EP-1819: Plan of the Day is the optimal approach to address organ motion for cervical cancer IMRT
Radiotherapy and Oncology
________________________________________________________________________________ illustrates a small disparity from the reference whereas the fourth category show strong differences. Our hypothesis is that these categories can be used to identify patients in need of treatment adaptation. The Figure 1 shows the V95(%) parameter extracted from either the planning CT or the daily CBCT plan, as function of the average γ value for all beams. This average γ value is evaluated on the whole EPID image
... e whole EPID image (Figure 1a ) or the projected PTV1 image (Figure 1b) . The horizontal dash line represent the dose tolerance for PTV1 (99%). There is a correlation between the average γ and the PTV1 V95(%) but the projected PTV1 on the EPID image does provide additional information regarding the degree of error. However, the V95(%) variation from the original and deformed contours is related to the degree of error as indicated in Table 1 . Conclusion: In summary, we demonstrated that PTV1 projection on the EPID plan does not provide new information on the plan deterioration. However, this method was more sensitive to anatomical changes and could be used as an indicator instead of the mean γ on the whole EPID image. In the following steps, the organs at risk projections will be evaluated to verify if they do provide new information. This approach is valuable for the treatment quality, but does not increase the dose to the patient or the time required for treating a fraction. Image acquisition and analysis can be easily automatized to further minimize the impact on the clinical workload. EP-1819 Plan of the Day is the optimal approach to address organ motion for cervical cancer IMRT Purpose or Objective: ART is a time-consuming process and the question "do we need to replan?" is not always easy to answer. In this work, we investigate: (i) if Deformable Image Registration (DIR) software can provide reliable criteria to decide if we need to replan; (ii) if we can use DIR to replan the treatment without performing a new planning CT.