Users Manual Part 2
IBA | 20-4 |
Clinical User’s Guide
Volume 1 - Treatment Session
|Part III
- The Pencil Beam Scanning (PBS) Suite Pencil Beam Scanning Principles
|
Figure 20-2. Organization of the Prescription Data
Transversal Distribution
In order to spread the dose delivery along the axes perpendicular to the beam
direction (that is to say, transversal to the beam axis), the beam is scanned in the
plane perpendicular to the beam direction for each defined layer using the two
scanning magnets in the nozzle.
Beam Delivery Characteristics in PBS
Spot Scanning
Spot scanning is the PBS technique by which the target volume is not only divided in
layers, but also divided in discrete spots, both longitudinally and transversally. Each
one of these spots will receive its prescribed dose in one or more ‘shots’ of the
proton beam, which will scan the target volume spot by spot. The proton beam is
interrupted while the beam is moved between spots.
This means that in order to deliver PBS with Spot Scanning, the scanning magnets
will modify the beam’s transversal position for each spot and the ESS will select a
different beam energy for each spot at a different layer (longitudinal dose
distribution).
Patient
Study 1
Plan 1 Beam 1
Layer 1
Layer n
Plan n Beam 1
Beam n
Study n