@misc{oai:repo.qst.go.jp:00071134,
 author = {Mizota, Manabu and 溝田 学},
 month = {Jun},
 note = {Aim:
For long periods of time, dose calibration measurements have been done for each therapeutic beam in HIMAC heavy ion radiotherapy.
These days the number of treatment is increasing, so we have developed a calculation method to deliver monitor units of high precision.
The computational derivation helps to avoid the heavy burden on medical staffs and errors from wrong measurement. 
\nMethod:
In carbon beam dosimetry, monitor unit depends primarily on the 3-dimensional field condition of broad beam method and secondary on the aperture made by collimator.
The aperture varies with patients infinitely whereas the number of field conditions is limited.
Precise aperture effect calculation is done using kernel beam model which is composed of two Gaussian functions.
For each field condition, parameters of the Gaussians are determined by optimization to fit measurement results of some stereotyped apertures. In addition, the kernel beam is weighted according to the flatness of the broad beam, which is effective especially in case of off-center positional calculation.
\nResults:
This method can calculate the fine differences among the value from the various apertures in shape with the same area.
The verification has been conducted by inspection, where calculated values of calibration factor using this method have been compared with the measured ones used for therapy. They are all in good agreement.
\nConclusions:
The monitor unit for broad beam carbon-ion therapy can be calculated in high precision, even in a small aperture. We have put it into practice since November, 2012., 52nd Annual Conference of the Particle Therapy Co-Operative Group},
 title = {Monitor Unit Calculation for Broad Beam Carbon-ion Therapy},
 year = {2013}
}