Radiotherapy X-ray dose and tumour control beyond air cavities

The use of convolution calculations in radiotherapy treatment planning systems has improved the accuracy of dose prediction in lung. The authors further test the accuracy of the collapsed cone convolution calculation method in a head/neck slab phantom where a larynx type air cavity is involved. Because the tumor control probability (TCP) versus dose curve is relatively steep any dose deficit in the secondary build up region which might compromise TCP is of concern.