saminathan madeswaran

To compare the three-dimensional conformal radiotherapy (3DCRT), dynamic conformal arc therapy (DCA), and volumetric modulated arc therapy (VMAT) in stereotactic body radiation therapy (SBRT) of liver cases using 6MV and 10 MV flattened beam (FB) and flattening filter-free beam (FFFB).Twenty liver SBRT patients were selected. The dose prescription was 40 Gy delivered in 5 fractions. 3DCRT, DCA and VMAT planning was performed using 6 MV FB, 6 MV FFFB, 10 MV FB and 10 MV FFFB. Planning target volume (PTV) coverage, organs at risk (OARs) doses, monitor units (MU), and beam on time (BOT) were noted.VMAT plan produces better PTV coverage in the D98% and D95% region. 6 MV and 10 MV VMAT FB and FFFB reduced the D700cc, V10Gy, and Dmean of the liver minus gross tumor volume region compared to 3DCRT and DCA plans. FFFB in combination with VMAT producing highly conformal plan (Conformit index=1.19), better conformity number (CN=0.85), and lowering Paddick gradient index (GIpad=3.29) in comparison to 3DCRT and DCA. The FFFB needs higher monitor units to achieve the plan in all the techniques. FFFB reduces the BOT, body-PTV mean dose in the non-tumour volume. VMAT combined with FFFB will produce a highly conformal plan, spare the OAR’s, deliver fast and dose fall off in the body-PTV region is more as compared to 3DCRT and DCA. The VMAT will more advantage to treat the multiple lesions simultaneously and reducing the intra-fraction motion error in liver SBRT.

To study the impact of 6 MV and 10 MV flattened beam (FB) and flattening filter free (FFF) beam in whole brain radiotherapy (WBRT) by using volumetric modulated arc therapy (VMAT). Twenty WBRTpatients were selected randomly. The dose prescription was 30 Gy, which was delivered in ten fractions. The planning target volume (PTV) and organs at risk (OARs) were contoured. Four VMAT plans, including 6 MV FB, 6 MV FFF, 10 MV FB, and 10 MV FFF beam plans, were generated. The 6MV FB and FFF beam plans were statistically significant (p <0.05) in terms of the dose received by 98% of the PTV (D98%) (26.86 Gy vs. 27.31 Gy, P=0.006), the dose received by 95% of the PTV (D95%) (28.28 Gy vs. 28.52 Gy, P=0.038), 107% isodose (V107%) of the PTV (2.43% vs. 3.74%, P=0.001), D100% of the hippocampus (9.31 Gy vs. 9.16 Gy, P=0.009), and the Dmean scalp (16.7 Gy vs. 16.8 Gy, p=0.035). The 10 MV FB and FFF beam plans showed significant differences in the conformity index (0.9 vs. 0.85, P=0.01), V107% of the PTV (1.68% vs. 4.54%, P=0.001), D100% (10.08 Gy vs. 9.81 Gy, P=0.036), and Dmean of the hippocampus (12.78 Gy vs. 12.57 Gy, P=0.018). The 6 MV and 10 MV FFF beams showed homogeneous conformal plans, which required 18-19% more MUs, compared to the FB plans. The 6 MV and 10 MV FB and FFFB spared the hippocampus and the scalp with acceptable target coverage in WBRT cases.