ESTRO 2024 - Abstract Book

S4877

Physics - Quality assurance and auditing

ESTRO 2024

Figure 1: Setup for the QC procedure

A kV Cone-Beam CT scan (“CTrue” as referred by Accuray) is acquired using 270mm as Field-Of-View (FOV) and “fine” quality (1mm slice interval). The scan is over 1000mm long, to cover both markers.

A python-based program has been developed to analyze the image stack. The program scans the image stack and looks for the highest pixel values, in order to detect both markers. It determines the position of the centroid of each marker, then calculates and returns the difference in position along the X axis, the Z axis, and the total distance, in both pixels and millimeters.

The markers are positioned on top of a 5 cm slab of virtual water phantom, in the same vertical and lateral position (with the use of the red lasers), separated one meter in the longitudinal axis.

This test checks for lateral and vertical deviation of the couch under load as it advances longitudinally, as well as transversal torsion.

Results:

Figure 2 shows the results screen of the program, with the markers position and the vertical, longitudinal and lateral deviation, as well as the two images where the program has found the markers.