Effects of diffusional kurtosis imaging parameters on diffusion quantification

Issei Fukunaga,Atsushi Senoo,Keigo Shimoji,Masatsugu Kosuge,Haruyoshi Hoshito,Shigeki Aoki,Atsushi Nakanishi,Masaaki Hori,Shuji Sato,Nozomi Hamasaki,Fumitaka Kumagai,Yuriko Suzuki,Yoshitaka Masutani,Koji Kamagata

doi:10.1007/s12194-013-0206-5

Abstract

Diffusional kurtosis imaging (DKI) is a new technique based on non-Gaussian water diffusion analysis. However, the original DKI protocol (six b values and 30 motion-probing gradient (MPG) directions) requires more than 10 min of scanning time, which is too long for daily clinical use. We aimed to find suitable b value, MPG direction, and diffusion time settings for faster DKI. Four normal healthy subjects participated in the study. All DKI data sets were acquired on a clinical 3T-MRI scanner (Philips Medical Systems) with use of three protocols of 0–7500 s/mm2 b values, 6–32 MPG directions, and 23–80 ms diffusion time. There was a remarkable difference in the standard deviation (SD) of the mean DK values in the number of MPG directions. The mean DK values were significantly higher in the posterior limb of the internal capsule (p = 0.003, r = 0.924) and thalamus (p = 0.005, r = 0.903), whereas the mean DK values of the cerebrospinal fluid (CSF) (p = 0.001, r = −0.976) were significantly lower when we used a longer diffusion time. Our results indicate that the SD of the mean DK values was higher in 15 MPG directions than in 20 MPG directions and more. Because the mean DK values of the CSF were significantly lower when we used longer diffusion times, we expect longer diffusion times to be useful for DKI. We propose the following imaging parameters for clinical use: 0, 1000, and 2000 s/mm2 b values; 20 MPG directions; Δ/δ 45.3/13.3 ms.

Highlights

In the technique known as diffusion-weighted imaging (DWI), the diffusion of water through biological tissue provides image contrast that depends on the Brownian motion of water molecules
The fractional anisotropy (FA), apparent diffusion coefficient (ADC), and mean DK values were lower in the white matter (WM) and gray matter (GM) with higher b values; this tendency was seen in the combination in which b values were above 6000 s/mm2 (Protocols 4 and 5) in the ADC (Table 1; Fig. 2)
Mulkern et al [19] reported that the water signal decay of the human brain departs from the mono exponential behavior commonly assumed when ADC maps are generated in clinical practice, once the b-factor range is extended above 6000 s/mm2

Summary

Introduction

In the technique known as diffusion-weighted imaging (DWI), the diffusion of water through biological tissue provides image contrast that depends on the Brownian motion of water molecules. This technique was introduced into clinical practice in the 1990s [1,2,3]. To date, few reports have been conducted on the imaging parameters of DKI [12, 13] compared with those of diffusion tensor imaging and DWI [14,15,16]

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