Date Approved


Graduate Degree Type


Degree Name

Medical Dosimetry (M.S.)

Degree Program

Health Professions

First Advisor

Karen Snyder

Academic Year





Stereotactic Body Radiotherapy (SBRT) has become a highly effective treatment option for patients with island-type lung lesions, offering precise targeting and minimal damage to the surrounding healthy tissue. Acuros XB dose calculation algorithm has shown promising results in delivering high radiation doses with improved accuracy. Dynamic Conformal Arc Therapy (DCAT) has shown promise with lesions that are uniform and non-concave. Combining Acuros and DCAT has potential to help when planning Island-type lung SBRT. However, determining the optimal block margins for this treatment approach remains a critical challenge to find a balance between tumor coverage and sparing of critical structures.


This study investigates the impact of block margins on treatment criteria in SBRT of island-type lung lesions using DCAT and Acuros XB. A retrospective analysis of patient treatment plans with varying block margins was used to evaluate the dose distribution and the dose fall off using RTOG-0915 criteria. Each of the 10 patients had 5 separate plans utilizing each margin.


The results demonstrate that smaller block margins lead to improved target coverage and conformity, thus reducing the dose to OARs. However, the effects of setup error or intrafraction movement are exacerbated with smaller margins. Conversely, wider block margins result in better homogeneity in the target but escalate the risk of adverse events due to the increased volume of OARs receiving high dose.


The combination of DCAT and Acuros XB in SBRT for island-type lung lesions presents a promising approach for achieving precise radiation delivery. The determination of optimal block margins becomes a crucial step in treatment planning, emphasizing the need for a balanced consideration of target coverage, dose fall off, and OAR sparing. Future research and clinical validation could pave the way for enhanced treatment strategies and improved patient outcomes in SBRT for lung lesions.