An Empirical Model for Describing the Small Field Penumbra in Radiation Therapy

Figure 7

(a, b) The regression lines of e^−μϖ, where ϖ = , versus the distance on the + axis in (a) and the − axis in (b), at different gantry angles. The slopes are 0.0021, 0.0019, 0.0015, and 0.0011 at gantry angles of 90°, 60°, 45°, and 30°, respectively.

(a)

(b)