UCLA Journal of Radiation Oncology Issue 4 - Flipbook - Page 26
UCLA RADIATION ONCOLOGY JOURNAL
Another important downstream application of 5DCT is translation of the motion model across imaging sessions
to provide motion compensation for CBCT. Using the 5DCT model can replace current 4D-CBCT efforts that
suffer from artifacts due to under sampling of projections in each phase bin. Current research has been dedicated
to first communicating the model from simulation to CBCT by calibrating the breathing amplitude signals. Then,
using the scaled motion model after calibration, we can correct for motion during CBCT reconstruction. The feasibility of this approach has already been shown by demonstrating that increasing the motion information from
the 5DCT model can lead to a sharper diaphragm during reconstruction, and thus accurate motion compensation.
In the image below, the first reconstruction was performed using SART, a technique with no motion compensation. In the other reconstructions, the amplitude of each projection was binned differently, and as the number of
bins increased, the diaphragm sharpened. “No Gating” indicates that the exact amplitude of each bin was used.
This technique will greatly reduce motion artifacts in CBCT to enable better target alignment and potentially aid
in adaptive radiotherapy.
The principal motivations for 5DCT have remained constant since its inception: firstly, to provide the field of
Radiation Oncology with a straightforward, quantitative, accurate, and efficient method of imaging tumors that
move due to respiration to better inform clinical, and additionally to provide high-quality imaging data that
facilitates scientific studies that would otherwise be greatly hindered by the limitations of commercial 4DCT
technology. To these ends, we look forward to continuing the development of our solution here at UCLA as well
as advocating for more widespread adoption. ☐
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