Assessment of metal artifacts from titanium wrist prostheses: photon-counting versus energy-integrating detector CT

Abstract

Background: We compared photon-counting detector computed tomography (PCD-CT) polyenergetic images, PCD-CT virtual monoenergetic images (VMI), and energy-integrating detector computed tomography (EID-CT) polyenergetic images regarding bone visualization and metal artifacts in patients with titanium wrist prostheses.

Methods: After ethical approval, 15 patients were examined with PCD-CT and EID-CT. Polyenergetic images were reconstructed, as well as 130-keV VMI for PCD-CT. Five radiologists evaluated bone visualization, interpretability at metal-bone interface and metal artifacts using a 7-point ordinal scale. Streak artifacts and artifacts at the bone-metal interface were quantitatively assessed. Differences between image setups were analyzed using Friedman test and one-way ANOVA with post hoc tests.

Results: Bone visualization was superior in PCD-CT polyenergetic images (median rating 6, range 3-7) compared with VMI (5, 3-7; p < 0.001) and EID-CT (5, 3-7; p = 0.018). Streak artifacts were more pronounced with PCD-CT polyenergetic images (4, 3-6) compared with EID-CT (5, 4-6; p = 0.003) and PCD-CT VMI (5, 3-7; p = 0.002), with quantitative results showing least streak artifacts in PCD-CT VMI, followed by EID-CT and PCD-CT polyenergetic images (50 ± 7%, 70 ± 6%, and 79 ± 5%, respectively; p < 0.001). Interpretability at bone-metal interface was better with PCD-CT polyenergetic images (5, 2-7; p = 0.045) and EID-CT (5, 3-6; p = 0.018) compared with PCD-CT VMI (4, 2-6), without quantitative differences.

Conclusion: Streak artifacts from titanium wrist prostheses were reduced using 130-keV PCD-CT VMI, while bone visualization was highest using PCD-CT polyenergetic images.

Relevance statement: In patients with wrist implants, photon-counting detector CT allows for effective metal artifact reduction using virtual monoenergetic images and improved bone visualization using polyenergetic images. As polyenergetic images and VMI have different advantages, access to both image setups may benefit diagnostic evaluation.

Key points: Virtual monoenergetic images (VMI) presented a substantial reduction of metal streak artifacts. Polyenergetic images exhibited better image quality for bone imaging compared with VMI. A combination of image reconstructions should be preferred depending on the diagnostic task.

Keywords: Arthroplasty; Artifacts; Titanium; Tomography (x-ray computed); Wrist joint.

Fig. 1

Three-dimensional reconstruction of a Motec® Wrist Joint Prosthesis acquired using photon-counting detector computed tomography (polyenergetic reconstruction)

Fig. 2

Description of the two different analysis methods used for the quantification of streak artifacts. a Quantification of proportion of artifacts in the image. b Quantification of frequency changes

Fig. 3

Observer ratings across imaging modalities. Violin plots depict ratings for overall image quality, visibility of trabecular bone structures, visibility of the bone-metal interface and streak artifacts. EID-CT, Energy-integrating detector computed tomography; PCD-CT, Photon-counting detector computed tomography; VMI, Virtual monoenergetic images

Fig. 4

Coronal reconstructions of images obtained using EID-CT (a), PCD-CT polyenergetic images (b), and PCD-CT VMI (c), showing the interface between bone and metal implant. The visibility of trabecular structures was rated highest with PCD-CT polyenergetic images, followed by EID-CT and PCD-VMI. The interpretability of the interface was rated fair or above for all image setups. EID-CT, Energy-integrating detector computed tomography; PCD-CT, Photon-counting detector computed tomography; VMI, Virtual monoenergetic images