title: Utilizing different methods for visualizing susceptibility from a single multi-gradient echo dataset.
abstract: OBJECTIVE
  Objects that cause a susceptibility gradient can generate regions of hypo-intensity in MRI. MR techniques developed for positive enhancement of such objects require sequence parameter optimization. Thus comparison of images acquired successively using different techniques is difficult since different parameter settings result in variations in signal and noise. A new method is presented that allows production of positive contrast images, a relaxation rate R*2-map and negative contrast images from a single dataset by post-processing.
  
  
  METHODS
  Positive contrast techniques considered include the "white marker" technique, inversion-recovery on-resonance (IRON) and susceptibility gradient mapping (SGM). The new method was tested in phantoms of iron-oxide agent gel solutions and prostate marker seeds. Images produced by post-processing were compared with those obtained directly. The post-processing technique was applied in vivo for the visualization of iron-oxide contrast agent uptake in a balloon-injured swine carotid model.
  
  
  RESULTS
  The images produced in the post-processing step allowed determination of optimal parameter settings for each technique. SGM was found to provide the greatest positive contrast, whilst the T*2-weighted images provide more sensitivity to regions that exhibited weaker susceptibility effects.
  
  
  CONCLUSIONS
  Combined T*2-weighted imaging and SGM using the same complex image data was found to provide complementary information and high sensitivity to detect distortion inducing agents.
authors: Division of Imaging Sciences, King's College London, St Thomas' Hospital, Westminster Bridge Road, London, SE1 7EH, UK. gopal.varma@kcl.ac.uk
authors: Gopal
authors: G
authors: Varma
authors: Steen Fjord
authors: SF
authors: Pedersen
authors: Matthias
authors: M
authors: Taupitz
authors: Rene Michael
authors: RM
authors: Botnar
authors: Hannes
authors: H
authors: Dahnke
authors: Stephen Frederick
authors: SF
authors: Keevil
authors: Tobias
authors: T
authors: Schaeffter
mesh_terms: D000818:Animals; D020212:Carotid Artery Injuries / Q000175:diagnosis / Q000473:pathology; D002404:Catheterization / Q000379:methods; D003287:Contrast Media / Q000737:chemistry; D004195:Disease Models, Animal; D017352:Echo-Planar Imaging / Q000379:methods*; D005290:Ferric Compounds / Q000737:chemistry; D005780:Gelatin / Q000737:chemistry; D007089:Image Enhancement / Q000379:methods*; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D013552:Swine
chemical_list: D003287:Contrast Media; D005290:Ferric Compounds; D012996:Solutions; C000499:ferric oxide; D005780:Gelatin