Estimating morphological, diffusion and susceptibility perfusion criteria in discrimination between the perplexing orbital lymphocytic mimickers: Lymphoma versus inflammatory pseudotumor

BACKGROUND Characterization of orbital masses is crucial in the therapeutic strategy planning owing to the fact that patient management greatly differs depending on the dignity of the orbital lesion. However, it is often difficult to differentiate malignant orbital masses from inflammatory pseudo tumors (IPT) due to their comparable clinical presentation with proptosis in terms of most common symptoms. Recently, magnetic resonance imaging (MRI) has become essential for the pre-treatment delineation of orbital tumors. PATIENTS & METHODS Retrospective study for 58 patients being retrieved form available records of Alexandria University Hospital between August 2021 to August 2023, diagnosed with either lymphoma or inflammatory pseudo-tumor. I) Conventional MR protocol had been tailored to include the orbits and brain The standard MR brain acquisition-parameters were as following: a) Rapid scout images, b) multi-planar axial, coronal, sagittal T1 and T2-weighed (with and without STIR), c) Diffusion weighted imaging had been obtained using single shot spin echo planar imaging in axial plane d) Dynamic T2* Perfusion: conventional post-contrast MRI fat-suppressed images are made in axial, sagittal and coronal planes, using same parameters as non-contrast axialT1 images, then subtraction is provided at axial images. Perfusion color maps images are interpreted on workstation. RESULTS Results demonstrated a wide ADC range = 0.53–1.20 x 10 ^− 3 cm ² /sec, with mean value of 0.73. The lymphomas had an ADC range = 0.53–0.82 x 10 ^− 3 cm ² /sec, and mean value is0.6482x 10 ^− 3 cm ² /sec. The IPTs had slightly higher ranges and values, showing ADC range of 0.63–1.20 x 10 ⁻ 3 cm ² /sec, and mean ADC was 0.90x 10 ^− 3 cm ² /sec. ADC differences yielded a statistically significant difference (p < 0.001*). Using a cut-off value of 0.82 x10 ^− 3 cm ² /sec yielded a sensitivity of 60%, 100% specificity, PPV = 100%, NPV = 62%, and accuracy of 76%. Lymphomas showed predominantly hyper-perfused pattern in susceptibility perfusion –seen in 21 lesions (= 91.3%), and only two (= 7.8%) showed iso- perfusion, and none of lymphomas was hypo-perfused. On the contrary, IPTs were predominantly hypo-perfused (n = 31; 88.6%), 2 were iso-perfused (5.7%) and 2 hyper- perfused (= 5.7%). CONCLUSIONS The combination of DWI and DCE MRI can improve diagnostic performance in differentiating lymphoma from in IPT, and are recommended to be used in appropriate clinical setting.