Apparent Diffusion Coefficient with Higher b-Value Correlates Better with Viable Cell Count Quantified from the Cavity of Brain Abscess

Abstract

BACKGROUND AND PURPOSE: DWI by using higher b-values provides tissue diffusivity with less T2 shinethrough effect. VCD in the abscess cavity correlates with ADC values. The purpose of this study was to investigate which b-valueϪderived ADC correlates better with VCD.

Efficient experimental designs for isotropic generalized diffusion tensor MRI (IGDTI)

“…We can also compute other useful rotation-invariant microstructural parameters that are related to these generalized mean diffusivities, such as the mean t-kurtosis (Eq. [9]):…”

“…It is derived from a polynomial expansion of the log signal attenuation (cumulant expansion) with respect to the b-matrix (15), not the q-vector, as in GDTI (10), hence the additional factors related to gradient pulse timings in Equation [9]. In the limit of an infinitely short gradient pulse duration, d, the two expansions are identical for fully symmetric diffusion.…”

“…To derive orientationally averaged DWIs and measure the mADCs at each b-value in the GDTI data sets, we averaged the log signal attenuations from DWIs acquired with multiple orientations densely and uniformly sampling the unit sphere. In addition, we measured the HOTs by fitting the densely sampled GDTI data sets to Equation [3] using the method described in Liu et al (10) and computed the HOT Traces and generalized mean diffusivities D ðnÞ up to order 6 using Equation [6] and, subsequently, the mean tkurtosis using Equation [9]. From the IGDTI data sets, we measured the orientation-averaged DWIs and mADCs at each diffusion sensitization using the linear combinations of log signal attenuations described in Table 2 for the corresponding b-value ranges and compared the results to those derived from the GDTI data.…”

“…The same analysis was applied to the IGDTI data sets acquired with rotated gradient sampling schemes, and the results were compared to those of the original sampling scheme (Table 1) to assess the rotation invariance of IGDTI. Finally, from the IGDTI-derived generalized mean diffusivities D ðnÞ of order 2 and 4, we computed the mean t-kurtosis using Equation [9], and compared the results to those obtained from the GDTI analysis.…”

“…Clinical studies have shown that the mADC measured at higher b-values improves conspicuity and discrimination in prostate tumors (6), breast lesions (7), and cerebral gliomas (8) and provides a better marker for cell viability (9).…”