Clinical experience using respiratory gated radiation therapy: comparison of free-breathing and breath-hold techniques.

Purpose: To investigate the clinical use of a commercially available gating system for minimizing respiratory-induced anatomic motion over a range of treatment sites.
Methods and Materials: The gating system consists of a reflective marker placed on the patient's anterior surface. The motion of the marker is tracked using a camera interfaced to a computer. Gated intervals were defined that limited the motion of the diaphragm to less than 1 cm during free breathing. Patients underwent a computed tomography virtual simulation using a breath-hold technique. At the time of treatment, verification of patient position and gating interval were performed using electronic portal imaging.
Results: Between September 2000 and January 2002, 136 patients were simulated with respiratory gating. Of these, 108 patients were treated to 110 sites for a total of 2301 treatment sessions. Ninety-seven percent of patients completed their entire course of therapy with gated treatment delivery.
Conclusions: Respiratory gating is a practical and achievable solution for minimizing respiratory-induced target motion during both simulation and treatment. With proper patient selection and training, it can be successfully implemented in a clinical radiation therapy department.