Surface doses of flattening filter free beams with volumetric modulated arc therapy dose delivery for breast cancer

Abstract

Background and purpose: Flattening filter free (FFF) beams enable high-dose rate irradiations and have the potential to speed up breast cancer radiotherapy (RT) treatments. In this work the surface doses of FFF beams were studied with various treatment plans for breast cancer RT. The near surface dose distributions were compared to the ones delivered with conventional flattening filter (FF) beams and to the calculated dose distributions. Materials and methods: The study was executed with radiochromic films. In addition to one open field, four techniques were investigated: tangential open field, tangential IMRT (IMRT), tangential VMAT (tVMAT) and continuous VMAT (cVMAT) techniques, respectively. The dose distributions were calculated with commercial Monte Carlo (MC) algorithm with energies of 6 and 10 MV with both FF and FFF. The surface areas investigated were divided into depths of 0-2, 2-5 and 5-8 mm. Results: The largest deviations (on average 5.9%) between the measured and calculated doses were recorded at the most shallowest depths (0-2 mm). At deeper depths, the differences were on average 1.4% and always less than 6%. The measured near surface doses were slightly lower (4.6%) with modulated 6MVFFF beams than with the corresponding flattened beams and on the contrary with 10 MV the surface doses by FFF were slightly higher (2.8%). Conclusions: The studied MC calculation algorithm was accurate in determine the near surface doses. There was no significant difference in measured or calculated surface doses between FFF and FF beams. With respect to surface dose uniformity the VMAT techniques overall resulted in the most uniform dose distributions.

The robustness of VMAT radiotherapy for breast cancer with tissue deformations

“…14 The Monaco VMC has been reported to achieve higher accuracy in near-surface doses. 17 Even though both VMC and AXB use Monte Carlo-based algorithms, the surface dose difference in the current study may be thus at least partly explained with differences between the algorithms.…”

“…found 2.4 ± 2.1 mm maximum swelling in 93 patients, with 12 patients (13%) having swelling exceeding 8 mm. 17 Jain et al . reported nine of ten patients having deformations between 6 and 8 mm, and one patient had 10-mm deformation.…”

Skin Surface Dose for Whole Breast Radiotherapy Using Personalized Breast Holder: Comparison with Various Radiotherapy Techniques and Clinical Experiences

“…Our results (Table 2) show that TPS seems to underestimate surface doses. There are many articles that use Monte Carlo to simulate the surface dose in breast cancer radiotherapy [47][48][49]. Arbor et al re ported a mean difference of 7% for Monte Carlo and 25% for the TPS compared with measurement data in the build-up range [50].…”

Investigation of Surface Dose Using Film Dosimetry and Commercial Treatment Planning System for Larynx Cancer Treatment with Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy

“…[12] Akino et al [13] compared the radiochromic film measurements with AAA calculations for different radiotherapy techniques including IMRT in breast cancer treatments and found that the calculation algorithm underestimated the doses near the surface by 15%-30%. They also reported that the et al [14] pointed out that an increase in dose uniformity might result in the reduction of surface dose. Another study explained that the dose distributed around the target causes lower doses at the surface.…”