CT images are obtained using a head phantom that is fabricated for clinical applications. In addition, IMRT treatment planning is performed using a Tomotherapy radiation treatment planning system. A program for analyzing the results is produced using Visual C. A comparison between the treatment planning and the CT images of irradiated gels is performed. The dose sensitivity is found to be 2.41卤0.04 HGy鈭?. The accuracies of dose evaluation at doses of 2 Gy and 4 Gy are 3.0%and 2.6%, respectively, and their reproducibilities are 2.0%and 2.1%, respectively. In the comparison of gel and Tomotherpay planning, the pass rate of the 纬-index, based on the reference values of a dose error of 3%and a DTA of 3 mm, is 93.7%.