Fast quantitative MRI: Spiral Acquisition Matching-Based Algorithm (SAMBA) for Robust T1 and T2 Mapping

Abstract

Conventional diagnostic images from Magnetic Resonance Imaging (MRI) are typically qualitative and require subjective interpretation. Alternatively, quantitative MRI (qMRI) methods have become more prevalent in recent years with multiple clinical and preclinical imaging applications. Quantitative MRI studies on preclinical MRI scanners are being used to objectively assess tissues and pathologies in animal models and to evaluate new molecular MRI contrast agents. Low-field preclinical MRI scanners (≤3.0T) are particularly important in terms of evaluating these new MRI contrast agents at human MRI field strengths. Unfortunately, these low-field preclinical qMRI methods are challenged by long acquisition times, intrinsically low MRI signal levels, and susceptibility to motion artifacts. In this study, we present a new rapid qMRI method for a preclinical 3.0T MRI scanner that combines a Spiral Acquisition with a Matching-Based Algorithm (SAMBA) to rapidly and quantitatively evaluate MRI contrast agents. In this initial development, we compared SAMBA with gold-standard Spin Echo MRI methods using Least Squares Fitting (SELSF) in vitro phantoms and demonstrated shorter scan times without compromising measurement accuracy or repeatability. These initial results will pave the way for future in vivo qMRI studies using state-of-the-art chemical probes.

Keywords: Quantitative MRI; Spiral Acquisition Matching-Based Algorithm (SAMBA); low-field preclinical MRI.

Fig. 1.

Linear regression and representative colormaps of T₁ (left) & T₂ measurements (right) obtained via conventional approach (Spin Echo Least Squares Fitting “SELSF” x axes) vs. proposed method (Spiral Acquisition Matching-Based Algorithm “SAMBA”, y axes). Dashed line represents the unity, error bars represent standard deviation between 8 measurements.

Fig. 2.

Analysis of measurement repeatability from T₁ & T₂ phantoms (left column): comparison of Coefficient of Variation (CV%) and CV% per time (middle columns), and ratio between conventional and proposed approaches (right column).