Purpose: To measure the elastic properties of the vastus lateralis (VL), vastus medialis (VM), and sartorius (Sr) muscles using magnetic resonance elastography (MRE).
Materials and Methods:To obtain a normative database of the aforementioned muscles, oblique scan directions were prescribed passing through each muscle. Shear waves were induced into the muscles using pneumatic and mechanical drivers at 90 and 120 Hz, respectively. These drivers were attached to the distal end of the right thigh with the knee flexed at 30°. The foot was placed in a footplate containing MR-compatible load cells to record the force during a contraction (10% and 20% of the maximum voluntary contraction).
Results:The shear moduli measured at rest in the VL (N ϭ 12), VM (N ϭ 14), and Sr (N ϭ 13) were 3.73 Ϯ 0.85 kPa, 3.91 Ϯ 1.15 kPa, and 7.53 Ϯ 1.63 kPa, respectively. The stiffness of both vasti increased with the level of contraction, while the stiffness of the Sr remained the same.
Conclusion:The MRE technique was able to approximate the stiffness of different thigh muscles. Furthermore, the wave length was sensitive to the morphology (unipennate or longitudinal) and fiber composition (type I or II) in each muscle.
Up to 11% of chondrosarcomas may undergo regional anaplastic change, resulting in a high-grade noncartilaginous sarcoma arising within a typically low-grade chondrosarcoma. Known as dedifferentiated chondrosarcomas, these tumors are highly malignant with a very poor prognosis. The most important factor affecting survival is an accurate preoperative diagnosis. Therefore, the ability to predict the possibility of dedifferentiation in a malignant cartilage tumor on the basis of imaging findings is critical to ensure adequate tumor sampling at the time of biopsy. Imaging findings at radiography, computed tomography (CT), and magnetic resonance (MR) imaging in 174 patients with dedifferentiated chondrosarcoma were reviewed to determine whether there are radiologic features that can help predict dedifferentiation. On approximately one-third of the radiographs, one-third of the MR images, and one-half of the CT scans, the tumors demonstrated bimorphic features (ie, distinctly different tumor features juxtaposed within the lesion), most frequently a dominant lytic area adjacent to a mineralized tumor at radiography and a large, unmineralized soft-tissue mass associated with an intraosseous chondroid-containing tumor at CT and MR imaging. In the initial evaluation of patients with a primary bone tumor, thorough evaluation of the radiologic features of the entire tumor is critical.
Musculoskeletal injury is an uncommon but usually self-limited complication of vaccine administration. We present a case of progressive inflammatory monoarthritis of the shoulder characterized by bone erosion, bursitis, and severe synovitis caused by an influenza vaccine administered to the ipsilateral deltoid region. Clinical symptoms began within 2 hours of vaccination, with progressive decline in function over 6 weeks. Magnetic resonance imaging examinations performed 5 months apart demonstrated progressive erosive changes of the greater tuberosity, rotator cuff injury, and extensive enhancing synovitis of the glenohumeral joint and subacromial/subdeltoid bursa. After the exclusion of septic arthritis and osteomyelitis, the patient underwent nonoperative treatment and experienced near-complete recovery at 32 months. Although inflammatory arthritis of the shoulder following vaccination is rare, there have been previous reports of it. Clinicians and radiologists need to be aware of this potential complication to ensure an accurate diagnosis.
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