An Update of Couch Effect on the Attenuation of Megavoltage Radiotherapy Beam and the Variation of Absorbed Dose in the Build-up Region

Shiraz University of Medical Sciences

Y Makhdoomi¹  M Momennezhad¹  T Sedaghatian²  S H Rasta² 

[1] Mashhad University of Medical Physics;Tabriz University of Medical Sciences

关键词: Beam Attenuation;    Carbon Fiber;    Couch Insert;    Surface Dose;    Megavoltage Radiotherapy;   

DOI  :  10.22086/jbpe.v0i0.626

学科分类：生物科学（综合）

来源: Shiraz University of Medical Sciences

【 摘 要 】

Purpose:Fiber carbon is the most common material used in treating couch as it causes less beam attenuation than other materials. Beam attenuation replaces build-up region, reduces skin-sparing effect and causes target volume under dosage. In this study, we aimed to evaluate beam attenuation and variation of build-up region in 550 TxT radiotherapy couch. Materials and Methods:In this study, we utilized cylindrical PMMA Farmer chamber, DOSE-1 electrometer and set PMMA phantom in isocenter of gantry and the Farmer chamber on the phantom. Afterwards, the gantry rotated 10°, and attenuation was assessed. To measure build-up region, we used Markus chamber, Solid water phantom and DOSE-1 electrometer. Doing so, we set Solid water phantom on isocenter of gantry and placed Markus chamber in it, then we quantified the build-up region at 0° and 180° gantry angels and compared the obtained values. Results:Notable attenuation and build-up region variation were observed in 550 TxT treatment table. The maximum rate of attenuation was 5.95% for 6 MV photon beam, at 5×5 cm2 field size and 130° gantry angle, while the maximum variation was 7 mm for 6 MV photon beam at 10×10 cm2 field size. Conclusion:Fiber carbon caused beam attenuation and variation in the build-up region. Therefore, the application of fiber carbon is recommended for planning radiotherapy to prevent skin side effects and to decrease the risk of cancer recurrence.

【 授权许可】

CC BY