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Program Information

Clinical IGRT: Treatment Site Uncertainties, IGRT Protocol Design and Informed Margins

K Wijesooriya

D Vile

K Wijesooriya1*, D Vile2*, (1) University of Virginia Health Systems, Charlottesville, VA, (2) Indiana University, Indianapolis, IN


2:00 PM : Treatment site uncertainties in IGRT - K Wijesooriya, Presenting Author
2:30 PM : IGRT protocol design and Informed margins - D Vile, Presenting Author

TH-F-205-0 (Thursday, August 3, 2017) 2:00 PM - 3:00 PM Room: 205

With advanced in-room imaging techniques, and frequency of imaging during treatment, the intra-fraction motion could be greatly reduced. The magnitude and probability of tumor movement from the initial set up to the moment of dose delivery completion will depend upon many factors such as treatment times, immobilization, treatment site, and patient obesity. In this session, we will review the imaging systems in terms of targeting accuracy and image quality. We will then discuss strategies on integrating these tools into image guidance protocols in the clinic that are tailored to specific disease sites like H&N, lung, pelvis, and cranial SRS. Differences in offline and on-line correction strategies and the importance of time efficiency and verification imaging will be included. Radiation treatment planning has relied on the concept of margins for many years in order to ensure adequate tumor coverage. Margins represent a compromise between ensuring adequate coverage and sparing normal tissue. Margin recipes have been published and traditionally used in order to compute the necessary margin. However, the advent and increased usage of image guidance, there has been a push to reduce these margins due to their potential for better target localization. Care must be taken in order to reduce margins safely. This presentation will break down the components of the margin and how these affect the overall margin. Emphasis will be placed on using published data to pair the treatment margin with the image guidance modality to maximize the likelihood of a successful outcome.

Learning Objectives:
1. Site specific image registration accuracies for different modalities
2. Site specific, inter and intra fraction mobility
3. Dosimetric consequences of exceeding the tolerances
4. Site and setup specific, influence in radiation therapy margin selection.
5. How margins are quantified, both on a population and patient specific basis.
6. How to couple the selected margin with image guidance in order to maximize likelihood of targeting the tumor


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