Optimal Contrast of Cerebral Dual-Energy Computed Tomography Angiography in Patients With Spontaneous Subarachnoid Hemorrhage

Objective: The aim of this study was to investigate the image quality of cerebral dual-energy computed tomography (CT) angiography using a nonlinear image blending technique as compared with the conventional linear blending method in patients with spontaneous subarachnoid hemorrhage (SAH). Methods: A retrospective review of 30 consecutive spontaneous SAH patients who underwent a dual-source, dual-energy (80 kV and Sn140 kV mode) cerebral CT angiography was performed with permission from hospital ethical committee. Optimized images using nonlinear blending method were generated and compared with the 0.6 linear blending images by evaluating cerebral artery enhancement, attenuation of SAH, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR), respectively. Two neuroradiologists independently assessed subjective vessel visualization per segment using a 5-point scale. Results: The nonlinear blending images showed higher cerebral artery enhancement (307.24 +/- 58.04 Hounsfield unit [HU]), lower attenuation of SAH (67.07 +/- 6.79 HU), and image noise (7.18 +/- 1.20 HU), thus achieving better SNR (43.92 +/- 11.14) and CNR (34.34 +/- 10.25), compared with those of linear blending images (235.47 +/- 46.45 HU for cerebral artery enhancement, 70.00 +/- 6.41 HU for attenuation of SAH, 8.39 +/- 1.25 HU for image noise, 28.86 +/- 8.43 for SNR, and 20.37 +/- 7.74 for CNR) (all P < 0.01). The segmental scorings of the nonlinear blending image (31.6% segments with a score of 5, 57.4% segments with a score of 4, 11% segments with a score of 3) ranged significantly higher than those of linear blending images (11.5% segments with a score of 5, 77.5% segments with a score of 4, 11% segments with a score of 3) (P < 0.01). The interobserver agreement was good (K = 0.762), and intraobserver agreement was excellent for both observers (K = 0.844 and 0.858, respectively). Conclusions: The nonlinear image blending technique improved vessel visualization of cerebral dual-energy CT angiography by optimizing contrast enhancement in spontaneous SAH patients.