The value of spectral CT combined with metal artifact reduction algorithms in improving the CT image quality for patients with 125I seeds implantation in the chest and abdomen / 中华放射学杂志

ABSTRACT

Objective:To investigate the value of the virtual monoenergetic image (VMI) obtained by a new dual-layer detector spectral CT combined with metal artifact reduction algorithms(O-MAR) in reduction of different types of artifacts caused by 125I seeds implantation and in improvement of the post-operative CT image quality. Methods:This was a cross-sectional study. Thirty-five patients who underwent dual-layer detector spectral CT scanning of the chest and abdomen after 125I seeds implantation were retrospectively included at the First Affiliated Hospital of Zhengzhou University from March to September 2022. The spectral data were collected and reconstructed into conventional CT image (CI), VMI image (50-150 keV, 20 keV/level), CI+O-MAR image, and VMI+O-MAR image (50-150 keV, 20 keV/level). The artifacts′ removal effects and image quality improvement in each group were evaluated. Two slices with the strongest artifacts were selected for analysis for each patient, resulting in a total of 70 slices. Objective indicators including artifact index (AI), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of soft tissue regions affected by artifacts were measured and calculated. Subjective indicators including the overcorrected artifacts and new artifacts, the different forms of artifacts, the diagnosis of artifacts, and the image quality were assessed. One-way analysis of variance was used for comparisons among multiple groups. Paired t test was used to compare the quantitative indicators between the combined O-MAR group and the non-O-MAR group. Kappa statistics was used to evaluate the consistency between observers. Results:In high/low-density artifacts (ROI H/L), the AI values in all groups showed decrease with increasing VMI keV. In artifact-affected tissue (ROI T), SNR of the CI/VMI (70-150 keV)+O-MAR group were significantly higher than those of the CI/VMI group ( P<0.05), CNR of the CI/VMI(50-150 keV)+O-MAR group were significantly higher than those of the CI/VMI group ( P<0.05). Both overcorrection and new artifacts mainly presented in VMI 50 keV and VMI 70 keV groups; Compared with VMI (50-70 keV) group, significantly less numbers of overcorrection and new artifacts were found in VMI (50-70 keV)+O-MAR group ( P<0.05); regarding the comparison of artifact types, with the VMI keV increasing, the number of a-type banded artifacts gradually decreased on images with high-density artifacts, reaching a minimum of 3 in the VMI 150 keV+O-MAR group; while the number of e-type artifacts with little or no artifacts increased, with the highest number of 23 in the VMI 150 keV+O-MAR group. The total number of high-density artifacts in each type decreased with increasing VMI keV. As VMI keV increased, the diagnostic and image quality scores of high-density artifacts in each group were significantly higher than those of low-density artifacts in the VMI+O-MAR group ( P<0.05). Conclusions:VMI combined with O-MAR can significantly improve the objective and subjective image quality of follow-up CT imaging after 125I seed implantation, enhancing lesion visibility and diagnostic confidence. Additionally, VMI+O-MAR showed more pronounced correction effect on high-density artifacts.