Jan-Hendrik Buhk MD, Abstract Co-Author: Nothing to Disclose

Azien Laqmani, Abstract Co-Author: Nothing to Disclose

Hans-Christoph von Schultzendorff, Abstract Co-Author: Nothing to Disclose

Diego Hammerle, Abstract Co-Author: Nothing to Disclose

Frank Oliver Henes MD, Abstract Co-Author: Nothing to Disclose

Michael Groth MD, Abstract Co-Author: Nothing to Disclose

Hans Dieter Nagel, Abstract Co-Author: Consultant, Koninklijke Philips Electronics NV

Gerhard B. Adam MD, Abstract Co-Author: Nothing to Disclose

Marc Regier, Presenter: Nothing to Disclose

To intraindividually compare and evaluate the influence of the 4th generation iterative reconstruction (IR) technique iDose™ on low-dose MDCT of the lungs with regard to anatomical delineation and artifact reduction.

In 29 consecutive patients suspected of suffering from infectious pneumonia the raw data of unenhanced MDCT scans (120 kV, standard resolution mode, mean CTDIvol: 2.6 mGy, mean DLP: 125 mGy x cm; 17 male, 12 female; mean age 47y) were reconstructed using a prototypic reconstruction processor featuring iDose4™ software (Philips, Best, the Netherlands). iDose™ level settings were varied between 0, 2, 4, 6 and 7. Additionally, for each setting three different thorax-specific filter kernels were applied (L, lung; B, standard; C, sharp). Images were reconstructed with a slice thickness of 1 mm (L) or 5 mm (B, C), respectively. Three radiologists blinded to the reconstruction technique independently performed image analysis. A 4-point grading scale was applied regarding the depiction of anatomical details of the lungs and mediastinal structures and the degree of artifacts observed (1, worst; 4, excellent). The signal-to-noise ratio (SNR) was assessed for each data set. Statistical evaluation included weighted kappa-analysis and Wilcoxon-test.

The highest image quality regarding the lung was assessed applying an iDose™ level of 4 (kernel L). Regarding mediastinal soft tissue iDose™ level of 4 (kernel C) scored best. Even at the lower iDose™ level of 2 the image ratings scored superior to standard filtered back-projection (= iDose™ level 0). Inter-rater reliability was at least substantial in all cases (κ > 0.6). With increasing iDose™ levels, reduction of streak artifacts was visible and successfully quantified by a decrease of the standard deviation at constant mean attenuation values.

Iterative reconstruction seems to be a powerful tool for improvement of image quality in low-dose MDCT of the lung and allows better depiction of the mediastinal structures as well. Even at relatively low iDose™ levels higher image quality and substantial reduction of streak artifacts compared to the filtered back-projection can be achieved.

The application of a 4th generation iterative reconstruction technique has the potential to remarkably improve image quality in low-dose MDCT of the lung and mediastinum.

Buhk, J, Laqmani, A, von Schultzendorff, H, Hammerle, D, Henes, F, Groth, M, Nagel, H, Adam, G, Regier, M, Impact of 4th Generation Iterative Reconstruction Technique on Image Quality in Low Dose Computed Tomography of the Lungs.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11016753.html