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Regulatory approval of ultrahigh field (UHF) MR imaging scanners for clinical use has opened new opportunities for musculoskeletal imaging applications. UHF MR imaging has unique advantages in terms of signal-to-noise ratio, contrast-to-noise ratio, spectral resolution, and multinuclear applications, thus providing unique information not available at lower field strengths. But UHF also comes with a set of technical challenges that are yet to be resolved and may not be suitable for all imaging applications. This review focuses on the latest research in musculoskeletal MR imaging applications at UHF including morphologic imaging, T2, T2∗, and T1ρmapping, chemical exchange saturation transfer, sodium imaging, and phosphorus spectroscopy imaging applications.

MR imaging is an indispensable instrument for the diagnosis of musculoskeletal diseases. In vivo MR imaging at 7T offers many advantages, including increased signal-to-noise ratio, higher spatial resolution, improved spectral resolution for spectroscopy, improved sensitivity for X-nucleus imaging, and decreased image acquisition times. There are also however technical challenges of imaging at a higher field strength compared with 1.5 and 3T MR imaging systems. We discuss the many potential opportunities as well as the challenges presented by 7T MR imaging systems and highlight recent developments in in vivo research imaging of musculoskeletal applications in general and cartilage, skeletal muscle, and bone in particular.

In postmenopausal women who do not have osteoporotic proximal femur bone mineral density (T scores > −2.5), MR imaging of proximal femur microarchitecture can allow discrimination of those with fracture (higher fracture risk) from those without fracture (lower fracture risk) better than chance and may provide different information about bone quality than that provided by dual-energy x-ray absorptiometry.

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Objective: It has remained ambiguous as to whether oral dosing of glucosamine (GlcN) would make its way to the joint and affect changes in the cartilage, particularly the integrity of cartilage and chondrocyte function. The objective of this study was to trace the fate of orally dosed GlcN and determine definitively if GlcN was incorporated into cartilage proteoglycans.Design: Two dogs were treated with 13C-GlcN-HCl by oral dosing (500 mg/dog/d for 2 weeks and 250 mg/dog/d for 3 weeks). Cartilage was harvested from the tibial plateau and femoral condyles along with tissue specimens from the liver, spleen, heart, kidney, skin, skeletal muscle, lung, and costal cartilage. Percentages of 13C and 13C-GlcN present in each tissue sample were determined by inductively coupled plasma mass spectroscopy (ICP-MS) and nuclear magnetic resonance spectroscopy, respectively.Results: In the case of dog 1 (2-week treatment), there was an increase of 2.3% of 13C present in the articular cartilage compared to the control and an increase of 1.6% of 13C in dog 2 compared to control. As to be expected, the highest percentage of 13C in the other tissues tested was found in the liver, and the remaining tissues had percentages of 13C less than that of articular cartilage.Conclusion: The results are definitive and for the first time provide conclusive evidence that orally given GlcN can make its way through the digestive tract and be used by chondrocytes in joint cartilage, thereby potentially having an effect on the available GlcN for proteoglycan biosynthesis.

Proton T1ρ‐dispersion MRI is demonstrated for indirect, in vivo detection of 17O in the brain. This technique, which may be readily implemented on any clinical MRI scanner, is applied towards high‐resolution, quantitative mapping of cerebral blood flow (CBF) in the rat by monitoring the clearance of 17O‐enriched water. Strategies are derived and employed for 1) quantitation of absolute H217O tracer concentration from a ratio of high‐ and low‐frequency spin‐locked T1ρimages, and 2) mapping CBF without having to transform the T1ρsignal to H217O tracer concentration. Absolute regional blood flow was mapped in a single 3‐mm brain slice at an in‐plane resolution of 0.4 × 0.8 mm within a 5‐min tracer washout time; these data are consistent with the less localized CBF measurements reported in the literature. T1ρ‐weighted imaging yields excellent signal‐to‐noise ratios, spatiotemporal resolution, and anatomical contrast for mapping CBF. Magn Reson Med 49:479–487, 2003. © 2003 Wiley‐Liss, Inc.

Proton T1ρ-dispersion MRI is demonstrated for indirect, in vivo detection of ¹⁷O in the brain. This technique, which may be readily implemented on any clinical MRI scanner, is applied towards high-resolution, quantitative mapping of cerebral blood flow (CBF) in the rat by monitoring the clearance of ¹⁷O-enriched water. Strategies are derived and employed for 1) quantitation of absolute H2¹⁷O tracer concentration from a ratio of high- and low-frequency spin-locked T1ρ images, and 2) mapping CBF without having to transform the T1ρ signal to H2¹⁷O tracer concentration. Absolute regional blood flow was mapped in a single 3-mm brain slice at an in-plane resolution of 0.4 × 0.8 mm within a 5-min tracer washout time; these data are consistent with the less localized CBF measurements reported in the literature. T1ρ-weighted imaging yields excellent signal-to-noise ratios, spatiotemporal resolution, and anatomical contrast for mapping CBF. Magn Reson Med 49:479–487, 2003. © 2003 Wiley-Liss, Inc.