Visualization of the middle meningeal artery on photon-counting detector CT: Comparison with energy-integrating detector CT.

Purpose: The middle meningeal artery (MMA) is the target arteries for the treatment of intracranial diseases. The purpose of this study was to investigate the ability of photon-counting detector CT (PCD-CT) to improve the visualization of the MMA compared to energy-integrated detector CT (EID-CT).

Methods: We retrospectively analyzed head CT angiography images from patients who underwent PCD-CT with ultra-high-resolution (UHR) mode between April 2023 and July 2024. We compared the images reconstructed with a slice thickness 0.2 mm and the matrix sizes 1024 × 1024 ('PCD-1024') and 512 × 512 ('PCD-512') with the same-patient images previously obtained by EID-CT with 0.75- or 1.0- mm slice thickness and the matrix size 512 × 512 ('EID-512'). Quantitatively, a region of interest (ROI) was placed on the maxillary artery near the origin of the MMA, and the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and contrast ratio (CR) were measured. Image sharpness was evaluated by measuring the full width at half maximum (FWHM) and the maximum intensity from the MMA vessel line profile. Qualitatively, the overall image quality, sharpness, and artifacts were evaluated using four-point Likert scales. The same evaluation was performed using PCD-CT with 0.2 mm ('0.2 mm') and virtual monoenergetic images (VMIs) ('45 keV', '55 keV', and '70 keV').

Results: 30 patients (19 males, 11 females; median age 65 years) were included. Quantitatively, the SNR (mean ± SD) for PCD-1024, PCD-512, and EID-512 were 16.9 ± 5.6, 20.3 ± 6.2, and 23.2 ± 7.8, respectively (P < 0.01 for PCD-1024 vs. EID-512). The CNR were 16.6 ± 4.5, 20.2 ± 5.5, and 44.4 ± 13.9. The CR were 0.74 ± 0.06, 0.74 ± 0.06, and 0.68 ± 0.08. The FWHM were 1.41 ± 0.17, 1.48 ± 0.15, and 1.77 ± 0.12, and the maximum intensity were 407.5 ± 71.7, 386.0 ± 72.5, and 218.2 ± 58.2 (P < 0.001 for PCD-1024 vs. EID-512 and PCD-512 vs. EID-512, respectively). Qualitatively, significant differences (P < 0.05) were identified among the PCD-1024, PCD-512, and EID-512 groups regarding the respective scores (median [IQR]) for overall image quality (4 [3-4], 3 [3-4], and 2 [2-3]), sharpness (4 [3-4], 3 [3-3], and 2 [2-3]), and artifacts (3 [3-3], 3 [2-3], and 2 [2-2]). In VMI analysis, quantitatively, 45 keV showed the highest values for SNR, CNR, CR, and maximum intensity; however, there were no differences in FWHM among the groups. Qualitatively, 0.2 mm was superior to the other groups in all evaluated aspects (P < 0.05).

Conclusion: PCD-1024 visualized the MMA better than both PCD-512 and EID-512. The 0.2 mm reconstruction was visually superior to the VMIs.