Dosimetric study of rapid arc and intensity modulated radiotherapy with and without flattening filter

Abstract

Author(s): Hridya VT, D. Khanna*, Aswathi Raj, Sathish Padmanabhan and P. Mohandass

Objective: This study aims to evaluate Intensity Modulated Radiotherapy (IMRT) and Rapid Arc based on Flattening Filter (FF) and Flattening Filter Free (FFF) beams.

Materials and Methods: Twelve patients with single brain metastases and dose prescription 25Gy in 5 fractions are selected and for each patient, both IMRT and Rapid arc plans are created with and without FF. All plans are analysed and compared based on various dosimetric parameters for Planning Target Volume (PTV) and Organ at Risks (OARs) along with technical parameters.

Results: The results among PTV dosimetric parameters improved with Rapid Arc plans from IMRT in both FF and FFF modes like the D98% bettered as (23.59 ± 0.85) and (23.65 ± 1.16) respectively with P values 0.011 and 0.025. The D80% of FFF arc plan has P value 0.030 with dose value (24.89 ± 0.59) and HI95% of both FF and FFF showed significant values (0.09 ± 0.04) and (0.10 ± 0.05) with P values 0.009 and 0.058. Conformation Number and Dose Gradient Index values of FF arc plan improved as (0.8 ± 0.06) and (0.27 ± 0.05) with P values 0.014 and 0.0001. Among OARs, the D0.1cc and Dmax of the Brainstem improved as (11.18 ± 6.59), (13.54 ± 7.09) in the FF arc plan, and (11.44 ± 8.33), (12.66 ± 8.38) in FFF arc plans. The V5, V10 and mean dose values of Healthy Tissue enhanced as (5.38 ± 3.98), (1.89 ± 1.61), (0.89 ± 0.51) the in FF arc plan, and (5.15 ± 3.35), (1.81 ± 1.35), (0.87 ± 0.46) in FFF arc plan with P values 0.022 and 0.017 for V5 and V10 of FFF arc plan. With Technical Parameters, the MU came better as (1148.5 ± 162.1) and (1297.5 ± 307.1) in FF and FFF arc plans whereas with TT, the FF arc plan improved to (4.38 ± 1.09) with a P value of 0.011.

Conclusion: The study reveals the benefits of Rapid arc from IMRT in all sectors of PTV dosimetric parameters, OAR dose values, and technical parameters in both FF and FFF modes.

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