K Martini1, J W Moon2, M P Revel3, S Dangeard2, C Ruan4, G Chassagnon5. 1. Department of Radiology, Cochin Hospital, AP-HP Centre, 75014 Paris, France; Diagnostic and Interventional Radiology, University Hospital Zurich, 8008 Zurich, Switzerland. 2. Department of Radiology, Cochin Hospital, AP-HP Centre, 75014 Paris, France. 3. Department of Radiology, Cochin Hospital, AP-HP Centre, 75014 Paris, France; Université de Paris, Descartes-Paris 5, 75006 Paris, France. 4. General Electric Healthcare, 78530 Buc, France. 5. Department of Radiology, Cochin Hospital, AP-HP Centre, 75014 Paris, France; Université de Paris, Descartes-Paris 5, 75006 Paris, France; Center for Visual Computing, École Centrale Supelec, 91190 Gif-sur-Yvette, France. Electronic address: guillaume.chassagnon@aphp.fr.
Abstract
PURPOSE: The purpose of this study was to analyze the impact of different options for reduced-dose computed tomography (CT) on image noise and visibility of pulmonary structures in order to define the best choice of parameters when performing ultra-low dose acquisitions of the chest in clinical routine. MATERIALS AND METHODS: Using an anthropomorphic chest phantom, CT images were acquired at four defined low dose levels (computed tomography dose index [CTDIvol]=0.15, 0.20, 0.30 and 0.40mGy), by changing tube voltage, pitch factor, or rotation time and adapting tube current to reach the predefined CTDIvol-values. Images were reconstructed using two different levels of iteration (adaptive statistical iterative reconstruction [ASIR®]-v70% and ASIR®-v100%). Signal-to-noise ratio (SNR) as well as contrast-to-noise ratio (CNR) was calculated. Visibility of pulmonary structures (bronchi/vessels) were assessed by two readers on a 5-point-Likert scale. RESULTS: Best visual image assessments and CNR/SNR were obtained with high tube voltage, while lowest scores were reached with lower pitch factor followed by high tube current. Protocols favoring lower pitch factor resulted in decreased visibility of bronchi/vessels, especially in the periphery. Decreasing radiation dose from 0.40 to 0.30mGy was not associated with a significant decrease in visual scores (P<0.05), however decreasing radiation dose from 0.30mGy to 0.15mGy was associated with a lower visibility of most of the evaluated structures (P<0.001). While image noise could be significantly reduced when ASIR®-v100% instead of ASIR®-v70% was used, the visibility-scores of pulmonary structures did not change significantly. CONCLUSION: Favoring high tube voltage is the best option for reduced-dose protocols. A decrease of SNR and CNR does not necessarily go along with reduced visibility of pulmonary structures.
PURPOSE: The purpose of this study was to analyze the impact of different options for reduced-dose computed tomography (CT) on image noise and visibility of pulmonary structures in order to define the best choice of parameters when performing ultra-low dose acquisitions of the chest in clinical routine. MATERIALS AND METHODS: Using an anthropomorphic chest phantom, CT images were acquired at four defined low dose levels (computed tomography dose index [CTDIvol]=0.15, 0.20, 0.30 and 0.40mGy), by changing tube voltage, pitch factor, or rotation time and adapting tube current to reach the predefined CTDIvol-values. Images were reconstructed using two different levels of iteration (adaptive statistical iterative reconstruction [ASIR®]-v70% and ASIR®-v100%). Signal-to-noise ratio (SNR) as well as contrast-to-noise ratio (CNR) was calculated. Visibility of pulmonary structures (bronchi/vessels) were assessed by two readers on a 5-point-Likert scale. RESULTS: Best visual image assessments and CNR/SNR were obtained with high tube voltage, while lowest scores were reached with lower pitch factor followed by high tube current. Protocols favoring lower pitch factor resulted in decreased visibility of bronchi/vessels, especially in the periphery. Decreasing radiation dose from 0.40 to 0.30mGy was not associated with a significant decrease in visual scores (P<0.05), however decreasing radiation dose from 0.30mGy to 0.15mGy was associated with a lower visibility of most of the evaluated structures (P<0.001). While image noise could be significantly reduced when ASIR®-v100% instead of ASIR®-v70% was used, the visibility-scores of pulmonary structures did not change significantly. CONCLUSION: Favoring high tube voltage is the best option for reduced-dose protocols. A decrease of SNR and CNR does not necessarily go along with reduced visibility of pulmonary structures.
Authors: Thomas Leger; Alexis Jacquier; Pierre-Antoine Barral; Maxime Castelli; Julie Finance; Jean-Christophe Lagier; Matthieu Million; Philippe Parola; Philippe Brouqui; Didier Raoult; Axel Bartoli; Jean-Yves Gaubert; Paul Habert Journal: PLoS One Date: 2020-11-03 Impact factor: 3.240