[CT and MRI image fusion in three-dimensional conformal radiotherapy for cranial carcinoma]

To investigate the advantage of CT and MRI image fusion in determining the target precisely during 3-dimensional conformal radiotherapy for cranial carcinoma.

Twenty-five patients received CT and MRI examination simultaneously for localizing the tumor and defining target before 3-dimensional conformal radiotherapy. The target defined by MRI image was used as gross tumor volume, whereas CT value was used to calculate dose, making plan for radiotherapy. The difference between the target defined by CT and MRI was compared.

All the 25 patients underwent CT and MRI image fusion for localizing the tumor and defining the target in order to make anatomic symbol and surface symbol superposed. The number of tumor nodual detected by CT was as same as that found by MRI in 23 cases except two. Compared with the GTV defined by MRI image, it was larger in 10 cases by CT image, whereas smaller in 15 cases. The response rate assessed by MRI image was 64.0% (CR + PR) at the end of radiotherapy.

CT and MRI image fusion technique is more precise than either by CT or MRI alone in defining the GTV of 3-dimensional conformal radiotherapy for cranial carcinoma.