Editorial for “Comparison of MR Ultrashort Echo Time and Optimized 3D‐Multiecho In‐Phase Sequence to Computed Tomography for Assessment of the Osseous Craniocervical Junction”

Abstract

In magnetic resonance imaging (MRI)-based qualitative imaging of different components of the bone, musculoskeletal radiologists and orthopedic researchers have significant interest. The biggest advantage of these techniques is to provide simultaneous assessment of bone and the surrounding soft tissues to be evaluated without irradiating the patients. Bone is made up of various components of mineral, collagenous organic matrix consisting of trabecular pattern, and water. As we know that routine clinical MRI techniques fail to detect signal from bone more precisely, newer qualitative MR techniques are currently being developed for the assessment of cortical bone. One of the technique includes ultrashort echo time (UTE) MRI, in which signals are detected from both bound water and pore water in bone, but with low contrast due to much higher signals from the surrounding soft tissues such as muscle and bone marrow fat. UTE-based sequences provide efficient suppression of long T2 tissues, allowing bound water imaging with computed tomography (CT)-like bone contrast. Other techniques, such as Ultrashort time echo-RS, Waterand fat-suppressed solid-state proton projection imaging, Zero TE, and Sweep Imaging with Fourier Transform also have potential for qualitative bone imaging. Some of the described techniques can be used for quantitative bone imaging and for microstructural evaluations. Direct trabecular bone imaging is technically challenging because of the fast signal decay of bone, as implied by its short T2; due to this, the UTE sequence is used and is achieved through an SPIR (spectral presaturation with inversion recovery) module to suppress marrow fat. With the advent of this UTE, MRI, due to the high resolution and long scan time requirements, still needs to be proven as compared to CT, which is fast and referred to as the gold standard. With UTE, the trabecular bone can be visualized and can measure the relaxation times, which is more precise for the evaluation of the osseous abnormalities of the craniovertebral junction. In the novel study by Deininger-Czermak et al in this issue, the authors compared the performance of these two MRI sequences, UTE and a 3D bone imaging sequence (FRACTURE), at 3T, to the already existing so-called gold standard CT for the assessment of structural changes in the craniocervical junction (CCJ). They compared the imaging findings of these three modalities based on measurements of imaging parameters of CCJ injuries; these criteria are the atlanto-dental interval (ADI), atlanto-occipital interval (AOI), basion-dens interval (BDI), and the basion-axis interval (BAI). Based on the visual appearance of degeneration on each image, a linear regression of differences between the MRI and CT measurements was made and assigned a score. This technique will be helpful for the evaluation of any bony involvement and associated soft-tissue involvement or changes. With the above-mentioned measurement criteria, also the more precise evaluation of CCJ will be possible, other than routine base of the skull evaluation parameters. The biggest advantage here will be that there is no radiation and the extremely high soft-tissue sensitivity of MRI can evaluate the CCJ to the best possible extent.