Aim: To measure and compare the head scatter factor for 7. MV unflattened and 6. MV flattened photon beam using a home-made designed mini phantom. Background: The head scatter factor (Sc) is one of the important parameters for MU calculation. There are multiple factors that influence the Sc values, like accelerator head, flattening filter, primary and secondary collimators. Materials and methods: A columnar mini phantom was designed as recommended by AAPM Task Group 74 with high and low atomic number material for measurement of head scatter factors at 10cm and dmax dose water equivalent thickness. Results: The Sc values measured with high- Z are higher than the low- Z mini phantoms observed for both 6MV-FB and 7MV-UFB photon energies. Sc values of 7MV-UFB photon beams were smaller than those of the 6MV-FB photon beams (0.6-2.2% (Primus), 0.2-1.4% (Artiste) and 0.6-3.7% (Clinac iX (2300CD))) for field sizes ranging from 10. cm. ×. 10. cm to 40. cm. ×. 40. cm. The SSD had no influence on head scatter for both flattened and unflattened beams. The presence of wedge filters influences the Sc values. The collimator exchange effects showed that the opening of the upper jaw increases Sc irrespective of FF and FFF. Conclusions: There were significant differences in Sc values measured for 6MV-FB and unflattened 7MV-UFB photon beams over the range of field sizes from 10. cm. ×. 10. cm to 40. cm. ×. 04. cm. Different results were obtained for measurements performed with low- Z and high- Z mini phantoms. © 2015 Greater Poland Cancer Centre.

Arunai Nambiraj N

Department of Physics

School of Advanced Sciences

Vellore Campus

Ashokkumar S

Sinha S.N

Yadav G

Raman K

Bhushan M

Thiyagarajan R.

Fulltext

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Reports of Practical Oncology & Radiotherapy

Aim The purpose of this study is to determine the central-axis dose in the buildup region and the surface dose delivered by a 6 MV flattened photon beam (6 MV-FB) and a higher energy unflattened (7 MV-FFF) therapeutic photon beam for different-sized square fields with open fields and modifying filters. Materials and methods The beams are produced by a Siemens Artiste linear accelerator with a NACP-02 ionization chamber and the dose is measured by using GafChromic film and two different, commonly used, dosimeters: a p-type photon semiconductor dosimeter (PFD) and a cylindrical ionization chamber (CC13). Results The results indicate that the surface dose increases linearly with FS for both open and wedged fields for the 6 MV-FB and 7 MV-FFF beams. The surface dose delivered by the 7 MV-UFB beam is consistent with that delivered by the 6 MV-FB beam for field sizes up to 10 cm × 10 cm, after which the surface dose decreases. The buildup dose for the 7 MV-UFB beam is slightly less than that for the 6 MV-FB beam for field sizes ranging from 5 cm × 5 cm to 15 cm × 15 cm. For both the 6 MV-FB and 7 MV-FFF beams, the measured surface dose clearly increases with increasing field size, regardless of the detector used in the measurement. The surface dose measured with the PFD dosimeter and the NACP-02 and CC13 chambers differ significantly from the results obtained when using GafChromic film. The 7 MV-FFF beam results in a slightly smaller surface dose in the buildup region compared with the 6 MV-FB beam. Conclusions The surface dose delivered by the higher energy 7 MV-FFF beam is less than that delivered by the energy-unmatched FFF beam in previously published works. © 2016 Greater Poland Cancer Centre

Comparison of surface dose delivered by 7 MV-unflattened and 6 MV-flattened photon beams

Initial experience of hypofractionated radiation retreatment with true beam and flattening filter free beam in selected case reports of recurrent nasopharyngeal carcinoma

Medical Physics

Report of AAPM Therapy Physics Committee Task Group 74: In-air output ratio, Sc, for megavoltage photon beams

Radiotherapy and Oncology

FLATTENING FILTER FREE BEAMS IN IMRT AND SBRT: DOSIMETRIC ASS ESSMENTOF PERIPHERAL DOSE

Physics in Medicine and Biology

The characterization of unflattened photon beams from a 6 MV linear accelerator

Introduction to Radiological Physics and Radiation Dosimetry

Cavity Theory

Measurement and comparison of head scatter factor for 7 MV unflattened (FFF) and 6 MV flattened photon beam using indigenously designed columnar mini phantom

Journal	Data powered by TypesetReports of Practical Oncology & Radiotherapy
Publisher	Data powered by TypesetElsevier BV
ISSN	1507-1367
Open Access	Yes