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

open access

Page views 173
Article views/downloads 290
Get Citation

Connect on Social Media

Connect on Social Media

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

Sigamani Ashokkumar12, Arunai Nambiraj2, Sujit Nath Sinha1, Girigesh Yadav1, Kothanda Raman1, Manindra Bhushan1, Rajesh Thiyagarajan12
DOI: 10.1016/j.rpor.2015.02.001
Rep Pract Oncol Radiother 2015;20(3):170-180.

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.

Article available in PDF format

View PDF Download PDF file



Reports of Practical Oncology and Radiotherapy