Yang Hou MD, Presenter: Nothing to Disclose

Qiyong Guo MD, Abstract Co-Author: Nothing to Disclose

Shu Xu MSc, Abstract Co-Author: Nothing to Disclose

Wenli Guo, Abstract Co-Author: Nothing to Disclose

Yong Yue PhD, MSC, Abstract Co-Author: Nothing to Disclose

To assess the image quality (IQ) of iterative reconstruction techniques (iDose) from helical cardiac CTA scans performed at successively reduced dose levels, compare them with filtered backprojection (FBP) of routine-dose scans and determine the optimal dose reduction using iDose that can provide IQ comparable to FBP.

109 consecutive patients (74 men, 35 women; age: 55±11y) were scanned with ECG-gated helical technique using 256-slice MDCT (Brilliance iCT, Philips Healthcare). The control group (Group A, n=21) were scanned using the conventional tube output (120 kVp, 1000 mAs) and reconstructed using FBP. The other 3 groups were scanned with the same kVp but successively reduced tube output as follows: B[n=30]: 600mAs; C[n=24]: 500mAs; D[n=34]: 400mAs) and reconstructed using levels of iDose that would result in image noise comparable to Group A. All images were reconstructed using the same kernel. IQ (noise, CNR, and scores of sharpness, contrast and acceptability [1: worst, 4: best]) and effective radiation dose (ED) were compared between four groups.

Noise (SD) in Group A was significantly higher than in Groups B, C, D (39.11±10.44 vs. 32.51±6.44, 34.41±6.02, 32.77±6.41, P = 0.00). The CNR in B, C, D was significantly higher than in Group A (P = 0.03) There were no differences in contrast, sharpness and acceptability of images between Group A and Groups B & C. There were significant differences in image contrast, sharpness and image acceptability between A and D (P < 0.05). Using the criterion of IQ (score 4), the ROC curve of dose levels and IQ acceptability established a reduction of 50% of tube output (Group C) as optimum cutoff point (AUC: 0.7, 95% CI: 0.57-0.82). The effective dose (ED) of Group C was 55% lower than that of Group A (5.45 ± 0.62mSv versus 12.02 ± 1.53mSv).

Iterative reconstruction techniques maintain 256-slice MDCT cardiac CTA image quality while providing ED reductions of at least 55%.

iDOSE (interative reconstruction) represents a new techinique to reduce radiation dose in coronary CTA study.

Hou, Y, Guo, Q, Xu, S, Guo, W, Yue, Y, Image Quality of Iterative Reconstruction Techniques from Low-Dose CCTA Scans on a 256-Slice MDCT: Comparison with Conventional Techniques.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11007329.html