Delineation of the brachial plexus by contrast-enhanced photon-counting detector CT and virtual monoenergetic images

Objectives: To improve the image quality of the brachial plexus in photon-counting detector CT (PCD-CT) using contrast media and virtual monoenergetic images (VMI). Materials & Methods: We retrospectively analyzed contrast-enhanced neck PCD-CT images scanned in March-July 2023. Unenhanced and contrast-enhanced images were compared, and then 40-, 70-, and 100-keV VMIs were compared. The qualitative evaluation used a five-point Likert scale regarding overall image quality (IQ), sharpness, and noise. The quantitative evaluation used the standard deviation (SD), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Freidman's test and one-way ANOVA were performed. Results: Forty patients (65 years +/- 17, 21 males) were included. The median scores [interquartile range, IQR] for the unenhanced and contrast-enhanced groups were IQ, 3 [2,3] and 4 [3,4] (P < 0.001); sharpness, 3 [2,3] and 4 [3,4] (P < 0.001); and noise, 3 [3,4] and 3 [3,4] (P = 0.63). Mean +/- SD scores were SD, 6.7 +/- 1.4 and 6.7 +/- 1.0 (P = 0.95); SNR, 5.1 +/- 1.2 and 5.4 +/- 1.4 (P = 0.04); and CNR, 4.8 +/- 1.5 and 8.1 +/- 2.3 (P < 0.001). The 40-, 70-, and 100-keV groups' IQ were 2 [2,3], 4 [3,4], and 3 [3,4]; their sharpness scores were 2 [2,3], 3 [3,4], and 3 [2,3] (all, P < 0.05). Those for noise were 2 [1-3], 3 [3,4], and 4 [3,4] (all, P < 0.001 except for 70-keV vs.100-keV: P = 0.16). The SDs were 13.1 +/- 2.5, 7.5 +/- 1.2, and 6.0 +/- 1.1. The SNRs were 4.2 +/- 1.9, 5.0 +/- 1.2, and 5.7 +/- 1.5 (all, P < 0.001). The CNRs were 8.7 +/- 4.0, 6.8 +/- 2.3, and 6.5 +/- 2.3 (all, P < 0.001 except for 70-keV vs.100-keV: P = 0.51). Conclusion: Contrast-enhanced PCD-CT and VMIs provided good delineation of the brachial plexus.