gms | German Medical Science

Background: In carbon ion therapy, high energy nuclear interaction between the projectile carbon ion and constituents of tissue such as hydrogen, nitrogen, carbon and oxygen nuclei leads to production of various nuclides through fragmentation process. The product particles introduce extra dose behind the tumor, inside the healthy tissue. This is the main drawback of carbon ion therapy.

The proposed solution is to apply a transverse static magnetic field, perpendicular to the direction of carbon ion beam. This makes the charged particles travel a circular trajectory with a decreasing radius due to decrease in charged particle energy as it goes on. The magnetic field should be restricted to the boundary between cancer tumor and healthy tissue.

Material and methods: Theoretical and modeling approach is undertaken through this work. Existing computer codes are employed. The research work is accomplished in the following steps:

• Study and computation of the kind and yield of nuclei produced by nuclear interaction between projectile carbon ion and soft tissue constituents inside the Bragg peak region. Computer codes such as Alice-91,TRIM and SRIM are utilized in this step.
• Feasibility of employing magnetic field is studied to prevent charged particle penetration into the healthy tissue at the posterior part of the tumor.

Result: Early and preliminary calculations show that the required static magnetic field intensity is around 4 Tesla. This could be produced with existing technology and not harmful for the patient. The study should be carried out on the method and techniques to produce magnetic field inside the patient's body with sufficient strength. One way is to use external magnets. Another way is to develop techniques in which small size magnets are employed to restrict the generated field in a space of few millimeters thick.

Conclusion: The big disadvantage of carbon ion therapy, unnecessary dose to the posterior part of the tumor would be studied and a solution will be presented by simulation methods. The exact magnitude of the static magnetic required for our purpose will be computed and the behavior of light charged particles inside the living soft tissue will be simulated. The absorbed dose in the growing layer of cancer tumor in presence of magnetic field will be computed precisely. The applicability of computer code FLUKA in special problems will be assessed.