Example of a head and neck IMRT case (not used for quantitative evaluation) with three adjacent, nested targets, partially abutting the patient outline. DVH for irradiation with 6 MV photons and bolus (thickness 5 mm): dashed line. Without bolus: solid line. Left diagram: Three nested, adjacent, non-overlapping PTV. Right diagram: Three nested PTV5 (PTV shrunk by 5 mm). From left to right: Outer (circumferential) to inner (central) PTV.