title: Evaluation of image quality of lumbar spine images: a comparison between FFE and VGA.
abstract: OBJECTIVE
  The aim of the present study is to compare two different methods for evaluation of the quality of clinical X-ray images.
  
  
  METHODS
  Based on fifteen lumbar spine radiographs, two new sets of images were created. A hybrid image set was created by adding two distributions of artificial lesions to each original image. The image quality parameters spatial resolution and noise were manipulated and a total of 210 hybrid images were created. A set of 105 disease-free images was created by applying the same combinations of spatial resolution and noise to the original images. The hybrid images were evaluated with the free-response forced error experiment (FFE) and the normal images with visual grading analysis (VGA) by nine experienced radiologists.
  
  
  RESULTS
  In the VGA study, images with low noise were preferred over images with higher noise levels. The alteration of the MTF had a limited influence on the VGA score. For the FFE study, the visibility of the lesions was independent of the sharpness and the noise level. No correlation was found between the two image quality measures.
  
  
  CONCLUSIONS
  FFE is a precise method for evaluation of image quality, but the results are only valid for the type of lesion used in the study, whereas VGA is a more general method for clinical image quality assessment. The results of the FFE study indicate that there might be a potential to lower the dose levels in lumbar spine radiography without losing important diagnostic information.
authors.affiliation: Department of Radiation Physics, Malmö University Hospital, SE-205 02 Malmö, Sweden. anders.tingberg@rfa.mas.lu.se
authors.forename: Anders
authors.initials: A
authors.lastname: Tingberg
authors.forename: Magnus
authors.initials: M
authors.lastname: Båth
authors.forename: Markus
authors.initials: M
authors.lastname: Håkansson
authors.forename: Joakim
authors.initials: J
authors.lastname: Medin
authors.forename: Jack
authors.initials: J
authors.lastname: Besjakov
authors.forename: Michael
authors.initials: M
authors.lastname: Sandborg
authors.forename: Gudrun
authors.initials: G
authors.lastname: Alm-Carlsson
authors.forename: Sören
authors.initials: S
authors.lastname: Mattsson
authors.forename: Lars Gunnar
authors.initials: LG
authors.lastname: Månsson
mesh_terms: D002138:Calibration; D005069:Evaluation Studies as Topic; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008161:Lumbosacral Region; D008962:Models, Theoretical; D012372:ROC Curve; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011859:Radiography; D013679:Technology, Radiologic; D013997:Time Factors; D014965:X-Rays