Johannes Greupner, Presenter: Nothing to Disclose

Bernd K. Hamm MD, Abstract Co-Author: Research Consultant, Bayer AG Research Consultant, Toshiba Corporation Stockholder, Siemens AG Stockholder, General Electric Company Research Grant, Toshiba Corporation Research Grant, Koninklijke Philips Electronics NV Research Grant, Siemens AG Research Grant, General Electric Company Research Grant, Elbit Medical Imaging Ltd Research Grant, Bayer AG Research Grant, Guerbet AG Research Grant, Bracco Group Research Grant, B. Braun Melsungen AG Research Grant, KRAUTH medical KG Research Grant, Boston Scientific Corporation Equipment support, Elbit Medical Imaging Ltd Investigator, Copenhagen Malmo Contrast AB

Marc Dewey MD, Abstract Co-Author: Research Grant, General Electric Company Research Grant, Bracco Group Research Grant, Guerbet SA Research Grant, Toshiba Corporation Speakers Bureau, Toshiba Corporation Speakers Bureau, Bayer AG Speakers Bureau, Guerbet SA Consultant, Guerbet SA Author, Springer Science+Business Media Deutschland GmbH Institutional research agreement, Siemens AG Institutional research agreement, Koninklijke Philips Electronics NV Institutional research agreement, Toshiba Corporation

To evaluate to potential of iterative reconstruction (IR) in comparison to filtered back projection (FBP) to reduce effective dose in multidetector computed tomography (CT) used for evaluation of global left ventricular function.

A moving cardiac phantom was repeatedly scanned with 320-row CT at fixed heart rate of 60 bpm using tube voltages of  80 kV and 120 kV and tube currents ranging from 10 mA to 500 mA. For each scan, image stacks were reconstructedusing both FBP and IR algorithms. Ejection fraction, end-diastolic, and end-systolic and stroke volume were calculated and compared to minimal and maximal volume of the cardiac phantom at rest. Furthermore signal-to-noise ratio (SNR) and contrast-to-noiseRESULTS ratio (CNR) were calculated to allow for assessment of image quality.

Ejection fraction was significantly underestimated (p<0.05 for all, t-test) at both 80kV and 120 kV using either reconstruction algorithm (Mean difference: FBP: 4.4±3.3% at 80 kV, 3.3±2.6% at 120 kV; IR: 3.9±1.1 % at 80 kV 3.9±0.9% at 120 kV) but there was no significant difference between measurements made using the IR or FBP reconstructed datasets for the same tube voltage (p>0.05 for both, t-test). Using IR, SNR and CNR were significantly higher at both 80 kV (mean difference: 5.0±2.6 and 2.1±0.9 respectively, p<0.05 for both, t-test) and 120 kV tube voltage (mean difference: 6.7±1.4 and 4.4±0.9 respectively, p<0.05 for both, t-test). Furthermore both SNR and CNR ratio were significantly higher using IR at 80 kV tube current than using FBP at 120 kV (mean difference: 3.1±1.5 and 0.7±1.8 respectively, p<0.05 for both, t-test), whereas dose length product was significantly higher using a tube voltage of 120 kV compared to using 80 kV (239.2±258.4 mGy*cm vs. 71.0±73.5 mGy*cm, p<0.05, t-test).  

Using iterative reconstruction instead of filtered back projection leads to significantly better image quality and may allow altering of scanning parameters to reduce effective dose.

Iterative reconstruction may allow assessment of cardiac function at the same time as coronary CT angiography at a reduced dose and may be of significance in exams using ECG-triggered tube modulation.

Greupner, J, Hamm, B, Dewey, M, Evaluation of Iterative Reconstruction Algorithms to Reduce Dose in Assessment of Global Left Ventricular Function Using Multidetector Computed Tomography: A Phantom Study.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043762.html