Detection of lung tumor movement in real-time tumor-tracking radiotherapy.

Abstract

PURPOSE:

External radiotherapy for lung tumors requires reducing the uncertainty due to setup error and organ motion. We investigated the three-dimensional movement of lung tumors through an inserted internal marker using a real-time tumor-tracking system and evaluated the efficacy of this system at reducing the internal margin.

METHODS AND MATERIALS:

Four patients with lung cancer were analyzed. A 2.0-mm gold marker was inserted into the tumor. The real-time tumor-tracking system calculates and stores three-dimensional coordinates of the marker 30 times/s. The system can trigger the linear accelerator to irradiate the tumor only when the marker is located within the predetermined "permitted dislocation." The value was set at +/-1 to +/-3 mm according to the patient's characteristics. We analyzed 10,413-14,893 data sets for each of the 4 patients. The range of marker movement during normal breathing (beam-off period) was compared with that during gated irradiation (beam-on period) by Student's t test.

RESULTS:

The range of marker movement during the beam-off period was 5.5-10.0 mm in the lateral direction (x), 6.8-15.9 mm in the craniocaudal direction (y) and 8.1-14.6 mm in the ventrodorsal direction (z). The range during the beam-on period was reduced to within 5.3 mm in all directions in all 4 patients. A significant difference was found between the mean of the range during the beam-off period and the mean of the range during the beam-on period in the x (p = 0.007), y (p = 0.025), and z (p = 0.002) coordinates, respectively.

CONCLUSION:

The real-time tumor-tracking radiotherapy system was useful to analyze the movement of an internal marker. Treatment with megavoltage X-rays was properly given when the tumor marker moved into the "permitted dislocation" zone from the planned position.

• Authors: S Shimizu, H Shirato, S Ogura, H Akita-Dosaka, K Kitamura, T Nishioka, K Kagei, M Nishimura, K Miyasaka
• Journal: International journal of radiation oncology, biology, physics (Int J Radiat Oncol Biol Phys) Vol. 51 Issue 2 Pg. 304-10 (Oct 01 2001) ISSN: 0360-3016 [Print] United States
• PMID: 11567803 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Topics

• Aged
• Aged, 80 and over
• Algorithms
• Computer Systems
• Humans
• Lung Neoplasms (diagnostic imaging, radiotherapy)
• Middle Aged
• Movement
• Particle Accelerators
• Radiotherapy, Conformal (methods)
• Tomography, X-Ray Computed