Austen Curcuru1, Deshan Yang1,2, and Michael Gach1,2,3
1Biomedical Engineering, Washinton University in Saint Louis, Saint Louis, MO, United States, 2Radiation Oncology, Washinton University in Saint Louis, Saint Louis, MO, United States, 3Radiology, Washinton University in Saint Louis, Saint Louis, MO, United States
1Biomedical Engineering, Washinton University in Saint Louis, Saint Louis, MO, United States, 2Radiation Oncology, Washinton University in Saint Louis, Saint Louis, MO, United States, 3Radiology, Washinton University in Saint Louis, Saint Louis, MO, United States
Radiotherapy gantry rotation can cause artifacts and B0 fluctuations that impact tumor tracking and RT/MRI isocenter coincidence. Sequence parameters were
adjusted at run time to reduce these issues by integrating a
navigator into a bSSFP sequence and measuring B0 variations in
real-time.
Figure 2: Resonant frequency offset during gantry rotation starting at 30° and
rotating around counterclockwise back to 33°. Offsets were calculated using a
navigator inserted into a bSSFP sequence (red) and by measuring the peak offset
in a FID sequence (blue).
Figure 4: Illustration of the ViewRay MRI-Linac gantry
showing the six mu-metal buckets and rotating passive shim tray. The 60° radial
spacing between the buckets results in the periodic B0 offsets
observed at different gantry angles.
