open access

Vol 20, No 3 (2015)
Original research articles
Published online: 2015-05-01
Submitted: 2013-08-19
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Measurement and comparison of head scatter factor for 7MV unflattened (FFF) and 6MV flattened photon beam using indigenously designed columnar mini phantom

Sigamani Ashokkumar, Arunai Nambiraj, Sujit Nath Sinha, Girigesh Yadav, Kothanda Raman, Manindra Bhushan, Rajesh Thiyagarajan
DOI: 10.1016/j.rpor.2015.02.001
·
Rep Pract Oncol Radiother 2015;20(3):170-180.

open access

Vol 20, No 3 (2015)
Original research articles
Published online: 2015-05-01
Submitted: 2013-08-19

Abstract

Aim

To measure and compare the head scatter factor for 7[[ce:hsp sp="0.25"/]]MV unflattened and 6[[ce:hsp sp="0.25"/]]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 10[[ce:hsp sp="0.25"/]]cm 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[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]10[[ce:hsp sp="0.25"/]]cm to 40[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]40[[ce:hsp sp="0.25"/]]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[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]10[[ce:hsp sp="0.25"/]]cm to 40[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]04[[ce:hsp sp="0.25"/]]cm. Different results were obtained for measurements performed with low-Z and high-Z mini phantoms.

Abstract

Aim

To measure and compare the head scatter factor for 7[[ce:hsp sp="0.25"/]]MV unflattened and 6[[ce:hsp sp="0.25"/]]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 10[[ce:hsp sp="0.25"/]]cm 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[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]10[[ce:hsp sp="0.25"/]]cm to 40[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]40[[ce:hsp sp="0.25"/]]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[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]10[[ce:hsp sp="0.25"/]]cm to 40[[ce:hsp sp="0.25"/]]cm[[ce:hsp sp="0.25"/]]×[[ce:hsp sp="0.25"/]]04[[ce:hsp sp="0.25"/]]cm. Different results were obtained for measurements performed with low-Z and high-Z mini phantoms.

Get Citation

Keywords

Sc factor; 7MV-UFB; 6MV-FB; Mini phantom; Linear accelerators

About this article
Title

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

Journal

Reports of Practical Oncology and Radiotherapy

Issue

Vol 20, No 3 (2015)

Pages

170-180

Published online

2015-05-01

DOI

10.1016/j.rpor.2015.02.001

Bibliographic record

Rep Pract Oncol Radiother 2015;20(3):170-180.

Keywords

Sc factor
7MV-UFB
6MV-FB
Mini phantom
Linear accelerators

Authors

Sigamani Ashokkumar
Arunai Nambiraj
Sujit Nath Sinha
Girigesh Yadav
Kothanda Raman
Manindra Bhushan
Rajesh Thiyagarajan

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