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

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-value−derived ADC correlates better with VCD.

MATERIALS AND METHODS: Thirty patients with brain abscess underwent conventional MR imaging and DWI with b = 1000, 2000, and 3000 s/mm² on a 3T MR imaging scanner. ADC values were quantified by placing regions of interest inside the abscess cavity in all sections where the lesion was apparent on coregistered ADC maps derived from different b-values. VCD was measured on pus aspirated.

RESULTS: An increase in b-value was associated with a decrease in ADC values in normal parenchyma as well as in the abscess cavity. The most significant negative correlation of VCD was observed with b = 3000 s/mm² (r = −0.98, P = .01).

CONCLUSIONS: VCD in the abscess cavity can be best assessed at b = 3000 s/mm² secondary to the reduction in the T2 shinethrough effect. DWI with b = 3000 s/mm² is of promising value in the assessment of the therapeutic response of brain abscess.