Figure 1. Dose-volume .histogram in a patient with T3N0M0 supraglottic laryngeal cancer illustrating the potential of image-guided radiotherapy to deliver a high radiation dose to the gross tumor while sparing the radiosensitive normal organs.

Mean tumor dose: 75.4 Gy; mean right parotid dose (light green):11.4 Gy; mean left parotid dose (violet): 11.3 Gy; mean right (dark green) and left (pink) cochlea dose: 2 Gy; maximum mandibular dose (orange): 59.5 Gy; maximum spinal cord dose (light blue): 31.2 Gy. The radiation dose to these normal structures was well below the threshold for normal tissue damage and could potentially improve the patient quality of life after treatment. The red color illustrated radiation dose (70 Gy) to the gross tumor volume (gtv) while the dark blue and green color demonstrated radiation dose to the high risk area (63 Gy) and low risk area (56 Gy) respectively. The brown color illustrated radiation dose to the pharyngeal muscles which was high (mean 67 Gy) because of the close proximity to the gross tumor and may explain the high rate of dysphagia following radiotherapy for locally advanced laryngeal cancer.