Evaluation of mediastinal lymphadenopathy by diffusion weighted MRI : Correlation with histopathological results / Menna Allah Helmy Mohammed Abdelgawad ; Supervised Hoda Ali Abou Youssef , Mahmoud Abdelrahman Elzorkany , Sabah Ahmed Mohamed

Thesis (Ph.D.) - Cairo University - Faculty of Medicine - Department of Chest Diseases and Tuberculosis

Background: Diffusion weighted imaging (DWI), a well known MRI-technique in neuroradiology, and has shown its potential to be a reliable non-invasive imaging technique for tissue characterization. DWI exploits the random motion of water in the targeted tissue, which reflects the tissue specific diffusion capacity. Thus, the diffusion capacity can be used for tissue characterization. In biologic tissues, the diffusivity of water molecules is confined by the intra-cellular and inter-cellular spaces. Hypercellular tissue, such as malignant tumours, results in decreased mobility of water protons and consequently in a restricted diffusion capacity of the tissue. Thus, tumors present with increased signals on DWI and low ADC values. Non-tumoral tissues such as oedema, inflammation, fibrosis, and necrosis are expected to show low cellularity in strong contrast with viable tumour. In these tissues the diffusion capacity is not restricted. This results consecutively in a signal loss on DWI and in a high ADC. (Herneth et al, 2010) Differential diagnosis of mediastinal-hilar lymphadenopathy is an issue of debate for radiologists, especially in cases suspicious for lymphoma versus sarcoidosis. CT has been widely used but is not sufficient for malignant-benign differentiation.Recently, diffusion-weighted imaging with Magnetic Resonance was introduced which could improve the diagnostic accuracy in the differential diagnosis between benign and malignant nodes in the mediastinum. (Perrone et al, 2011)

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