title: Importance of Fractional b Value for Calculating Apparent Diffusion Coefficient in DWI.
abstract: OBJECTIVE
  The purpose of this study is to examine how the fractional b value affects the calculation of apparent diffusion coefficient (ADC) using DWI. The fractional b value is the point of intersection between the fast and slow components of biexponential decay in DWI.
  
  
  METHODS
  Human brains were imaged using multiple b values on echo-planar DWI. The ADCs of white matter, gray matter, and thalamus were calculated using the combination of b values by two-point and multipoint methods, and the characteristics of each ADC value were compared.
  
  
  RESULTS
  When the two selected points for calculation were smaller than the fractional b value (b = 1700 s/mm2), the ADC value was 0.0007-0.0008 mm2/s, but when the two points used for calculation were greater than the fractional b value, the ADC value was 0.0003-0.0004 mm2/s. When a range of b values was included in the fast and slow components by use of the multipoint method, the ADC value showed a statistically significant increase as the number of multiple b values increased.
  
  
  CONCLUSIONS
  The ADC value fluctuated when the b values used for calculation were higher than the fractional b value. Therefore, it is important to determine the fractional b value of the target tissue.
authors: 1 Graduate School of Radiological Technology, Gunma Prefectural College of Health Sciences, 323-1, Kamioki-machi, Maebashi, Gunma 371-0052, Japan.
authors: Akio
authors: A
authors: Ogura
authors: 1 Graduate School of Radiological Technology, Gunma Prefectural College of Health Sciences, 323-1, Kamioki-machi, Maebashi, Gunma 371-0052, Japan.|2 Department of Radiology, Jichi Medical University Hospital, Tochigi, Japan.
authors: Isamu
authors: I
authors: Hatano
authors: 1 Graduate School of Radiological Technology, Gunma Prefectural College of Health Sciences, 323-1, Kamioki-machi, Maebashi, Gunma 371-0052, Japan.|3 Department of Radiology, Gunma Saiseikai Maebashi Hospital, Gunma, Japan.
authors: Kohki
authors: K
authors: Osakabe
authors: 1 Graduate School of Radiological Technology, Gunma Prefectural College of Health Sciences, 323-1, Kamioki-machi, Maebashi, Gunma 371-0052, Japan.|4 Department of Radiology, Tokyo Metropolitan Tama Medical Center, Tokyo, Japan.
authors: Natsumi
authors: N
authors: Yamaguchi
authors: 1 Graduate School of Radiological Technology, Gunma Prefectural College of Health Sciences, 323-1, Kamioki-machi, Maebashi, Gunma 371-0052, Japan.|5 Department of Radiology, National Hospital Organization Matsumoto Medical Center, Nagano, Japan.
authors: Daisuke
authors: D
authors: Koyama
authors: 1 Graduate School of Radiological Technology, Gunma Prefectural College of Health Sciences, 323-1, Kamioki-machi, Maebashi, Gunma 371-0052, Japan.
authors: Haruyuki
authors: H
authors: Watanabe
mesh_terms: D000328:Adult; D000465:Algorithms; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D066128:Gray Matter / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013788:Thalamus / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D066127:White Matter / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D055815:Young Adult
keywords: DWI; apparent diffusion coefficient; biexponential; fractional b value; multipoint method