The role of the CT scanner in RT planning

Work has already been done showing the benefits and difficulties of CT planning. I have tried to discuss here the more practical aspects involved. Some 100 patients have now been planned using the CT scanner in conjunction with the planning computer. After a few initial problems (mainly concerning the transfer of data between the two computers), all the plans seem to fit well and set up on the treatment machines satisfactorily. Everything is verified using the simulator. In general, it takes only a little extra time on the CT scanner, and time is saved on the simulator. The benefits are:--1. More accurate dose distribution in the planning--tissue densities previously measured, for instance lung correction factors etc. 2. Bladder and prostate tumours--a cystogram can be avoided and also the possibilities of infection inherent in this invasive procedure. 3. Bladder tumours--a more realistic picture of the bladder as it will be when treated, that is, not fully drained (Figures 7a and 7b). 4. More accurate outline information over the whole length of the area to be treated. 5. More accurate information regarding the position of critical organs in relation to the tumour volume and the treatment volume.