Salim A Si-Mohamed1,2,3, Joel Greffier4, Jade Miailhes5, Sara Boccalini6,5, Pierre-Antoine Rodesch6, Aurélie Vuillod7, Niels van der Werf8,9, Djamel Dabli4, Damien Racine10, David Rotzinger11, Fabio Becce11, Yoad Yagil12, Philippe Coulon13, Alain Vlassenbroek14, Loic Boussel6,5, Jean-Paul Beregi4, Philippe Douek6,5,15. 1. INSA-Lyon, University of Lyon, University Claude-Bernard Lyon 1, UJM-Saint-Étienne, CNRS, Inserm, CREATIS UMR 5220, U1206, 69100, Villeurbanne, France. salim.si-mohamed@chu-lyon.fr. 2. Radiology Department, Hospices Civils de Lyon, 69500, Lyon, France. salim.si-mohamed@chu-lyon.fr. 3. Department of Cardiovascular and Thoracic Radiology, CHU Cardiologique Louis Pradel, 59 Boulevard Pinel, 69500, Bron, France. salim.si-mohamed@chu-lyon.fr. 4. Department of Medical Imaging, CHU Nimes, Univ Montpellier, Medical Imaging Group, 2415, Nimes, EA, France. 5. Radiology Department, Hospices Civils de Lyon, 69500, Lyon, France. 6. INSA-Lyon, University of Lyon, University Claude-Bernard Lyon 1, UJM-Saint-Étienne, CNRS, Inserm, CREATIS UMR 5220, U1206, 69100, Villeurbanne, France. 7. Medical Physics Department, Hospices Civils de Lyon, 69000, Lyon, France. 8. Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands. 9. Department of Radiology & Nuclear Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands. 10. Institute of Radiation Physics, Lausanne University Hospital and University of Lausanne, Rue du Grand-Pré 1, 1007, Lausanne, Switzerland. 11. Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Rue du Bugnon 46, 1011, Lausanne, Switzerland. 12. Philips Research, Haifa, Israel. 13. Philips Research, Suresnes, France. 14. CT Clinical Science, 5682, Best, The Netherlands. 15. Department of Cardiovascular and Thoracic Radiology, CHU Cardiologique Louis Pradel, 59 Boulevard Pinel, 69500, Bron, France.
Abstract
OBJECTIVES: To evaluate the image quality (IQ) of a spectral photon-counting CT (SPCCT) using filtered back projection (FBP) and hybrid iterative reconstruction (IR) algorithms (iDose4), in comparison with a dual-layer CT (DLCT) system, and to choose the best image quality according to the IR level for SPCCT. METHODS: Two phantoms were scanned using a standard lung protocol (120 kVp, 40 mAs) with SPCCT and DLCT systems. Raw data were reconstructed using FBP and 9 iDose4 levels (i1/i2/i3/i4/i5/i6/i7/i9/i11) for SPCCT and 7 for DLCT (i1/i2/i3/i4/i5/i6/i7). Noise power spectrum and task-based transfer function (TTF) were computed. Detectability index (d') was computed for detection of 4 mm ground-glass nodule (GGN) and solid nodule. Two chest radiologists performed an IQ evaluation (noise/nodule sharpness/nodule conspicuity/overall IQ) in consensus, and chose the best image for SPCCT. RESULTS: Noise magnitude was -47% ± 2% lower on average with SPCCT than with DLCT for iDose4 range from i1 to i6. Average NPS spatial frequencies increased for SPCCT in comparison with DLCT. TTF also increased, except for the air insert with FBP, and i1/i2/i3. Higher detectability was found for SPCCT for both GGN and solid nodules. IQ for both types of nodule was rated consistently higher with SPCCT than with DLCT for the same iDose4 level. For SPCCT and both nodules, the scores for noise and conspicuity improved with increasing iDose4 level. iDose4 level 6 provided the best subjective IQ for both types of nodule. CONCLUSIONS: Higher IQ for GGN and solid nodules was demonstrated with SPCCT compared with DLCT with better detectability using iDose4. KEY POINTS: Using spectral photon-counting CT compared with dual-layer CT, noise magnitude was reduced with improvements in spatial resolution and detectability of ground-glass nodules and solid lung nodules. As the iDose4 level increased, noise magnitude was reduced and detectability of ground-glass and solid lung nodules was better for both CT systems. For spectral photon-counting CT imaging, two chest radiologists determined iDose4 level 6 as the best image quality for detecting ground-glass nodules and solid lung nodules.
OBJECTIVES: To evaluate the image quality (IQ) of a spectral photon-counting CT (SPCCT) using filtered back projection (FBP) and hybrid iterative reconstruction (IR) algorithms (iDose4), in comparison with a dual-layer CT (DLCT) system, and to choose the best image quality according to the IR level for SPCCT. METHODS: Two phantoms were scanned using a standard lung protocol (120 kVp, 40 mAs) with SPCCT and DLCT systems. Raw data were reconstructed using FBP and 9 iDose4 levels (i1/i2/i3/i4/i5/i6/i7/i9/i11) for SPCCT and 7 for DLCT (i1/i2/i3/i4/i5/i6/i7). Noise power spectrum and task-based transfer function (TTF) were computed. Detectability index (d') was computed for detection of 4 mm ground-glass nodule (GGN) and solid nodule. Two chest radiologists performed an IQ evaluation (noise/nodule sharpness/nodule conspicuity/overall IQ) in consensus, and chose the best image for SPCCT. RESULTS: Noise magnitude was -47% ± 2% lower on average with SPCCT than with DLCT for iDose4 range from i1 to i6. Average NPS spatial frequencies increased for SPCCT in comparison with DLCT. TTF also increased, except for the air insert with FBP, and i1/i2/i3. Higher detectability was found for SPCCT for both GGN and solid nodules. IQ for both types of nodule was rated consistently higher with SPCCT than with DLCT for the same iDose4 level. For SPCCT and both nodules, the scores for noise and conspicuity improved with increasing iDose4 level. iDose4 level 6 provided the best subjective IQ for both types of nodule. CONCLUSIONS: Higher IQ for GGN and solid nodules was demonstrated with SPCCT compared with DLCT with better detectability using iDose4. KEY POINTS: Using spectral photon-counting CT compared with dual-layer CT, noise magnitude was reduced with improvements in spatial resolution and detectability of ground-glass nodules and solid lung nodules. As the iDose4 level increased, noise magnitude was reduced and detectability of ground-glass and solid lung nodules was better for both CT systems. For spectral photon-counting CT imaging, two chest radiologists determined iDose4 level 6 as the best image quality for detecting ground-glass nodules and solid lung nodules.
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Authors: David C Rotzinger; Damien Racine; Fabio Becce; Elias Lahoud; Klaus Erhard; Salim A Si-Mohamed; Joël Greffier; Anaïs Viry; Loïc Boussel; Reto A Meuli; Yoad Yagil; Pascal Monnin; Philippe C Douek Journal: Diagnostics (Basel) Date: 2021-12-16