Investigation of the Backscatter and Attenuation Effect of the IntraOp Mobetron Attenuation Plate
X Kong*, A Zacarias, J Harris, Avera Medical Group - Radiation Oncology, Sioux Falls, SDSU-E-T-289 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
To investigate the backscatter and attenuation effect of the IntraOp Mobetron attenuation plate.
Method and Materials:
IntraOp Mobetron is a transportable LINAC which provides surgeons and radiation oncologists the option to deliver radiation right after the surgery procedure in the operating room. A single fraction IORT protocol is adapted in our institution as an option in Breast-Conserving treatment for operated breast cancer stages 0, I and II.
An 8cm diameter attenuation plate option is provided by vendor for protecting normal tissue and chest wall posterior to the tumor site. A 0.125cc PTW TN31010 semiflex chamber is used with IBA Blue Phantom2 for the measurement. The attenuation plate is taped to the IntraOp 10cm flat cone right below and above the chamber to measure the back scatter and attenuation effect. All the measurements were acquired at dref for 6MeV, 9MeV and 12MeV based on AAPM TG51.
The attenuation plate is made by about 7.1mm PMMA coated above 2.5mm copper layer. The percentage penetration radiation for 6Mev, 9MeV and 12MeV is 0.5%, 1.6% and 8.7% correspondingly. And the dose increase due to backscatter is negligible for all 6MeV, 9MeV and 12MeV (less than 0.5%).
Due to the 7.1mm PMMA layer and short range of backscatter radiation, the attenuation plate provides negligible dose increase to the tissue above. While the plate can dramatically reduced the dose below and well protect the tissue under and chest wall.