Particle therapy

The figure shows how beams of electrons, X-rays or protons of different energies (expressed in MeV) penetrate human tissue.

Bremsstrahlung X-rays penetrate more deeply, but the dose absorbed by the tissue then shows the typical exponential decay with increasing thickness.

For protons and heavier ions, on the other hand, the dose increases while the particle penetrates the tissue and loses energy continuously.

If, in addition, the beam energy and hence the depth of penetration is varied, an entire target volume can be covered in three dimensions, providing an irradiation exactly following the shape of the tumor.

At the end of 2008, 28 treatment facilities were in operation worldwide and over 70,000 patients had been treated by means of pions,[7][8] protons and heavier ions.

This facility was the first to utilize carbon ions clinically, marking a significant advancement in particle therapy for cancer treatment.

The therapeutic advantages of carbon ions were recognized earlier, but NIRS was instrumental in establishing its clinical application.

It also has clear advantages to treat otherwise intractable hypoxic and radio-resistant cancers while opening the door for substantially hypo-fractionated treatment of normal and radio-sensitive disease.

All proton and other heavy ion beam therapies exhibit a defined Bragg peak in the body so they deliver their maximum lethal dosage at or near the tumor.

However, carbon-ions are heavier than protons and so provide a higher relative biological effectiveness (RBE), which increases with depth to reach the maximum at the end of the beam's range.

The higher outright cell mortality produced by CIRT may also provide a clearer antigen signature to stimulate the patient's immune system.

[19][20] The precision of particle therapy of tumors situated in thorax and abdominal region is strongly affected by the target motion.