Comparison of image quality of shoulder CT arthrography conducted using 120 kVp and 140 kVp protocols

Abstract

Objective: To compare the image quality of shoulder CT arthrography performed using 120 kVp and 140 kVp protocols.

Materials and methods: Fifty-four CT examinations were prospectively included. CT scans were performed on each patient at 120 kVp and 140 kVp; other scanning parameters were kept constant. Image qualities were qualitatively and quantitatively compared with respect to noise, contrast, and diagnostic acceptability. Diagnostic acceptabilities were graded using a one to five scale as follows: 1, suboptimal; 2, below average; 3, acceptable; 4, above average; and 5, superior. Radiation doses were also compared.

Results: Contrast was better at 120 kVp, but noise was greater. No significant differences were observed between the 120 kVp and 140 kVp protocols in terms of diagnostic acceptability, signal-to-noise ratio, or contrast-to-noise ratio. Lowering tube voltage from 140 kVp to 120 kVp reduced the radiation dose by 33%.

Conclusion: The use of 120 kVp during shoulder CT arthrography reduces radiation dose versus 140 kVp without significant loss of image quality.

Keywords: Image quality; Radiation dose; Shoulder CT arthrography; Tube voltage.

Fig. 1

Axial CT arthrographic images obtained by thin-slab-averaging reformation and conventional reconstruction in 24-year-old man for postoperative evaluation of SLAP lesion. A. Thin-slab-averaging reformation (used in this study). Image was obtained using two steps. Primary thin-section images were reconstructed using section thickness of 1.0 mm and reconstruction interval of 0.7 mm. Then, thin-slab-averaging reformation was applied to generate this image with section thickness of 2.0 mm and interval of 2.0 mm. B. Conventional reconstruction (for comparison). Image was reconstructed directly from raw projection data with section thickness of 2.0 mm and reconstruction interval of 2.0 mm. Image looks less smooth and noisier than that obtained by thin-slab-averaging reformation.

Fig. 2

Axial CT arthrographic images obtained at 120 kVp and 140 kVp in 24-year-old man for postoperative evaluation of superior labral anterior-to-posterior lesion. A. Image was taken in neutral position at 120 kVp, and shows better contrast between intraarticular contrast media solution and adjacent soft tissues and more noise than image obtained at 140 kVp. B. Image was taken in stress position at 140 kVp.