Treatment Times For 3D Conformal Radiation Therapy

With Respiratory Motion-Gated Technique In The Treatment of Lung Tumors

Cheng B Saw, PhD, Edward Brandner, PhD, Krishni Wijesooriya, PhD,

Krishna Komanduri, PhD, M. Saiful Huq, PhD, and Dwight E Heron, MD

University of Pittsburgh Cancer Institute, Pittsburgh, PA 15232

Large fields are often necessary to ensure that moving targets are within the treatment portals for patients treated with 3DCRT for lung cancer. The recent introduction of respiratory motion-gated technique has allow the possibility of field reduction by energizing the photon beam only when the targets are within the portal window. This study examines the range of treatment times associated with respiratory motion-gated technique.

To assess the treatment times, 10 treatments with free breathing and nine treatments with respiratory motion-gated technique were studied on twelve patients with lung cancers. 3DCRT utilizing three- to five-field techniques was used as initial treatment or subsequent boost. The gating technique is based on surface marker placed on the patient’s chest to provide the surrogate signal for phase gating. During a certain range of the phase where the target displacements are less than 5 mm from the end exhaled state, the beam is energized.

The phase gating was found to range from 24% to 73% where the targets are within the 5 mm limit. The average treatment times with respiratory motion-gated technique is about 10.8 ± 1.1 min compare with free breathing of 5.4 ± 1.0 min. Although the treatment times vary with tumor displacement from the end exhaled state for gated technique, it can doubled compared to the free breathing treatment times. However treatments with many fields will not show a significant increase of overall treatment times since the setup times are the dominant component.