SU‐E‐T‐819: Impact of Dental Extractions on Dose Distribution and Planning for Head and Neck Intensity Modulated Radiation Therapy (IMRT)
Purpose: To investigate the equivalence of Head and Neck IMRT plans generated on a 1) pre‐dental extraction CT, with teeth to be removed contoured‐out as compared to 2) an actual post dental procedure CT. Ultimate goal is to improve clinic efficiency and through‐put by planning treatment during the patient recovery time from a dental extraction rather then after. Methods: A jaw phantom (constructed using 28 human teeth embedded in Aqua‐Plast mandible structures, submersed in a HN most with metal dental fillings) were contoured‐out; assigned HU=0. Simulating the post‐extraction CT, the 4 teeth were physically removed from the jaw. IMRT plans were then generated on these datasets simulating 5 clinically representative situations; critical structures and artefacts contoured and 3 PTVs of varying sizes representing stage T1, T2 and T3 oral cavitycancers were explored. Planning utilized a Pencil‐Beam Convolution algorithm and the Modified Batho tissue heterogeneity correction. Results: No perceptible differences were noted between IMRT plans optimized on pre‐extraction CTs with extracted teeth contoured‐out and plans optimized on the post‐extraction CTs in DVH and isodose coverage. Furthermore, IMRT plans calculated on post‐extraction datasets using fluences from pre‐extraction plans also showed no significant differences, validating the simulation of physical extraction by the contouring‐out process. Finally, plans calculated with teeth not contoured‐out showed underdosing in nearby regions as well as inferior DVHs. Conclusions: Results indicate that clinically comparable plans can be generated by contouring‐out teeth on a pre‐extraction CT. This suggests that our current practice of scheduling a planning CT at least 2 weeks after dental procedure may be unnecessary; instead this time can be used for treatment planning if swelling/jaw‐changes are deemed insignificant, thus saving significant wait times and increasing patient through‐put and clinic efficiency.