Program Information
Effect of Deconvolution in Analysis of Mega Voltage Photon Beam Profiles
M Muthukumaran1*, D Manigandan2 , V Murali3 , S Chitra4 , S Vikraman5 , K Ganapathy6 , (1) Apollo Speciality Hospitals, Chennai, Tamil Nadu, (2) Fortis Cancer Institute, Mohali, Punjab, (3) Apollo Speciality Hospital, Chennai, Tamil Nadu, (4) Apollo Speciality Hospital, Chennai, Tamil Nadu, (5) JAYPEE HOSPITAL- RADIATION ONCOLOGY, Noida, UTTAR PRADESH, (6) Apollo Speciality Hospital, Chennai, Tamil Nadu
Presentations
SU-F-T-478 (Sunday, July 31, 2016) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:
To study and compare the penumbra of 6 MV and 15 MV photon beam profiles after deconvoluting different volume ionization chambers.
Methods:
0.125cc Semi-Flex chamber, Markus Chamber and PTW Farmer chamber were used to measure the in-plane and cross-plane profiles at 5 cm depth for 6 MV and 15 MV photons. The profiles were measured for various field sizes starting from 2x2 cm till 30x30 cm. PTW TBA scan software was used for the measurements and the “deconvolution” functionality in the software was used to remove the volume averaging effect due to finite volume of the chamber along lateral and longitudinal directions for all the ionization chambers. The predicted true profile was compared and the change in penumbra before and after deconvolution was studied.
Results:
After deconvoluting the penumbra decreased by 1 mm for field sizes ranging from 2 x 2 cm till 20 x20 cm. This is observed for along both lateral and longitudinal directions. However for field sizes from 20 x 20 till 30 x30 cm the difference in penumbra was around 1.2 till 1.8 mm. This was observed for both 6 MV and 15 MV photon beams. The penumbra was always lesser in the deconvoluted profiles for all the ionization chambers involved in the study. The variation in difference in penumbral values were in the order of 0.1 till 0.3 mm between the deconvoluted profile along lateral and longitudinal directions for all the chambers under study. Deconvolution of the profiles along longitudinal direction for Farmer chamber was not good and is not comparable with other deconvoluted profiles.
Conclusion:
The results of the deconvoluted profiles for 0.125cc and Markus chamber was comparable and the deconvolution functionality can be used to overcome the volume averaging effect.
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