title: Characterization and correction of beam-hardening artifacts during dynamic volume CT assessment of myocardial perfusion.
abstract: OBJECTIVE
  To fully characterize beam-hardening effects caused by iodinated contrast medium in the left ventricular (LV) cavity and aorta in the assessment of myocardial perfusion at computed tomography (CT) and to validate a beam-hardening artifact correction algorithm that considers fluid-filled vessels and chambers important sources of beam hardening.
  
  
  METHODS
  The Johns Hopkins University animal care and use committee approved all procedures. An anatomically correct LV and myocardial phantom to characterize beam-hardening artifacts was designed. Following validation in the phantom, the beam-hardening correction (BHC) algorithm was applied to 256-detector row dynamic volume CT images in a canine ischemia model (n = 5) during adenosine stress, and the effect of beam hardening was determined by comparing regional dynamic volume CT perfusion metrics (myocardial upslope normalized by maximum LV blood pool attenuation) with microsphere-derived myocardial blood flow (MBF). A paired Student t test was used to compare continuous variables from the same subject but under different conditions, while linear regression analysis was performed to estimate the slope and statistical significance of the relationship between CT-derived perfusion metrics and microsphere-derived MBF.
  
  
  RESULTS
  Beam-hardening artifacts were successfully reproduced in phantom studies and were eliminated with the BHC algorithm. The correlation coefficient of CT-derived perfusion metrics and microsphere-derived MBF improved from 0.60 to 0.74 (P > .05) following correction in the animal model.
  
  
  CONCLUSIONS
  Beam-hardening artifacts confound dynamic volume CT assessment of myocardial perfusion. Application of the BHC algorithm is helpful for improving accuracy of myocardial perfusion at dynamic volume CT.
authors.affiliation: Department of Medicine, Division of Cardiology, Johns Hopkins University School of Medicine, 1042 Ross Building, Baltimore, MD 21205, USA.
authors.forename: Kakuya
authors.initials: K
authors.lastname: Kitagawa
authors.forename: Richard T
authors.initials: RT
authors.lastname: George
authors.forename: Armin
authors.initials: A
authors.lastname: Arbab-Zadeh
authors.forename: João A C
authors.initials: JA
authors.lastname: Lima
authors.forename: Albert C
authors.initials: AC
authors.lastname: Lardo
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000465:Algorithms; D000818:Animals; D016477:Artifacts; D003287:Contrast Media / Q000008:administration & dosage; D017023:Coronary Angiography / Q000379:methods*; D003326:Coronary Circulation; D004285:Dogs; D004562:Electrocardiography; D007479:Iopamidol / Q000008:administration & dosage; D016014:Linear Models; D008863:Microspheres; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012984:Software; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007479:Iopamidol; D000241:Adenosine