Carotid artery dissection on non-contrast CT: does color improve the diagnostic confidence?

PURPOSE: The purpose of this work was to evaluate if the use of color maps, instead of conventional grayscale images, would improve the observer's diagnostic confidence in the non-contrast CT evaluation of internal carotid artery dissection (ICAD). MATERIALS AND METHODS: One hundred patients (61 men, 39 women; mean age, 51 years; range, 25-78 years), 40 with and 60 without ICAD, underwent non-contrast CT and were included in this the retrospective study. In this study, three groups of patients were considered: patients with MR confirmation of ICAD, n=40; patients with MR confirmation of ICAD absence, n=20; patients who underwent CT of the carotid arteries because of atherosclerotic disease, n=40. Four blinded observers with different levels of expertise (expert, intermediate A, intermediate B and trainee) analyzed the non-contrast CT datasets using a cross model (one case grayscale and the following case using the color scale). The presence of ICAD was scored on a 5-point scale in order to assess the observer's diagnostic confidence. After 3 months the four observers evaluated the same datasets by using the same cross-model for the alternate readings (one case color scale and the following case using the grayscale). Statistical analysis included receiver operating characteristics (ROC) curve analysis, the Cohen weighted test and sensitivity, specificity, PPV, NPV, accuracy, LR+ and LR-. RESULTS: The ROC curve analysis showed that, for all observers, the use of color scale resulted in an improved diagnostic confidence with AUC values increasing from 0.896 to 0.936, 0.823 to 0.849, 0.84 to 0.909 and 0.749 to 0.861 for expert, intermediate A, intermediate B and trainee observers, respectively. The increase in diagnostic confidence (between the AUC areas) was statistically significant (p=0.036) for the trainee. Accuracy as well as sensitivity, specificity, PPV, NPV, LR+ and LR- were improved using the color scale. CONCLUSION: Our study suggests that the use of a color scale instead the conventional grayscale improves the diagnostic confidence, accuracy and inter-observer agreement of the readers, in particular of junior ones, in the diagnosis of ICAD on non-contrast CT.

Association between carotid artery plaque volume, composition, and ulceration: a retrospective assessment with MDCT.

OBJECTIVE: The purpose of this study was to evaluate the relationship between MDCT angiography-assessed carotid artery plaque volume and composition and the presence of ulceration. MATERIALS AND METHODS: Seventy consecutive patients (46 men and 24 women; mean age, 63 years; age range, 42-81 years) were studied using MDCT and were retrospectively analyzed. Component types of the carotid plaque were defined according to attenuation value ranges (lipid, < 60 HU; fibrous tissue, 60-130 HU; and calcification, > 130 HU). The plaque volumes of each component were calculated. Statistical analysis was performed using the receiver operating characteristic (ROC) statistic and Wilcoxon signed rank test to evaluate the association between the presence of ulceration and specific plaque components and their volume. RESULTS: Eighteen carotid arteries were excluded, and 16 ulcerated plaques were detected in the remaining 122 carotid arteries. Wilcoxon and ROC curve analysis showed a statistically significant association between increased relative lipid volume and ulceration (p = 0.0001; area under the ROC curve, 0.916). The total volume of the plaque did not show an association with the presence of ulceration (p = 0.0526). CONCLUSION: The results of our retrospective study suggest that there is no correlation between total carotid atherosclerotic plaque volume and ulcerations, whereas plaque relative lipid volume (using attenuation of < 60 HU) is associated with the presence of ulceration. This finding could indicate vulnerable plaques and increased risk for cerebrovascular events.

Analysis of carotid artery plaque and wall boundaries on CT images by using a semi-automatic method based on level set model.

INTRODUCTION: The purpose of this study was to evaluate the potentialities of a semi-automated technique in the detection and measurement of the carotid artery plaque. METHODS: Twenty-two consecutive patients (18 males, 4 females; mean age 62 years) examined with MDCTA from January 2011 to March 2011 were included in this retrospective study. Carotid arteries are examined with a 16-multi-detector-row CT system, and for each patient, the most diseased carotid was selected. In the first phase, the carotid plaque was identified and one experienced radiologist manually traced the inner and outer boundaries by using polyline and radial distance method (PDM and RDM, respectively). In the second phase, the carotid inner and outer boundaries were traced with an automated algorithm: level-set-method (LSM). Data were compared by using Pearson rho correlation, Bland-Altman, and regression. RESULTS: A total of 715 slices were analyzed. The mean thickness of the plaque using the reference PDM was 1.86 mm whereas using the LSM-PDM was 1.96 mm; using the reference RDM was 2.06 mm whereas using the LSM-RDM was 2.03 mm. The correlation values between the references, the LSM, the PDM and the RDM were 0.8428, 0.9921, 0.745 and 0.6425. Bland-Altman demonstrated a very good agreement in particular with the RDM method. CONCLUSION: Results of our study indicate that LSM method can automatically measure the thickness of the plaque and that the best results are obtained with the RDM. Our results suggest that advanced computer-based algorithms can identify and trace the plaque boundaries like an experienced human reader.