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E1074. Challenges in Interpretation of MRI Examinations Without Radiographic Correlation: Pearls and Pitfalls to Avoid
Authors
  1. Ryan Richter; San Antonio Military Medical Center; Wilford Hall Ambulatory Surgical Center
  2. Douglas Byerly; Uniformed Services University Health Sciences; Wilford Hall Ambulatory Surgical Center
  3. Liem Mansfield; Shannon Medical Center
  4. Donald Schultz; San Antonio Military Medical Center
Background
Nearly 40 million MR examinations were performed in the United States in 2016; roughly 20% were of the extremities. It is not uncommon for radiologists to be faced with interpretation of MR examinations without radiographic correlation; however, lack of comparison radiographs may lead to misinterpretation, additional unnecessary imaging, or unnecessary treatments. Radiographs have been shown to be essential to MRI interpretation in 61-75% of cases in one study. (1) In this educational exhibit, we will present a variety of conditions in which radiographs are helpful in the interpretation of MRI examinations while focusing on imaging pearls and pitfalls to avoid when radiographs are not available. We will discuss the findings that can be expected if comparison radiographs were available.

Educational Goals / Teaching Points
Review common conditions encountered on musculoskeletal MRI examinations in which comparison radiographs are helpful. These conditions will be grouped into six categories: arthropathy, crystalline deposition disease, metabolic disorders, trauma, infection and tumor (osseous and soft tissue) or tumor-like lesions. Review the pathogenesis of these entities, which lead to the sometimes confusing or easily misinterpreted MRI findings. Provide specific case examples of pathologic processes focusing on the challenging MR imaging features and the corresponding radiographic findings. Present important clinical factors, imaging pearls and pitfalls to avoid when interpreting MRI without a comparison radiograph as well as emphasize examples when radiographs should be obtained if not available.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The strengths of MR imaging are excellent soft tissue contrast resolution, multiplanar imaging, and the lack of ionizing radiation. However, it is difficult to detect calcification and gas on MR imaging. Radiography is helpful in MR interpretation since calcification and gas are clearly detectable on radiographs. Some bone lesions may have misleading aggressive appearance on MR imaging, such as stress fracture, osteoid osteoma, chondroblastoma, and eosinophilic granuloma, which have more innocuous appearance on radiography.

Conclusion
Radiologists are commonly faced with interpreting MR examinations in the absence of comparison radiographs. Radiographs have been shown to be helpful in the interpretation of MR examinations in a majority of cases. There are numerous processes to include various arthropathies, infection, trauma, and neoplasm, which may have nonspecific, easily overlooked, or confusing features on musculoskeletal MRI examinations. Comparison radiographs, when available, can allow for a more specific differential diagnosis, more clearly delineate findings that may be subtle on MRI, and decrease the likelihood of further unnecessary work-up. Knowledge of these entities and their sometimes subtle or confusing MR appearance is essential to successful interpretation of musculoskeletal MRI.