Improved detection of multiple sclerosis lesions with T2-prepared double inversion recovery at 3T

Abstract

Background and purpose: Double inversion recovery (DIR) imaging is used in multiple sclerosis (MS) clinical protocols to improve the detection of cortical and juxtacortical gray matter lesions by nulling confounding signals originating from the cerebrospinal fluid and white matter. Achieving a high isotropic spatial resolution, to depict the neocortex and its typically small lesions, is challenged by the reduced signal-to-noise ratio (SNR) determined by multiple tissue signal nulling. Here, we evaluate both conventional and optimized DIR implementations to improve tissue contrast (TC), SNR, and MS lesion conspicuity.

Methods: DIR images were obtained from MS patients and healthy controls using both conventional and prototype implementations featuring a T2-preparation module (T2P), to improve SNR and TC, as well as an image reconstruction routine with iterative denoising (ID). We obtained quantitative measures of SNR and TC, and evaluated the visibility of MS cortical, cervical cord, and optic nerve lesions in the different DIR images.

Results: DIR implementations adopting T2P and ID enabled improving the SNR and TC of conventional DIR. In MS patients, 34% of cortical, optic nerve, and cervical cord lesions were visible only in DIR images acquired with T2P, and not in conventional DIR images. In the studied cases, image reconstruction with ID did not improve lesion conspicuity.

Conclusions: DIR with T2P should be preferred to conventional DIR imaging in protocols studying MS patients, as it improves SNR and TC and determines an improvement in cortical, optic nerve, and cervical cord lesion conspicuity.

Keywords: cervical cord; gray matter; magnetic resonance imaging; multiple sclerosis; optic nerve.

FIGURE 1

Signal‐to‐noise ratio (SNR) (top panel) and tissue contrast (bottom panel) in three healthy controls (HC) in conventional double inversion recovery (DIR), DIR reconstructed with iterative denoising (DIR+ID), DIR with T2‐preparation module (T2PDIR), and T2PDIR with iterative denoising reconstruction (T2PDIR+ID). GM, gray matter; WM, white matter

FIGURE 2

Pie charts indicating the number of lesions detected in the cortical gray matter, optic nerve, and cervical cord, showing in gray the number of lesions detected with both conventional double inversion recovery (DIR) and DIR with T2‐preparation module (T2PDIR), in dark gray the lesions visible only in T2PDIR acquisitions, and in white the lesions detected only in conventional DIR acquisition

FIGURE 3

Examples of cortical, optic nerve, and spinal cord lesions, detected with different confidence levels, in conventional double inversion recovery (DIR), DIR reconstructed with iterative denoising (DIR+ID), DIR with T2‐preparation module (T2PDIR), and T2PDIR with iterative denoising reconstruction (T2PDIR+ID). Dotted arrows indicate possible lesions (score = 1); thin arrows indicate probable lesions (score = 2); thick arrows indicate obvious lesions (score = 3).