Characterization of a prototype rapid kilovoltage x-ray image guidance system designed for a linear accelerator radiation therapy unit.

Abstract

Purpose: This study evaluates a novel cone-beam computed tomography (CBCT) imaging solution integrated onto a conventional C-arm linear accelerator (linac) with increased gantry speed. The purpose is to assess the impact of improved imaging hardware and reconstruction algorithms on image quality.

Methods: Hypersight-CBCT (HS-CBCT) system was compared with the original system (OG-CBCT) on a TrueBeam linac. Performance tests included mechanical, geometric, setup accuracy, and image quality assessment. Image quality metrics were evaluated using conventional CBCT reconstruction and advanced iterative reconstruction (iCBCT), fast iCBCT, and iCBCT with metal artifact reduction. Dosimetry measurements were acquired.

Results: The HS-CBCT system acquired images in 24.0-44.0s (half trajectory/full trajectory), faster than the OG-CBCT system's acquisition time of 33.5-60.5s (half trajectory/full trajectory). The HS-CBCT system's faster gantry speed resulted in comparable image quality to the OG-CBCT. It improved high-contrast resolution, modulation transfer function, and low-contrast visibility. The faster gantry speed also produced lower radiation doses. The system's uniformity and resolution also improved, particularly with full-fan acquisition techniques.

Conclusion: The novel HS-CBCT system on a conventional C-arm linac exhibits superior imaging capabilities compared to the OG-CBCT. Faster gantry speed, larger imaging area, and advanced reconstruction algorithms contribute to enhanced image quality and reduced dose. The study provides comprehensive insights into the new system's performance, serving as a benchmark for future linac installations and highlighting potential benefits in clinical applications. Further investigations are suggested for 4D acquisitions and long-term machine performance.