Schematic flow diagram for the VORTE. Step 1: The designed-target (target in this study is defined as the targeted area to be treated) motion is used as an input to the real-time control system. Step 2: The same target motion is used as an input to the analysis software. Step 3: Real-time tracking is simulated by positioning the MLC leaves to compensate for the target motion. Step 4: The EPID in the continuous-acquisition mode takes sequential images of the moving apertures controlled during the real-time tracking. Step 5: These sequential images of the aperture motion are used as inputs to the analysis software. Step 6: The analysis software compares the target and aperture motions to evaluate the accuracy of the real-time tracking.
Film image of a static field used to measure the accuracy of the VORTE.
Frequency distribution of the deviations in the leaf positions measured with film and the EPID system used for the VORTE. The spatial accuracy of the VORTE, which is defined as a of the distribution, is 0.5 mm.
Verification of DRRT tracking with the VORTE. The track of the aperture centroid (solid line) was controlled using DRRT to synchronize with the target centroid (dotted line). (a) The target and aperture motions over time in the direction parallel to the leaf motion. (b) The target and aperture motions over time in the direction perpendicular to the leaf motion. ( rate. DR1 is 400 MU/min, DR2 200 MU/min, DR3 400 MU/min, and DR4 600 MU/min.)
Distribution of deviations in the leaf positions for all leaves from all frames using DRRT, our real-time tumor-tracking technique.
MLC-leaf speed analysis. (a) Distribution of the MLC-leaf speed for the 2-D displacement (solid line), the deformable 2-D displacement (dotted line), and the deformable 2-D displacement combined with rotation (dashed line). (b) MLC-leaf speed versus positional deviation of the MLC leaves. The higher the MLC-leaf speed, the larger is the positional deviation of the leaves.
The live target motion with period variations.
Identification of the leaves that show a positional deviation of for the 2-D displacement case.
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