The peripheral dose enhancement may have less importance than the hotspots, which can have greater contribution to cell kill via radical creation. Hence, aggregate formation may be beneficial in nanoparticle-aided radiotherapy.
Purpose
Provide a projection‐based algorithm to solve the class of optimization problems encountered in intensity modulated proton therapy (IMPT). The algorithm can handle percentage dose–volume constraints (DVCs) that are usually found in such problems.
Methods
To seek a feasible solution, the automatic relaxation method was used to project the spot weight vector onto the interval defined by lower and upper bound target dose constraints. The obtained solution was optimized separately based on the objective of each organ at risk (OAR) in addition to maximizing the minimum target dose using the bisection search method using a stopping criterion of 10 cGy. The combined weight was used in the CQ algorithm to solve the split feasibility problem but with a special projection technique due to the nonconvexity of DVCs. The algorithm was applied to four clinical IMPT cases (meningioma, prostate, tongue, and oropharynx) and compared to the corresponding treatment plans optimized in Eclipse.
Results
The treatment plans obtained, for the four cases, using the BCQ‐ARM algorithm have dosimetric endpoints that are similar to their counterparts generated from Eclipse. The algorithm worked equally well with all cases, including the complex head and neck ones. The stopping criterion of 10 cGy results in making the generated plans slightly less optimal (ε$\epsilon$–optimal) rather than optimal, but with the advantage of the possibility of generating a database of plans.
Conclusions
The application of the BCQ‐ARM algorithm to different cases of IMPT plans with DVCs was demonstrated. The algorithm is successful in generating plans that are dosimetrically equivalent to their corresponding Eclipse plans. Thus, it is suitable to generate optimized treatment plans in a clinically reasonable time frame.
Purpose:
An increasing number of studies show that cancer stem cells (CSCs) become more invasive (metastatic) and may escape into the blood stream and lymph nodes during radiotherapy (RT), before they have received a lethal dose during RT. Other Studies have shown that Graphene oxide (GO) can selectively inhibit the proliferative expansion of CSCs across multiplicative tumor types. In this study we investigate the feasibility of using GO during radiotherapy (RT) to minimize the escape of CSCs towards preventing cancer metastasis or recurrence.
Methods:
We hypothesize that sufficient amount of GO nano‐flakes (GONFs) released from new design radiotherapy biomaterials (fiducials or spacers) loaded with the GONFs can reach all tumor cells within typical times of 14 or 21days before the beginning of image‐guided radiotherapy (IGRT) following implantation. To test this hypothesis, the space‐time diffusion of the GONFs was investigated. Knudsen's and Cunningham's numbers were calculated to get the Stokes’ velocities and mobility values, according to these values, diffusion coefficients were calculated. In a previous study it was shown that GONFs concentration of 50 µg/ml were effective. In the diffusion study, 100 µg/ml was chosen as an initial concentration because it has been shown to be relatively non‐toxic.
Results:
The 50 µg/ml concentration in a 2 cm diameter volume of lung tumor could be only achieved using 2 nm and 6 nm GONFs with respective diffusion times of 14 and 21 days. As expected, increased nanoflake size requires longer times to achieve the target 50 µg/ml concentration.
Conclusion:
The preliminary results indicate the potential of using GONFs delivered via new design radiotherapy biomaterials (e.g. fiducials) to inhibit the proliferative expansion of CSCs. The study avails ongoing in‐vivo studies on using GONFs to enhance treatment outcomes for cancer patients.
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