Simulator-assisted setting of scan protocols for X-ray CT: development and clinical usefulness of the Scan Plan Simulator.

To assist in the selection of complicated computed tomography (CT) scan protocols and to obtain stable image SD values, prototype "Scan Plan Simulator" software with the following functions was developed and evaluated. 1) The image SD value that will be obtained in actual scanning is estimated by entering the patient's body size and scan protocol, after which a simulated image is displayed so that the estimated image SD value can be checked. The exposure dose can also be estimated in the Scan Plan Simulator. 2) The appropriate tube current is automatically set by entering the required image SD value. We evaluated the accuracy of the Scan Plan Simulator by comparing the simulation results with the image SD values and exposure dose obtained in actual scanning and assessed the usefulness of this method using Monte Carlo simulation based on body thickness data obtained in clinical examinations. The results showed that the Scan Plan Simulator not only stabilizes image SD by minimizing the effects of body size but also permits the exposure dose to be reduced by optimizing tube current.