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. To increase the dose to the tumor and to reduce margins, tumor movement during treatment must be minimized. Currently, several types of breath-synchronized systems are in use. These systems include respiratory gating, deep inspiration breath-hold, active breathing control, and voluntary breath-hold. We used a linear position transducer (LPT) to monitor changes in a 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's 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. This allows a patient performing the deep inspiration breath-hold maneuver to send a signal to trigger the CT scanner acquisitions. The LPT system, when interfaced to a LINAC, 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 to 3 breath-holds. This technique has been used successfully to combine automatically gated radiation delivery with the deep inspiration breath-hold technique. This improves the accuracy of treatment for moving tumors, providing better target coverage, sparing more healthy tissue, and saving machine time. PACS numbers: 87.53.2j, 87.57.-s
Highlights
Lung cancer is the second most common cancer and considered to be the leading cause of cancer death among both men and women.[1]
Our system is based on the use of a new external motion sensor, an linear position transducer (LPT), to monitor patient breathing-induced organ motion by tracking changes in the patient’s abdominal cross-sectional area
As found by previous users of breathing-synchronized radiotherapy,(8) our first deep inspiration breath-hold (DIBH) patient experience shows a significant increase in treatment time compared to the conventional radiotherapy (15 min to 30 min)
Summary
Lung cancer is the second most common cancer and considered to be the leading cause of cancer death among both men and women.[1]. The magnitude of the respiratory movement in the thorax and abdomen is estimated to be up to 3 cm during normal breathing.[4,5,6,7] In cases where there is a considerable range of tumor move-. Breathing-synchronized radiotherapy allows the correlation of treatment delivery with the respiratory cycle. The radiation field can be reduced substantially to avoid normal tissue complications. This allows higher doses to the tumor and improves chances of local tumor control. The indirect approaches estimate tumor displacement from chest wall movement, monitor air volume in the lungs, and measure airflow temperature variations or changes in a cross-sectional area of the thorax. Good correlation between the motion of the tumor and the motion of the diaphragm, as monitored by external detectors, has been demonstrated by several authors.[6,8,13]
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