In vivo quantification of T_1ρ using a multislice spin‐lock pulse sequence

Abstract

A multislice spin-lock (MS-SL) pulse sequence is implemented on a clinical scanner to acquire multiple images with spin-lockgenerated contrast of the knee joints of six healthy human subjects. The MS-SL sequence produces images with T 1 contrast with an additional factor of intrinsic T 2 weighting, which hinders direct measurement of T 1 . A method is presented to compensate the MS-SL-generated data with regard to T 2 in an effort to accurately calculate multislice T 1 maps in a feasible experimental time. The T 2 -compensated multislice T 1 maps produced errors in the measurement of T 1 in healthy patellar cartilage of ϳ5% compared to the gold standard measurement of T 1 acquired with single-slice spin-lock pulse sequence. The MS-SL sequence has potential as an important clinical tool for the acquisition of multislice T 1 -weighted images and/or quantitative multislice T 1 maps.

Dependence of nuclear spin singlet lifetimes on RF spin-locking power

“…For example, at 4.7 T glycerol formal's protons have a frequency difference ∆ν ≈ 16 Hz; hence ν opt n ≈ 80 Hz is sufficient to achieve significant singlet-state lifetime enhancement. For common biomolecules such as citric acid and aspartic acid, ν opt n < 100 Hz at 1.5 T, which is well within the spin-locking regime commonly used in clinical MRI [27,28]. The spin-locking times and strengths used in [27,28] imply that a 60 Hz spin-lock could be safely applied for 3.5 s, and a 20 Hz spin-lock for 30 s. These timescales are of the same order as the singlet lifetimes we measured for typical small molecules, and thus should be sufficient to conduct a variety of in vivo measurements using singlets.…”

Noninvasive Quantification of Human Nucleus Pulposus Pressure with Use of T1ρ-Weighted Magnetic Resonance Imaging

“…Several preliminary studies have demonstrated this feasibility of in vivo T1r-weighted imaging of articular cartilage [28][29][30] and the spine 13,14 . This study was also limited to twodimensional magnetic resonance scans acquired at the midsagittal section of the disc, with which it would be difficult to register locations across sequential imaging sessions in an in vivo longitudinal study.…”

Sodium and T1ρ MRI for molecular and diagnostic imaging of articular cartilage

“…Small variations in T 1r dispersion profiles were observed in spectroscopic studies of cartilage specimens (229). However, except for a constant shift, there were no significant changes observed in the T 1r dispersion curve with varying levels of GAG depletion by trypsin (25).…”

“…In one of the spectroscopic studies of T 1r dispersion in bovine cartilage, it was suggested that the exchange between protons on -OH and -NH of GAG with bulk water may be the dominant source for the low frequency (0-1.5 kHz) T 1r dispersion in cartilage (229). Low-frequency dispersion changes are correlated with loss of PG from the ECM of cartilage.…”