Figure 1.

Clinical target volumes (red) and proton planning target volume (pPTV; magenta) for an example patient. The density of the green contour in (a-c) is assigned to air and tissue density on the computed tomography air and computed tomography tissue, respectively. The blue, orange, and cyan filled contour are the pPTV_RT, pPTV_PA, and pPTV_LT volumes. Typical field dose for the right-lateral (d-f), posterior-anterior (g-i), and left-lateral (j-l) beams demonstrates that superiorly, the 3 fields cover the pelvic nodes, with all portions of the target covered by at least 2 beams. Only the 2 lateral fields cover the prostate; the posterior-anterior beam (i) does not cover the target to avoid beam passing through the rectum.