Visualization of wrist anatomy-a comparison between 7T and 3T MRI.

OBJECTIVE: Injuries to the wrist are, due to its small size and complex anatomical structures, difficult to assess by MR, and surgical interventions such as diagnostic arthroscopy are often necessary. Therefore, improved visualization using non-invasive methods could be of clinical value. As a first step of improvement, the purpose of this study was to evaluate visualization of anatomical structures at 7T compared with 3T MR. METHODS: Eighteen healthy volunteers (three males and three females from each age decade between 20 and 49 years) were examined with 7T and 3T MR. Four musculoskeletal radiologists graded 2D and 3D images on a five-level grading scale for visibility of ligaments, cartilage, nerves, trabecular bone, and tendons, as well as overall image quality (i.e., edge sharpness, perceived tissue contrast, and presence of artefacts). Statistical analysis was done using a visual grading characteristics (VGC) analysis. RESULTS: Visibility of cartilage, trabecular bone, tendons, nerves, and ligaments was graded significantly higher at 7T with an area under the curve (AUCVGC) of 0.62-0.88 (95% confidence interval [CI] 0.50-0.97, p = < 0.0001-0.03) using either 2D or 3D imaging. Imaging with 3T was not graded as superior to 7T for any structure. Image quality was also significantly superior at 7T, except for artefacts, where no significant differences were found. CONCLUSIONS: Tendons, trabecular bone, nerves, and ligaments were all significantly better visualized at 7T compared to 3T. KEY POINTS: • MRI of the wrist at 7T with a commercially available wrist coil is feasible at similar acquisition times as for 3T MRI. • The current study showed 7T to be superior to 3T in the visualization of anatomical structures of the wrist, including ligaments, tendons, nerves, and trabecular bone. • Image quality was significantly superior at 7T, except for artefacts, where no significant differences were found.

Visualization of wrist ligaments with 3D and 2D magnetic resonance imaging at 3 Tesla.

BACKGROUND: Wrist ligaments are challenging to visualize using magnetic resonance imaging (MRI). Injuries involving the scapholunate ligament (SLL), the lunotriquetral ligament (LTL), and the triangular fibrocartilage complex (TFCC) are common and difficult to diagnose, often requiring diagnostic arthroscopy. PURPOSE: To compare the visualization of wrist ligaments on a three-dimensional (3D) sequence with two-dimensional (2D) sequences on 3-T MRI. MATERIAL AND METHODS: Eighteen healthy volunteers were examined with a 3D SPACE (sampling perfection with application optimized contrasts using different flip angle evolution) sequence and 2D coronal, axial, and sagittal proton density-weighted (PD) sequences. Four musculoskeletal radiologists graded the anatomical visibility of the SLL, LTL, TFCC, and the image quality, using five grades in a visual grading characteristics (VGC) evaluation. After Bonferroni correction, a P value ≤0.005 was considered statistically significant. RESULTS: The 3D images were graded significantly better than the 2D images in the visualization of the dorsal and palmar parts of the SLL and the LTL. Regarding the TFCC, the 3D images were graded significantly better for visualization of the foveal attachment. 2D imaging was not found significantly superior to 3D imaging in any aspect. CONCLUSION: The 3D SPACE sequence was scored as superior to the 2D sequences at 3 T in the assessment of the SLL, the LTL, and the foveal attachment of the TFCC. Thus, 3D SPACE can replace 2D PD sequences when these ligaments need to be assessed.

Tomosynthesis of the thoracic spine: added value in diagnosing vertebral fractures in the elderly.

OBJECTIVES: Thoracic spine radiography becomes more difficult with age. Tomosynthesis is a low-dose tomographic extension of radiography which may facilitate thoracic spine evaluation. This study assessed the added value of tomosynthesis in imaging of the thoracic spine in the elderly. METHODS: Four observers compared the image quality of 50 consecutive thoracic spine radiography and tomosynthesis data sets from 48 patients (median age 67 years, range 55-92 years) on a number of image quality criteria. Observer variation was determined by free-marginal multirater kappa. The conversion factor and effective dose were determined from the dose-area product values. RESULTS: For all observers significantly more vertebrae were seen with tomosynthesis than with radiography (mean 12.4/9.3, P < 0.001) as well as significantly more fractures (mean 0.9/0.7, P = 0.017). The image quality score for tomosynthesis was significantly higher than for radiography, for all evaluated structures. Tomosynthesis took longer to evaluate than radiography. Despite this, all observers scored a clear preference for tomosynthesis. Observer agreement was substantial (mean κ = 0.73, range 0.51-0.94). The calibration or conversion factor was 0.11 mSv/(Gy cm2) for the combined examination. The resulting effective dose was 0.87 mSv. CONCLUSION: Tomosynthesis can increase the detection rate of thoracic vertebral fractures in the elderly, at low added radiation dose. KEY POINTS: • Tomosynthesis helps evaluate the thoracic spine in the elderly. • Observer agreement for thoracic spine tomosynthesis was substantial (mean κ = 0.73). • Significantly more vertebrae and significantly more fractures were seen with tomosynthesis. • Tomosynthesis took longer to evaluate than radiography. • There was a clear preference among all observers for tomosynthesis over radiography.