Soft tissue mycetoma: "Dot-in-circle" sign on magnetic resonance imaging.

A 36-year-old Mexican female with a slowly growing foot mass was referred to orthopedic surgery clinic for further evaluation. Foot magnetic resonance imaging revealed an infiltrative soft tissue mass along the dorsal aspect of the fourth metatarsal. T2-weighted images revealed multiple central low-signal "dots" surrounded by areas of bright signal intensity, known as the "dot-in-circle" sign, which is highly specific for mycetoma. Surgical biopsy confirmed the diagnosis of bacterial mycetoma in this patient. Mycetoma can lead to progressive deformity and loss of function, as well as possible limb amputation in the case of delayed diagnosis or misdiagnosis. The "dot-in-circle" sign on magnetic resonance imaging can assist in rendering a final diagnosis and distinguish mycetoma from other etiologies of a soft tissue mass, such as a sarcoma or benign soft tissue lesions.

Radiation dose reduction for musculoskeletal computed tomography of the pelvis with preserved image quality.

OBJECTIVE: To analyze the impact of pelvic computed tomography (CT) technique optimization on estimated dose and subjective and objective image quality. MATERIALS AND METHODS: An institutional review board (IRB)-approved retrospective records review was performed with waived informed consent. Five CT scanners (various manufacturers/models) were standardized to match the lowest dose profile on campus via subjective assessment of clinical images by experienced musculoskeletal radiologists. The lowest dose profile had previously been established through image assessment by experienced musculoskeletal radiologists after a department-wide radiation dose reduction initiative. A consecutive series of 60 pre- and 59 post-optimization bony pelvis CTs were analyzed by two residents, who obtained signal-to-noise ratio for femoral cortex and marrow, gluteus medius muscle, and subcutaneous and visceral fat in a standardized fashion. Two blinded attending radiologists ranked image quality from poor to excellent. RESULTS: Pre- and post-optimization subjects exhibited no difference in gender, age, or BMI (p > 0.2). Mean CT dose index (CTDIvol) and dose-length product (DLP) decreased by approximately 45%, from 39± 14 to 18± 12 mGy (p < 0.0001) and 1,227± 469 to 546± 384 mGy-cm (p < 0.0001). Lower body mass index (BMI) was associated with a larger dose reduction and higher BMI with higher DLP regardless of pre- or post-optimization examination. Inter-observer agreement was 0.64-0.92 for SNR measurements. Cortex SNR increased significantly for both observers (p < 0.02). Although qualitative image quality significantly decreased for one observer (p < 0.01), adequate mean quality (3.3 out of 5) was maintained for both observers. CONCLUSION: Subjective and objective image quality for pelvic CT examination remains adequate, despite a substantially reduced radiation dose.

Magnetic Resonance Neurography of the Pelvic Nerves.

Chronic pelvic pain syndrome is commonly caused by nerve injury, inflammation, or entrapment. Owing to the complex anatomy and branching patterns of pelvic nerves, pelvic neuropathies are often difficult to illustrate and diagnose. High-resolution 3-T magnetic resonance neurography is a promising technique for the evaluation of peripheral neuropathy. In this article, the authors discuss the normal anatomy of major pelvic nerves, technical considerations of high-resolution imaging, and normal and abnormal imaging appearances with relevant case examples.

Role of Diffusion Weighted Imaging in Musculoskeletal Infections: Current Perspectives.

Accurate diagnosis and prompt therapy of musculoskeletal infections are important prognostic factors. In most cases, clinical history, examination and laboratory findings help one make the diagnosis, and routine magnetic resonance imaging (MRI) is useful to identify the extent of the disease process. However, in many situations, a routine MRI may not be specific enough especially if the patient cannot receive contrast intravenously, thereby delaying the appropriate treatment. Diffusion-weighted imaging (DWI) can help in many such situations by providing additional information, accurate characterization and defining the extent of the disease, so that prompt treatment can be initiated. In this article, we illustrate the imaging findings of the spectrum of musculoskeletal infections, emphasizing the role of DWI in this domain. KEY POINTS: • Abscess in background cellulitis is detected on DWI. • Infectious tenosynovitis shows diffusion restriction as compared to mechanical tenosynovitis. • Pyomyositis with abscess can be differentiated from diabetic myonecrosis on DWI. • Intraosseous abscess is bright on DWI versus devitalized tissue, sequestrum and air. • DWI can be used to differentiate spine infection from simple Modic changes.