AbstractID: 6605 Title: Tracking of Intrafraction Target Motion: A 30 Frames Per Second
Megavoltage Fluoroscopic Imaging System
Intrafraction motion of targets, such as lung tumors, is one of the main concerns
in high precision radiation therapy. Our overall goal is to develop a novel imagingguided treatment delivery system, i.e., a system in which dynamic information
from an imaging system will be used to redirect radiation therapy beams in real
time to ensure coverage of a moving target. As a first step toward this goal, we
have developed a megavoltage imaging system that can be used to track
intrafraction target motion in real time during radiation therapy. This system was
based on a clinical video-based EPID but with two modifications: (1) The
conventional camera was replaced by an avalanche-multiplication-based video
camera in order to improve the imaging quality of the system. (2) A 30 frames per
second fluoroscopic mode (with real-time digital image processing) was added to
the system.
Compared to other systems [e.g., S. Shimizu et al., Int. J. Radiat. Oncol. Biol.
Phys. 48, 166 (2000)], our system does not require an extra diagnostic x-ray
source. We first tested our system with a phantom. A radio-opaque gold marker of
1.0mm (diameter) x 5mm (length) was embedded in the lung region of an Alderson
Rando phantom. In order to simulate the lung motion of a patient, the phantom was
placed on a motor driven table supported on the treatment couch. With the 6MV
beam, the gold marker and its movement could be clearly seen on the fluoroscopic
monitor of our system.