From the Department of Radiology, University of Colorado, Anschutz Medical Campus, Aurora, CO (W.Z., D.H., L.P.B., J.W.); Department of Radiology, Children's Hospital Colorado, Aurora, CO (L.P.B., J.W.); and Bioinformatics and Computational Biology, University of Minnesota, St Paul, MN (X.Z.).
Invest Radiol. 2024 Oct 1;59(10):719-726. doi: 10.1097/RLI.0000000000001080. Epub 2024 Apr 10.
The purpose of this study is to determine if a universal 120-kV ultra-high pitch and virtual monoenergetic images (VMIs) protocol on the photon-counting computed tomography (PCCT) system can provide sufficient image quality for pediatric abdominal imaging, regardless of size, compared with protocols using a size-dependent kV and dual-source flash mode on the energy-integrating CT (EICT) system.
One solid water insert and 3 iodine (2, 5, 10 mg I/mL) inserts were attached or inserted into phantoms of variable sizes, simulating the abdomens of a newborn, 5-year-old, 10-year-old, and adult-sized pediatric patients. Each phantom setting was scanned on an EICT using clinical size-specific kV dual-source protocols with a pitch of 3.0. The scans were performed with fixed scanning parameters, and the CTDI vol values of full dose were 0.30, 0.71, 1.05, and 7.40 mGy for newborn to adult size, respectively. In addition, half dose scans were acquired on EICT. Each phantom was then scanned on a PCCT (Siemens Alpha) using a universal 120-kV protocol with the same full dose and half dose as determined above on the EICT scanner. All other parameters matched to EICT settings. Virtual monoenergetic images were generated from PCCT scans between 40 and 80 keV with a 5-keV interval. Image quality metrics were compared between PCCT VMIs and EICT, including image noise (measured as standard deviation of solid water), contrast-to-noise ratio (CNR) (measured at iodine inserts with solid water as background), and noise power spectrum (measured in uniform phantom regions).
Noise at a PCCT VMI of 70 keV (7.0 ± 0.6 HU for newborn, 14.7 ± 1.6 HU for adult) is comparable ( P > 0.05, t test) or significantly lower ( P < 0.05, t test) compared with EICT (7.8 ± 0.8 HU for newborn, 15.3 ± 1.5 HU for adult). Iodine CNR from PCCT VMI at 50 keV (50.8 ± 8.4 for newborn, 27.3 ± 2.8 for adult) is comparable ( P > 0.05, t test) or significantly higher ( P < 0.05, t test) to the corresponding EICT measurements (57.5 ± 6.7 for newborn, 13.8 ± 1.7 for adult). The noise power spectrum curve shape of PCCT VMI is similar to EICT, despite PCCT VMI exhibiting higher noise at low keV levels.
The universal PCCT 120 kV with ultra-high pitch and postprocessed VMIs demonstrated equivalent or improved performance in noise (70 keV) and iodine CNR (50 keV) for pediatric abdominal CT, compared with size-specific kV images on the EICT.
本研究旨在确定光子计数计算机断层扫描（PCCT）系统上的通用 120kV 超高螺距和虚拟单能量图像（VMI）协议是否可以提供足够的图像质量，用于儿科腹部成像，而与能量积分 CT（EICT）系统上基于大小的 kV 和双源闪光模式的协议相比，无论大小如何。
将一个实心水插件和 3 个碘（2、5、10mg I/mL）插件附着或插入到不同大小的体模中，模拟新生儿、5 岁、10 岁和成人大小的儿科患者的腹部。每个体模设置均在 EICT 上使用临床特定大小的 kV 双源协议以 3.0 的螺距进行扫描。使用固定的扫描参数进行扫描，全剂量的 CTDIvol 值分别为 0.30、0.71、1.05 和 7.40mGy，用于新生儿至成人大小。此外，还在 EICT 上获取半剂量扫描。然后，将每个体模使用通用 120kV 协议在 PCCT（西门子 Alpha）上进行扫描，该协议的全剂量和半剂量与上述 EICT 扫描仪上的相同。所有其他参数均与 EICT 设置匹配。在 PCCT 扫描中从 40 到 80keV 以 5keV 的间隔生成虚拟单能量图像。在 PCCT VMI 和 EICT 之间比较图像质量指标，包括图像噪声（用水的标准偏差测量）、对比噪声比（以水为背景的碘插件测量）和噪声功率谱（在均匀体模区域测量）。
PCCT VMI 上 70keV 的噪声（新生儿为 7.0±0.6HU，成人为 14.7±1.6HU）与 EICT 相比具有可比性（P＞0.05，t 检验）或显著降低（P＜0.05，t 检验）。PCCT VMI 在 50keV 时的碘 CNR（新生儿为 50.8±8.4，成人为 27.3±2.8）与相应的 EICT 测量值相当（P＞0.05，t 检验）或显著更高（P＜0.05，t 检验）。尽管 PCCT VMI 在低 keV 水平下表现出更高的噪声，但 PCCT VMI 的噪声功率谱曲线形状与 EICT 相似。
与 EICT 上基于大小的 kV 图像相比，通用 PCCT 120kV 超高螺距和后处理 VMI 技术在儿科腹部 CT 的噪声（70keV）和碘 CNR（50keV）方面表现出等效或改善的性能。
