Radiation Physics, Department of Hematology, Oncology and Radiation Physics, Skåne University Hospital, Lund, Sweden.
Medical Radiation Physics, Department of Translational Medicine, Lund University, Malmö, Sweden.
Neuroradiology. 2023 Sep;65(9):1333-1342. doi: 10.1007/s00234-023-03190-1. Epub 2023 Jul 15.
Reduction in iodinated contrast medium (CM) dose is highly motivated. Our aim was to evaluate if a 50% reduction of CM, while preserving image quality, is possible in brain CT angiography (CTA) using virtual monoenergetic images (VMI) on spectral CT. As a secondary aim, we evaluated if VMI can salvage examinations with suboptimal CM timing.
Consecutive patients older than 18 years without intracranial stenosis/occlusion were included. Three imaging protocols were used: group 1, full CM dose; group 2, 50% CM dose suboptimal timing; and group 3, 50% CM dose optimized timing. Attenuation, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were measured in the internal carotid artery, M2 segment of the middle cerebral artery, and white matter for conventional images (CI) and VMI (40-200 keV). Qualitative image quality for CI and VMI (50 and 60 keV) was rated by 4 experienced reviewers.
Qualitatively and quantitatively, VMI (40-60 keV) improved image quality within each group. Significantly higher attenuation and CNR was found for group 3 VMI 40-50 keV, with unchanged SNR, compared to group 1 CI. Group 3 VMI 50 keV also received significantly higher rating scores than group 1 CI. Group 2 VMI (40-50 keV) had significantly higher CNR compared to group 3 CI, but the subjective image quality was similar.
VMI of 50 keV with 50% CM dose increases qualitative and quantitative image quality over CI with full CM dose. Using VMI reduces non-diagnostic examinations and may salvage CTA examinations deemed non-diagnostic due to suboptimal timing.
降低碘造影剂（CM）剂量的需求非常迫切。本研究旨在评估在能谱 CT 上使用虚拟单能量成像（VMI）时，脑 CT 血管造影（CTA）是否可以将 CM 剂量减半而不影响图像质量。次要目的是评估 VMI 是否可以改善因 CM 注射时机不佳而导致的诊断性不佳的 CTA 检查。
纳入年龄大于 18 岁且无颅内狭窄/闭塞的连续患者。使用三种成像方案：组 1，全剂量 CM；组 2，CM 半量且注射时机不佳；组 3，CM 半量且优化注射时机。在常规图像（CI）和 VMI（40-200keV）上测量颈内动脉、大脑中动脉 M2 段和脑白质的衰减、噪声、信噪比（SNR）和对比噪声比（CNR）。由 4 位经验丰富的阅片者对 CI 和 VMI（50 和 60keV）的图像质量进行定性评估。
在每组内，VMI（40-60keV）均可改善定性和定量图像质量。与组 1 CI 相比，组 3 VMI 40-50keV 时的衰减和 CNR 显著升高，而 SNR 不变。组 3 VMI 50keV 的评分也显著高于组 1 CI。组 2 VMI（40-50keV）的 CNR 明显高于组 3 CI，但主观图像质量相似。
CM 剂量减半至 50%时，50keV 的 VMI 可提高全剂量 CM 下 CI 的定性和定量图像质量。使用 VMI 可减少非诊断性检查，并可能挽救因 CM 注射时机不佳而导致的诊断性不佳的 CTA 检查。
