ABSTRACT
Total scatter factor (Scp), head scatter factor (Sc) and phantom scatter factor (Sp) are very important for accurate radiation therapy at stereotactic radiosurgery (SRS) with irregular field shape using micro-MLC and intensity modulated radiation therapy (IMRT) including many small field sizes. In this study we measured and compared Scp with reference ion chamber, pinpoint chamber and diode detector and adapted the resuls form diode detector. Head scatter factors for small field sizes were also measured with diode detector covered 1.5 cm-thick solid water build-up cap. Some errors like as electron contamination of 1~3% were included in the values of Sc but trend of total results of Sc was coincided with basic theory. Phantom scatter factors for small field sizes were calculated form Scp and Sc. The results of Sp were compared and were well-agreed with those of other authors.