Articular Cartilage Assessment Using Ultrashort Echo Time MRI: A Review

Abstract

Articular cartilage is a major component of the human knee joint which may be affected by a variety of degenerative mechanisms associated with joint pathologies and/or the aging process. Ultrashort echo time (UTE) sequences with a TE less than 100 µs are capable of detecting signals from both fast- and slow-relaxing water protons in cartilage. This allows comprehensive evaluation of all the cartilage layers, especially for the short T2 layers which include the deep and calcified zones. Several ultrashort echo time (UTE) techniques have recently been developed for both morphological imaging and quantitative cartilage assessment. This review article summarizes the current catalog techniques based on UTE Magnetic Resonance Imaging (MRI) that have been utilized for such purposes in the human knee joint, such as T1, T2∗, T1ρ, magnetization transfer (MT), double echo steady state (DESS), quantitative susceptibility mapping (QSM) and inversion recovery (IR). The contrast mechanisms as well as the advantages and disadvantages of these techniques are discussed.

Updates on Compositional MRI Mapping of the Cartilage: Emerging Techniques and Applications

“…shorter T 2 relaxation times where the use of UTE or zero echo time (ZTE) sequences is needed to capture a signal. 79 This is important in clinical applications, such as OA, 80 where UTE and ZTE can better quantify the short T 2 /T 1ρ tissues such as calcified cartilage, menisci, ligaments and tendons. UTE cones and adiabatic T 1ρ were used to assess cartilage degeneration, 81 while the study by Wu et al 82 also shows that adiabatic T 1ρ was more robust to magic angle effects.…”

“…Most RF pulse sequences for quantitative mapping can measure tissues with relaxation times greater than 5 msec. However, some tissues in the knee joint including the deep and calcified cartilage, ligaments, tendons, and menisci have shorter T 2 relaxation times where the use of UTE or zero echo time (ZTE) sequences is needed to capture a signal 79 . This is important in clinical applications, such as OA, 80 where UTE and ZTE can better quantify the short T 2 /T 1ρ tissues such as calcified cartilage, menisci, ligaments and tendons.…”

Achilles tendon and enthesis assessment using ultrashort echo time magnetic resonance imaging (UTE‐MRI) T1 and magnetization transfer (MT) modeling in psoriatic arthritis

“…Conventional MRI techniques such as T1‐weighted and T2‐weighted fat‐suppressed fast‐spin echo (FSE) sequences can demonstrate morphological changes of the Achilles tendon and enthesis when grossly abnormal. Quantitative MRI (qMRI) biomarkers such as T1, magnetization transfer ratio (MTR), and T2* can provide valuable information about the microstructural and compositional changes in PsA‐affected tissues without requiring high spatial resolutions 9–11 . The presence of edema, inflammation, fibrosis, and tissue erosion are common features of PsA that involve microstructural and compositional changes 11–13 .…”

“…Quantitative MRI (qMRI) biomarkers such as T1, magnetization transfer ratio (MTR), and T2* can provide valuable information about the microstructural and compositional changes in PsA-affected tissues without requiring high spatial resolutions. [9][10][11] The presence of edema, inflammation, fibrosis, and tissue erosion are common features of PsA that involve microstructural and compositional changes. [11][12][13] However, intact tendons and entheses, as well as fibrotic tissues, have short T2s and show little or no signal, which limits their ability to be quantified by routine qMRI.…”

Added value of ultra-short echo time and fast field echo using restricted echo-spacing MR imaging in the assessment of the osseous cervical spine

“…After applying two radiofrequency impulses, a fast radial read out of the k -space can be provided, and thus, the induced signal can be measured before the signal of the osseous tissue drops to zero. Until now UTE sequences have already been investigated to evaluate bony, cartilaginous or ligamentous structures, focusing on the implementation in a clinical setup [ 8 – 11 ]. Beside UTE sequences, other technical approaches have been developed and investigated, such as “Slab-selective UTE” applying a modified radio frequency pulse, or zero-echo time (ZTE) sequences turning on readout gradients even before the radio frequency pulse.…”