Optimizing Imaging Parameters for Assessment of Hepatocellular Carcinoma Using Photon-Counting Detector Computed Tomography-Impact of Reconstruction Kernel and Slice Thickness.

BACKGROUND

The use of photon-counting detector computed tomography (PCD-CT) has improved image quality in cardiac, pulmonary, and musculoskeletal imaging. Abdominal imaging research, especially about the use of PCD-CT in hepatocellular carcinoma (HCC), is sparse.

OBJECTIVES

We aimed to compare the image quality of tumors, the liver parenchyma, and the vasculature in patients with HCC using PCD-CT reconstructions at different slice thicknesses and kernels to identify the most appropriate settings for the clinical routine.

METHODS

CT exams from twenty adult patients with HCC performed with a clinically approved, first-generation PCD-CT scanner (Naeotom Alpha, Siemens Healthineers), were retrospectively reviewed. For each patient, images were reconstructed at four different sharp kernels, designed for abdominal imaging (Br40; Br44; Br48; Br56) and at three slice thicknesses (0.4 mm; 1 mm; 3 mm). The reconstruction with the Br40 kernel at 3 mm (Br40) was used as a clinical reference. Three readers independently assessed the image quality of different anatomical abdominal structures and hypervascular HCC lesions using a five-point Likert scale. In addition, image sharpness was assessed using line-density profiles.

RESULTS

Compared with the clinical reference, the Br44 and Br48 reconstructions were rated superior for the assessment of the hepatic vasculature (median difference +0.67 [+0.33 to +1.33], < 0.001 and +1.00 [+0.67 to +1.67], < 0.001). Reconstructions for Br40 (+0.33 [-0.67 to +1.00], < 0.001), and Br44 (+0.0 [0.0 to +1.00], = 0.030) were scored superior for overall image quality. The noise demonstrated a continuous increase when using sharper kernels and thinner slices than Br40 ( < 0.001), leading to a decrease in contrast-to-noise ratio. Although there was a trend toward increased image sharpness using the slope analysis with higher kernels, this was not significantly different compared with the reference standard.

CONCLUSION

PCD-CT reconstruction Br40 was the most suitable setting for overall image quality, while reconstructions with sharper kernels (Br44 and Br48) can be considered for the assessment of the hepatic vasculature in patients with HCC.