A dosimetry system for fast measurement of 3D depth±dose pro®les in charged-particle tumor therapy with scanning techniques

The high complexity and high instantaneous dose rates of the intensity modulated treatment plans performed using carbon beams at GSI require a good granularity of the dose veri®cation procedures. As a consequence, a new detector system was developed in order to obtain a 3D reconstruction of the relative depth±dose distributions in a short time, with high granularity and over large volumes. The system takes advantage of the active beam delivery system operative in the therapy facility of GSI and consists of one position sensitive detector with a stack of ionization chambers and a range-shifter. After a technical description of the apparatus, the procedure to reconstruct the 3D measurements is explained and the possible sources of errors in the measurements are analyzed. Finally, the results of the measurement of some treatment plans are shown. Ó 2000 Elsevier Science B.V. All rights reserved. 1