Marth Adrian A, Goller Sophia S, Kajdi Georg W, Marcus Roy P, Sutter Reto
From the Swiss Center for Musculoskeletal Imaging, Balgrist Campus AG, Zurich, Switzerland (A.A.M.); and Department of Radiology, Balgrist University Hospital, Faculty of Medicine, University of Zurich, Zurich, Switzerland (A.A.M., S.S.G., G.W.K., R.P.M., R.S.).
Invest Radiol. 2024 Aug 1;59(8):545-553. doi: 10.1097/RLI.0000000000001058. Epub 2024 Jan 10.
The aim of this study was to compare the effectiveness and clinical utility of virtual monoenergetic image (VMI) reconstructions in computed tomography (CT) scans with and without tin prefiltration on a photon-counting detector (PCD) CT system to reduce metal implant artifacts in the postoperative ankle.
This retrospective study included patients with internal fixation of the ankle scanned with and without tin prefiltration (Sn) on a PCD CT scanner between March and October 2023. Virtual monoenergetic images between 60 and 190 keV were reconstructed with a 10-keV increment in a bone kernel for both acquisitions (VMI Sn and VMI Std , respectively). Noise measurements assessed artifact reduction in the most prominent near-metal image distortions and were compared between acquisitions modes as well as between polychromatic images and VMIs. Three readers assessed the visibility of osseous healing along with interpretability and artifact extent for 5 reconstruction levels.
A total of 48 patients (21 females, 27 males; mean age, 55.1 ± 19.4 years) were included in this study. Tin-prefiltered acquisitions (n = 30) had a lower artifact level for polychromatic images and VMIs compared with non-tin-prefiltered acquisitions (n = 18; P ≤ 0.043). A significant reduction of metal artifacts was observed for VMI Sn ≥120 keV compared with polychromatic images (hyperdense artifacts: 40.2 HU [interquartile range (IQR) 39.8] vs 14.0 HU [IQR 11.1]; P ≤ 0.01 and hypodense artifacts: 91.2 HU [IQR 82.4] vs 29.7 HU [IQR 39.6]; P ≤ 0.001). For VMI Std , this applied to reconstructions ≥100 keV (hyperdense artifacts: 57.7 HU [IQR 33.4] vs 19.4 HU [IQR 27.6]; P ≤ 0.001 and hypodense artifacts: 106.9 HU [IQR 76.1] vs 57.4 HU [IQR 55.7]; P ≤ 0.021). For visibility of osseous healing, VMI Sn at 120 keV yielded higher ratings compared with polychromatic images ( P ≤ 0.001), whereas image interpretability was rated better ( P = 0.023), and artifact extent was rated lower ( P ≤ 0.001) compared with polychromatic images.
Tin-prefiltered VMI at 120 keV showed a significant reduction in metal artifacts compared with polychromatic images, whereas visibility of osseous healing and image interpretability was improved. Therefore, tin-prefiltration PCD CT with VMI reconstructions may be a helpful complement to postsurgical CT imaging of the ankle in patients with metal implants.
本研究旨在比较在光子计数探测器（PCD）CT系统上，有锡预过滤和无锡预过滤的计算机断层扫描（CT）中虚拟单能图像（VMI）重建在减少术后踝关节金属植入物伪影方面的有效性和临床实用性。
这项回顾性研究纳入了2023年3月至10月期间在PCD CT扫描仪上进行有锡预过滤（Sn）和无锡预过滤扫描的踝关节内固定患者。两种扫描方式（分别为VMI Sn和VMI Std）均使用骨内核，以10 keV增量重建60至190 keV之间的虚拟单能图像。通过噪声测量评估最显著的近金属图像失真处的伪影减少情况，并在不同扫描方式之间以及多色图像和VMI之间进行比较。三位阅片者评估5个重建层面的骨愈合可见性以及图像的可解释性和伪影程度。
本研究共纳入48例患者（21例女性，27例男性；平均年龄55.1±19.4岁）。与无锡预过滤扫描（n = 18）相比，有锡预过滤扫描（n = 30）的多色图像和VMI的伪影水平更低（P≤0.043）。与多色图像相比，VMI Sn≥120 keV时金属伪影显著减少（高密度伪影：40.2 HU[四分位数间距（IQR）39.8]对14.0 HU[IQR 11.1]；P≤0.01；低密度伪影：91.2 HU[IQR 82.4]对29.7 HU[IQR 39.6]；P≤0.001）。对于VMI Std，≥100 keV的重建图像也有同样情况（高密度伪影：57.7 HU[IQR 33.4]对19.4 HU[IQR 27.6]；P≤0.001；低密度伪影：106.9 HU[IQR 76.1]对57.4 HU[IQR 55.7]；P≤0.021）。在骨愈合可见性方面，120 keV的VMI Sn与多色图像相比评分更高（P≤0.001），而图像可解释性评分更好（P = 0.023），伪影程度评分更低（P≤0.001）。
与多色图像相比，120 keV的有锡预过滤VMI显示金属伪影显著减少，同时骨愈合可见性和图像可解释性得到改善。因此，有锡预过滤的PCD CT结合VMI重建可能是金属植入物患者踝关节术后CT成像的有益补充。
