QA tests on beam therapy equipment must be carried out for what variation?

Quality Assurance (QA) tests on beam therapy equipment are essential to ensure safe and effective treatment delivery. The correct choice points towards the importance of performing QA at different gantry angles, as this is vital for accurately assessing the performance of the treatment device throughout its range of motion.

Different gantry angles can influence how radiation is delivered to the patient, impacting dose distribution and potential exposure to surrounding tissues. Variability in beam characteristics, such as output consistency, flatness, symmetry, and other mechanical properties, can occur when the gantry is positioned at varying angles. By conducting QA tests at multiple gantry angles, practitioners can identify any discrepancies or malfunctions in the equipment's operation that may not be evident when testing only at a single angle. This comprehensive evaluation helps ensure reliable and precise radiation delivery, which is crucial for patient safety and treatment efficacy.

Though other factors like treatment types, patient sizes, and radiation doses play important roles in the overall treatment process, the QA testing specifically focuses on ensuring the beam's performance across different angles to maintain consistent and accurate radiation therapy coverage.