Subchondral bone and cartilage thickness from MRI: effects of chemical-shift artifact

Abstract

Magnetic resonance imaging (MRI) is the modality of choice for visualizing and quantifying articular cartilage thickness. However, difficulties persist in MRI of subchondral bone using spoiled gradient-echo (SPGR) and other gradient-echo sequences, primarily due to the effects of chemical-shift artifact. Fat suppression techniques are often used to reduce these artifacts, but they prevent measurement of bone thickness. In this report, we assess the magnitude of chemical-shift effects (phase-cancellation and misregistration artifacts) on subchondral bone and cartilage thickness measurements in human femoral heads using a variety of pulse sequence parameters. Phase-cancellation effects were quantified by comparing measurements from in-phase images (TE=13.5 ms) to out-of-phase images (TE=15.8 ms). We also tested the assumption of the optimal in-phase TE by comparing thickness measures at small variations on TE (13.0, 13.5 and 14.0 ms). Misregistration effects were quantified by comparing measurements from water+fat images (water-only+fat-only images) to the measurements from in-phase (TE=13.5) images. A correction algorithm was developed and applied to the in-phase measurements and then compared to measurements from water+fat images. We also compared thickness measurements at different image resolutions. Results showed that both phase-cancellation artifact and misregistration artifact were significant for bone thickness measurement, but not for cartilage thickness measurement. Using an in-phase TE and correction algorithm for misregistration artifact, the errors in bone thickness relative to water+fat images were non-significant. This information may be useful for developing pulse sequences for optimal imaging of both cartilage and subchondral bone.

Accuracy of cartilage and subchondral bone spatial thickness distribution from MRI

“…Special consideration must be given to the SB thickness comparisons, however. As we showed previously (16), the apparent SB thickness is affected by both phase‐cancellation and misregistration effects caused by chemical shift. Phase‐cancellation effects can be minimized by using an in‐phase TE (such as 13.5 msec), which we used in our imaging protocol.…”

“…However, one way to eliminate misregistration effects is to acquire separate water and fat suppressed images, followed by addition of the separate images (creating a single water and fat image). In our prior report (16), we found that a simple trigonometric correction factor applied to the thickness vector's readout direction gave a good approximation of the subchondral bone thickness from the combined water and fat images. Thus, we compared SB thickness from Faxitron‐based measurements to thickness from MRI‐based measurements with and without this correction.…”

“…We report in‐plane errors in thickness from MRI relative to a “gold standard” microradiograph (Faxitron x‐ray) measurement and assess the contribution of the three‐dimensional model and volume‐averaging effects to three‐dimensional thickness errors in both AC and SB. We also apply a previously published (16) method of correcting for chemical‐shift misregistration effects specific to SB measurement.…”

Acute Injury of the Articular Cartilage and Subchondral Bone: A Common but Unrecognized Lesion in the Immature Knee

“…Differentiation of the deep layers of articular cartilage and subchondral bone using routine MRI is difficult [18][19][20]. The transition between cartilage and bone will appear to vary depending on factors such as TE and the orientation of the cartilage.…”

MRI of the temporo-mandibular joint: which sequence is best suited to assess the cortical bone of the mandibular condyle? A cadaveric study using micro-CT as the standard of reference

“…Cortical bone surface irregularities to previously described and well-known chemical shift and susceptibility artefacts occurring at the bordering regions between cortical bone and cartilage, fluid or soft-tissue structures of the TMJ [10][11][12][15][16][17][18][19]. The resulting overor underestimation, however, may lead to misinterpretation of the cortical bone surface and structure.…”