Validation of Geometric and Dosimetric Accuracy of Edge Accelerator Gating With Electromagnetic Tracking: A Phantom Study

Abstract

This work was to devise a comprehensive testing scheme to evaluate the geometric and dosimetric accuracy of the Edge accelerator gating with electromagnetic tracking (EMT) for its safety in clinical application. A CIRS thorax phantom was scanned with four-dimensional cone-beam CT (4D-CBCT) on an Edge accelerator while the simulated tumor was simultaneously tracked with an EMT system using Calypso. The geometric accuracy was validated by comparing the motion trajectories derived from Calypso and 4D-CBCT with the ground truth from motion control software. The two-dimensional and three-dimensional dynamic doses were measured with the Matrixx and ArcCHECK installed on a motion platform, both with and without EMT. For tumor motion with 5, 7.5 mm amplitudes, the average absolute differences of sample position between Calypso and the ground truth were 0.286±0.234 mm, 0.407±0.331 mm respectively. Dosimetric accuracy was validated with 3 mm/3% gamma criterion. The average gamma pass rates of 2D dynamic dose validation based on Matrixx were less than 46% without EMT, 97.3% using 2 mm gating limit, 96% using 3 mm gating limit and 93.4% using 5mm gating limit respectively. The mean 3D dynamic dose validation pass rates based on ArcCHECK were 65.9% without EMT, 96.2% using 3 mm gating limit, and 92.5% using 5 mm gating limit with EMT respectively. The geometric accuracy of the Calypso system in tracking the moving target area was stable at the submillimeter level. The dosimetric accuracy could be improved significantly with EMT using an appropriate gating limit. INDEX TERMS Radiotherapy, accuracy, electromagnetic tracking.

The first internal electromagnetic motion monitoring implementation for stereotactic liver radiotherapy in China: procedures and preliminary results

“…It was found that only three articles were reported by Chinese institutions. Two of them were talking about the accuracy evaluation (27,28) , and the third was focusing on algorithms comparison for localizing prostate tumor (29) . All of them were medical physical researches rather than clinical experiences.…”

A robotically assisted 3D printed quality assurance lung phantom for Calypso

“…As the interest in the use of Calypso is becoming more prevalent for lung SABR treatments (Jaccard et al 2019, Sarkar et al 2020), there is a transparent need for a QA phantom to facilitate commissioning and acceptance testing. Previous investigations have focused on evaluating Calypso using commercially available phantoms, such as those provided from the vendor (Santanam et al 2009), solid water on a motion platform (Sawant et al 2009), or Dynamic Thorax Motion Phantom (CIRS, Norfolk, VA, USA) (Dai et al 2019). Additionally, a recent study has tested the use of a six-degree of freedom robotic arm to evaluate position accuracy in an acrylic phantom with embedded Calypso markers (Alnaghy et al 2019).…”

“…To date, there is no standardized QA phantom to perform such a task specifically for lung Calypso treatments, albeit the manufacture provides a universal phantom available for QA, in addition to multiple research phantoms (Santanam et al 2009, Sawant et al 2009, Dai et al 2019. In this study, we developed, designed and validated a novel phantom that combines robotics and 3D printing, to provide a clinically practical approach for performing lung Calypso QA.…”

Evaluation of target volume and dose accuracy in intrafractional cases of lung cancer based on 4D-CT and 4D-CBCT images using an in-house dynamic thorax phantom

“…Mohatt et al evaluated the combination of imaging techniques which is obtained from 4D dataset and computational algorithms best compensates for dosimetric accuracy on moving target using Quasar dynamic phantom [ 15 ]. Dai et al in their investigation had done 3D dose verification for time dependant lung target displacement with Electromagnetic Tracking (EMT) system and 4D-CBCT using CIRS phantom [ 16 ]. In this study, in-house dynamic phantom was schemed based on the clinical investigations mentioned in the background, the phantom was designed to be able to mimic breathing-induced tumour movement with several variations in peak-to-peak amplitude ranging from 4.99 ± 0.04 mm to 29.61 ± 0.22 mm in the superior-inferior direction and angle variations in rotational movement ranging from 0 to 90.2 ± 0.22° in a sinusoidal waveform.…”