SWI(Susceptibility Weighted Imaging) in infiltrative glial tumors grading

Objective: Tumor staging not only guides the treatment strategy but also provides valuable prognostic information. Although histopathological examination represents the gold standard method for the determination of the tumor type and staging, radiological imaging studies are commonly used pre-operatively for staging. In this study, SWI was used for this purpose. Materials and Methods: The SWI sequences in pre-operative MRI images were retrospectively assessed in a total of 67 patients (mean age, 36.7 years; age range, 4-79 years; 29 female, 38 male) who were diagnosed with a glial tumor based on histopathological examination. The numbers of punctate ITSS in SWI sequence of the tumors were determined by two separate radiologists on a consensus based approach who were blinded to pathological diagnoses. Lesions with no ITSS were staged as ITSS Stage 0, while those having 1-5, 6-15, >15 ITSS were categorized as ITSS Stage 1, ITSS Stage 2, and ITSS Stage 3, respectively. Susceptible lesions not classified as ITSS, "non-punctate lesions with blurred margins" and diffuse lesions were categorized as >15. ITSS stages were compared with the results of histopathological staging and diagnosis. Also, the general intensity of the tumor tissue was classified as iso-intense, hypo-intense, or hyper-intense in contrast with the surrounding normal tissue in SWI sequences; also homogeneity or heterogeneity of the intensity was recorded. Results: The sensitivity, specificity, negative predictive value, and positive predictive value of the presence of ITSS in terms of differentiating high and low stage glial tumors were 97.6%, 88%, 95.65%, and 93.18%, respectively. On the other hand, intensity of the tumors in SWI did not exhibit a significant correlation with the tumor stage. Conclusion: In glial tumors, while presence of ITSS is indicative of high stage tumors, its absence is associated with low stage tumors. These data suggest that the presence rather than the number of ITSS yields more information on the stage of this type of tumor.