DEVELOPMENT OF 3D DOSE VERIFICATION SYSTEM FOR SCANNED ION BEAM AT HIMAC

A 3D (three-dimensional) dose verification system has been developed as a part of new project involving 3D pencil beam scanning at HIMAC (Heavy Ion Medical Accelerator in Chiba). This system provides the easy and rapid dose measurements. It consists of a water column, a scintillator and a charge-coupled device, set at isocentor. The scinillator is directly attached to the downstream side of the water column. One of the great advantages of this system is to obtain 2D dose map at once, by correcting LET-dependent quenching. Quenching is corrected by measurement slice-by-slice, of a certain water depth. We present the results of 3D dose measurement and comparison with the ionization chamber measurement