Manual versus Automated Carotid Artery Plaque Component Segmentation in High and Lower Quality 3.0 Tesla MRI Scans

<div><p>Purpose</p><p>To study the interscan reproducibility of manual versus automated segmentation of carotid artery plaque components, and the agreement between both methods, in high and lower quality MRI scans.</p><p>Methods</p><p>24 patients with 30–70% carotid artery stenosis were planned for 3T carotid MRI, followed by a rescan within 1 month. A multicontrast protocol (T1w,T2w, PDw and TOF sequences) was used. After co-registration and delineation of the lumen and outer wall, segmentation of plaque components (lipid-rich necrotic cores (LRNC) and calcifications) was performed both manually and automated. Scan quality was assessed using a visual quality scale.</p><p>Results</p><p>Agreement for the detection of LRNC (<i>Cohen’s</i> kappa (<i>k)</i> is 0.04) and calcification (<i>k</i> = 0.41) between both manual and automated segmentation methods was poor. In the high-quality scans (visual quality score ≥ 3), the agreement between manual and automated segmentation increased to <i>k</i> = <i>0</i>.55 and <i>k</i> = 0.58 for, respectively, the detection of LRNC and calcification larger than 1 mm². Both manual and automated analysis showed good interscan reproducibility for the quantification of LRNC (intraclass correlation coefficient (ICC) of 0.94 and 0.80 respectively) and calcified plaque area (ICC of 0.95 and 0.77, respectively).</p><p>Conclusion</p><p>Agreement between manual and automated segmentation of LRNC and calcifications was poor, despite a good interscan reproducibility of both methods. The agreement between both methods increased to moderate in high quality scans. These findings indicate that image quality is a critical determinant of the performance of both manual and automated segmentation of carotid artery plaque components.</p></div

Interscan reproducibility of quantification of plaque components using manual and automated segmentation.

<p>Interscan reproducibility of quantification of plaque components using manual and automated segmentation.</p

Representative images of manual and automated segmentation of LRNC and calcifications.

<p>Representative images of the manual and automated segmentation of a calcified plaque area and a lipid-rich necrotic core (LRNC) using a multicontrast MRI protocol of the carotid artery. Shown are all the individual MRI sequences (T1w,PDw,T2w,TOF), as well as the manual and automated analysis. Lumen contours were delineated in red for both methods, and outer wall contours were delineated in green for manual segmentation, and light blue for automated segmentation. Calcified plaque areas were coloured orange in manual segmentation, and delineated white in automated segmentation. LRNCs were delineated yellow in both manual and automated segmentation. In these examples, both methods agree on the identification of a large calcified plaque area (left example) and large LRNC (right example). Please also note the identification of three small LRNC areas using automated segmentation (*), which are not detected by manual segmentation.</p

Agreement between manual and automated detection of plaque components.

<p>Agreement between the detection of LRNC- and calcification- containing plaques by manual and automated analysis. Cohen’s kappa values for agreement between manual and automated analysis are shown for all plaque components in all scans; plaque components > 1 mm² in all scans; and plaque components > 1 mm² in high quality scans only.</p

Post-hoc manual analysis of patients with a mismatch in the detection of LRNC and calcifications by manual and automated analysis.

<p>Post-hoc manual analysis of patients with a mismatch in the detection of LRNC and calcifications by manual and automated analysis.</p