Protonisädehoito

Protonisädehoito, also known as proton beam therapy, is a form of external beam radiation therapy that uses protons rather than conventional X‑ray photons to treat cancer. Because protons have mass and charge, they can be accelerated to high energies and then directed into the body with great precision. As a proton travels through tissue, its energy deposition follows a characteristic Bragg peak: the dose rises gradually, reaches a maximum near the end of the range, and then falls off sharply. This allows the treatment plan to concentrate the destructive dose on the tumour while sparing the surrounding healthy tissue and vital organs.

The technique is typically delivered in a linear accelerator or cyclotron that produces proton beams of 70 to 250 megavolts, sufficient for most tumours in the head and neck, thorax, pelvis, and prostate. Images from CT, MRI or PET are used to define the target volume, and modern treatment planning software adjusts the beam angle, energy, and intensity to achieve the desired dose distribution. In many cases, the approach is combined with image guidance and motion‑control techniques to compensate for patient movement during the session.

Clinical outcomes of protonisädehoito show high local control rates for many halting tumors, and studies suggest lower rates of late toxicity compared with conventional photon therapy in certain sites such as the sacrum, skull base and pediatric cancers. However, the widespread adoption of the therapy is limited by its high infrastructure cost, the requirement of specialised facilities, and the limited volume of evidence for some tumour types.

Research continues to refine the technology, reduce treatment times, and expand the indications. Protonisädehoito remains an important and continually evolving tool in modern oncology, valued for its ability to spare normal tissue while delivering effective tumour control.