Currently, the most prevalent form of proton therapy delivery is double or single scattering. With this technology, the entire volume of a tumor is treated at the same time and with the same intensity using a beam of protons delivered through an aperture adapted to the tumor’s precise size. One of the problems with double scattering is that neutron generation in healthy tissues cannot be avoided before reaching the tumor.

Conversely, proton therapy delivered with PBS allows the doctor to essentially paint, layer by layer, only the volume of the tumor with a precise proton beam, as well as adjust the intensity of the beam. PBS provides a very focused and small beam spot which ensures better precision. Magnets are used to focus the beam and achieve this small spot size at what is called the isocenter, the place where the center of the tumor would be positioned. One of the great strengths of PBS therapy is its adaptability in treating different layers of a tumor with more or less intensity, depending upon clinical need. Instead of giving one constant dose on each layer, it is possible to modulate the beam intensity if there is potentially a hot spot or place on the layer that needs more intense treatment.