Automatic Contrast Phase Estimation in CT Volumes

Abstract

We propose an automatic algorithm for phase labeling that relies on the intensity changes in anatomical regions due to the contrast agent propagation. The regions (specified by aorta, vena cava, liver, and kidneys) are first detected by a robust learning-based discriminative algorithm. The intensities inside each region are then used in multi-class LogitBoost classifiers to independently estimate the contrast phase. Each classifier forms a node in a decision tree which is used to obtain the final phase label. Combining independent classification from multiple regions in a tree has the advantage when one of the region detectors fail or when the phase training example database is imbalanced. We show on a dataset of 1016 volumes that the system correctly classifies native phase in 96.2% of the cases, hepatic dominant phase (92.2%), hepatic venous phase (96.7%), and equilibrium phase (86.4%) in 7 seconds on average.

Results

Figure 1: Detected anatomical structures (rows) used in contrast phase estimation (cols 1-4). Anatomy enhancement specific to each phase can be clearly seen. Incorrectly classified HADP as a HVP phase for a scan in phase transition (5th col.). The lower contrast of aorta and the beginning of liver parenchyma, renal cortex and renal medulla enhancement are characteristic for a HVP phase (compare to 2nd and 3rd col.).

Publications and Further Reading