Reducing the radiation dose for CT colonography using adaptive statistical iterative reconstruction: A pilot study.
OBJECTIVE
The purpose of our study was to evaluate the feasibility of preserving image quality during CT colonography (CTC) using a reduced radiation dose with adaptive statistical iterative reconstruction (ASIR).


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 setting. Eighteen patients were then scanned with a standard CTC dose (50 mAs) in the supine position 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 different colon locations. A score difference of > or = 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 higher 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.


CONCLUSIONS
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 image quality when ASIR is used. Further evaluation in a larger patient group is warranted.
Flicek
Kristina T
KT
Department of Radiology, Mayo Clinic, Scottsdale, AZ 85259, USA.
Hara
Amy K
AK
Silva
Alvin C
AC
Wu
Qing
Q
Peter
Mary B
MB
Johnson
C Daniel
CD
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D023881:Colonography, Computed Tomographic / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D056888:Patient Positioning; D019047:Phantoms, Imaging; D010865:Pilot Projects; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted