Diffusion-weighted MRI for distinguishing non-neoplastic cysts from solid masses in the mediastinum: problem-solving in mediastinal masses of indeterminate internal characteristics on CT
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To evaluate the usefulness of diffusion-weighted (DW) magnetic resonance images for distinguishing non-neoplastic cysts from solid masses of indeterminate internal characteristics on computed tomography (CT) in the mediastinum.
We enrolled 25 patients with pathologically proved mediastinal masses who underwent both thoracic CT and magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI). MRI was performed in patients with mediastinal masses of indeterminate internal characteristics on CT. Two thoracic radiologists evaluated the morphological features and quantitatively measured the net enhancement of the masses at CT. They also reviewed MR images including unenhanced T1- and T2-weighted images, gadolinium-enhanced images and DW images.
The enrolled patients had 15 solid masses and ten non-neoplastic cysts. Although the morphological features and the extent of enhancement on CT did not differ significantly between solid and cystic masses in the mediastinum (P > 0.05), non-neoplastic cysts were distinguishable from solid masses by showing signal suppression on high-b-value DW images or high apparent diffusion coefficient (ADC) values of more than 2.5 × 10-3 mm2/s (P < 0.001). ADC values of non-neoplastic cysts (3.67 ± 0.87 × 10-3 mm2/s) were significantly higher than that of solid masses (1.46 ± 0.50 × 10-3 mm2/s) (P < 0.001).
DWI can help differentiate solid and cystic masses in the mediastinum, even when CT findings are questionable.
• Non-invasive diagnosis of non-neoplastic cysts can save surgical biopsy or excision.
• Conventional CT or MRI findings cannot always provide a confident diagnosis.
• Mediastinal masses can be well-characterised with DWI.
• Non-neoplastic mediastinal cysts show significantly higher ADC values than cystic tumours.
• DWI is useful to determine treatment strategy.
KeywordsMediastinal neoplasms Mediastinal cyst Magnetic resonance image Diffusion-weighted imaging (DWI) Apparent diffusion coefficient (ADC)
Apparent diffusion coefficient
Diffusion-weighted MR imaging
Region of interest
C.A. Yi was a guarantor of entire study. C.A. Yi and K.E. Shin developed the design and the organisation of this study, participated in all stages of the study, made the initial interpretation of the study findings, and prepared the first draft of the manuscript. C.A. Yi was responsible for the MRI scanning and had overall responsibility for all MRI features of the study. T.S. Kim and H.Y. Lee researched on references and contributed to manuscript writing. Y.S. Choi, H.K. Kim and J. Kim were responsible for patient enrolment and the management of the clinical data.