RapidArc vs IMRT: Our Experience in Head and Neck Cancers-A Dosimetric Study - Abstract
Introduction: To compare double arc (DA), Sliding window (SW) & Step and shoot (SS) IMRT in Head & neck cancer (HNC) by different dosimetric parameters.
Materials and methods: 25 cases of HNC were planned for DA, SW & SS IMRT by Treatment Planning System-Eclipse (version 10.0) between September 2012 to February 2013. Primary end points were target coverage and doses to organs at risk (OARs). The secondary end points were the treatment time (TT) and the monitor units (MUs). Statistical analysis was done using K independent sample test and paired t test.
Results: The coverage for target volumes were similar by all the three techniques (p>0.05). There were also no difference in Homogenity Index (HI) and Conformity Index (CI) (p>0.05). Dmean to OARs were maximum with DA followed by SW and SS IMRT. Ipsilateral parotids, contralateral parotids and dysphagia aspiration risk structures (DARS) received higher mean dose by DA than by SW and SS IMRT (p<0.05). The Dmax for Brain stem and 1% volume of spinal cord was least by SS IMRT (p<0.05). The difference in Dmean between SW and SS IMRT for oral cavity was 0.5 ± 0.10Gy (p<0.05). However, DA had the advantage of requiring minimum number of MUs (p<0.05) and TT (p<0.05) in comparison to SW and SS IMRT.
Conclusion: DA gave the advantage of minimum number of monitor units and least total treatment time over SS and SW IMRT. However, it was indifferent for target coverage, homogeneity and OAR sparing.