title: Spatial and spatio-temporal feature extraction from 4D echocardiography images.
abstract: BACKGROUND
  Ultrasound images are difficult to segment because of their noisy and low contrast nature which makes it challenging to extract the important features. Typical intensity-gradient based approaches are not suitable for these low contrast images while it has been shown that the local phase based technique provides better results than intensity based methods for ultrasound images. The spatial feature extraction methods ignore the continuity in the heart cycle and may also capture spurious features. It is believed that the spurious features (noise) that are not consistent along the frames can be excluded by considering the temporal information.
  
  
  METHODS
  In this paper, we present a local phase based 4D (3D+time) feature asymmetry (FA) measure using the monogenic signal. We have investigated the spatio-temporal feature extraction to explore the effect of adding time information in the feature extraction process.
  
  
  RESULTS
  To evaluate the impact of time dimension, the results of 4D based feature extraction are compared with the results of 3D based feature extraction which shows the favorable 4D feature extraction results when temporal resolution is good. The paper compares the band-pass filters (difference of Gaussian, Cauchy and Gaussian derivative) in terms of their feature extraction performance. Moreover, the feature extraction is further evaluated quantitatively by left ventricle segmentation using the extracted features.
  
  
  CONCLUSIONS
  The results demonstrate that the spatio-temporal feature extraction is promising in frames with good temporal resolution.
authors.affiliation: School of Electrical Engineering and Computer Science (SEECS), National University of Sciences & Technology (NUST), Islamabad, Pakistan. Electronic address: 12mscsrawan@seecs.edu.pk.
authors.forename: Ruqayya
authors.initials: R
authors.lastname: Awan
authors.affiliation: School of Electrical Engineering and Computer Science (SEECS), National University of Sciences & Technology (NUST), Islamabad, Pakistan; College of Computer Science & Information Technology (CCSIT), King Faisal University (KFU), Al-Hofuf, Saudi Arabia. Electronic address: kashif.rajpoot@oxfordalumni.org.
authors.forename: Kashif
authors.initials: K
authors.lastname: Rajpoot
mesh_terms: D000465:Algorithms; D019561:Echocardiography, Four-Dimensional / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*
keywords: 4-D echocardiography; Band-pass filter; Feature asymmetry; Feature extraction; Local phase