacle and RS commissioning at our institution included a successful irradiation of the Imaging and Radiation Oncology Core (IROC) Houston HN end-to-end test phantom. 39 A number of studies closely examined the effects of using Type C dose algorithms in the HN plans.…”