Free-breathing phase-sensitive inversion recovery T1-weighted imaging for improved visualization of focal liver lesions.

Abstract

Purpose: Gadoxetic acid-enhanced hepatobiliary phase T₁-weighted (T₁w) MRI is effective for the detection of focal liver lesions but lacks sufficient T₁ contrast to distinguish benign from malignant lesions. Although the addition of T₂, diffusion, and dynamic contrast-enhanced T₁w imaging improves lesion characterization, these methods often do not provide adequate spatial resolution to identify subcentimeter lesions. This work proposes a high-resolution, volumetric, free-breathing liver MRI method that produces colocalized fat-suppressed, variable T₁w images from a single acquisition, thereby improving both lesion detection and characterization.

Theory and methods: This method combines stack-of-stars radial sampling, magnetization preparation, and chemical shift encoding to enable free-breathing, T₁w imaging with water/fat separation. A model-based image reconstruction algorithm reconstructs images from highly undersampled k-space data. Pseudo-T₁ relaxation maps are calculated from the variable T₁w images. The feasibility of this method was investigated in patients undergoing clinical contrast-enhanced MRI examinations for detection and characterization of focal liver lesions at both 1.5 and 3.0 T. An expert reader study was conducted to evaluate the method's performance, compared with the hepatobiliary phase-navigated T₁w MRI based on image quality and lesion conspicuity.

Results: Expert readers found that at shorter inversion times (TIs) (˜500 ms), the proposed method had superior liver-lesion contrast for characterizing simple cysts and metastases, compared with navigated T₁w images.

Conclusion: The proposed method produces colocalized fat-suppressed, variable T₁w images from a single acquisition that may improve focal liver lesion detection and characterization.