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2 25 | Validation CHS and PiU were scanned for the inter-observer variability; and 15 healthy subjects were scanned for the inter-system variability. Baseline values are presented in the footnote of the tables. Intra-observer variability The LOA for C-IMT of Observer X were 0.005±0.035 mm (p=0.60), and the ICC was 0.98 (95% CI: 0.94-0.99). Similarly, the LOA for C-IMT of Observer Y were 0.015±0.043 mm (p=0.21), and the ICC was 0.96 (95% CI: 0.89-0.99). Intra-observer variability of plaque presence was not determined, since measurements were made in quick succession and it is unlikely to forget the presence of a plaque in the first measurement. Inter-observer variability Results of C-IMT measurements at all four scan positions, the mean C-IMT per patient, and plaque scans are depicted in table 1. The Bland Altman plot is shown in figure 3a. The LOA for C-IMT was not significantly different between the observers. The SD of the LOA was approximately 50% lower for the mean C-IMT of the four scans per subject. Similarly, the ICC improved by taking the mean C-IMT per patient. Plaque presence was similar between observers as indicated by the high intraclass kappa. In linear regression analysis, the C-IMT difference between observers did not increase with C-IMT value, indicating that the inter-observer variability was independent of C-IMT values. Table 2.2 | Variability between the Panasonic CHS and the Philips PiU of the four scan positions in the healthy volunteers. 2* CHS PiU Inter-system Acquisition time (minutes) 2±1 4±1 (p<0.001) C-IMT: Mean C-IMT (±SD) 0.516±0.077 mm 0.531±0.087 mm Difference between both C-IMT measurements (LOA) (±SD) 0.0154 ±0.0522 mm (p=0.03) Intra-class coefficient (95%CI) 0.89 (0.81-0.93) Correlation of the C-IMT differ- ence and the mean C-IMT R= -0.38; (p= 0.16) Plaques: Plaques found 1 1 1 2* Subjects were 38±14 years old, BMI was 23.2±2.3, and 47% were male.