Purpose: To explore the dosimetric consequences of uncorrected rotational setup errors during SBRT for pancreatic cancer patients. Methods: This was a retrospective study utilizing data from ten (n=10) previously treated SBRT pancreas patients. For each original planning CT, we applied rotational transformations to derive additional CT images representative of possible rotational setup errors. This resulted in 6 different sets of rotational combinations, creating a total of 60 CT planning images. The patients’ clinical dosimetric plans were then applied to their corresponding rotated CT images. The 6 rotation sets encompassed a 3, 2 and 1‐degree rotation in each rotational direction and a 3‐degree in just the pitch, a 3‐degree in just the yaw and a 3‐degree in just the roll. After the dosimetric plan was applied to the rotated CT images, the resulting plan was then evaluated and compared with the clinical plan for tumor coverage and normal tissue sparing. Results: PTV coverage, defined here by V33 throughout all of the patients’ clinical plans, ranged from 92–98%. After an n degree rotation in each rotational direction that range decreased to 68–87%, 85–92%, and 88– 94% for n=3, 2 and 1 respectively. Normal tissue sparing defined here by the proximal stomach V15 throughout all of the patients’ clinical plans ranged from 0–8.9 cc. After an n degree rotation in each rotational direction that range increased to 0–17 cc, 0–12 cc, and 0–10 cc for n=3, 2, and 1 respectively. Conclusion: For pancreatic SBRT, small rotational setup errors in the pitch, yaw and roll direction on average caused under dosage to PTV and over dosage to proximal normal tissue. The 1‐degree rotation was on average the least detrimental to the normal tissue and the coverage of the PTV. The 3‐degree yaw created on average the lowest increase in volume coverage to normal tissue. This research was sponsored by the AAPM Education Council through the AAPM Education and Research Fund for the AAPM Summer Undergraduate Fellowship Program.

We report the orbital rotation of biological cells using two tapered fibre probes. We launched laser beams into the probes at a wavelength of 980 nm and rotated 5 µm-diameter yeast cells and 13.5 µm-diameter human leukemic K562 by optical force. The rotation period varied from 1.59 to 2.41 s for the yeast cells and was 4.83 s for the human leukemic K562. The rotation direction of the cells can be controlled by adjusting the position of the two probes. The experimental results were interpreted by theoretical analysis and numerical simulations.