Magnetic Resonance Imaging of Asymptomatic Knees in Collegiate Basketball Players: The Effect of One Season of Play.

OBJECTIVE: To determine the prevalence of abnormal structural findings using 3.0-T magnetic resonance imaging (MRI) in the asymptomatic knees of male and female collegiate basketball players before and after a season of high-intensity basketball. DESIGN: Institutional review board-approved prospective case series. PARTICIPANTS: Asymptomatic knees of 24 NCAA Division I collegiate basketball players (12 male, 12 female) were imaged using a 3.0-T MRI scanner before and after the end of the competitive season. Three subjects did not undergo scanning after the season. MAIN OUTCOME MEASURES: Images were evaluated for prepatellar bursitis, fat pad edema, patellar and quadriceps tendinopathy, bone marrow edema, and articular cartilage and meniscal injury. RESULTS: Every knee imaged had at least 1 structural abnormality both preseason and postseason. A high preseason and postseason prevalence of fat pad edema (75% and 81%), patellar tendinopathy (83% and 90%), and quadriceps tendinopathy (75% and 90%) was seen. Intrameniscal signal change was observed in 50% preseason knees and 62% of postseason knees, but no discrete tears were found. Bone marrow edema was seen in 75% and 86% of knees in the preseason and postseason, respectively. Cartilage findings were observed in 71% and 81% of knees in the preseason and postseason, respectively. The cartilage injury score increased significantly in the postseason compared with the preseason (P = 0.0009). CONCLUSIONS: A high prevalence of abnormal knee MRI findings was observed in a population of asymptomatic young elite athletes. These preliminary data suggest that high-intensity basketball may have potentially deleterious effects on articular cartilage.

High-resolution, three-dimensional diffusion-weighted breast imaging using DESS.

PURPOSE: To evaluate the use of the double-echo steady-state (DESS) sequence for acquiring high-resolution breast images with diffusion and T2 weighting. MATERIALS AND METHODS: Phantom scans were used to verify the T2 and diffusion weighting of the DESS sequence. Image distortion was evaluated in volunteers by comparing DESS images and conventional diffusion-weighted images (DWI) to spoiled gradient-echo images. The DESS sequence was added to a standard clinical protocol, and the resulting patient images were used to evaluate overall image quality and image contrast in lesions. RESULTS: The diffusion weighting of the DESS sequence can be easily modulated by changing the spoiler gradient area and flip angle. Radiologists rated DESS images as having higher resolution and less distortion than conventional DWI. Lesion-to-tissue contrast ratios are strongly correlated between DWI and DESS images (R=0.83) and between T2-weighted fast spin-echo and DESS images (R=0.80). CONCLUSION: The DESS sequence is able to acquire high-resolution 3D diffusion- and T2-weighted images in short scan times, with image quality that facilitates morphological assessment of lesions.

Advances in musculoskeletal MRI: technical considerations.

The technology of musculoskeletal magnetic resonance imaging (MRI) is advancing at a dramatic rate. MRI is now done at medium and higher field strengths with more specialized surface coils and with more variable pulse sequences and postprocessing techniques than ever before. These innumerable technical advances are advantageous as they lead to an increased signal-to-noise ratio and increased variety of soft-tissue contrast options. However, at the same time they potentially produce more imaging artifacts when compared with past techniques. Substantial technical advances have considerable clinical challenges in musculoskeletal radiology such as postoperative patient imaging, cartilage mapping, and molecular imaging. In this review we consider technical advances in hardware and software of musculoskeletal MRI along with their clinical applications.

Simultaneous estimation of T(2) and apparent diffusion coefficient in human articular cartilage in vivo with a modified three-dimensional double echo steady state (DESS) sequence at 3 T.

T(2) mapping and diffusion-weighted imaging complement morphological imaging for assessing cartilage disease and injury. The double echo steady state sequence has been used for morphological imaging and generates two echoes with markedly different T(2) and diffusion weighting. Modifying the spoiler gradient area and flip angle of the double echo steady state sequence allows greater control of the diffusion weighting of both echoes. Data from two acquisitions with different spoiler gradient areas and flip angles are used to simultaneously estimate the T(2) and apparent diffusion coefficient of each voxel. This method is verified in phantoms and validated in vivo in the knee; estimates from different regions of interest in the phantoms and cartilage are compared to those obtained using standard spin-echo methods. The Pearson correlations were 0.984 for T(2) (∼2% relative difference between spin-echo and double echo steady state estimates) and 0.997 for apparent diffusion coefficient (˜1% relative difference between spin-echo and double echo steady state estimates) for the phantom study and 0.989 for T(2) and 0.987 for apparent diffusion coefficient in regions of interest in the human knee in vivo. High accuracy for simultaneous three-dimensional T(2) and apparent diffusion coefficient measurements are demonstrated, while also providing morphologic three-dimensional images without blurring or distortion in reasonable scan times.

In vivo sodium imaging of human patellar cartilage with a 3D cones sequence at 3 T and 7 T.

PURPOSE: To compare signal-to-noise ratios (SNRs) and T*(2) maps at 3 T and 7 T using 3D cones from in vivo sodium images of the human knee. MATERIALS AND METHODS: Sodium concentration has been shown to correlate with glycosaminoglycan content of cartilage and is a possible biomarker of osteoarthritis. Using a 3D cones trajectory, 17 subjects were scanned at 3 T and 12 at 7 T using custom-made sodium-only and dual-tuned sodium/proton surface coils, at a standard resolution (1.3 x 1.3 x 4.0 mm(3)) and a high resolution (1.0 x 1.0 x 2.0 mm(3)). We measured the SNR of the images and the T*(2) of cartilage at both 3 T and 7 T. RESULTS: The average normalized SNR values of standard-resolution images were 27.1 and 11.3 at 7 T and 3 T. At high resolution, these average SNR values were 16.5 and 7.3. Image quality was sufficient to show spatial variations of sodium content. The average T*(2) of cartilage was measured as 13.2 +/- 1.5 msec at 7 T and 15.5 +/- 1.3 msec at 3 T. CONCLUSION: We acquired sodium images of patellar cartilage at 3 T and 7 T in under 26 minutes using 3D cones with high resolution and acceptable SNR. The SNR improvement at 7 T over 3 T was within the expected range based on the increase in field strength. The measured T*(2) values were also consistent with previously published values.