The aim of the work was to determine the best
beams number and segments in order to improve the
plans conformity and homogeneity that generate low
monitor units (MUs) and faster irradiated time for
different types of head and neck cancer (HNC).
This study includes 30 patients with different HNC.
Intensity modulated radiotherapy (IMRT) treatment
planning techniques were done with step and shoot
delivery technique, 5, 7 and 9 beams IMRT were carried
out for each patient. The treatment plans for all patients
were calculated and optimized using fast superposition
algorithm. All plans were generated using equal spaced
odd beam number around the target. 6 MV were used in
all beams. Multiple segments were created for each
beam. Typically maximum iteration was carried out to
achieve optimized plans. The beam weight optimized to
generate the plan, then the segment weight optimized for
all plans by using sliding window methods. The final
optimization maps were converted into a way of step and
shoot sequence map which delivered by linear
accelerator using multi leaf collimator (MLC). IMRT
plans were compared based on several criteria: Isodose
distributions, the mean and standard deviation with pvalues for planning target volume (PTV) 95%,
conformity index (CI), homogeneity index (HI), organs
at risk (OARs), number of segments, MUs and total
irradiated time were presented and compared in all
patients. Statically analyses were compared for all
patients used ANOVA testes.
Keywords : IMRT, Radiotherapy Techniques, Beam Number, Treatment Planning.