Optimization of Image Reconstruction and Tube Voltage in CT Arthrography of Shoulder

Abstract

Introduction: To determine an optimal reconstruction method and tube voltage in computed tomography (CT) arthrography of the shoulder regarding radiation dose and image quality. Materials and Methods: : The institutional review board approved the study and written informed consents were obtained. Sixty-two CT exams were prospectively included. CT scans were obtained twice in each patient at 120kVp and 140kVp in two different shoulder positions, while other scanning parameters were kept constant. For each scan, we obtained two axial image-sets of 2.0 mm: direct reconstruction and thin-slab averaging reformation. Image quality was subjectively compared regarding contrast and noise between reconstruction methods and between 120kVp and 140kVp. Mean attenuation of intraarticular contrast media, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and radiation dose were quantitatively compared between 120kVp and 140kVp. Results: In comparison between reconstruction methods, thin-slab averaging reformation showed better image quality than direct reconstruction in all cases. In qualitative assessment, contrast was better in 120kVp, whereas noise was more. In quantitative analysis, mean attenuation of intraarticular contrast media was higher (2210 HU±474 vs 1873 HU±427

p<0.001), and noise more (26.1±5.8 vs 20.9±4.7

p<0.001) in 120kVp than 140kVp. There was no significant difference between 120kVp and 140kVp in SNR (89.9±29.8 vs 94.3±28.9

p= 0.17) and CNR (87.4±29.3 vs 91.3±28.4

p= 0.21). Lowering tube voltage from 140kVp to 120kVp reduced radiation dose by 33 %. Conclusion: Thin-slab averaging reformation improves image quality by decreasing noise in CT arthrography. Moreover, use of 120 kVp in combination with thin-slab reformation achieves a decrease in radiation dose compared to 140 kVp without significant loss of image quality.