[Development of picture and voice gated intermittent irradiation system connected without linear accelerator for voluntary breath-hold synchronized with respiration].

In patients with lung cancer of the lower lobes and liver cancer, treatment volume including respiratory motion is an important therapeutic problem. We developed a voluntary breath-hold system using pictures and voice messages so as to reduce the excessive safety margin that covers respiratory motion. The system consists of two sets of monitor and speaker, and a computer and software for control without direct connection to a linear accelerator. When the patient repeatedly holds his or her breath in response to a picture and voice message, irradiation is manually performed and then proceeds intermittently. Although safety problems remain to be solved because of off-line, synchronized irradiation with our system is simple, inexpensive, and could be widely used. It also would be expected to reduce the tumor target volume around the diaphragm.