Quantitative assessment of changes in carotid plaques during cilostazol administration using three-dimensional ultrasonography and non-gated magnetic resonance plaque imaging.

INTRODUCTION: Cilostazol, an antiplatelet agent, is reported to induce the regression of atherosclerotic changes. However, its effects on carotid plaques are unknown. Hence, we quantitatively investigated the changes that occur within carotid plaques during cilostazol administration using three-dimensional (3D) ultrasonography (US) and non-gated magnetic resonance (MR) plaque imaging. METHODS: We prospectively examined 16 consecutive patients with carotid stenosis. 3D-US and T1-weighted MR plaque imaging were performed at baseline and 6 months after initiating cilostazol therapy (200 mg/day). We measured the volume and grayscale median (GSM) of the plaques from 3D-US data. We also calculated the contrast ratio (CR) of the carotid plaque against the adjacent muscle and areas of the intraplaque components: fibrous tissue, lipid, and hemorrhage components. RESULTS: The plaque volume on US decreased significantly (median at baseline and 6 months, 0.23 and 0.21 cm(3), respectively; p = 0.03). In the group exhibiting a plaque volume reduction of more than 10%, GSM on US increased significantly (24.8 and 71.5, respectively; p = 0.04) and CR on MRI decreased significantly (1.13 and 1.04, respectively; p = 0.02). In this group, in addition, the percent area of the fibrous component on MRI increased significantly (68.6% and 79.4%, respectively; p = 0.02), while those of the lipid and hemorrhagic components decreased (24.9% and 20.5%, respectively; p = 0.12) (1.0% and 0.0%, respectively; p = 0.04). There were no substantial changes in intraplaque characteristics in either US or MRI in the other group. CONCLUSIONS: 3D-US and MR plaque imaging can quantitatively detect changes in the size and composition of carotid plaques during cilostazol therapy.

Altered carotid plaque signal among different repetition times on T1-weighted magnetic resonance plaque imaging with self-navigated radial-scan technique.

INTRODUCTION: Magnetic resonance (MR) plaque imaging for carotid arteries is usually performed by using an electrocardiograph (ECG)-gating technique to eliminate pulsation-related artifacts, which can affect the plaque signals because of varied repetition time (TR) among patients. Hence, we investigated whether differences in TR causes signal alterations of the carotid plaque by using a non-gated plaque imaging technique. METHODS: We prospectively examined 19 patients with carotid stenosis by using a T1-weighted self-navigated radial-scan technique with TRs of 500, 700, and 900 ms. The signal intensity of the carotid plaque was measured, and the contrast ratio (CR) relative to the adjacent muscle was calculated. RESULTS: CRs of the carotid plaques were 1.39 +/- 0.39, 1.29 +/- 0.29, and 1.23 +/- 0.24 with TRs of 500, 700, and 900 ms, respectively, and were significantly different. Among the plaques, those with a hyperintensity signal (CR > 1.5) and moderate-intensity signal (CR 1.2-1.5) at 500 ms showed a TR-dependent signal decrease (hyperintensity plaques, 1.82 +/- 0.26; 1.61 +/- 0.19; and 1.48 +/- 0.17; moderate-intensity plaques, 1.33 +/- 0.08; 1.26 +/- 0.08; and 1.19 +/- 0.07), while those with an isointensity signal (CR < 1.2) remained unchanged regardless of TR (0.96 +/- 0.12, 0.96 +/- 0.11, and 0.97 +/- 0.13). CONCLUSION: The signal intensity of the carotid plaque on T1-weighted imaging significantly varies among different TRs and tends to decrease with longer TR. MR plaque imaging with short and constant TR settings that the ECG-gating method cannot realize would be preferable for evaluating plaque characteristics.