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Objective To determine the ability of conventional spin echo (SE) T2 and ultrashort echo time (UTE) T2* relaxation times to characterize pathology in cadaveric meniscus samples. Materials and methods From 10 human donors, 54 triangular (radially cut) meniscus samples were harvested. Meniscal pathology was classified as normal (n = 17), intrasubstance degenerated (n = 33), or torn (n = 4) using a modified arthroscopic grading system. Using a 3-T MR system, SE T2 and UTE T2* values of the menisci were determined, followed by histopathology. Effect of meniscal pathology on relaxation times and histology scores were determined, along with correlation between relaxation times and histology scores. Results Mean ± standard deviation UTE T2* values for normal, degenerated, and torn menisci were 3.6 ± 1.3 ms, 7.4 ± 2.5 ms, and 9.8 ± 5.7 ms, respectively, being significantly higher in degenerated (p p = 0.0002) menisci compared to that in normal. In contrast, the respective mean SE T2 values were 27.7 ± 9.5 ms, 25.9 ± 7.0 ms, and 35.7 ± 10.4 ms, without significant differences between groups (all p > 0.14). In terms of histology, we found significant group-wise differences (each p p = 0.007, Rs2 = 0.19), unlike the correlation between SE T2 and histology (p = 0.09, Rs2 = 0.05). Conclusion UTE T2* values were found to distinguish normal from both degenerated and torn menisci and correlated significantly with histopathology.

Foot and ankle disorders are commonplace in everyday clinical practice. Magnetic resonance imaging (MRI) is frequently required for accurate diagnosis given the broad spectrum of pathology and complexity of foot and ankle anatomy. While conventional MRI plays a significant role for diagnosis, contemporary management increasingly relies upon advanced imaging for monitoring therapeutic response. Subsequently, there is an expanding need for identification of biomarkers for musculoskeletal tissues such as cartilage, tendon, bone and nerves. Advanced imaging techniques capable of imaging these tissue substrates will be increasingly utilized in routine clinical practice. Radiologists should therefore become familiar with these innovative MR techniques. Many such techniques are already widely used in other organ systems, such as isotropic 3D imaging acquisitions, diffusion weighted imaging, and kinematic imaging. Other techniques have until recently been limited to the research realm, and include MR neurography, ultrashort TE MRI and quantitative MRI.

ObjectivesTo determine T2* relaxation in articular cartilage using ultrashort echo time (UTE) imaging and bi-component analysis, with an emphasis on the deep radial and calcified cartilage.MethodsTen patellar samples were imaged using two-dimensional (2D) UTE and Car-Purcell-Meiboom-Gill (CPMG) sequences. UTE images were fitted with a bi-component model to calculate T2* and relative fractions. CPMG images were fitted with a single-component model to calculate T2. The high signal line above the subchondral bone was regarded as the deep radial and calcified cartilage. Depth and orientation dependence of T2*, fraction and T2 were analyzed with histopathology and polarized light microscopy (PLM), confirming normal regions of articular cartilage. An interleaved multi-echo UTE acquisition scheme was proposed for invivo applications (n=5).ResultsThe short T2* values remained relatively constant across the cartilage depth while the long T2* values and long T2* fractions tended to increase from subchondral bone to the superficial cartilage. Long T2*s and T2s showed significant magic angle effect for all layers of cartilage from the medial to lateral facets, while the short T2* values and T2* fractions are insensitive to the magic angle effect. The deep radial and calcified cartilage showed a mean short T2* of 0.80±0.05ms and short T2* fraction of 39.93±3.05% invitro, and a mean short T2* of 0.93±0.58ms and short T2* fraction of 35.03±4.09% invivo.ConclusionUTE bi-component analysis can characterize the short and long T2* values and fractions across the cartilage depth, including the deep radial and calcified cartilage. The short T2* values and T2* fractions are magic angle insensitive.

Background context Degenerative disc disease is a common pathologic disorder accompanied by both structural and biochemical changes. Changes in stress distribution across the disc can lead to annulus fibrosus (AF) damage that can affect the strength and integrity of the disc. Given that some present degeneration therapies incorporate biological regrowth of the nucleus pulposus (NP), it is crucial that the AF remains capable of containing this newly grown material. Purpose To examine the resistance of AF to delamination using an adhesive peel test in experimentally degenerated rabbit discs. Study design Experimentally induced disc degeneration; excised AF tissue study. Methods Disc degeneration was induced in eight New Zealand white rabbits by annular puncture; four additional rabbits served as controls. In experimental rabbits, an 18-gauge needle was inserted into the anterolateral AF region of levels L2–L3 and L4–L5, and disc height was monitored by X-ray. Animals were sacrificed at 4 and 12 weeks postsurgery and magnetic resonance images and X-rays were taken. Four discs were excised from the experimental animals; two punctured (L2–L3 and L4–L5) and two controls (L3–L4 and L6–L7). The same four discs were also excised from the age-matched control animals and served as nonpunctured control discs. To determine resistance to delamination, AF samples were dissected from each disc and subjected to a mechanical peel test at 0.5 mm/s. Results Magnetic resonance imaging and X-ray images confirmed dehydration of the NP and reduced disc height, similar to that found in clinical degeneration. Resistance to delamination was significantly lower in punctured/degenerated discs compared with both the nonpunctured discs from the same animal (27% lower) and the nonpunctured control discs (30% lower) (p=.024). Conclusions The findings of this study suggest that degeneration increases the potential for delamination between AF layers. Given this substantial change to the integrity of the AF after degeneration, clinical treatments should not only target rehydration or regrowth of the NP, but should also target repair and strengthening of the AF to confine the NP.

© 2014. The purpose of this study was to evaluate a magnetic resonance imaging (MRI) technique for quantifying the proton density water fraction (PDWF) as a biomarker of bone marrow cellularity. Thirty-six human bone marrow specimens from 18 donors were excised and subjected to different measurements of tissue composition: PDWF quantification using a multiple gradient echo MRI technique, three biochemical assays (triglyceride, total lipid and water content) and a histological assessment of cellularity. Results showed a strong correlation between PDWF and bone marrow cellularity from histology (. r=. 0.72). A strong correlation was also found between PDWF and the biochemical assay of water content (. r=. 0.76). These results suggest the PDWF is a predictor of bone marrow cellularity in tissues and can provide a non-invasive assessment of bone marrow changes in clinical patients undergoing radiotherapy.