Diagnostic and Interventional Radiology, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany.
German Center for Cardiovascular Research (DZHK), Partner-Site Rhine-Main, Mainz, Germany.
Cancer Imaging. 2023 Jul 21;23(1):69. doi: 10.1186/s40644-023-00592-5.
Excellent image quality is crucial for workup of hepatocellular carcinoma (HCC) in patients with liver cirrhosis because a signature tumor signal allows for non-invasive diagnosis without histologic proof. Photon-counting detector computed tomography (PCD-CT) can enhance abdominal image quality, especially in combination with a novel iterative reconstruction algorithm, quantum iterative reconstruction (QIR). The purpose of this study was to analyze the impact of different QIR levels on PCD-CT imaging of HCC in both phantom and patient scans.
Virtual monoenergetic images at 50 keV were reconstructed using filtered back projection and all available QIR levels (QIR 1-4). Objective image quality properties were investigated in phantom experiments. The study also included 44 patients with triple-phase liver PCD-CT scans of viable HCC lesions. Quantitative image analysis involved assessing the noise, contrast, and contrast-to-noise ratio of the lesions. Qualitative image analysis was performed by three raters evaluating noise, artifacts, lesion conspicuity, and overall image quality using a 5-point Likert scale.
Noise power spectra in the phantom experiments showed increasing noise suppression with higher QIR levels without affecting the modulation transfer function. This pattern was confirmed in the in vivo scans, in which the lowest noise levels were found in QIR-4 reconstructions, with around a 50% reduction in median noise level compared with the filtered back projection images. As contrast does not change with QIR, QIR-4 also yielded the highest contrast-to-noise ratios. With increasing QIR levels, rater scores were significantly better for all qualitative image criteria (all p < .05).
Without compromising image sharpness, the best image quality of iodine contrast optimized low-keV virtual monoenergetic images can be achieved using the highest QIR level to suppress noise. Using these settings as standard reconstruction for HCC in PCD-CT imaging might improve diagnostic accuracy and confidence.
对于肝硬化患者的肝细胞癌（HCC）检查，出色的图像质量至关重要，因为典型的肿瘤信号可实现无创诊断，而无需组织学证实。光子计数探测器 CT（PCD-CT）可以增强腹部图像质量，特别是与新型迭代重建算法——量子迭代重建（QIR）结合使用时。本研究旨在分析不同 QIR 水平对 PCD-CT 成像 HCC 的影响，包括体模和患者扫描。
使用滤波反投影和所有可用的 QIR 水平（QIR 1-4）重建虚拟单能量图像 50keV。在体模实验中研究了客观的图像质量特性。该研究还包括 44 例经 PCD-CT 三时相扫描的有活力 HCC 病变患者。定量图像分析包括评估病变的噪声、对比度和对比噪声比。定性图像分析由三位评估者进行，使用 5 分李克特量表评估噪声、伪影、病变显著性和整体图像质量。
体模实验中的噪声功率谱显示，随着 QIR 水平的升高，噪声抑制作用增强，而调制传递函数不受影响。这一模式在体内扫描中得到了证实，其中 QIR-4 重建的噪声水平最低，与滤波反投影图像相比，中位数噪声水平降低了约 50%。由于 QIR 不影响对比度，因此 QIR-4 也产生了最高的对比噪声比。随着 QIR 水平的升高，所有定性图像标准的评估者评分均显著提高（均 p<0.05）。
在不影响图像锐度的情况下，通过使用最高的 QIR 水平抑制噪声，可以获得碘对比优化的低 keV 虚拟单能量图像的最佳图像质量。将这些设置作为 PCD-CT 成像 HCC 的标准重建可能会提高诊断准确性和信心。
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