Flexible methods for segmentation evaluation: results from CT-based luggage screening.
BACKGROUND
Imaging systems used in aviation security include segmentation algorithms in an automatic threat recognition pipeline. The segmentation algorithms evolve in response to emerging threats and changing performance requirements. Analysis of segmentation algorithms' behavior, including the nature of errors and feature recovery, facilitates their development. However, evaluation methods from the literature provide limited characterization of the segmentation algorithms.


OBJECTIVE
To develop segmentation evaluation methods that measure systematic errors such as oversegmentation and undersegmentation, outliers, and overall errors. The methods must measure feature recovery and allow us to prioritize segments.


METHODS
We developed two complementary evaluation methods using statistical techniques and information theory. We also created a semi-automatic method to define ground truth from 3D images. We applied our methods to evaluate five segmentation algorithms developed for CT luggage screening. We validated our methods with synthetic problems and an observer evaluation.


RESULTS
Both methods selected the same best segmentation algorithm. Human evaluation confirmed the findings. The measurement of systematic errors and prioritization helped in understanding the behavior of each segmentation algorithm.


CONCLUSIONS
Our evaluation methods allow us to measure and explain the accuracy of segmentation algorithms.
University of California, San Diego, CA, USA.
Seemeen
S
Karimi
University of California, San Diego, CA, USA.
Xiaoqian
X
Jiang
University of California, San Diego, CA, USA.
Pamela
P
Cosman
Lawrence Livermore National Laboratories, Livermore, CA, USA.
Harry
H
Martz
D059028:Airports; D000465:Algorithms; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012637:Security Measures; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014195:Travel; D014481:United States
Segmentation evaluation; computed tomography; feature recovery; luggage screening