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Peripelvic and periureteric areas are frequently overlooked in the imaging evaluations of the urinary system on computed tomography and magnetic resonance imaging. Several neoplastic and non-neoplastic disorders and diseases including lipomatosis, angiomyolipoma and angiolipomatous proliferation, vascular lesions, lymphangiomatosis, Rosai-Dorfman disease, Erdheim-Chester disease, extramedullary hematopoiesis, IgG4-related disease, lymphoma, mesenchymal tumors, trauma, and Antopol-Goldman lesion may involve these areas. Differentiation of these benign or malignant pathologies among themselves and from primary renal pathologies is of utmost importance to expedite the triage of patients for correct treatment approach. In this article, we aim to increase the awareness of the imaging specialists to the typical and atypical imaging features of the entities affecting these areas.

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Primary involvement of leptomeninges with melanocytic tumours is rarely seen and its diagnosis is challenging. Here we summarise two cases of primary leptomeningeal melanomatosis presenting as subacute meningitis. Both cases have pleocytosis and high protein on cerebrospinal fluid analysis, and demonstrated atypical cells on cytology. On magnetic resonance imaging, there is diffuse leptomeningal thickening and avid enhancement of intracranial and intraspinal leptomeninges. One of them demonstrates T1 shortening due to magnetic effects of melanin, the other case is amelanotic and shows hypointensity on precontrast T1-weighted images. Both cases can be diagnosed with biopsy. In conclusion, these cases highlight the importance of the correct interpretation of cytological and magnetic resonance imaging findings in patients with atypical findings.

Objectives: Diffusion weighted imaging (DWI) has become important for orbital imaging. However, the echoplanar imaging (EPI) DWI has inherent obstacles due to susceptibility to magnetic field inhomogeneities. We conducted a comparative study assessing the image quality of orbits in a patient cohort with uveal melanoma (UM). We hypothesized that single shot turbo spin echo (ssTSE) DWI would have better image quality in terms of less distortion and artifacts and yield better tissue evaluation compared to ssEPI-DWI. Methods: ssEPI-DWI and ssTSE-DWI of orbits were obtained from 50 patients with uveal melanoma who were prospectively enrolled in the study. Distortion ratio (DR), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), diffusion signal properties, and apparent diffusion coefficient (ADC) values were collected and compared between ssEPI-DWI and ssTSE-DWI. Two reviewers evaluated and compared the geometric distortion, susceptibility and ghosting artifacts, resolution, demarcation of ocular mass, and overall quality. Results: A higher DR was found in ssEPI-DWI compared to ssTSE-DWI (p < 0.001). SNR and CNR were lower for the temporal lobe cortex (p ≤ 0.004), but higher for melanoma in ssEPI-DWI than ssTSE-DWI (p ≤ 0.037). Geometric distortion and artifacts were more common in ssEPI-DWI (p < 0.001). Resolution (p ≤ 0.013) and overall quality (p < 0.001) were better in ssTSE-DWI. Ocular masses were demarcated better on ssEPI-DWI (p ≤ 0.002). Significant negative correlations between T1 and T2 signal intensities (r = −0.369, p ≤ 0.008) and positive correlations between T2 and both DWI signal intensities (r = 0.686 and p < 0.001 for ssEPI-DWI, r = 0.747 and p < 0.001 for ssTSE-DWI) were revealed. Conclusion: With less geometric distortion and susceptibility artifacts, better resolution, and overall quality, ssTSE-DWI can serve as an alternative to ssEPI-DWI for orbital DWI. Advances in knowledge: ssTSE-DWI can be a better alternative of diffusion imaging of orbits with less susceptibility artefact and geometric distortion compared to ssEPI-DWI.

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BACKGROUND AND PURPOSE: Synthetic MRI enables the generation of various contrast-weighted images and quantitative data in a reasonable scanning time. We aimed to use synthetic MRI to assess the detection and underlying tissue characteristics of focal areas of signal intensity and normal-appearing brain parenchyma and morphometric alterations in the brains of patients with neurofibromatosis type 1. MATERIALS AND METHODS:Conventional MR imaging and synthetic MRI were prospectively obtained from 19 patients with neurofibromatosis type 1 and 18 healthy controls. Two neuroradiologists independently evaluated focal areas of signal intensity on both conventional MR imaging and synthetic MRI. Additionally, automatically segmented volume calculations of the brain in both groups and quantitative analysis of myelin, including the focal areas of signal intensity and normal-appearing brain parenchyma, of patients with neurofibromatosis type 1 were performed using synthetic MRI. RESULTS:The comparison of conventional MR imaging and synthetic MRI showed good correlation in the supratentorial region of the brain (k ¼ 0.82-1). Automatically segmented brain parenchymal volume, intracranial volume, and GM volumes were significantly increased in the patients with neurofibromatosis type 1 (P , .05). The myelin-correlated compound, myelin fraction volume, WM fraction volume, transverse relaxation rate, and longitudinal relaxation rate values were significantly decreased in focal areas of signal intensity on myelin and WM maps (P , .001); however, GM, GM fraction volume, and proton density values were significantly increased on the GM map (P , .001).CONCLUSIONS: Synthetic MRI is a potential tool for the assessment of morphometric and tissue alterations as well as the detection of focal areas of signal intensity in patients with neurofibromatosis type 1 in a reasonable scan time.