VP.71 Simultaneous texture and relaxation estimation in skeletal muscle in cystinosis patient compared to healthy control with high-field MRI

Abstract

Magnetic resonance imaging (MRI) is a powerful imaging method for skeletal muscle due to its good soft tissue contrast and wide imaging options. MRI can provide not only morphological images of anatomy but also quantitative metrics of the tissue on a microscopic scale. This includes the metric of T2 relaxation, which has been related to tissue inflammation and hydration. In this work, we demonstrate how quantitate Double-Echo in Steady-State (qDESS) MRI measurements obtained in a 7 Tesla MRI scanner can simultaneously provide T2 measurements as well as a measure of muscle texture using high-resolution measurements of tissue signal variation. We ran a qDESS scan axially in the lower thigh of a 32-year-old male cystinosis patient using a flip angle of 20°, a repetition/echo times of 22.5/6.3 ms, and a voxel size of 0.148×0.148×2 mm, with a total scan time of 11.5 minutes. A region of interest (ROI) was drawn in 25 slices covering the vastus medialis muscle, thus spanning 5 cm in the slice direction with the most distal slice at the upper tip of the patella. Tissue texture was assessed by computing the standard deviation of the MRI signal in the muscle in each ROI, divided by the mean signal value (σ/μ). Also, using established qDESS methodologies, we computed the T2 relaxation by comparing the amplitudes of the qDESS signals in the ROIs of each of the 25 slices. This process was repeated in a 38-year-old male healthy control. The results gave a an average σ/μ of 17.6% and an average T2 of 29.8 ms in the patient, while for the healthy control the values were 19.8% and 30.7 ms. While this feasibility study had too small a sample size to determine differences between patients and controls, it demonstrates the feasibility to obtain a combined morphological and quantitative biomarker with a single MRI sequence, potentially providing a metric for assessing disease severity and aiding in the development of treatments and therapeutics.