2006 Volume 18 Issue 4 Pages 185-190
Stereotactic irradiation (STI) therapy has recently been reported to effective for early lung cancer and possible to be decreased in harmful side effects. This treatment included a high dose per fraction with hypo-fraction compared to a dose of conventional irradiation. If the dose-precision of STI for lung cancer was not corrected, the treatment possibly resulted in the decline in the therapeutic effect and the increase in a harmful matter. The lung is a hypo-density structure consists of the air and the irregular alveolar organization. It is very difficult to calculate the correct therapeutic dose in STI therapy using non-coplanar, irregular fields and multi-direction. So, we originally produced an irregular density phantom which was on-line taken in the treatment planning system as computed tomographic images. Then the plan was rewritten and recomputed on the phantom, and we compared the recomputed doses with measured dose. We started the STI treatment, when the discrepancy is within plus/minus 3 %.
