ACCURACY OF FIELD ALIGNMENT IN RADIOTHERAPY OF HEAD AND NECK-CANCER UTILIZING INDIVIDUALIZED FACE MASK IMMOBILIZATION - A RETROSPECTIVE ANALYSIS OF CLINICAL-PRACTICE

Deviations between simulation and first check films were quantitativel y assessed for 95 unselected head and neck cancer patients. All measur ed deviations - calculated on the basis of a total of 190 simulation a nd 380 verification films - were normally distributed, with mean value s of 0-3 mm and standard deviations of 3-5 mm. Of the absolute deviati ons, 50% and 95% were within 3 mm and 9 mm, respectively. These result s should be considered in clinical practice when prescribing safety ma rgins and adequate cut off doses for sparing critical organs in head a nd neck cancer.