In pre-clinical studies, researchers are using tools that should mimic what is used in clinical treatments.
In aligning with a Radiation Oncology Clinic, there is a large focus on Dose Algorithms, Dose Commissioning and Planning. The SARRP was created to mimic the human radiation treatment as close as possible with a planning system and targeting capabilities. Before all of this is available the dose profile must be attained and used in a dose algorithm that is suited for the 220kV energy. This allows Planning to be most accurate.
There are several different Treatment Planning System Algorithms. SARRP’s Treatment Planning Software, MuriPlan, offers a similar Clinical experience in a pre-clinical environment. Using a CBCT obtained from the SARRP, users can register DICOM images, create contours of organs at risk and tumors, create an isocenter in the region of interest, compute and view the Isodose lines and DVH. These steps were created in MuriPlan to allow the user the closest clinical experience.
These Physicists used the Pinnacle algorithm, Superposition Convolution, to modify for Pre-clinical studies. Unlike the MV spectrum, the kV spectrum is very large. The researchers created 25 kernels at 10kV bins so that the calculations truly model the spectrum of the beam and the presence of different filters. The algorithm was created to run on a computer’s GPU. All of the kernels were generated using Monte Carlo simulations. The algorithm accommodates beam modifiers such as independent jaws. It has been incorporated into the SARRP Planning System, MuriPlan.
In cases where radiation is a common course of treatment but not very effective, radiosensitizers can increase the benefit from this treatment in a great way. Gold Nanoparticles are great tools in radiotherapy. They can be used to sensitize tissues to radiation, tumor detection and meditate drug delivery.
Previously Gold Nanoparticles were used as single molecules. These researchers created micelles of several gold nanoparticles (GPM) that are much smaller and therefore offer rapid dissolution and excretion of gold. 4 groups were tested to evaluate the efficacy of smaller gold nanoparticles delivered in a micelle. Survival time was the measuring the tool. When the tumors reached 1300mm3 they were sacrificed. The control group had a survival of 22 days. The group with GPM only survived 20 days. The group with just RT (6Gy) survived 38 days. GPMs were injected 24 hours before radiation to allow for contrast enhancement on the CBCT. This combined treatment proved to have a longer survival rate; 68 days.
If using an Image Guided MicroIrradiator, it is more important to have the Percent Depth Doses for each filter and collimator. Having these parameters built in a treatment planning system is essential for a good treatment plan. SARRP allows users to mimic human treatment planning techniques with the tools in MuriPlan. This offers image registration, contouring, isocenter placement, treatment planning with multiple isocenters, beams and arcs and a verify step that allows the user to view the dose with Isodose lines and review the Dose to Volume Histogram (DVH).
These researchers attempted to use SARRP to mimic a clinical treatment. They used a head and neck human tumor in a nude mouse model. They imaged these mice on a PET and created a plan based on the area of interest and a boost to the area of high FDG uptake. This PET image was fused with SARRP CT image while the mouse was anesthetized. 10Gy was given using a 15mm collimator to the whole tumor. The boost was treated with 10Gy using a non-coplanar dynamic arc with the 5mm collimator. The researchers found that a PET/CT with the SARRP can allow for pre-clinical validation of PET image-guided dose escalation IMRT treatments.
Unlike human machines there is no collimation to the beam. This allows many organs at risk to be fully dosed. This keeps the researcher from achieving clinically relevant doses.
This study focuses around a Cabinet Irradiator (220kV 17mA), the Standford MicroIrradiator (120kV 50mA) and the SARRP Platform (225kV 13mA). Each system was modeled in Monte Carlo for comparison of 2 different planning techniques. The first setup was using a single large beam for a subcutaneous model. The Cabinet Irradiator and SARRP gave overall homogeneous dose distributions. The Stanford Irradiator was a bit more heterogeneous due to the kV and mA used.
For an orthotopic model, the Cabinet Irradiator gave the same field. The Stanford MicroIrradiator and SARRP used a 9 beam arrangement. The multi-beam conformal methods showed superior organ at risk sparing. The Stanford MicroIrradiator again showed a more heterogeneous dose distribution across the animal due to the lower energy. SARRP was shown to deliver a homogenous dose distribution as well as a faster beam on time (2.7 minutes vs. 3.8 minutes on the Stanford MicroIrradiator).