Comparative Dosimetric Analysis of IMRT and VMAT in Head and Neck Cancers

Purpose: The aim of study was to dosimetrically evaluate and compare IMRT and VMAT plans for irradiation of local head and neck cancers focusing on target coverage, conformity index, homogeneity index and dose perceived by the organs at risk (OAR). Methods: Prospective study conducted on 50 patients selected randomly and divided in two groups in which one group receive IMRT plan and another received VMAT plan. Results: PTV coverage was similar for both the techniques. The conformity index was higher for VMAT in comparison to IMRT which is statistically significant. The homogeneity index was also better in VMAT plans as compared to IMRT except for higher PTV volume where IMRT had better plans. The mean dose to parotid were significantly lesser in parotid glands in VMAT plans. Also, the point max dose to spinal cord, brainstem, vestibulocochlear nerve was lesser. There was no significant difference in dose received by spinal cord in both arms. Conclusion: VMAT provides better dose conformity, more homogenous target coverage and OAR sparing in comparison to IMRT.