title: In vivo contrast free chronic myocardial infarction characterization using diffusion-weighted cardiovascular magnetic resonance.
abstract: BACKGROUND
  Despite the established role of late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) in characterizing chronic myocardial infarction (MI), a significant portion of chronic MI patients are contraindicative for the use of contrast agents. One promising alternative contrast free technique is diffusion weighted CMR (dwCMR), which has been shown ex vivo to be sensitive to myocardial fibrosis. We used a recently developed in vivo dwCMR in chronic MI pigs to compare apparent diffusion coefficient (ADC) maps with LGE imaging for infarct characterization.
  
  
  METHODS
  In eleven mini pigs, chronic MI was induced by complete occlusion of the left anterior descending artery for 150 minutes. LGE, cine, and dwCMR imaging was performed 8 weeks post MI. ADC maps were derived from three orthogonal diffusion directions (b = 400 s/mm2) and one non-diffusion weighted image. Two semi-automatic infarct classification methods, threshold and full width half max (FWHM), were performed in both LGE and ADC maps. Regional wall motion (RWM) analysis was performed and compared to ADC maps to determine if any observed ADC change was significantly influenced by bulk motion.
  
  
  RESULTS
  ADC of chronic MI territories was significantly increased (threshold: 2.4 ± 0.3 μm2/ms, FWHM: 2.4 ± 0.2 μm2/ms) compared to remote myocardium (1.4 ± 0.3 μm2/ms). RWM was significantly reduced (threshold: 1.0 ± 0.4 mm, FWHM: 0.9 ± 0.4 mm) in infarcted regions delineated by ADC compared to remote myocardium (8.3 ± 0.1 mm). ADC-derived infarct volume and location had excellent agreement with LGE. Both LGE and ADC were in complete agreement when identifying transmural infarcts. Additionally, ADC was able to detect LGE-delineated infarcted segments with high sensitivity, specificity, PPV, and NPV. (threshold: 0.88, 0.93, 0.87, and 0.94, FWHM: 0.98, 0.97, 0.93, and 0.99, respectively).
  
  
  CONCLUSIONS
  In vivo diffusion weighted CMR has potential as a contrast free alternative for LGE in characterizing chronic MI.
authors.forename: Christopher
authors.initials: C
authors.lastname: Nguyen
authors.forename: Zhaoyang
authors.initials: Z
authors.lastname: Fan
authors.forename: Yibin
authors.initials: Y
authors.lastname: Xie
authors.forename: James
authors.initials: J
authors.lastname: Dawkins
authors.forename: Eleni
authors.initials: E
authors.lastname: Tseliou
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Bi
authors.forename: Behzad
authors.initials: B
authors.lastname: Sharif
authors.forename: Rohan
authors.initials: R
authors.lastname: Dharmakumar
authors.forename: Eduardo
authors.initials: E
authors.lastname: Marbán
authors.forename: Debiao
authors.initials: D
authors.lastname: Li
mesh_terms: D000465:Algorithms; D000818:Animals; D057205:Automation, Laboratory; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging; D004195:Disease Models, Animal; D007090:Image Interpretation, Computer-Assisted; D019028:Magnetic Resonance Imaging, Cine; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000473:pathology*; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013552:Swine; D013556:Swine, Miniature; D013997:Time Factors; D016277:Ventricular Function, Left
chemical_list: D003287:Contrast Media