Assessment of the mechanical performance of a novel CT-linac treatment couch

Abstract

Purpose: This study aims to systematically evaluate the mechanical performance of the novel treatment couch for the uLinac VisionaryTx CT-Linac (United Imaging Healthcare, China).

Materials and methods: Quality assurance protocols were developed by integrating AAPM TG-142 and TG-66 guidelines. The following key parameters were assessed: (1) couch top movement accuracy, including translational/rotational precision and perpendicularity to the CT imaging plane; (2) couch top rigidity under varying loads (0-135 kg) and extensions; (3) couch base movement accuracy, covering longitudinal travel reproducibility and rotational homing; (4) efficacy of the laser rangefinder-based sag correction and the stability of the rangefinder itself; and (5) comprehensive end-to-end evaluation of IGRT workflows to determine the overall impact of couch mechanical performance on delivery accuracy. All tests were conducted under clinically representative loaded conditions.

Results: The couch top demonstrated high accuracy in translational movement (≤ 0.5 mm), rotation (< 0.12°), and perpendicularity relative to the CT imaging plane. Under maximum load, the couch top showed a sag of 4.1 mm, demonstrating superior rigidity to a dedicated CT simulator while being slightly less rigid than conventional linac couches. The couch base achieved precise longitudinal movement (≤ 1 mm) and rotational homing accuracy (< 0.1°). The laser rangefinder-based correction method achieved good agreement between calculated and measured height variations (deviation < 0.6 mm) with excellent stability in both angular and distance measurements. End-to-end tests verified sub-millimeter (0.5 mm) and sub-degree (0.5°) accuracy for IGRT workflows across various loading conditions.

Conclusion: The novel CT linac couch system (uLinac VisionaryTx) exhibits exceptional mechanical performance and fully satisfies the precision requirements for CT acquisition, image guidance, and setup error correction.

Keywords: IGRT; ct-linac; mechanical performance; quality assurance; treatment couch.