Ho Yun Lee MD, Presenter: Nothing to Disclose

Chang Hyun Lee MD, Abstract Co-Author: Nothing to Disclose

Jin Mo Goo MD, PhD, Abstract Co-Author: Nothing to Disclose

Sung-Joon Ye PhD, Abstract Co-Author: Nothing to Disclose

To investigate the optimal type of AEC for the combined use of breast shield in chest MDCT.

CT pulmonary angiography was performed on a female anthropomorphic phantom with a 64 MDCT scanner (Brilliance 64, Philips). A set of 4 thermoluminescent dosimeters (TLD) were placed on the surfaces of each breast. Five scans with a right side breast shield were obtained in each of the four protocols: breast shield only (A), size AEC and breast shield (B), angular AEC and breast shield (C), and z-axis AEC and breast shield (D). For each protocol, the radiation dose in both breasts, Hounsfield Units (HU) and SD (noise) in the same anatomic regions (anterior and posterior chest walls and lungs) were compared. Dose-Length Products (DLPs) were also calculated. Repeated ANOVA, Wilcoxon signed-rank test and Mann-Whitney U test were used for statistical analysis.

Radiation dose decreased with the application of different AEC systems compared to protocol A of breast shield only (A, 0.91cGy; B, 0.7cGy, 23%; C, 0.73cGy, 19.7%; D, 0.25cGy, 72.5%). Noise was significantly increased in protocol D compared to other modulation systems; (A, 17HU; B, 11HU; C, 12HU; D, 28HU; P< 0.05). The attenuation values of anterior and posterior lung were not significantly different among the four protocols (P>0.05). DLP of protocol D was the lowest (A, 254.8 mGy*cm; B, 237.8 mGy*cm; C, 194.5 mGy* cm; D, 97.1 mGy*cm).

Among the different types of AEC systems for the combined use of breast shield in chest MDCT, size or angular modulation systems shows more breast dose reduction with acceptable image noise.

For the use of AEC with breast shield in chest MDCT, size or angular modulation systems show greater breast dose reduction with acceptable noise and may be recommended over Z-axis modulation system.

Lee, H, Lee, C, Goo, J, Ye, S, Comparison of Different Types of Automatic Exposure Control Systems (Size, Z-axis, and Angular Modulation) for the Combined Use of Breast Shield in Chest MDCT.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6007288.html