AJR:195, July 2010
Kristina T. Flicek, Amy K. Hara, Alvin C. Silva, Qing Wu, Mary B.Peter, C. Daniel Johnson
OBJECTIVE. The purpose of our study was to evaluate the feasibility of preserving im¬age quality during CT colonography (CTC) using a reduced radiation dose with adaptive sta¬tistical iterative reconstruction (ASIR).
MATERIALS AND METHODS. A proven colon phantom was imaged at standard dose settings (50 mAs) and at reduced doses (10-40 mAs) using six different ASIR levels (0-100%). We assessed 2D and 3D image quality and noise to determine the optimal dose and ASIR set¬ting. Eighteen patients were then scanned with a standard CTC dose (50 mAs) in the supine po¬sition and at a reduced dose of 25 mAs with 40% ASIR in the prone position. Three radiologists blinded to the scanning techniques assessed 2D and 3D image quality and noise at three differ¬ent colon locations. A score difference of > 1 was considered clinically important. Actual noise measures were compared between the standard-dose and low-dose acquisitions.
RESULTS. The phantom study showed image noise reduction that correlated with a high¬er percentage of ASIR. In patients, no significant image quality differences were identified between standard- and low-dose images using 40% ASIR. Overall image quality was reduced for both image sets as body mass index increased. Measured image noise was less with the low-dose technique using ASIR.
CONCLUSION. The results of this pilot study show that the radiation dose during CTC can be reduced 50% below currently accepted low-dose techniques without significantly affecting im¬age quality when ASIR is used. Further evaluation in a larger patient group is warranted.