3D Visual Guide to Lines and Stripes in Chest Radiography.

Chest radiography continues to be the first-line imaging modality for evaluation of the chest. Interpretation is based on the understanding of complex three-dimensional (3D) structural relationships, which are translated into a two-dimensional (2D) plane. These 2D projections form multiple "lines and stripes" on chest radiographs, representing the interfaces between the pulmonary parenchyma, pleura, and normal mediastinal structures. Given the subtlety of overlying tissue and the need to mentally synthesize planar images into three dimensions, structural relationships may be difficult to appreciate. An understanding of these relationships forms the basis of recognizing pathologic conditions and providing an accurate differential diagnosis, which can assist in targeted appropriate further workup. On a 2D radiograph, this means recognizing the normal lines and stripes as well as their appearance when effaced or displaced. Once this abnormality is identified, a focused differential diagnosis can be generated, which can be further narrowed on the basis of other factors, such as patient history or ancillary findings. Three-dimensional cinematic rendering is an innovative tool that can help radiologists grasp these anatomic relationships and discern subtle findings at radiography. This technique allows improved visualization of structures such as the pleura that are difficult to appreciate with traditional imaging modalities. The authors provide an updated review of lines and stripes on chest radiographs, using 3D cinematic rendering as a teaching tool. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Pediatric solid intra-articular masses of the knee: prevalence, imaging features and etiologies.

BACKGROUND: The etiologies of pediatric solid intra-articular soft-tissue masses are not well described and can present diagnostic dilemmas. OBJECTIVE: Our hypothesis was that these entities have a limited differential diagnosis and are mostly benign. MATERIALS AND METHODS: We reviewed knee magnetic resonance imaging (MRI) scans performed at our tertiary care institution between 2001 and 2019 (n=3,915). Our inclusion criterion was knee MRI with a solid intra-articular soft-tissue mass. Our exclusion criteria were cases with no masses or non-solid intra-articular lesions with clear radiologic diagnoses. Multiple radiologic characteristics were evaluated. Radiologic and histological diagnoses were collected when available. Cases without histology were assigned a suspected diagnosis. RESULTS: Twenty-five out of 3,915 (<1%) cases met the inclusion/exclusion criteria. Twenty patients underwent biopsy. Patient age ranged from 1 to 19 years with a mean age of 12 years. Lesion size ranged from 1 to 7 cm with a mean of 3.3 cm. The top three histological diagnoses were pigmented villonodular synovitis (PVNS) (7/20, 35%), vascular malformations (2/20, 10%) and inflammatory arthritis (2/20, 10%). There was one malignant case of synovial sarcoma (1/20, 5%). Of the five cases without biopsies, PVNS was the most common diagnosis (3/5, 60%). Five out of 10 (50%) PVNS cases were focal and 5/10 (50%) were multifocal. All PVNS cases (10/10, 100%) had hypointense signal on T2. CONCLUSION: Solid intra-articular soft-tissue masses of the knee in children are rare, with a prevalence of <1% in our study. The vast majority are benign with PVNS being the most common diagnosis.