Official websites use. Share sensitive information only on official, secure websites. We have evaluated a verification system that uses a webcam and a printed calibrated grid to verify tracking accuracy over three different motion patterns.
A box with an attached printed calibrated grid and four fiducial markers was attached to the motion phantom. A target marker was positioned at the grid's center.
The box was set up using the other three markers. Target tracking accuracy was evaluated under three conditions: 1 stationary; 2 sinusoidal motion with different amplitudes of 5, 10, 15, and 20 mm for the same cycle of 4 s and different cycles of 2, 4, 6, and 8 s with the same amplitude of 15 mm; and 3 irregular breathing patterns in six human volunteers breathing normally.
The webcam captured the grid's motion and a laser beam was used to simulate the CyberKnife's beam. Tracking error was defined as the difference between the grid's center and the laser beam.
With a stationary target, mean tracking error was measured at 0. For sinusoidal motion, tracking error was less than 2 mm for any amplitude and breathing cycle. Therefore, accurate lesion targeting requires individual quality assurance for each patient. Keywords: CyberKnife, synchrony, motion tracking, quality assurance, verification system. Respiratory motion varies substantially between patients, 1 and the consequent tumor motion during radiotherapy can compromise the accuracy of dose delivery and produce interplay and blurring effects.
