10-Mv SBRT FFF Irradiation Technique Is Associated to the Lowest Peripheral Dose: The Outcome of 142 Treatment Plans for the 10 Most Common Tumour Locations

Abstract

There is a growing interest in the combined use of Stereotactic Body Radiation Therapy (SBRT) with Flattening Filter Free (FFF) due to the high local control rates and reduced treatment times, compared to conventionally fractionated treatments. It has been suggested that they may also provide a better radiation protection to radiotherapy patients as a consequence of the expected decrease in peripheral doses. This work aims to determine this reduction in unattended out-of-field regions, where no CT information is available but an important percentage of second primary cancers occur. For that purpose, ten different cases suitable for SBRT were chosen. Thus, 142 different treatment plans including SBRT, as well as 3D‐CRT, IMRT and VMAT (with standard fractionation) in low and high energies for Varian (FF and FFF), Siemens and Elekta machines were created. Then, photon and neutron peripheral dose in 14 organs were assessed and compared using two analytical models. For the prostate case, uncomplicated and cancer free control probability estimation was also carried out. As a general behavior, SBRT plans led to the lowest peripheral doses followed by 3D-CRT, VMAT and IMRT, in this order. Unflattened beams proved to be the most effective in reducing peripheral doses, especially for 10 MV. The obtained results suggest that FFF beams for SBRT with 10 MV represent the best compromise between dose delivery efficiency and peripheral dose reduction.

Real‐time in vivo dosimetry system based on an optical fiber‐coupled microsized photostimulable phosphor for stereotactic body radiation therapy

“…Therefore, the increase in the photon fluences and difference in the kerma factors at energies below 400 keV could contribute to the differences in the response of PSP and water at a field size of 10 × 10 cm 2 . However, in actual SBRT, an open field size of 10 × 10 cm 2 or more is rarely used because of the increasing use of IMRT and VMAT 37 . Furthermore, in IMRT or VMAT beam delivery, it was estimated that the effect of over‐response would be reduced even with a field size of 5 × 5 cm 2 or more since a very small flux is superimposed.…”

“…In the case of delivery using the VMAT technique, the dose rate varies during delivery. Recently, the use of VMAT with an FFF beam has increased in SBRT 37 . Therefore, it is necessary to evaluate the dose‐rate dependence in the range of the FFF beam dose rates.…”

“…Recently, the use of VMAT with an FFF beam has increased in SBRT. 37 Therefore, it is necessary to evaluate the dose-rate dependence in the range of the FFF beam dose rates. The measurements were performed at dose rates ranging from 400 to 2400 cGy/min.…”

“…However, in actual SBRT, an open field size of 10 9 10 cm 2 or more is rarely used because of the increasing use of IMRT and VMAT. 37 Furthermore, in IMRT or VMAT beam delivery, it was estimated that the effect of over-response would be reduced even with a field size of 5 9 5 cm 2 or more since a very small flux is superimposed. The simulated response of PSP using MC simulation demonstrates that our dosimetry system is less sensitive to energy dependence for field sizes <5 9 5 cm 2 .…”

Technical Note: Induced radioactivity in stereotactic body radiation therapy with a flattening‐filter‐free 10 MV beam model

“…[1][2][3][4] With precise beam delivery, SBRT can achieve superior local control rates. [4][5][6][7] Compared with the conventional fractionation, SBRT is characterized by higher fractional dose, fewer fractions, and longer delivery time. The flattening-filter-free 10 MV beam model (10 FFF) is generally used to reduce the delivery time, and it can achieve better target coverage and less peripheral dose.…”