(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: the accuracy of the Varian carbon fiber treatment couch virtual model and the impact of radiation therapy.
Methods: and analyze the actual structure of the treatment couch, establish the actual treatment couch model A, virtual couch model B (-300HU, -1000HU), virtual couch model C (-580HU, -950HU) and no treatment couch model D, compare the wear under different angles Shooting factor. The effects of the couch model were evaluated using different conditions: AAA, AXB dose algorithm, 6MV, 6FFF, 8MV, 10MV, 10FFF five-field field energy, thin, medium and thick three couch thickness and mold surface dose.
Results: actual treatment couch ray attenuation was 3.11±1.57%, and the highest at 115° was 6.75%. Model C is closer to the actual couch than model B, with deviations of 0.45 ± 0.57% and -0.38 ± 0.97%, respectively. Under different planning conditions, the AAA algorithm overestimated the attenuation of the treatment couch by 0.71±0.44%; the lower the ray energy, the greater the couch attenuation; the difference in thickness of different models was not statistically significant; the surface dose of the phantom increased by 30.8%, and the maximum dose point became shallower 0.3cm.
Conclusion: of the virtual couch models can simulate the actual treatment couch, but in the curved high-density areas on both sides of the couch, the virtual model underestimates the attenuation of the treatment couch, and the model still needs further correction. The -580HU, -950HU parameters and AXB algorithm are recommended for clinical work. The built-in effect of the treatment couch increases the patient's skin dose and changes the target dose distribution, especially under low energy ray conditions.
Keywords
Taxonomy
TH- External Beam- Photons: General (most aspects)
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