Doozan, Brian

There are many available options today for treating small lesion cancer cells. Two of the
most used options are the planning systems BrainLab and Eclipse. The main difference between
the two is the algorithms that are used to calculate the dose distribution of external beam
radiation therapy. BrainLab offers a Monte Carlo based algorithm while Eclipse utilizes the
Anisotropic Analytical Algorithm. An investigative study on the quality of the planning system
is done for cases in lung, head and neck and prostate. In particular, lung cases are highly
heterogeneous which can lead to problems in the calculation. The ability to be able to plan on the
best system for individual cases can lead to better and more consistent treatments for cancer
patients.

The goal of this study was to improve dosimetry for pelvic, lung, head and neck, and other cancers sites with aspherical planning target volumes (PTV) using a new algorithm for collimator optimization for intensity modulated radiation therapy (IMRT) that minimizes the x-jaw gap (CAX) and the area of the jaws (CAA) for each treatment field.
A retroactive study on the effects of collimator optimization of 20 patients was performed by comparing metric results for new collimator optimization techniques in Eclipse version 11.0. Keeping all other parameters equal, multiple plans are created using four collimator techniques: CA0, all fields have collimators set to 0°, CAE, using the Eclipse collimator optimization, CAA, minimizing the area of the jaws around the PTV, and CAX, minimizing the x-jaw gap. The minimum area and the minimum x-jaw angles are found by evaluating each field beam’s eye view of the PTV with ImageJ and finding the desired parameters with a custom script. The evaluation of the plans included the monitor units (MU), the maximum dose of the plan, the maximum dose to organs at risk (OAR), the conformity index (CI) and the number of fields that are calculated to split.
Compared to the CA0 plans, the monitor units decreased on average by 6% for the CAX method with a p-value of 0.01 from an ANOVA test. The average maximum dose remained within 1.1% difference between all four methods with the lowest given by CAX. The maximum dose to the most at risk organ was best spared by the CAA method, which decreased by 0.62% compared to the CA0. Minimizing the x-jaws significantly reduced the number of split fields from 61 to 37.
In every metric tested the CAX optimization produced comparable or superior results compared to the other three techniques. For aspherical PTVs, CAX on average reduced the number of split fields, lowered the maximum dose, minimized the dose to the surrounding OAR, and decreased the monitor units. This is achieved while maintaining the same control of the PTV.

Empirical methods of beam angle optimization (BAO) are tested against the BAO
that is currently employed in Eclipse treatment planning software. Creating an improved
BAO can decrease the amount of time a dosimetrist spends on making a treatment plan,
improve the treatment quality and enhance the tools an inexperienced dosimetrist can use
to develop planning techniques. Using empirical data created by experienced dosimetrists
from 69 patients treated for lung cancer, the most frequently used gantry angles were
applied to four different regions in each lung to gather an optimal set of fields that could
be used to treat future lung cancer patients. This method, given the moniker FAU BAO,
is compared in 7 plans created with the Eclipse BAO choosing 5 fields and 9 fields. The
results show that the conformality index improved by 30% or 3% when using the 5 and 9
fields. The conformation number was better by 12% from the 5 fields and 9% from the 9
fields. The organs at risk (OAR) were overall more protected to produce fewer
nonstochastic effects from the radiation treatment with the FAU BAO.