MDCT and US of intrathoracic extrapleural space soft tissue-containing lesions: US extrapleural fat sign and MDCT fat ghost ribs sign

Purpose: The purpose of this study was to review the normal anatomy of the extrapleural space, its soft tissue-containing lesions, and to illustrate the extrapleural fat sign with Multidetector Computed Tomography (MDCT) and Ultrasound (US), which was never described so far.

Materials and methods: The study includes 28 patients. 24 with histologically or surgically proven extrapleural soft tissue-containing lesions and 4 pleural lesions. Six patients underwent unenhanced MDCT of the chest, while 22 patients had a contrast-enhanced chest MDCT. Furthermore, 9/28 patients underwent Thoracic Ultrasound after MDCT. The lesions included 12 extrapleural hematomas (8 post-traumatic and 4 from other causes), 3 extrapleural lesions from pleural infection extension, 9 extrapleural lesions from metastases. MDCT multiplanar Minimum Intensity Projection (MinIP) reconstructions were always obtained; T-US and MDCT findings were correlated.

Results: Among 9 patients who underwent T-US 4/9 showed the "UltraSonography fat extrapleural sign". Among 24 patients who underwent chest MDCT all show the well-known computed tomography (CT) extrapleural fat sign and new auxiliary (MDCT) findings that serve to "strengthen" the diagnosis of correct intrathoracic extrapleural space attribution of lesion.

Conclusions: MDCT with its multiplanar capabilities and post-processing MinIP reconstructions and Thoracic US play a prominent role in the identification and characterization of abnormalities of the frequently overlooked extrapleural space. In conjunction with main CT thoracic findings they provides relevant information in the diagnostic process and correct management.