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

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

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.

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.

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.