scholarly journals Feasibility of output quality assurance considering gantry angle using “Stealth Chamber”

2021 ◽  
Vol 27 (4) ◽  
pp. 299-302
Author(s):  
Hideharu Miura ◽  
Fumika Takeichi ◽  
Tsubasa Enosaki ◽  
Kiyoshi Yamada ◽  
Shuichi Ozawa ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Correction Factor ◽  
Field Size ◽  
Correction Factors ◽  
X Ray ◽  
Dose Rates ◽  
Flattening Filter Free ◽  
Output Quality ◽  
Flattening Filter ◽  
Gantry Angle

Abstract Purpose: This study was conducted to demonstrate the feasibility of X-ray output constancy quality assurance (QA) of a linear accelerator for various gantry angles using the Stealth Chamber. Methods: The X-ray output constancy of a Varian TrueBeam STx was evaluated under various gantry angles and a 10 × 10 cm2 field size using a Stealth Chamber. Specifically, 10X and 10X-flattening-filter-free beams with dose rates of 600 and 2400 monitor units (MU)/min, respectively, were used. The Stealth Chamber was attached to the gantry head, and irradiation was performed every 45° for gantry angles of 0-315°. To evaluate the variations in the output constancy with respect to the gantry angle, the acquired values were normalized to the value corresponding to a 0° gantry angle. The obtained results were utilized to determine the correction factors for all gantry angles. To verify the correction factors, additional measurements were performed for five days. Results: The maximum variation in the output constancy measurement relative to the output constancy at a 0° gantry angle was found to be approximately 4.0% for both energy beams at a gantry angle of 180°. Furthermore, the measured values were dependent on the gantry angle. Upon applying the correction factor, the variation in the output constancy with respect to the gantry angle was less than 0.5%. Conclusions: Output constancy QA using the Stealth Chamber for various gantry angles was found to be feasible with the application of a correction factor.

scholarly journals Effect of X-ray dose rates higher than 8 Gy/min on the functioning of cardiac implantable electronic devices

2020 ◽  
Vol 61 (3) ◽  
pp. 419-425 ◽  
Author(s):  
Kazuhiko Nakamura ◽  
Takahiro Aoyama ◽  
Naoki Kaneda ◽  
Masashi Otsuji ◽  
Yoshitaka Minami ◽  
...  
Keyword(s):  
Dose Rate ◽  
Treatment Plan ◽  
Electronic Devices ◽  
Normal Function ◽  
X Ray ◽  
Dose Rates ◽  
Cardiac Implantable Electronic Devices ◽  
Flattening Filter Free ◽  
Direct Irradiation ◽  
Flattening Filter

Abstract Direct irradiation may cause malfunctioning of cardiac implantable electronic devices (CIEDs). Therefore, a treatment plan that does not involve direct irradiation of CIEDs should be formulated. However, CIEDs may be directly exposed to radiation because of the sudden intrafractional movement of the patient. The probability of CIED malfunction reportedly depends on the dose rate; however, reports are only limited to dose rates ≤8 Gy/min. The purpose of this study was to investigate the effect of X-ray dose rates >8 Gy/min on CIED function. Four CIEDs were placed at the center of the radiation field and irradiated using 6 MV X-ray with flattening filter free (6 MV FFF) and 10 MV X-ray with flattening filter free (10 MV FFF). The dose rate was 4–14 Gy/min for the 6 MV FFF and 4–24 Gy/min for 10 MV FFF beams. CIED operation was evaluated with an electrocardiogram during each irradiation. Three CIEDs malfunctioned in the 6 MV FFF condition, and all four CIEDs malfunctioned in the 10 MV FFF condition, when the dose rate was >8 Gy/min. Pacing inhibition was the malfunction observed in all four CIEDs. Malfunction occurred simultaneously along with irradiation and simultaneously returned to normal function on stopping the irradiation. An X-ray dose rate >8 Gy/min caused a temporary malfunction due to interference. Therefore, clinicians should be aware of the risk of malfunction and manage patient movement when an X-ray dose rate >8 Gy/min is used for patients with CIEDs.

Adaptation of NCS report 24 for flattening filter free VMAT quality assurance

2018 ◽  
Vol 52 ◽  
pp. 177
Author(s):  
Sean Gillespie ◽  
Terence Casey ◽  
Patrick Monnelly
Keyword(s):  
Quality Assurance ◽  
Flattening Filter Free ◽  
Flattening Filter

scholarly journals Differentiation of Using Flattening Filter Free Energy in Vmat Plans for Prostate Cancer

2018 ◽  
Vol 22 ◽  
pp. 01049 ◽  
Author(s):  
Yonca Yahşi Çelen ◽  
Atilla Evcin
Keyword(s):  
Prostate Cancer ◽  
Planning System ◽  
Treatment Planning System ◽  
Conformity Index ◽  
Dose Rates ◽  
Advantages And Disadvantages ◽  
Flattening Filter Free ◽  
Significant Difference ◽  
Treatment Plans ◽  
Flattening Filter

It is aimed to compare the values of conformity index (CI), homogeneity index (HI), monitor unit (MU) of volumetrically adjusted arthritis therapy (VMAT) plans using 10 prostate cancer patients with flattened filter (FF) and without flattening filter (FFF). In the study, treatment plans were prepared using 6 FF and 6 FFF in the Eclipse (ver.13.6) treatment planning system with Varian Trilogy Linear Accelerator. When planning was completed, CI averaged 0.87, HI averaged 0.44 and MU values were found to be 591 ± 26.8, 650 ± 33.06, respectively. When the PTV coverage, CI, HI and MU comparisons were made as a result of planning, there was no significant difference when comparing VMAT plans in FFF and FF energies. When we compare the MU values, the MU increase is seen when the straightening filter is removed. In both energy modes, good homogeneity in PTV was achieved with conventional francitation and close dose rates. No significant advantages and disadvantages of the unfiltered energy mode were observed in the assessment of plan quality in terms of CI, HI.

SU-E-T-555: Small Field Dosimetry of the Flattening Filter Free (FFF) X-Ray Photons

2011 ◽  
Vol 38 (6Part19) ◽  
pp. 3617-3617
Author(s):  
Y Wang ◽  
S Easterling ◽  
J Ting
Keyword(s):  
Small Field ◽  
X Ray ◽  
Small Field Dosimetry ◽  
Flattening Filter Free ◽  
Flattening Filter

Flattening filter free beams from TrueBeam and Versa HD units: Evaluation of the parameters for quality assurance

2015 ◽  
Vol 43 (1) ◽  
pp. 205-212 ◽  
Author(s):  
Antonella Fogliata ◽  
Jens Fleckenstein ◽  
Frank Schneider ◽  
Marc Pachoud ◽  
Sarah Ghandour ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Flattening Filter Free ◽  
Flattening Filter

scholarly journals Estimation of Dosimetric Parameters based on KNR and KNCSF Correction Factors for Small Field Radiation Therapy at 6 and 18 MV Linac Energies using Monte Carlo Simulation Methods

2019 ◽  
Vol 9 (1Feb) ◽  
Author(s):  
S A Rahimi ◽  
B Hashemi ◽  
S R Mahdavi
Keyword(s):  
Monte Carlo ◽  
Correction Factor ◽  
Reference Conditions ◽  
Field Size ◽  
Monte Carlo Code ◽  
Small Field ◽  
Correction Factors ◽  
Photon Beams ◽  
Small Field Dosimetry ◽  
Circular Field

Background: Estimating dosimetric parameters for small fields under non-reference conditions leads to significant errors if done based on conventional protocols used for large fields in reference conditions. Hence, further correction factors have been introduced to take into account the influence of spectral quality changes when various detectors are used in non-reference conditions at different depths and field sizes.Objective: Determining correction factors (KNR and KNCSF) recommended recently for small field dosimetry formalism by American Association of Physicists in Medicine (AAPM) for different detectors at 6 and 18 MV photon beams.Methods: EGSnrc Monte Carlo code was used to calculate the doses measured with different detectors located in a slab phantom and the recommended KNR and KNCSF correction factors for various circular small field sizes ranging from 5-30 mm diameters. KNR and KNCSF correction factors were determined for different active detectors (a pinpoint chamber, EDP-20 and EDP-10 diodes) in a homogeneous phantom irradiated to 6 and 18 MV photon beams of a Varian linac (2100C/D).Results: KNR correction factor estimated for the highest small circular field size of 30 mm diameter for the pinpoint chamber, EDP-20 and EDP-10 diodes were 0.993, 1.020 and 1.054; and 0.992, 1.054 and 1.005 for the 6 and 18 MV beams, respectively. The KNCSF correction factor estimated for the lowest circular field size of 5 mm for the pinpoint chamber, EDP-20 and EDP-10 diodes were 0.994, 1.023, and 1.040; and 1.000, 1.014, and 1.022 for the 6 and 18 MV photon beams, respectively.Conclusion: Comparing the results obtained for the detectors used in this study reveals that the unshielded diodes (EDP-20 and EDP-10) can confidently be recommended for small field dosimetry as their correction factors (KNR and KNCSF) was close to 1.0 for all small field sizes investigated and are mainly independent from the electron beam spot size.

MO-D-BRB-05: Skin Dose Study of the Flattening Filter Free (FFF) X-Ray Photons

2011 ◽  
Vol 38 (6Part25) ◽  
pp. 3710-3710
Author(s):  
Y Wang ◽  
S Easterling ◽  
J Ting
Keyword(s):  
Skin Dose ◽  
X Ray ◽  
Flattening Filter Free ◽  
Dose Study ◽  
Flattening Filter
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