Combining 120 keV virtual monoenergetic imaging (VMI120) with iterative metal artifact reduction (iMAR) achieved the strongest reduction of metal artifacts after anterior cervical discectomy and fusion (ACDF), particularly around titanium implants.
Despite superior artifact suppression, standard polychromatic PCCT images remained best for assessing bone fusion, while VMI120+iMAR frequently introduced pseudo-osteolysis and white-zone artifacts that could mimic pseudoarthrosis or false bony bridging.
The study supports a reconstruction-specific workflow, using standard images for fusion assessment and VMI120+iMAR for improved implant visualization and bone-metal interface evaluation.
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FIGURE 1. Exemplary artifact measurements on axial PCD-CT images of a 65-year-old female after anterior cervical discectomy and fusion at the C7/Th1 level with a titanium cage and plate. All regions of interest (0.8 mm²) were placed on the most pronounced hypodense (blue circle) and hyperdense (yellow circle) areas near the implants on polychromatic images (T3D, A) and then copied to the corresponding positions on the other reconstructions (T3DiMAR, VMI120, VMI120+iMAR; B–D). Near-implant hyperdense (yellow arrowhead) and hypodense (blue arrowhead) streak-like metal artifacts were less pronounced with iMAR reconstructions (B) and VMI at 120 keV (C), while the most effective artifact reduction was achieved with the combined VMI120+iMAR reconstruction (D). Note that the iMAR reconstructions (B, D) are inferior for visualization of osseous bridging within the cage. iMAR, iterative metal artifact reduction; PCD, photon-counting detector; VMI, virtual monoenergetic imaging.
Protocol
Detail | Value |
|---|
Scanner | NAEOTOM Alpha |
Software | VB10 |
Scan area | Cervical spine (skull base to T1) |
Scan mode | Tin-filtered PCCT |
Acquisition mode | QuantumSn |
Scan direction | Head-first supine |
Tube voltage [kV] | Automatic 100 or 140 kVp |
Effective mAs [mAs] | Quality reference 590 mAs (100 kVp) / 192 mAs (140 kVp) |
IQ level | 90 |
Dose modulation | CARE keV + CARE Dose4D |
CTDIvol [mGy] | 5.0 median (3.2 at 100 kVp; 5.6 at 140 kVp) |
DLP [mGy*cm] | 111 median |
Temporal resolution [ms] | n.a. |
Rotation time [s] | 0.5 |
Pitch | 0.8 |
Matrix | 512 × 512 |
Field of view [mm] | 130 × 130 |
Slice collimation [mm] | 144 × 0.4 |
Slice width [mm] | 0.8 |
Reconstruction increment [mm] | 0.6 |
Reconstruction kernel | Br64 |
Iterative reconstruction | QIR 3 |
Reconstruction comparison | T3D vs T3DiMAR vs VMI120 vs VMI120+iMAR |
ECG padding | n.a. |
Contrast agent | None (non-contrast CT) |
Contrast volume | n.a. |
Flow rate | n.a. |
Bolus triggering | n.a. |
Patient preparation | Standard cervical spine positioning |
Phase selection | n.a. |
Key Reconstruction Settings
Detail | Value |
|---|
VMI energy level | 120 keV |
Metal artifact reduction | iMAR |
Combined reconstruction | VMI120 + iMAR |
Spectral mode | QuantumSn |
Tin filtration | Yes |
Implant types | Titanium cages; PEEK-tantalum cages |
Abel F, Curti M, Marth T, Marcus RP, Farshad M, Sutter R. Photon-counting CT in Anterior Cervical Discectomy and Fusion: Improved Metal Artifact Reduction and Impact on Bone Fusion Assessment. Invest Radiol. 2026. doi:10.1097/RLI.0000000000001298.
