Abstract
In this study, we aimed to precisely localize the hyperintense signal that is generated at the osteochondral junction when using ultrashort echo time magnetic resonance imaging (MRI) and to investigate the osteochondral junction using sweep imaging with Fourier transformation (SWIFT) MRI. Furthermore, we seek to evaluate what compositional properties of the osteochondral junction are the sources of this signal. In the study, we obtained eight samples from a tibial plateau dissected from a 68-year-old male donor, and one additional osteochondral sample of bovine origin. The samples were imaged using high-resolution ultrashort echo time SWIFT MRI and microcomputed tomography (μCT) scans. Localization of the bright signal in the osteochondral junction was performed using coregistered data sets. Potential sources of the signal feature were examined by imaging the bovine specimen with variable receiver bandwidths and by performing variable flip angle T1 relaxation time mapping. The results of the study showed that the hyperintense signal was found to be located entirely in the deep noncalcified articular cartilage. The intensity of this signal at the interface varied between the specimens. Further tests with bovine specimens indicated that the imaging bandwidth and T1 relaxation affect the properties of the signal. Based on the present results, the calcified cartilage has low signal intensity even in SWIFT imaging. Concomitantly, it appears that the bright signal seen in ultrashort echo time imaging resides within the noncalcified cartilage. Furthermore, the most likely sources of this signal are the rapid T1 relaxation of the deep cartilage and the susceptibility-induced effects arising from the calcified tissues.
Highlights
| INTRODUCTIONOf OA are limited.[3]. Recently, the role of the osteochondral junction, the interface between cartilage and the underlying bone, has re-
From the co‐registered data sets, it was evident that the increase in sweep imaging with Fourier transformation (SWIFT) signal appeared spatially before anything that was visible in the μCT, that is, the signal originated from the noncalcified cartilage
Our results indicate that the bright signal is not located in the calcified cartilage, which remained almost invisible even in the SWIFT images
Summary
Of OA are limited.[3]. Recently, the role of the osteochondral junction, the interface between cartilage and the underlying bone, has re-. A bright signal from the osteochondral junction has been observed using different UTE sequences.[12,13,14,15] In a study with 2D dual inversion prepared UTE sequence (DIR‐UTE), it was shown that the signal has contributions from the deepest parts of hyaline cartilage and from the calcified cartilage. Another study using same the sequence revealed the same signal from cartilaginous endplates.[16] One study applying DIR‐UTE reported that this signal has T2* relaxation time around 2 milliseconds, T1rho around 3.5 milliseconds and T1 around 300 milliseconds.[15] A study incorporating sweep imaging with Fourier transformation (SWIFT) sequence showed that similar signal can be seen using 3D SWIFT MRI.[14] the defects in this hyperintense signal, as observed with 3D UTE, appear to co‐locate with bone marrow lesions.[17]. We obtained high‐resolution SWIFT18 scans of human and bovine osteochondral samples at 9.4 T and the resulting 3D MR images were compared with both high‐resolution 3D μCT data as well as histological images of the same samples
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