Treatment planning (cont'd)
- Enter the number of treatment sessions, or fractions. For our head and neck case, there are 20 fractions. Daily target dose = total dose / number of fractions. Thus, daily dose = 30 Gy / 20 fractions = 1.5 Gy / fraction. Time = 10 sec.
- For target and critical structures, enter positioning uncertainty. For our case, we assume CTV1 localization uncertainty = 0 mm. Spinal cord positioning uncertainty = 3 mm. Time = 5 min.
- Select linac, energy and number of intensity levels. We use 6 MV with 10 intensity levels on all IMRT plans. Time = 10 sec.
- Enter number of fields. For our case, 7 equally-spaced, non-overlapping fields were desired. Time = 10 sec.
- For each field, enter gantry, collimator, and table angles. For our case, the collimator and table were in the home position. Gantry angles (IEC convention) were 0, 51, 103, 154, 206, 257 and 308°. Time = 1 min.