SP 0214: Auto contouring system: Changing the practice
Devices that use a scintillating screen viewed via a CCD camera have shown to be very efficient in the collection of large amount of data during clinical commissioning (e.g. beam width in air for different energies in case of scanning) The electronic read out of such devices can be very advantageous since it allows on line analysis of the data just measured. Amorphous silicon detectors are also worth mentioning since they have shown promising properties and may play an important role in the future. Relative dosimetry along the beam direction has the purpose to measure pencil beam depth dose curves or depth dose profile for homogenous SOBP. Large plane parallel ICs (e.g. diameter 8cm) are ideal tools for integral depth dose measurements in case of scanning. In addition to the charged deposited by the primary beam, the wide active area of large plane parallel ICs allows collecting the charged deposited also by secondary proton propagation under larger angles. Alternatively, small plane parallel ICs in broad beams could also be employed to obtain pencil beam depth dose curves when the chamber is significantly smaller than the lateral size of the field, which is usually the case in passive scattering. Plane parallel chambers are also ideal for measurements of the distal fall off. Multi layer ionization chambers (MLIC) can effectively measure and verify the range of a large number of beam energies and can be used for routine QA. Detectors for relative 3D dosimetry, which combine 1) and 2) such as, gel and PRESAGE, were tested under proton radiation but, as of today, they are still not employed routinely, mainly because of the LET and energy dependence and the time consuming preparation and evaluation.