Dosimetric properties of the liquid ionization chamber electronic portal imaging device (EPID).

In the relation between the pixel values of the electronic portal imaging device (EPID) and dose rate, pixel values have been reported to be proportional to the square roots of the dose rates although some researchers have reported that each EPID pixel value was almost proportional to the dose rates when they were more than 1 Gy/min. To resolve this contradiction, in this study we have investigated the dosimetric properties of the liquid ionization chamber EPID based on a two-dimensional matrix of liquid- filled ionization chambers. Our results show that the pixel values of this EPID were proportional to the square roots of the dose rates when they were less than 0.

[Output factor calculations for intensity modulation radiation therapy as dosimetry quality assurance].

Because intensity-modulated radiation therapy (IMRT) is complicated by many small, irregular, and off-center fields, dosimetry quality assurance (QA) is extremely important. QA is performed with verifications of both dose distributions and some arbitrary point doses. In most institutes, verifications are carried out in comparison with dose values generated from radiation treatment planning systems (RTPs) and actually measured doses.