Validation of Catalyst⁺ HD System Under Varying Postural, Couch Angle, and Isocenter Conditions in Intracranial...

This study assessed the positional detection accuracy of the Catalyst⁺ HD system for intracranial stereotactic irradiation (STI) under clinically relevant conditions, including variations in head posture, isocenter position, and couch angle.

An anthropomorphic head phantom was used to simulate three head postures, chin-up, neutral, and chin-down, each stabilized with a corresponding thermoplastic mask. Seven isocenter positions were defined: one central position and six offset positions, each 5 cm away in a cardinal direction. Treatment plans incorporated multiple couch angles (0°, 30°, 45°, 60°, and 90°). The Catalyst⁺ HD system's accuracy was evaluated by comparing its detected displacements to predefined shifts applied using a HexaPOD evo RT system. Translational shifts of ±3 mm and rotational shifts of ±2° were introduced. Statistical analysis was conducted using the Wilcoxon signed-rank test.

Under standard conditions (neutral posture, central isocenter, and 0° couch angle), the system demonstrated submillimeter accuracy (mean translational error: 0.08 mm; mean rotational error: 0.12°). Detection errors were significantly larger in the chin-up posture compared to the neutral posture (p=0.028). Similarly, a superior isocenter position resulted in considerably larger errors (p=0.026). A couch rotation of 30° led to a significant increase in error, whereas other couch angles maintained high precision.

The Catalyst⁺ HD system exhibits high accuracy for intracranial STI under most tested conditions. However, to optimize performance and accuracy, configurations involving a chin-up posture or a superior isocenter position should be avoided.