title: X-ray beam equalization: feasibility and performance of an automated prototype system in a phantom and swine.
abstract: OBJECTIVE
  To investigate the feasibility of an automated implementation of a beam equalization technique and to evaluate the experimental performance of the prototype system.
  
  
  METHODS
  X-ray beam equalization involved the process of low-dose image acquisition, attenuator thickness calculation, mask generation, mask positioning, equalized image acquisition, and mask reshaping. The entire equalization process was performed in approximately 7 seconds. The equalized images were assessed both qualitatively and quantitatively by using a humanoid phantom and a swine animal model. The general image quality was assessed for the ability to visualize arterial branches and other anatomic structures. The level of equalization was quantitatively assessed by segmenting the images into an 8 x 8 matrix of square regions.
  
  
  RESULTS
  The ratio of the root-mean-squared variance for the equalized and unequalized images from humanoid phantom and swine animal studies was 0.49 and 0.59, respectively. Furthermore, qualitative assessment of the images showed substantial improvement in image quality and visualization of arterial branches after beam equalization in phantom and animal studies.
  
  
  CONCLUSIONS
  Automated area beam equalization is feasible and improves image quality in previously underpenetrated regions of the image.
authors.affiliation: Department of Radiological Sciences, Medical Sciences I, B-140, University of California, Irvine, CA 92697, USA. symolloi@uci.edu
authors.forename: S
authors.initials: S
authors.lastname: Molloi
authors.forename: A
authors.initials: A
authors.lastname: Van Drie
authors.forename: F
authors.initials: F
authors.lastname: Wang
mesh_terms: D000818:Animals; D017023:Coronary Angiography; D005240:Feasibility Studies; D006801:Humans; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement / Q000379:methods*; D013902:Radiography, Thoracic; D013552:Swine