Dynamic cardiac phantom. (a) A view of the entire apparatus immediately surrounding the elastic cylinder, which corresponds to the left ventricle of the heart. The cardiac and respiratory motions of the cylinder are driven by two pistons, which are connected to a pneumatic system (not shown). (b) A close-up view of the elastic cylinder with embedded tubes representing coronary arteries.
Workstation interface used by observers to assign assessability indices.
Flowchart detailing computerized method for acquiring ANN-predicted assessability indices.
Phase-correlated images, segmentations, and feature values of two different plaques at 70 bpm from a single iteration of the bootstrap resampling scheme. The features are 3D velocity (VEL), 3D acceleration (ACC), edge-based volume (VOL-E), threshold-based volume (VOL-T), sphericity (SPHER), and standard deviation of intensity (STD INT).
Flowchart detailing the evaluation of ANN-predicted and observer-assigned assessability indices. Note that ROC analysis was performed on each set of assessability indices, separately. CCC represents the repeated measures concordance correlation coefficient. AUC represents the area under the curve.
Histogram of observer-assigned assessability indices. The lighter and darker bars represent assessability indices assigned by OBS1 and OBS2, respectively.
Phase-correlated images and assessability indices of the same two plaques shown in Fig. 4. Observer-assigned assessability indices (OBS1 and OBS2), corresponding ANN-predicted assessability indices (ANN1 and ANN2), and absolute calcium score (CS) errors are listed within each panel. Assessability indices indicative of better image quality (1 and 2) and lower absolute CS errors (less than the cut-off value of 8.4) are shaded.
Performance characteristics of the observer-assigned and ANN-predicted assessability indices for the same iteration of the bootstrap resampling scheme corresponding to the plaques in Fig. 7. (a) Bubble plot of OBS1-ANN1 assessability indices. Circle size correlates with the number of images associated with a given pairing of assessability indices. The CCC was 0.52. (b) Bubble plot of OBS2-ANN2 assessability indices. The CCC was 0.61. (c) ROC curves of assessability indices provided by OBS1 (light dashed), ANN1 (light solid), OBS2 (dark dashed), and ANN2 (dark solid) for the task of identifying diagnostic quality images. Corresponding AUC values were 0.81, 0.92, 0.87, and 0.88 for this iteration.
Assessability indices and representative images .
Typical intensity ranges for the physical dynamic cardiac phantom and the human heart. Intensity ranges are provided for the heart muscle (myocardium) and calcified plaques. The lower limits of the intensity ranges for the plaques are defined by the intensity thresholds used to calculate the calcium score.
Performances of observer-assigned and ANN-predicted indices in identifying plaque images with diagnostic calcium scores. Performances for subgroups based on heart rate, cardiac phase, and plaque location are also included. Mean number of diagnostic images represents the mean number of images with diagnostic calcium scores selected over all bootstrap iterations.
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