Radiobiology of proton therapy, heavy ion therapy and neutron therapy - Essay Example

For example, tumor cells often lack the necessary mechanisms required to effectively repair radiation damages. Despite the relative efficacy, safety and reliability of most conventional radiation modalities one of the key problems associated with many photon beams therapies is how to deliver an ideal dose that will kill all the tumor cells without affecting the surrounding normal tissues. However, this is often difficult to achieve due to the unavoidable deposition of radiation dose at the point of radiation entrance (Durante and Loeffler, 2010, p.42). The therapeutic application of charged particle energy beams began in 1946 after the discovery of the radiobiological properties of proton beams.

Since then, the use of particle beam radio therapy procedures such as proton therapy, heavy ion therapy and neutron therapy is increasingly gaining importance in therapeutic radiobiology particularly in the treatment of diseases such as cancer (Cunha, 2010, p.1505). The delivery of the radiation in sessions (fractionation) in particle beam therapy also ensures that the target cells are destroyed while the surrounding normal tissues are able to repair themselves. This is particularly attributed to their characteristic physical depth-dose distribution ability that ensures maximum high precision impact on the target tumor cells.

Compared to the conventional photon radiotherapy, the use of high energy beams of charged protons, neutrons and heavy ions provides significant advantages particularly in the treatment of deep localized tumors. For example, treating cancerous or tumor cells using beams of charged particles allow a more precise approach than most of the conventional radiotherapy modalities. This consequently shortens the treatment time while at the same time minimizing the irradiation of the surrounding disease free tissues.

This paper critically analyzes the radiobiology of proton therapy, heavy ion therapy and neutron therapy as well as their potential benefits and limitations. Figure 1: Comparative lateral penumbra for photons, protons and heavy ions (carbon ions) Proton Therapy Proton beam radiotherapy is increasingly being used due to its numerous potential physical and radiobiological advantages over the conventional radiotherapy techniques. According to Schulz-Ertner and Tsujii (2007, p.954), protons are particularly preferred as a radio therapy option due to their distinct depth –dose profile which makes them particularly suitable for therapeutic use in deep seated, localized and radioresistant tumors.

Although the use of proton therapy for tumor treatment is currently a well established therapeutic modality in many parts of the world, the application of other heavy ions and neutrons is still restricted to a few medical facilities due to the potential dangers associated with such high energy beams. Proton particle therapy works by directing energetic ionizing particles such as protons, neutrons or heavy ions towards the target tumor cells. The particles then damage the DNA of the target cells thereby causing their ultimate death.

The radiation induced cell death is primarily caused by the damage to the nuclear materials due to secondary electron production. For example, particle beams such as protons often deposit their energy at higher linear energy transfer (LET) compared to electromagnetic radiation (Fokas et al., 2009, pp.224). The dose deposited in the surrounding tissues is one of the most important aspects of particle beam