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Comparative Study
. 2025 Aug;67(8):2021-2030.
doi: 10.1007/s00234-025-03650-w. Epub 2025 Jun 2.

Photon-counting CT-angiography in comparison to digital subtraction angiography for assessing intracranial aneurysms after coiling or clipping

Frederic De Beukelaer  1 , Laura Wuyts  2 , Sophie De Beukelaer  3 , Steven Van Hedent  2 , Omid Nikoubashman  4 , Martin Wiesmann  4 , Michael Veldeman  4   5 , Rastislav Pjontek  4   5 , Anke Höllig  4   5 , Hani Ridwan #  4 , Charlotte Weyland #  6
Affiliations
Comparative Study

Photon-counting CT-angiography in comparison to digital subtraction angiography for assessing intracranial aneurysms after coiling or clipping

Frederic De Beukelaer et al. Neuroradiology. 2025 Aug.

Abstract

Purpose: To evaluate the potential of Photon-Counting Detector CT Angiography (PCD-CTA) for the post-interventional assessment of intracranial aneurysms treated with coil-embolization or clipping, compared to digital subtraction angiography (DSA).

Methods: Retrospective analysis of consecutive patients treated with coils or clips between April 2023 and May 2024, who underwent PCD-CTA and, if necessary, DSA as part of their clinical routine. Polyenergetic images and spectral reconstructions were performed at different kiloelectron volt (keV) levels (40, 80 and 120) and with reconstruction kernels: Quantitative (Qr56 and Qr72) and Head vessel (Hv56 and Hv72), both with and without iterative metal artifact reduction (iMAR). Three independent readers assessed image quality using a 5-point Likert scale and region of interest analysis. A blinded, independent reading was performed to determine the presence of aneurysm remnants and intracranial vessel stenosis in the parent vessel.

Results: A total of 21 patients (mean age 58 ± 14 years; range 36-74; 18 women) with intracranial, saccular aneurysms treated with either clipping (17/21) or coiling (4/21) were included. Reconstructions using smooth kernels (Hv56, Qr56) at a low keV level (40 keV) yielded increased signal- and contrast-to-noise ratios compared to sharper kernels (Hv72, Qr72) and higher keV levels (80 and 120 keV) (p < 0.001). Unexpectedly, reconstructions with iMAR negatively impacted evaluation, with only 6/21 diagnostic images at the clip site. The sensitivity of PCD-CTA for detecting aneurysm remnants was 100% (7 of 7 aneurysm clip/coil site), while specificity was 89% for patients with clips (8/9). A 100% negative predictive value was observed for all readers regarding aneurysm remnants.

Conclusion: Photon-Counting CT-Angiography demonstrated adequate diagnostic value in most patients with intracranial clips. However, while coil artifacts were reduced, spectral reconstructions and iMAR were not sufficient to fully minimize these artifacts.

Keywords: Aneurysm treatment; CT angiography; Coil-embolization; Microsurgial clipping; Photon Counting CT.

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Conflict of interest statement

Declarations. Ethical approval: The local ethics committee approved the study (local registration number: EK 24-270). Patient consent was waived due to the retrospective nature of the study design. The study is reported in adherence to the STROBE criteria Informed consent: All procedures performed in studies involving human participants were in accordance with the 1964 Helsinki Declaration and its later amendments. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Illustration of reconstruction protocol for VMI with three different kernels and three keV levels. In the three rows, from left to right, the three keV levels (40, 80 and 120) are listed and in the three columns, from top to bottom Hv56 kernel without iMAR, Hv56 with iMAR and Hv 72. In detail: a = 40 keV, Hv 56; b = 80 keV, Hv 56; c = 120 keV, Hv 56; d = 40 keV, Hv56 with iMAR; e = 80 keV, Hv 56 with iMAR; f = 120 keV, Hv56 with iMAR; g = 40 keV, Hv 72; h = 80 keV; Hv72; i = 120 keV, Hv72. Abbreviations: Hv: Head vascular kernel, iMAR: iterative metal artefact reduction, keV: kiloelectron Volt, VMI: Virtual Monoenergetic Imaging
Fig. 2
Fig. 2
Illustration of the effect of coil artefacts in different reconstructions on the vascular representation in the immediate vicinity of the coiled aneurysm. In the three rows, from left to right, the three keV levels (40, 80 and 120) are listed and in the three columns, from top to bottom Hv56 kernel without iMAR, Hv56 with iMAR and Hv 72. In detail: a = 40 keV, Hv 56; b = 80 keV, Bv 56; c = 120 keV, Bv 56; d = 40 keV, Hv56 with iMAR; e = 80 keV, Hv 56 with iMAR; f = 120 keV, Hv56 with iMAR; g = 40 keV, Hv 72; h = 80 keV; Hv72; i = 120 keV, Hv72. Abbreviations: Hv: Head vascular kernel, iMAR: iterative metal artefact reduction, keV: kiloelectron Volt, VMI: Virtual Monoenergetic Imaging
Fig. 3
Fig. 3
Illustration of the effect of the iMAR reconstruction on the vessel visibility in the immediate vicinity of the clip. A and B show an aneurysm remnant in the distal M1-segment of the right medial cerebral artery next to three clips. A is a VMI reconstruction with Hv56, B is a VMI reconstruction with Hv56 and iMAR. C and D show an axial reformation of a 3D DSA and a dedicated lateral 2D projections of the right medial cerebral artery. Abbreviations: Hv: Head vascular kernel, iMAR: iterative metal artefact reduction, keV: kiloelectron Volt, VMI: Virtual Monoenergetic Images
Fig. 4
Fig. 4
Qualitative image quality scores of the vessel segment at clip site for VMI with QrA) and Hv(B) with different kernels (Hv56 with an without iMAR, Qr56 with an without iMAR, Hv72 and Qr72) and keV levels (40, 80, 120). Stacked bar charts show pooled percentages of three raters for the vessel segment at clip site. Interpretation of scores: 5 = excellent image quality, 4 = good image quality, 3 = acceptable image quality, 2 = barely satisfactory image quality, 1 = unacceptable image quality. Abbreviations: Hv: Head vascular kernel, iMAR: iterative metal artefact reduction, keV: kiloelectron Volt, Qr: Quantitative kernel, VMI: Virtual Monoenergetic Images
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