• Diffusion-based Heterogeneity Models in Magnetic Resonance Imaging for Characterization of Brain Tumors: An Introductory Study

      Goettl, Christopher; The University of Arizona College of Medicine - Phoenix; Karis, John (The University of Arizona., 2012-04-30)
      Recently developed diffusion-based magnetic resonance (MR) protocols have proven useful in assessing the heterogeneity of water diffusion in neural tissues, including brain tumors1. Based on theoretical increase in tumor cell heterogeneity compared to healthy brain2, these emerging imaging modalities offer several potentially useful applications, such as in identifying tumor margins, establishing tumor type and grade, and for differentiating tumor recurrence from post-treatment effect. In this study an introductory subset of five patients were scanned using a multi b-value Diffusion-Weighted Image (DWI) sequence, fitted with two previously described higher-order diffusion models. The first utilized a stretched exponential model (α-DWI)3; the second applied a cumulant expansion model (Diffusional Kurtosis Image, DKI)4. These models quantified water diffusion heterogeneity using the fitted parameters α and Kapp, respectively. The intent of this project was to gauge the potential utility of these MR models to apply diffusion heterogeneity information for characterization of brain tumors. Early results confirmed initial 6 hypotheses for high-grade gliomas, that (1) diffusion heterogeneity appeared greater in tumoral regions than in surrounding tissue, (2) high-grade tumors exhibited a relatively more heterogeneous diffusion pattern (lower α and higher K app) compared with low-grade glioma, and (3) the metastatic tumor had unique diffusion behavior compared to the primary tumors. Overall, this introductory study generally supports the potential ability of higher-order diffusion heterogeneity models to characterize brain tumors. More detailed investigation of this application across a larger subset of patients and tumor types may be beneficial.
    • MRI Findings Common to Infantile Hemangiomas

      Patel, Nirav; The University of Arizona College of Medicine - Phoenix; O'Haver, Judith; Price, Harper; Towbin, Richard (The University of Arizona., 2012-05-02)
      Background: Infantile hemangiomas (IH) are the most common vascular tumors of infancy. Children may have Magnetic Resonance Imaging (MRI) to establish or confirm the diagnosis or to further evaluate lesions that do not improve with treatment. Objective: Describe specific MRI findings common to infantile hemangiomas. Compare the imaging diagnosis with the clinical diagnosis of IH to determine diagnostic accuracy. Methods: A descriptive retrospective chart review on a convenience sample. Twenty-six patients had a total of 31 MR studies in the group. From these 31 studies, 16 also had magnetic resonance angiography (MRA). Results: Clinical diagnosis matched imaging diagnosis 96.8% of the time. Findings from imaging of the infantile hemangiomas included increased signal intensity on T2-weighted sequences (96.8%), isointense or decreased signal with T1-weighted sequences (83.9%) and moderate to marked contrast enhancement (78.5%). Lesions appeared to be high flow (64.5%), demonstrated lobulation (58.1%), and displayed central, low signal intensity dots on T2-weighted sequences (54.8%). In contrast, cystic spaces, intralesional DIC, phleboliths, focal intralesional inhomogenities, septation, edema, fat stranding, aneurysms, venous ectasia, and shunts were not features regularly seen in imaging of IHs in this study. Limitations: Small sample size on a convenience sample based at one institution. Conclusion: There are specific features to infantile hemangiomas on MR imaging that can be used for aid in diagnosis.