Hidden Infarcts Detected by a High b-Value Diffusion-Weighted Imaging: A Parameter-Optimized Study

Abstract

Objective: Small infarcts are easily missed on conventional sequences or a standard b-value diffusion-weighted imaging (DWI). This study aims to investigate the signal characteristics of DWI with different b-values and matrixes in acute cerebral infarction, and evaluate the feasibility of high b-values used in DWI. Methods: Twenty-nine cases of clinically diagnosed acute cerebral infarction were included prospectively in this study. The patients underwent MRI examinations, including routine T1WI, T2WI, T2 Flair, and different b-value DWIs (b = 1000, 1500, and 2000 s/mm2 with matrix 160 × 160. In addition, b = 1000 DWI was divided into two groups with different matrixes of 128 × 128 and 160 × 160. The differences of the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), contrast ratio (CR), and apparent diffusion coefficient (ADC) values between the different b-values and matrixes DWI were compared. Results: Visually, b =1500 and b = 2000 DWI showed more scattering and micro-lesions than a standard DWI. The lesions shown in the high b-value DWI were more conspicuous and brighter. Quantitatively, with the increase in b-values, the SNR, CNR, and ADC values decreased gradually, but the CR increased gradually. With a reduction in the matrix size, the SNR and CNR improved (all the results were statistically significant with good inter-observer reliability). Conclusions: A high b-value for DWI is beneficial for the detection of micro- and hyperacute infarction, but the image quality declines. However, reducing the matrix size appropriately could make up for this deficiency.