With an improvement in the temporal and spatial resolution, computed tomography (CT) is indicated in the evaluation of a great many osteoarticular diseases. New exploration techniques such as the dynamic CT and CT bone perfusion also provide new indications. However, CT is still an irradiating imaging technique and dose optimisation and reduction remains primordial. In this paper, the authors first present the typical doses delivered during CT in osteoarticular disease. They then discuss the different ways to optimise and reduce these doses by distinguishing the behavioural factors from the technical factors. Among the latter, the optimisation of the milliamps and kilovoltage is indispensable and should be adapted to the type of exploration and the morphotype of each individual. These technical factors also benefit from recent technological evolutions with the distribution of iterative reconstructions. In this way, the dose may be divided by two and provide an image of equal quality. With these dose optimisation and reduction techniques, it is now possible, while maintaining an excellent quality of the image, to obtain low-dose or even very low-dose acquisitions with a dose sometimes similar that of a standard X-ray assessment. Nevertheless, although these technical factors provide a major reduction in the dose delivered, behavioural factors, such as compliance with the indications, remain fundamental. Finally, the authors describe how to optimise and reduce the dose with specific applications in musculoskeletal imaging such as the dynamic CT, CT bone perfusion and dual energy CT.
Due to the configuration of its bony elements, the glenohumeral joint is the most mobile joint of the body, but also an inherently unstable articulation. Stabilization of the joint is linked to a complex balance between static and dynamic soft tissue stabilizers. Because of complex biomechanics, and the existence of numerous classifications and acronyms to describe shoulder instability lesions, this remains a daunting topic for most radiologists. In this article we provide a brief review of the anatomy of the glenohumeral joint, as well as the classifications and the pathogenesis of shoulder instability. Technical aspects related to the available imaging techniques (including computed tomography [CT] arthrography, magnetic resonance imaging [MRI], and MR arthrography) are reviewed. We then describe the imaging findings related to shoulder instability, focusing on those elements that are important to the clinician.
To determine the technical feasibility of four-dimensional (4D) CT for analysis of the variation of radioscaphoid angle (RSA) and lunocapitate angle (LCA) during wrist radioulnar deviation. Materials and Methods: In this prospective study, 37 participants suspected of having scapholunate instability were evaluated from January 2015 to December 2016 with 4D CT and CT arthrography (mean age 6 standard deviation, 42.3 years 6 15; range, 21-75 years; 27 men [mean age, 44 years 6 15] and 10 women [mean age, 38 years 6 14]). Five angular parameters for RSA and LCA variation during radioulnar deviation were calculated by two independent readers. CT arthrography was used as the reference standard method for scapholunate ligament tear identification. Results: In the control group (n = 23), the mean values for RSA were 103° 6 8 and 104° 6 9, whereas the mean values for LCA were 86° 6 9° and 90° 6 11° with a coefficient of variation of 11% and 13% for reader 1 and reader 2, respectively. The interobserver and intraobserver agreements were excellent for RSA and substantial to excellent for LCA. In the pathologic group (n = 14), LCA amplitude, standard deviation, and maximal angle were lower for both readers with respect to the control group, measuring 36% and 44% (P = .003), 37% and 44% (P = .002), and 13% and 19% (P = .003), respectively. RSA amplitude did not show statistically significant results in the pathologic group (P. .13). LCA yielded the highest sensitivity (71%-93%), whereas RSA yielded the highest specificity (87%-100%). Conclusion: Semiautomatic four-dimensional CT analysis of the wrist during radioulnar deviation is technically feasible and reproducible for evaluation of carpal kinematic abnormalities.
Whilst the detailed X-ray features of thoracic manifestations of sarcoidosis are now clearly defined and known by most radiologists, the same does not apply to osteoarticular and muscular features of the disease, which may however raise major diagnostic problems, either because they are the presenting features of the disease (7% of cases) or because they develop during its course. The bony lesions of sarcoid dactylitis (classical Perthes-Jüngling disease) are very characteristic and well known. Many other presentations of bone and bone marrow sarcoidosis may however raise major diagnostic difficulties, particularly uni- or multifocal osteolytic and sclerotic forms of the disease. The articular manifestations of sarcoidosis are difficult to distinguish from those of the other inflammatory and degenerative arthropathies. The muscular lesions in sarcoidosis are generally clinically silent and therefore often missed. MRI has shown them to be very common in active sarcoidosis. Acute forms carry a good prognosis whereas chronic lesions are a presenting feature of multi-organ sarcoidosis. Finally, clinicians should always think about the possibility of an iatrogenic origin for musculoskeletal abnormalities seen in sarcoidosis, particularly those related to corticosteroid therapy.
The identification of an early and steep enhancement with short time to peak and a short delay between the arterial and nidus peaks on MR perfusion in the postoperative setting is highly indicative of an osteoid osteoma recurrence. Key points • Magnetic resonance perfusion is becoming widely used for several tumours. • MR perfusion measurements correlate well with osteoid osteoma-related symptoms. • MR perfusion has high diagnostic performance for osteoid osteoma recurrence. • MR perfusion can improve the diagnostic confidence of osteoid osteoma recurrence.
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