Dosimetric study of RapidArc plans with flattened beam (FB) and flattening filter-free (FFF) beam for localized prostate cancer based on physical indices

Birendra Kumar Rout, Kanaparthy R Muralidhar, Mirza Ali, Mukka C Shekar, Alok Kumar

Abstract


Purpose: To identify the continual diversity between flattening photon beam (FB) and Flattening Filter Free (FFF) photon beams for localized prostate cancer; and to determine potential benefits and drawbacks of using unflattened beam for this type of treatment.

Methods: Eight prostate cases including seminal vesicles selected for this study. The primary planning target volume (PTVP) and boost planning target volume (PTVB) were contoured. The total prescription dose was 78 Gy (56 Gy to PTVP and an additional 22 Gy to PTVB). For all cases, treatment plans using 6MV with FB and FFF beams with identical dose-volume constraints, arc angles and number of arcs were developed. The dose volume histograms for both techniques were compared for primary target volume and critical structures.

Results: A low Sigma index (FFF: 1.65 + 0.361; FB: 1.725 + 0.39) indicating improved dose homogeneity in FFF beam. Conformity index (FFF: 0.994 + 0.01; FB: 0.993 + 0.01) is comparable for both techniques. Minimal difference of Organ at risk mean dose was observed. Normal tissue integral dose in FB plan resulted 1.5% lower than FFF plan. All the plans displayed significant increase (1.18 times for PTVP and 1.11 for PTBB) in the average number of necessary MU with FFF beam.

Conclusion: Diversity between FB and FFF beam plans were found. FFF beam accelerator has been utilized to develop clinically acceptable Rapid Arc treatment plans for prostate cancer with 6 MV.

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Cite this article as: Rout BK, Muralidhar KR, Ali M, Shekar MC, Kumar A. Dosimetric study of RapidArc plans with flattened beam (FB) and flattening filter-free (FFF) beam for localized prostate cancer based on physical indices. Int J Cancer Ther Oncol 2014; 2(4):02046.  DOI: 10.14319/ijcto.0204.6


Keywords


Flattening Filter-Free; Flattened Beam; Sigma-Index; Conformity Index; Normal Tissue Integral Dose; Rapid Arc

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DOI: http://dx.doi.org/10.14319/ijcto.0204.6

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