[Respiration gated CT scanning for radiation treatment planning by guided respiration method]

In Proton Medical Research Center (PMRC), we have performed the respiration-gated irradiation for treating the tumor in the body trunk. In the conventional method, patients must hold their expiration during CT scanning. The phase of holding expiration is different from the end-expiration phase. This results in difference of anatomical location in the body between CT scanning and the respiration-gated irradiation. For the sake of highly-accurate irradiation, a respiration gated CT scanning system is introduced. In case of natural respiration, it has been difficult to achieve the gated CT scanning because a stable period of end-expiratory is not so long as CT scanning time (1 second in our case). In this study, we developed a guided respiration method, which leads a patient to maintain the end-expiratory phase during required time. The respiration gated CT scanning is performed by using this. The phase of the acquired CT image can be approximated to that of respiration-gated irradiation.