Room: Karl Dean Ballroom C
Purpose: Adaptive radiation therapy (ART) is a new motion management modality where dose re-planning is rapidly performed before the start of each treatment fraction while the patient is on the LINAC treatment table. However, ART cannot address real-time tumor motion or other volumetric changes that may take place during actual radiation delivery. To overcome this limitation, we present a feasibility study on a method to perform intra-fractional ART based on ultra-fast beamlet optimization.
Methods: It is assumed that beamlets are located 360 degree around the patient in either a ring or cylinder configuration such as formed by a radiation source that rapidly rotates around the patient, and that beamlets can be turned on/off at near real-time speeds. It is also assumed that there a suitable image tracking system that can track the internal motion of the PTV and OARs in real-time. Given these assumptions an ideal fluence map is first calculated for the patient using the initial CT scan. This is used until a patient motion that larger than certain threshold is detected, the radiation beam was then turned off, and the fast proximal operator graph solver (POGS) algorithm was started to run based on the delivered dose accumulation. The delivery was continued once an optimal fluence was obtained
Results: The efficiency of the system was demonstrated by Common Optimization for Radiation Therapy (CORT) library. The different amplitude and direction of organs motion was simulated. And different optimization parameters was tested. The numerical results showed that it improves PTV-D95 by 10-20%. The time of each re-planning was within 10 seconds.
Conclusion: A hypothetical system with ultra-fast algorithm was presented for real time re-planning during radiation delivery. It was showed that the system can improve the delivery accuracy and can be implemented in real time.