Purpose To assess the added value of contrast-enhanced (CE) MR sequences (static CE-MR sequences, dynamic CE-MR sequences) to noncontrast enhanced MR sequences (non-CE-MR sequences) including T1, fluid-sensitive, and diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping for characterizing “indeterminate” soft tissue masses (STMs) as benign or malignant. Materials and Methods Thirty-nine patients with indeterminate STMs (27 benign, 12 malignant) underwent 3 Tesla MRI with conventional non-CE-MR sequences (T1-weighted, fluid-sensitive), DWI (b-values 50, 400, 800, ADC mapping), dynamic CE-MR sequences (7-s time resolution), and static CE-MR sequences. Two readers independently reviewed imaging in four sessions (conventional non-CE-MR sequences alone, conventional+DWI/ADC, conventional+DWI/ADC+static CE-MR sequences, conventional+DWI/ADC+static CE-MR sequences dynamic CE-MR sequences). Readers recorded the potential of malignancy at each session; reader diagnostic performance (receiver operating characteristics analysis) and inter-observer variability (weighted kappa [k]) were determined. Results Diagnostic performance for distinguishing benign and malignant STMs was highest with the addition of dynamic CE-MR sequences (reader 1, area under the curve [AUC] 0.91; reader 2, AUC 0.88). The diagnostic performance of static CE-MR sequences (reader 1, AUC 0.86; reader 2, AUC 0.84) was not superior to non-CE-MR sequences with DWI (reader 1, AUC 0.88; reader 2, AUC 0.8). Interobserver agreement was: k = 0.82 (static CE-MRI), k = 0.79 (dynamic CE-MRI), k = 0.53 (non-CE-MR sequences without DWI), and k = 0.63 (with DWI). Conclusion Non-CE-MR sequences offer similar diagnostic performance to imaging with the addition of static CE-MR sequences, but their interobserver reliability is lower. The addition of dynamic CE-MR sequences offers the higher diagnostic performance for distinguishing benign and malignant indeterminate STMs. Level of Evidence: 3 J. Magn. Reson. Imaging 2017;45:390–400.
The World Health Organisation (WHO) classification categorises musculoskeletal soft tissue tumours (STT) based on their similarity to normal adult tissue. The most recent WHO classification provides an updated scheme that integrates biological behaviour as a distinguishing feature in each subcategory; STTs are further subdivided as benign, intermediate (locally aggressive or rarely metastasising), and malignant. Although malignant STTs are infrequent in routine orthopaedic radiology practice, musculoskeletal radiologists must be familiar with the imaging appearance of malignant STTs and distinguish them from their benign counterparts for appropriate management. Magnetic resonance imaging (MRI) is the ideal modality for the detection, characterisation, and local staging of STT. This review will discuss the most recent updates to the WHO classification of STT that are relevant to radiologists in a routine clinical practice with MRI correlation. The utility of advanced MRI sequences such as diffusion weighted imaging, dynamic contrast enhanced sequences, and magnetic resonance spectroscopy to provide insight into the biological behaviour of various STTs is highlighted.
Whole-body MRI (WB-MRI) is increasing in clinical acceptance and utilization for a range of indications. WB-MRI is currently an established screening tool for children and adults at high risk of developing malignancy, with the strongest supporting evidence in patients with Li-Fraumeni syndrome. WB-MRI has been added to professional society guidelines for staging disease in patients with certain malignancies including multiple myeloma and has been proposed as a technique to screen for metastatic disease in patients with visceral malignancies including prostate cancer and breast cancer. Emerging data support the utility of WB-MRI in children with malignancies such as Ewing sarcoma, in adults with myxoid liposarcoma, and in pregnant patients with occult or newly detected malignancy. WB-MRI can further help evaluate disease extent and treatment response in patients with nononcologic conditions such as chronic nonbacterial osteomyelitis, myopathy, inflammatory arthritis, and fever of unknown origin. This AJR Expert Panel Narrative Review summarizes available evidence and recommendations supporting the clinical applications of WB-MRI. This article also highlights limitations, barriers, and controversies associated with utilization of WB-MRI in routine clinical practice.
e13584 Background: Symptomatic peripheral nerve sheath tumors (PNSTs) or those with features concerning for malignancy may require surgical intervention. However, the rate of symptomatic progression or malignant conversion is not known. Methods: An institutional review of the radiology database was conducted for terms relevant to the differential of PNSTs (Jan 1 2000 - Jan 1 2017). Syndromic cases and cranial lesions were excluded. The proportion and rate of tumor growth in the observation cohort was calculated. Predictors of successful long-term observation were identified using multivariate logistic regression. Chi-squared test was used to compare intraoperative blood loss, neurological deficit, and length of stay between upfront and delayed surgery cohorts to determine whether the latter was associated with additional risk to patients. Results: 265 patients were identified: 117 (44%) were resected upfront. Pain was the indication for surgery in the majority (76/117, 65%).148/265 (56%) were initially assigned to observation with 24 (16%) ultimately requiring surgery. Peripheral location and symptomatic presentation were independent predictors for upfront surgery (P < 0.01). Only 41/124 (33%) tumors in the observation cohort had progression at mean follow-up 32 months. Those with growth grew 2.2mm/year. In the observation cohort, incidental presentation (85/124, 68%) and location within spinal canal (84/124, 68%) were most common. In the 24 tumors requiring surgery after initial observation, symptom progression (11/24, 46%) and peripheral nerve location (9/24, 38%) were most common. Among 167 histopathological specimens (141 surgical and 26 biopsy samples), 146 (87%) were schwannomas. Only one malignant tumor was identified, which was resected upfront. There was no malignant conversion in the observation cohort. There were no differences in adverse events between upfront and delayed surgical intervention. Conclusions: Among non-syndromic PNSTs, asymptomatic lesions can often be managed with surveillance as there was no malignant conversion in lesions recommended for observation and many lesions did not grow. A preliminary decision algorithm for isolated PNST is proposed.
Peripheral nerve pathology can be detected on high-resolution MRI on the basis of primary or secondary findings. Primary findings of nerve pathology include alterations in signal, course, and caliber; secondary findings include skeletal muscle denervation. Although two-dimensional (2D) MRI sequences comprised of a combination of fluid-sensitive and non–fat-suppressed anatomical sequences can detect changes in nerve size, signal, course, and architecture, three-dimensional (3D) imaging can play an important role in the detection and characterization of nerve pathology including caliber changes at typical compression sites, anomalous course, and nerve discontinuity. This article discusses the benefits of 3D MRI with respect to lower limb neuropathies. The article also reviews the normal anatomy of the nerves in the lower extremity from the hip joint to the foot, and it illustrates common causes and the imaging appearance of lower limb peripheral neuropathy.
