Arterial Spin-Labeling in the Assessment of Pediatric Nontraumatic Orbital Lesions

Distribution of ADC ratios (n = 21) by diagnostic subgroups. Lesion-to-cortex ADC ratios were calculated by dividing the lesion mean ADC by the ipsilateral temporal cortex mean ADC (both directly obtained for each patient by drawing an ellipsoid ROI over an area similar to that used for ASL measurements, taking care to avoid volume averaging with adjacent structures, particularly fat and bone). The distinct subportions of infectious processes (eg, abscessed areas with characteristic diffusion restriction and denser tissular inflammatory parts, cellulitis) were assessed separately. Colors correspond to the ASL perfusion profile groups presented in Fig 1 (pattern 1: blue; pattern 2: orange; pattern 3: red).

Summary algorithm for radiologic interpretation. There are 3 distinct patterns derived from ASL perfusion analysis: Pattern 1 (blue) corresponds to benign masses presenting homogeneous low lesion blood flow; pattern 2 (orange) describes heterogeneous iso- or hyperperfused lesions, including malignancies; pattern 3 (red) is characteristic of hemangiomas (benign vascular lesions), presenting specific homogeneous and very intense hyperperfusion. ADC assessment within pattern 2 contributed to differentiating malignant tumors (presenting diffusion restriction) from benign lesions like orbital cellulitis (with increased diffusion). Lymphatic malformations (pattern 1) and IHs (pattern 3), two frequent vascular orbital anomalies (underlined) in pediatric population, presented with very distinct ASL perfusion homogeneous profiles.