Program Information
Quantification the Dosimetric Impact of the Elekta IBEAM Evo Couchtop EP in Different Beam Energies
R Zhang1 , Y Gao2 , W Bai1*, X Fan1 , Z Chi1 , (1) The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei, (2) Hebei General Hospital, Shijiazhuang, Hebei
Presentations
PO-BPC-Exhibit Hall-17 (Saturday, March 5, 2016) Room: Exhibit Hall
Purpose:To quantification the dosimetric impact of the Elekta Couchtop EP in different beam energies and different depths were measured to evaluate the impact of treatment couch on surface dose distributions.
Methods:Film measurements were performed with EBT3 film with an MLCi2-shaped of a (10x10) cm2 field on a solid water phantom surface. Measurements were performed at different depths (1 mm, 5 mm, 10 mm, 15 mm, 20 mm and 25 mm) at an SSD = 100cm, irradiated with 400MU. The absorbed doses of deliveries at gantry angles 180° and 0° were compared. Using the ImageJ software to extract the digitized films red channel intensity value, and the intensity value is adjusted to 1 MU corresponds to a dose of 1 cGy at the depth of dose maximum. By interpolation to get the Percent Depth Dose curves with and without the Couchtop at the gantry angle 180° and 0°.
Results:The Couchtop EP showed a significant change in surface dose from 184 cGy, 140 cGy and 117 cGy to 383 cGy, 352 cGy and 296 cGy with the introduction of the treatment couch into the 6MV, 10 MV and 18 MV beam at the phantom depth 1mm, increased 109% , 151% and 153 %, respectively. We can get that the depth of maximum dose also decreased by almost 10 mm across all experimental setups for all the beam energies we have measured when the Couchtop EP was introduced into the treatment beam.
Conclusion:When the beam intersects the treatment couch surface the buildup effect occurred in a clinical setting. The Couchtop EP can approximately double the surface dose, relative to the maximum delivered dose, on the skin of the patient which should be taking more notice. This buildup interference by the treatment couch is most prevalent for lower treatment energies.
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