Kakuya Kitagawa MD, Presenter: Nothing to Disclose

Motonori Nagata MD, PhD, Abstract Co-Author: Nothing to Disclose

Yuriko Mitsuya MD, Abstract Co-Author: Nothing to Disclose

Toshikazu Aoki MD, Abstract Co-Author: Nothing to Disclose

Hajime Sakuma MD, Abstract Co-Author: Departmental research grant, Toshiba Corporation Departmental research grant, Koninklijke Philips Electronics NV Departmental research grantt, General Electric Company Departmental research grant, Bayer AG Departmental research grant, Eisai Co, Ltd

The purpose of this study is to determine the effect of raw-data-based iterative reconstruction on signal, noise, and image quality of cardiac computed tomography.

We evaluated 20 consecutive patients (M:F=14:6, mean age 72±10 years) who underwent clinically indicated CTA using 64-MDCT scanner (SOMATOM Definition AS+, Siemens, Germany). Images were reconstructed using filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE) of different strength (1 to 5). The signal and noise were measured in the aortic root and left main artery and right coronary artery. Image sharpness of coronary arteries was assessed by comparing with FBP images (1=worse, 2=slightly worse, 3=comparable to FBP, 4=slightly better, 5=better). Presence of seemingly artificial texture which is caused by the process of removing image noise was evaluated by two blinded readers using 4-point scale (1=not noticeable, 2=mild, 3=moderate, 4=unacceptable).

In comparison with FBP, the use of SAFIRE strength 1, 2, 3, 4, and 5 resulted in reduced noise (-9±2%, -17±3%, -25±5%, -32±7%, and -39±8%, respectively; p<0.001) and increased contrast-to-noise in the coronary arteries (+8±2%, +18±7%, +28±9%, +40±14%, and +54±22%, respectively; p<0.001), while no differences were observed in aortic signal (487±76HU, 487±76HU, 487±76HU, 487±76HU, and 487±76HU, respectively; p=ns) and image sharpness of coronary arteries (3.00±0.00, 3.00±0.00, 3.00±0.00, 2.99±0.12 and 2.98±0.14, respectively, p=ns). Artificial texture increased as SAFIRE strength increased (1.1±0.2, 1.3±0.5, 2.2±0.7, 3.1±0.7, and 3.6±0.5, respectively; p<0.001). However, the artificial texture did not compromise image interpretation as far as SAFIRE strength 3 or less is used for reconstruction.

Raw-data-based iterative reconstruction resulted in noise reduction without degradation of image sharpness. For cardiac computed tomography, SAFIRE of strength 3 provided the best image quality offering 25% less noise with limited artificial texture.

Raw-data-based iterative reconstruction significantly reduces the image noise without compromising the image sharpness and texture of coronary CT angiography and will help to reduce radiation exposure

Kitagawa, K, Nagata, M, Mitsuya, Y, Aoki, T, Sakuma, H, Sinogram Affirmed Iterative Reconstruction: Assessment of Image Noise and Image Quality in Cardiac Computed Tomography.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034323.html