A gated deep inspiration breath-hold radiation therapy technique using a linear position transducer

Abstract

For patients with thoracic and abdominal lesions, respiration-induced internal organ motion and deformations during radiation therapy are limiting factors for the administration of high radiation dose. In order to escalate the dose to tumor and reduce margins, the tumor movement during treatment must be minimized. Currently, several types of breath-synchronized systems are in use. These methods include respiratory gating, deep inspiration breath-hold, active breathing control and voluntary breath-hold. We have used a Linear Position Transducer (LPT) to monitor changes in patient?s abdominal cross-sectional area. The LPT tracks changes in body circumference during the respiratory cycle using a strap connected to the LPT and wrapped around the patient torso. The LPT signal is monitored by a computer that provides a real-time plot of the patient?s breathing pattern. In our technique we use a CT study with multiple gated acquisitions. The Philips Medical Systems Q series CT imaging system is capable of operating in conjunction with a contrast injector, which allows triggering the CT scanner acquisitions by a signal from a patient during the Deep Inspiration Breath-Hold maneuver. The LPT system, when interfaced to a linear accelerator, allows treatment to be delivered only during deep inspiration breath-hold periods. Treatment stops automatically if the lung volume drops from a preset value. The whole treatment can be accomplished with 1-3 breath-holds. This technique has been used successfully to combine automatically gated radiation delivery with the Deep Inspiration Breath-Hold technique to improve the accuracy of treatment for moving tumors, provide better target coverage, spare more healthy tissue and save time.