Abstract
Bone is comprised of mineral, collagenous organic matrix, and water. X-ray-based techniques are the standard approach for bone evaluation in clinics, but they are unable to detect the organic matrix and water components in bone. Magnetic resonance imaging (MRI) is being used increasingly for bone evaluation. While MRI can non-invasively assess the proton pools in soft tissues, cortical bone typically appears as a signal void with clinical MR techniques because of its short T2*. New MRI techniques have been recently developed to image bone while avoiding the ionizing radiation present in x-ray-based methods. Qualitative bone imaging can be achieved using ultrashort echo time (UTE), single inversion recovery UTE (IR-UTE), dual-inversion recovery UTE (Dual-IR-UTE), double-inversion recovery UTE (Double-IR-UTE), and zero echo time (ZTE) sequences. The contrast mechanisms as well as the advantages and disadvantages of each technique are discussed.
Highlights
Osteoporosis (OP) is a bone disease which affects millions of people around the world [1] and can lead to serious long-term disability in many patients
ultrashort echo time (UTE) AND inversion recovery UTE (IR-UTE) PULSE SEQUENCES AND THEIR CONTRAST MECHANISM. Both UTE and inversion recovery (IR)-UTE sequences have been developed for imaging of cortical and trabecular bone as described in the Visualized bone signal proton pool
Since conventional clinical Magnetic resonance imaging (MRI) techniques fail to detect signal from bone, here are several qualitative MR techniques currently being developed for assessment of cortical bone
Summary
Osteoporosis (OP) is a bone disease which affects millions of people around the world [1] and can lead to serious long-term disability in many patients. OP development always occurs in synchrony with increases in cortical bone porosity and with trabecular bone deterioration [2]. The development of non-invasive imaging techniques to evaluate bone structural properties and stability is crucial to improved diagnosis of OP and monitoring of OP patients undergoing medical treatments. From the architectural point of view, cortical bone (compact) and trabecular bone (spongy) are two main morphologies of the bone tissue with approximate porosities under 20% and over 80%, respectively [2, 4]. Cortical bone comprises around 80% of human bone mass [5, 6]. Trabecular bone generally exists surrounded by cortical bone near joints. Despite large pores in trabecular bone sites, most cortical porosities are limited to pores below 100 μm in size [7, 8]
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