Quantitative Magnetic Resonance Imaging of Cortical and Trabecular Bone

Abstract

Bone is a composite material consisting of mineral, organic matrix, and water. Water in bone can be categorized as bound water (BW), which is bound to bone mineral and organic matrix, or as pore water (PW), which resides in Haversian canals as well as in lacunae and canaliculi. Bone is generally classified into two types: cortical bone and trabecular bone. Cortical bone is much denser than trabecular bone that is surrounded by marrow and fat. Magnetic resonance (MR) imaging has been increasingly used for noninvasive assessment of both cortical bone and trabecular bone. Bone typically appears as a signal void with conventional MR sequences because of its short T2*. Ultrashort echo time (UTE) sequences with echo times 100 to 1,000 times shorter than those of conventional sequences allow direct imaging of BW and PW in bone. This article summarizes several quantitative MR techniques recently developed for bone evaluation. Specifically, we discuss the use of UTE and adiabatic inversion recovery prepared UTE sequences to quantify BW and PW, UTE magnetization transfer sequences to quantify collagen backbone protons, UTE quantitative susceptibility mapping sequences to assess bone mineral, and conventional sequences for high-resolution imaging of PW as well as the evaluation of trabecular bone architecture.

Bone hydration: How we can evaluate it, what can it tell us, and is it an effective therapeutic target?

“…NMR spectroscopy and MRI represent the primary methods used to nondestructively study bone hydration ( Jerban et al, 2020c ; Mroue et al, 2015 ; Singh et al, 2013 ). Compelling progress in solid-state NMR (ssNMR) has allowed us to study the direct relationship of bound water to a host of extracellular matrix components.…”

Ultrashort Echo Time Magnetic Resonance Imaging Techniques: Met and Unmet Needs in Musculoskeletal Imaging

“…For example, Wurnig et al proposed to use the SPIR-UTE sequence to image trabecular bone 31 and reported a T2* of 2.42 AE 0.56 msec at 3 T, which is much longer than the T2* of 0.31 AE 0.01 msec for trabecular bone measured with STAIR-UTE, 28 or a T2* of $0.3 msec for cortical bone measured with various IR-based UTE techniques. [32][33][34] The much longer T2* suggests that SPIR-UTE imaging of trabecular bone is subject to significant fat signal contamination. Meanwhile, the STAIR-UTE-measured T2* values for trabecular bone are very close to the IR-UTE-measured T2* values for cortical bone, which suggests that marrow fat is nearly completely suppressed, with signals from trabeculae being selectively detected in STAIR-UTE imaging.…”

“…The residual fat signal can be much higher than that from trabecular bone. For example, Wurnig et al proposed to use the SPIR‐UTE sequence to image trabecular bone 31 and reported a T2* of 2.42 ± 0.56 msec at 3 T, which is much longer than the T2* of 0.31 ± 0.01 msec for trabecular bone measured with STAIR‐UTE, 28 or a T2* of ~0.3 msec for cortical bone measured with various IR‐based UTE techniques 32–34 . The much longer T2* suggests that SPIR‐UTE imaging of trabecular bone is subject to significant fat signal contamination.…”

MRI-based porosity index (PI) and suppression ratio (SR) in the tibial cortex show significant differences between normal, osteopenic, and osteoporotic female subjects

“…Notably, T2* of bone is on the order of hundreds of microseconds, while the echo times (TEs) in conventional clinical MRI sequences are typically several milliseconds or longer ( 11 , 17 ). On the other hand, ultrashort echo time (UTE) MRI sequences have TEs on the order of several to tens of microseconds, which are short enough to detect signal from cortical bone directly and consequently enable quantitative assessment of cortical bone ( 7 – 9 , 11 , 12 , 18 , 19 ).…”