RSNA 2012 

Abstract Archives of the RSNA, 2012


SSK16-01

Comparison of Low Contrast Detection of Filtered Back Projection (FBP), Partially and Fully Iterative Reconstruction Techniques in a Phantom Study: 12-Alternative Forced-Choice Detectability Experiments and Contrast to Noise-Ratio (CNR)

Scientific Formal (Paper) Presentations — Quality Assurance/Quality Improvement,

Presented on November 28, 2012
Presented as part of SSK16: Physics (CT Dose Optimization)

Participants

Zsuzsanna Deak MD, Presenter: Research Grant, General Electric Company
Lucas L. Geyer MD, Abstract Co-Author: Speaker, General Electric Company
Jochen Martin Grimm MD, Abstract Co-Author: Nothing to Disclose
Fabian Mueck, Abstract Co-Author: Nothing to Disclose
Maximilian F. Reiser MD, Abstract Co-Author: Nothing to Disclose
Stefan Wirth MD, Abstract Co-Author: Nothing to Disclose

PURPOSE

To investigate dose reduction potential of a fully and a partially iterative image reconstruction algorithm in comparison to the established analytic method of filtered back projection (FBP).

METHOD AND MATERIALS

Images were obtained on a 64-row MDCT scanner (CT 750HD; GE-Healthcare, USA) using a CATPHAN600® phantom (The Phantom Laboratory, USA). A tube-voltage of 120kVp and incrementally decreasing tube current-time products (240mAs, 200mAs, 160mAs, 120mAs, 80mAs, 40mAs) were applied. Raw data were reconstructed with FBP, partially (ASIR® with 50% blending) and fully (Veo®) iterative algorithms. Attenuation value in HU and standard deviation were measured using identical and multiple sampling on images of 0.625mm, 2.5mm and 5.0mm slice thickness. CNR values were calculated and ten experienced radiologists performed 12-alternative forced-choice (12-AFC) experiments to assess the detectability of low-contrast disks embedded in the phantom with 1.0 and 0.5% nominal contrast value. CNR values were tested with one-way ANOVA.

RESULTS

Results show that ASIR strongly increases CNR and moderately improves the detectibility of low contrast objects for all dose levels in comparison to FBP. Veo performes similar to ASIR at normal dose levels (240-160mAs) for 1.0% low contrast objects, but significantly improves low contrast detection at low dose levels (40-80mAs), for decreased contrast objects with 0.5% nominal contrast and even for thin slices (0.625mm). At 40mAs with Veo, CNR increased between 80-118% and 26-67% compared to FBP and ASIR, respectively (both p<0.05) and 0.5% contrast targets were detectable down to 7 mm diameter. ASIR and FBP provided the same low contrast detection only at 160mAs and 240mAs, respectively.

CONCLUSION

The fully iterative reconstruction method allows for a dose reduction of 75% and 83% compared to partially iterative reconstruction and FBP without compromising low contrast detection.

CLINICAL RELEVANCE/APPLICATION

The fully iterative reconstruction algorithm shows tremendous potential for low dose CT applications.

Cite This Abstract

Deak, Z, Geyer, L, Grimm, J, Mueck, F, Reiser, M, Wirth, S, Comparison of Low Contrast Detection of Filtered Back Projection (FBP), Partially and Fully Iterative Reconstruction Techniques in a Phantom Study: 12-Alternative Forced-Choice Detectability Experiments and Contrast to Noise-Ratio (CNR).  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12033964.html