title: Comparison between two-point and four-point methods for quantification of apparent diffusion coefficient of normal liver parenchyma and focal lesions. Value of normalization with spleen.
abstract: OBJECTIVE
  To compare two quantification techniques of apparent diffusion coefficient (ADC), both in normal liver parenchyma and focal lesions, and to investigate any potential value of normalization.
  
  
  METHODS
  Fifty-six consecutive patients underwent MRI examination of the liver, including a single shot spin-echo echo planar imaging diffusion sequence with four b-values (0, 50, 500 and 1000s/mm(2)). ADC maps were reconstructed based on a two-point method (b-values: 500 and 1000s/mm(2)) and a four-point method (b-values: 0, 50, 500 and 1000s/mm(2)). Comparison of absolute ADC measurements of the liver, benign and malignant focal lesions was performed between the two- and four-point techniques. The same analysis was done on normalized ADC values (absolute ADC values divided by spleen ADC values).
  
  
  RESULTS
  The difference between mean two-point and four-point ADC values of normal liver (absolute: 1.237x10(-3), 1.615x10(-3)mm(2)/s, normalized: 1.40, 1.52, respectively) was statistically significant (p<0.0001 and p=0.0061). Significantly higher absolute ADC values of benign and malignant lesions were recorded with the four-point method (2.860x10(-3) and 1.307x10(-3)mm(2)/s) over the two-point method (2.243x10(-3), and 1.011x10(-3)mm(2)/s) (p<0.0001 in both) while the same differences in normalized values were proven statistically non-significant for benign lesions (p=0.788) and statistically significant for malignant lesions (p=0.015). Both differences in absolute and normalized ADC values of benign versus malignant lesions based on two- and four-point methods were found to be significant (p<0.0001).
  
  
  CONCLUSIONS
  ADC quantification of the liver may be performed with a two-point method (b-values of 500 and 1000s/mm(2)), while normalization of ADC measurements with the spleen is not further improving lesion characterization.
authors.affiliation: Dept of Radiology, University Hospital of Heraklion, Medical School, University of Crete, Greece.
authors.forename: Nickolas
authors.initials: N
authors.lastname: Papanikolaou
authors.forename: Sofia
authors.initials: S
authors.lastname: Gourtsoyianni
authors.forename: Spyros
authors.initials: S
authors.lastname: Yarmenitis
authors.forename: Thomas
authors.initials: T
authors.lastname: Maris
authors.forename: Nicholas
authors.initials: N
authors.lastname: Gourtsoyiannis
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D005260:Female; D006115:Greece; D006801:Humans; D007089:Image Enhancement / Q000379:methods* / Q000592:standards; D007090:Image Interpretation, Computer-Assisted / Q000379:methods* / Q000592:standards; D016247:Information Storage and Retrieval / Q000379:methods*; D008113:Liver Neoplasms / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013154:Spleen / Q000473:pathology*; D055815:Young Adult