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Wu Z.,McMaster University | Li S.,Capital Medical University | Lei J.,Tianjin Huan Hu Hospital | An D.,Capital Medical University | And 3 more authors.
American Journal of Neuroradiology | Year: 2010

BACKGROUND AND PURPOSE: SWI is an MR imaging technique that is very sensitive to hemorrhage. Our goal was to compare SWI and CT to determine if SWI can show traumatic SAH in different parts of the subarachnoid space. MATERIALS AND METHODS: Twenty acute TBI patients identified by CT with SAH underwent MR imaging scans. Two neuroradiologists analyzed the CT and SWI data to decide whether there were SAHs in 8 anatomical parts of the subarachnoid space. RESULTS: Fifty-five areas with SAH were identified by both CT and SWI. Ten areas were identified by CT only and 13 by SWI only. SAH was recognized on SWI by its very dark signal intensity surrounded by CSF signal intensity in the sulci or cisterns. Compared with the smooth-looking veins, SAH tended to have a rough boundary and inhomogeneous signal intensity. In many instances, blood in the sulcus left an area of signal intensity loss that had a "triangle" shape. SWI showed 5 more cases of intraventricular hemorrhage than did CT. CONCLUSIONS: SAH can be recognized by SWI through its signal intensity and unique morphology. SWI can provide complementary information to CT in terms of small amounts of SAH and hemorrhage inside the ventricles. Source

Ayaz M.,MRI Institute for Biomedical Research | Ayaz M.,Massachusetts General Hospital | Boikov A.S.,MRI Institute for Biomedical Research | Boikov A.S.,Wayne State University | And 4 more authors.
Journal of Magnetic Resonance Imaging | Year: 2010

Purpose: To monitor changes in the number of cerebral microbleeds (CMBs) in a longitudinal study of healthy controls (HC) and mild-cognitively impaired (MCI) patients using susceptibility weighted imaging (SWI). Materials and Methods: SWI was used to image 28 HC and 75 MCI patients annually at 1.5 Tesla over a 4-year period. Magnitude and phase data were used to visualize CMBs for the first and last scans of 103 subjects. Results: Preliminary analysis revealed that none of the 28 HC had more than three CMBs. In the 75 MCI patients, five subjects had more than three CMBs in both first and last scans, while one subject had more than three bleeds only in the last scan. In five of these six MCI patients, the number of CMBs increased over time and all six went on to develop progressive cognitive impairment (PCI). Of the 130 total CMBs seen in the last scans of the six MCI cases, most were less than 4 mm in diameter. Conclusion: SWI can reveal small CMBs on the order of 1 mm in diameter and this technique can be used to follow their development longitudinally. Monitoring CMBs may be a means by which to evaluate patients for the presence of microvascular disease that leads to PCI. © 2009 Wiley-Liss, Inc. Source

Tang J.,McMaster University | Liu S.,McMaster University | Neelavalli J.,Wayne State University | Cheng Y.C.N.,Wayne State University | And 4 more authors.
Magnetic Resonance in Medicine | Year: 2013

To improve susceptibility quantification, a threshold-based k-space/image domain iterative approach that uses geometric information from the susceptibility map itself as a constraint to overcome the ill-posed nature of the inverse filter is introduced. Simulations were used to study the accuracy of the method and its robustness in the presence of noise. In vivo data were processed and analyzed using this method. Both simulations and in vivo results show that most streaking artifacts inside the susceptibility map caused by the ill-defined inverse filter were suppressed by the iterative approach. In simulated data, the bias toward lower mean susceptibility values inside vessels has been shown to decrease from around 10% to 2% when choosing an appropriate threshold value for the proposed iterative method. Typically, three iterations are sufficient for this approach to converge and this process takes less than 30 s to process a 512 × 512 × 256 dataset. This iterative method improves quantification of susceptibility inside vessels and reduces streaking artifacts throughout the brain for data collected from a single-orientation acquisition. This approach has been applied to vessels alone as well as to vessels and other structures with lower susceptibility to generate whole brain susceptibility maps with significantly reduced streaking artifacts. © 2012 Wiley Periodicals, Inc. Source

Haacke E.M.,Wayne State University | Haacke E.M.,MRI Institute for Biomedical Research | Miao Y.,Dalian Medical University | Liu M.,Wayne State University | And 7 more authors.
Journal of Magnetic Resonance Imaging | Year: 2010

Purpose: To establish a correlation between putative iron content using susceptibility weighted imaging (SWI) phase and T2* weighted magnitude values in the basal ganglia and the thalamus as a function of age in healthy human brains. Materials and Methods: One hundred healthy adults (range, 20-69 years; mean, 43 years) were evaluated for this study using a gradient echo sequence. The original magnitude and high pass filtered phase data were analyzed as proxy variables for iron content in the substantia nigra, red nucleus, globus pallidus, putamen, caudate nucleus, thalamus, and pulvinar thalamus. Each structure was broken into two parts, a high iron content region and a low iron content region. Results: Both magnitude and phase data showed an increase in putative iron content with age. However, the high iron content region revealed two new pieces of information: both the average iron content per pixel and the area of high iron increased with age. Furthermore, significant increase in iron uptake as a function of age was found past the age of 40. Conclusion: A two region of interest analysis of iron is a much more sensitive means to evaluate iron content change over time. Contrary to the current belief that iron content increases level off with age, the putative iron deposition in the high iron content region is seen to increase with age. © 2010 Wiley-Liss, Inc. Source

Hopp K.,University of Saskatchewan | Popescu B.F.Gh.,University of Saskatchewan | McCrea R.P.E.,University of Saskatchewan | Harder S.L.,Loma Linda University | And 5 more authors.
Journal of Magnetic Resonance Imaging | Year: 2010

Purpose: To test the ability of susceptibility weighted images (SWI) and high pass filtered phase images to localize and quantify brain iron. Materials and Methods: Magnetic resonance (MR) images of human cadaver brain hemispheres were collected using a gradient echo based SWI sequence at 1.5T. For X-ray fluorescence (XRF)mapping, each brain was cut to obtain slices that reasonably matched the MR images and iron was mapped at the iron K-edge at 50 or 100 μm resolution. Iron was quantified using XRF calibration foils. Phase and iron XRF were averaged within anatomic regions of one slice, chosen for its range of iron concentrations and nearly perfect anatomic correspondence. X-ray absorption spectroscopy (XAS) was used to determine if the chemical form of iron was different in regions with poorer correspondence between iron and phase. Results: Iron XRF maps, SWI, and high pass filtered phase data in nine brain slices from five subjects were visually very similar, particularly in high iron regions. The chemical form of iron could not explain poor matches. The correlation between the concentration of iron and phase in the cadaver brain was estimated as cFe [μg/g tissue] = 850Δφ + 110. Conclusion: The phase shift Δφ was found to vary linearly with iron concentration with the best correspondence found in regions with high iron content. © 2010 Wiley-Liss, Inc. Source

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