Date Approved


Graduate Degree Type


Degree Name

Medical Dosimetry (M.S.)

Degree Program

Health Professions

First Advisor

Sarah Johnson

Academic Year




This retrospective study will aim compare Cyberknife SBRT and VMAT SBRT lung plans quality when the Cyberknife plans are replanned to have a comparable treatment time to the VMAT plans. Having data to show the difference in plan quality between the two treatment techniques could be a useful tool when deciding the best treatment option.


Select ten SBRT lung patients who were all treated using the Cyberknife and plan a comparable VMAT treatment for each. Modify the original Cyberknife treatment plan so that the treatment time is similar to that of the corresponding VMAT plan. Then, evaluate and compare the quality of the two plans based on maximum heart dose, conformity index, mean heart dose, and ipsilateral lung V20.

Preliminary Literature Review

While researching this topic, many studies were found comparing the quality of SBRT lung treatments on the Cyberknife compared with conventional linac SBRT lung treatments. Other studies compared the doses to critical normal structures and tumor dose, as well as local control and recurrence, but what was not found in these studies was the delivery time difference between the two methods.


Cyberknife plans have good plan quality when treatment times are relatively long. However, the plan quality is degraded when plans are modified to have similar treatment times as VMAT plans. VMAT SBRT lung treatments have shown to have better plan quality in terms of conformity index, ipsilateral lung V20 dose, and maximum heart dose.