INSA-Lyon, University of Lyon, University Claude-Bernard Lyon 1, UJM-Saint-Étienne, CNRS, Inserm, CREATIS UMR 5220, U1206, 69100, Villeurbanne, France.
Radiology Department, Hospices Civils de Lyon, 69500, Lyon, France.
Eur Radiol. 2022 Jan;32(1):524-532. doi: 10.1007/s00330-021-08103-5. Epub 2021 Jun 29.
To evaluate the image quality (IQ) of a spectral photon-counting CT (SPCCT) using filtered back projection (FBP) and hybrid iterative reconstruction (IR) algorithms (iDose), in comparison with a dual-layer CT (DLCT) system, and to choose the best image quality according to the IR level for SPCCT.
Two phantoms were scanned using a standard lung protocol (120 kVp, 40 mAs) with SPCCT and DLCT systems. Raw data were reconstructed using FBP and 9 iDose levels (i1/i2/i3/i4/i5/i6/i7/i9/i11) for SPCCT and 7 for DLCT (i1/i2/i3/i4/i5/i6/i7). Noise power spectrum and task-based transfer function (TTF) were computed. Detectability index (d') was computed for detection of 4 mm ground-glass nodule (GGN) and solid nodule. Two chest radiologists performed an IQ evaluation (noise/nodule sharpness/nodule conspicuity/overall IQ) in consensus, and chose the best image for SPCCT.
Noise magnitude was -47% ± 2% lower on average with SPCCT than with DLCT for iDose range from i1 to i6. Average NPS spatial frequencies increased for SPCCT in comparison with DLCT. TTF also increased, except for the air insert with FBP, and i1/i2/i3. Higher detectability was found for SPCCT for both GGN and solid nodules. IQ for both types of nodule was rated consistently higher with SPCCT than with DLCT for the same iDose level. For SPCCT and both nodules, the scores for noise and conspicuity improved with increasing iDose level. iDose level 6 provided the best subjective IQ for both types of nodule.
Higher IQ for GGN and solid nodules was demonstrated with SPCCT compared with DLCT with better detectability using iDose.
Using spectral photon-counting CT compared with dual-layer CT, noise magnitude was reduced with improvements in spatial resolution and detectability of ground-glass nodules and solid lung nodules. As the iDose level increased, noise magnitude was reduced and detectability of ground-glass and solid lung nodules was better for both CT systems. For spectral photon-counting CT imaging, two chest radiologists determined iDose level 6 as the best image quality for detecting ground-glass nodules and solid lung nodules.
使用滤波反投影（FBP）和混合迭代重建（IR）算法（iDose）评估光谱光子计数 CT（SPCCT）的图像质量（IQ），并将其与双层 CT（DLCT）系统进行比较，并根据 SPCCT 的 IR 水平选择最佳图像质量。
使用标准的肺协议（120 kVp，40 mAs）对两个体模进行 SPCCT 和 DLCT 系统扫描。使用 FBP 和 9 个 iDose 水平（i1/i2/i3/i4/i5/i6/i7/i9/i11）对 SPCCT 进行重建，对 DLCT 进行 7 个重建（i1/i2/i3/i4/i5/i6/i7）。计算噪声功率谱和基于任务的传递函数（TTF）。计算 4mm 磨玻璃结节（GGN）和实性结节的检测指数（d'）。两位胸部放射科医生进行了 IQ 评估（噪声/结节锐利度/结节显著性/整体 IQ），并达成共识，选择了 SPCCT 的最佳图像。
与 DLCT 相比，iDose 范围从 i1 到 i6，SPCCT 的噪声幅度平均降低了-47%±2%。与 DLCT 相比，SPCCT 的平均 NPS 空间频率增加。除了 FBP 和 i1/i2/i3 的空气插入外，TTF 也增加了。对于 GGN 和实性结节，SPCCT 的检测能力均高于 DLCT。对于相同的 iDose 水平，SPCCT 的两种类型的结节的 IQ 评分均高于 DLCT。对于 SPCCT 和两种结节，随着 iDose 水平的增加，噪声和显著性评分均得到提高。对于两种类型的结节，iDose 水平 6 提供了最佳的主观 IQ。
与 DLCT 相比，SPCCT 对 GGN 和实性结节具有更高的 IQ，并且使用 iDose 提高了检测的可检测性。
与双层 CT 相比，使用光谱光子计数 CT，通过提高空间分辨率和磨玻璃结节和实性肺结节的检测能力，降低了噪声幅度。随着 iDose 水平的增加，两种 CT 系统的噪声幅度降低，磨玻璃和实性肺结节的检测能力提高。对于光谱光子计数 CT 成像，两位胸部放射科医生确定 iDose 水平 6 是检测磨玻璃结节和实性肺结节的最佳图像质量。
