Figure 1.

Comparative radiation dose distributions on plans for IMRT (panels a–c), PSPT (panels d–f), and IMPT (g–i) for a patient with locally advanced non-small cell lung cancer with a large right upper lung mass and involved contralateral hilar node. The red dose colorwash represents the high-dose distribution (100% isodose line); the blue dose colorwash depicts the low dose bath (10% isodose line); and the orange and green colorwashes represent intermediate dose. The GTV is contoured in red; the CTV in yellow; and the PTV in light blue. Both PSPT and IMPT are associated with significant reductions in the “low dose bath,” and IMPT provides better dose conformity to the target volumes than either PSPT or IMRT. CTV, clinical target volume; GTV, gross tumor volume; IMPT, intensity-modulated proton treatment; IMRT, intensity-modulated radiation therapy; PSPT, passively scattering proton therapy; PTV, planning target volume.