A new phantom developed for testing the ATCM performance for chest CT scan.

For testing the performance of the automatic tube current modulation (ATCM) of CT scanners, a new ATCM phantom was developed in this study. Based on the Chinese reference man and Monte Carlo simulations of X-ray attenuation, a more conformal ATCM phantom made by the polymethyl methacrylate (PMMA) was developed. The phantom has a length of 20 cm, and it can be used to measure the dose profile along the central axis with 19 pieces of the real-time MOSFET detectors. The image noise could be calculated slice by slice in the phantom center. Test experiments showed that the phantom could initiate the tube current modulation under the different modulation levels of CT scans, and the actual effects of ATCM could be evaluated by the aid of the dose profile measurements. With measured dose profiles, image noise, the better dose utilization between different modulation levels could be easily identified. The new phantom developed in this study can be used for testing the ATCM performance of CT scanners, and it is useful for further studies on the optimization of CT scan protocols with the ATCM.