Importance of Fractional b Value for Calculating Apparent Diffusion Coefficient in DWI

• Published in: American journal of roentgenology (1976) Vol. 207; no. 6; pp. 1239 - 1243
• Main Authors: Ogura, Akio, Hatano, Isamu, Osakabe, Kohki, Yamaguchi, Natsumi, Koyama, Daisuke, Watanabe, Haruyuki
• Format: Journal Article
• Language: English
• Published: United States 01.12.2016
• Subjects: Adult; Algorithms; Diffusion Magnetic Resonance Imaging - methods; Female; Gray Matter - anatomy & histology; Gray Matter - diagnostic imaging; Humans; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Male; Middle Aged; Reference Values; Reproducibility of Results; Sensitivity and Specificity; Thalamus - anatomy & histology; Thalamus - diagnostic imaging; White Matter - anatomy & histology; White Matter - diagnostic imaging; Young Adult; multipoint method; apparent diffusion coefficient; biexponential; DWI; fractional b value
• ISSN: 0361-803X; 1546-3141; 1546-3141
• DOI: 10.2214/AJR.15.15945

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. 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. When the two selected points for calculation were smaller than the fractional b value (b = 1700 s/mm ), the ADC value was 0.0007-0.0008 mm /s, but when the two points used for calculation were greater than the fractional b value, the ADC value was 0.0003-0.0004 mm /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. 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.