The development and use of a chest phantom for optimizing scanning techniques on a variety of low-dose helical computed tomography devices.

Purpose: To develop a chest phantom for determining the optimal scan conditions for chest computed tomography (CT) screening.

Methods: The basic structure of the phantom is an arms-elevated-positioned anthropomorphic chest phantom. The internal structure includes simulated tumors (which are assumed to be the target lesions of chest CT screening examinations) placed at the levels of the lung apex, the bifurcation of the trachea, and the lung base of both simulated lungs. The image contrast of the simulated tumors is taken as the difference in CT value and is specified as 1 of 2 target values: Delta270 and Delta100. An opening for placement of a dosimeter is provided on the central axis of the phantom. Initial field tests were conducted focusing on the scan conditions for chest CT screening.

Results: Images similar to those obtained in chest CT screening examinations and clearly showing pathologic changes were obtained. The dose measurement at the center was 2.0 mGy. The diameters of the simulated tumors that could be detected were 6 mm for Delta270 and 10 mm for Delta100.

Conclusion: The use of this phantom makes it possible to determine the optimal scan conditions for chest CT screening based on objective evaluation criteria.