SU-F-T-289: MLC Fluence Sonogram Based Delivery Quality Assurance for Bilateral Breast Irradiation

Purpose: Performing DQA for Bilateral (B-L) breast tomotherapy is a challenging task due to the limitation of any commercially available detector array or film. Aim of this study is to perform DQA for B-L breast tomotherapy plan using MLC fluence sinogram. Methods: Treatment plan was generated on To...

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Bibliographic Details
Published in:Medical physics (Lancaster) 2016-06, Vol.43 (6), p.3529-3529
Main Authors: Thiyagarajan, Rajesh, Karrthick, KP, Kataria, Tejinder, Arunai, N, Raj, Nambi, Mahendran, Ramu, Selvan, Tamil, Duraikannu, Palani
Format: Article
Language:English
Subjects:
60 APPLIED LIFE SCIENCES
Cancer
Computed tomography
COMPUTER CODES
Computer software
COMPUTERIZED TOMOGRAPHY
CT-GUIDED RADIOTHERAPY
Detector arrays
ELECTRIC POTENTIAL
IONIZATION CHAMBERS
MAMMARY GLANDS
Multileaf collimators
PHOTON BEAMS
Photons
QUALITY ASSURANCE
RADIATION DOSES
RADIATION PROTECTION AND DOSIMETRY
WHOLE-BODY IRRADIATION
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Summary:Purpose: Performing DQA for Bilateral (B-L) breast tomotherapy is a challenging task due to the limitation of any commercially available detector array or film. Aim of this study is to perform DQA for B-L breast tomotherapy plan using MLC fluence sinogram. Methods: Treatment plan was generated on Tomotherapy system for B-L breast tumour. B-L breast targets were given 50.4 Gy prescribed over 28 fractions. Plan is generated with 6 MV photon beam & pitch was set to 0.3. As the width of the total target is 39 cm (left & right) length is 20 cm. DQA plan delivered without any phantom on the mega voltage computed tomography (MCVT) detector system. The pulses recorded by MVCT system were exported to the delivery analysis software (Tomotherapy Inc.) for reconstruction. The detector signals are reconstructed to a sonogram and converted to MLC fluence sonogram. The MLC fluence sinogram compared with the planned fluence sinogram. Also point dose measured with cheese phantom and ionization chamber to verify the absolute dose component Results: Planned fluence sinogram and reconstructed MLC fluence sinogram were compared using Gamma metric. MLC positional difference and intensity of the beamlet were used as parameters to evaluate gamma. 3 mm positional difference and 3% beamlet intensity difference were used set for gamma calculation. A total of 26784 non-zero beamlets were included in the analysis out of which 161 beamlets had gamma more than 1. The gamma passing rate found to be 99.4%. Point dose measurements were within 1.3% of the calculated dose. Conclusion: MLC fluence sinogram based delivery quality assurance performed for bilateral breast irradiation. This would be a suitable alternate for large volume targets like bilateral breast, Total body irradiation etc. However conventional method of DQA should be used to validate this method periodically.
ISSN:0094-2405
2473-4209
DOI:10.1118/1.4956429