Leakage-Penumbra effect in intensity modulated radiation therapy step-and-shoot dose delivery

Figure 1 Segment sequence, dose distribution and segment profiles of an anterior-posterior intensity modulated radiation therapy beam. A: The shapes of the beam segments; B: The dose distribution caused by the segment sequence; C: The beam and segment beam profiles. BP: Beam profile.

Figure 2 A comparison between beam profile for a beam affected by the overshoot effect of the biggest segment in the sequence (thin curve), and a beam with smaller segment (bold curve) on the first position in the segment sequence. A, B and C are the dosimetric points of dose delivery.

Figure 3 Penumbra errors caused by the neighbouring segments. MRI: Magnetic resonance imaging.

Figure 4 Three-dimensional dose distribution of the beam from Figure 1. 3D: 3-dimensional; CA: Central Axis.

Figure 5 A comparison between the beam profiles from Pinnacle³, static (reference) and intensity modulated radiation therapy beams. P3: Pinnacle³.

Figure 6 A corrected leakage-penumbra profile from the isocenter of the beam, as shown in Figure 1. LP: Leakage-penumbra.

Figure 7 Corrected dose profile (beam profile-leakage penumbra) vs original delivered profile (central axis beam profile). LP: Leakage-penumbra; P3: Pinnacle³.

Figure 8 Three-dimensional dose distribution of the leakage-penumbra extracted from the beam in Figure 1.

Math 1 Math(A1).