Part I | Chapter 4 74 Isometric volume expansion Left Seminal Vesicle volume covered ≥ 95% of the time (%) Right Seminal Vesicle volume covered ≥ 95% of the time (%) Prostate volume covered ≥ 95% of the time (%) 1 mm 89.0 87.7 97.4 2 mm 94.6 93.7 98.7 3 mm 97.5 96.8 99.3 4 mm 98.8 98.4 99.7 5 mm 99.4 99.1 99.9 6 mm 99.8 99.6 99.9 7 mm 99.9 99.8 100 8 mm 99.9 99.9 100 9 mm 100 100 100 10 mm 100 100 100 Figure 4 – Visualised example showing the volume expansion of 5 mm for the seminal vesicles (left seminal vesicle: cyan, right seminal vesicle: magenta) and prostate (green). The dark area in the graph on the left hand side visualises the initial position of each target on the first cine-MR dynamic. The position of the targets due to intrafraction motion captured in a certain cine-MR frame is visualised as the dark areas in the graph on the righthand side. In this graph can be observed that the targets reach outside the 5 mm boundaries used in this example. Table 2 – Results from the coverage probability analysis using isometric volume expansion, providing the percentage of volume which is covered at least 95 percent of the time. Isometric volume expansion with the listed values was applied to the original masks created by the clinician on the first cine-MR dynamic of every fraction.
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