Browsing by Subject "Brain Mapping"

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Assessment of Brain Perfusion and Vascular Compliance with Magnetic Resonance Imaging
(2018-02-28) Li, Yang; Choi, Changho; Lu, Hanzhang; Vinogradov, Elena; Shang, Ty; Liu, Hanli
Brain perfusion is an index that reflects the amount of blood received by the brain tissue in a given time period. Normal brain perfusion ensures that sufficient oxygen, glucose, and other nutrients are delivered to the neurons and glial cells in the brain. While perfusion is relatively static index of brain vascular function, vascular compliance represents the dynamic ability of arteries to dilate or retract in response to blood pressure alternations. An artery vessel with high compliance can better buffer the pulsatility of blood flow, thereby protecting the downstream arterioles and capillaries from damage. Consequently, brain perfusion and vascular compliance are complementary properties of brain's vascular system and may be important indicators of cerebrovascular health. Therefore, noninvasive imaging of brain perfusion and vascular compliance will provide valuable biomarkers to study cerebral physiology and function. Furthermore, these biomarkers may also yield crucial pathophysiological knowledge and guide therapies in brain disorders, such as stroke, small-vessel disease, and neurodegenerative disease. This thesis consists of three novel tools toward brain perfusion and vascular compliance imaging. I first developed a cardiac-triggered Arterial-Spin-Labeling (ASL) technique to enhance the sensitivity of brain perfusion MRI without using exogenous contrast agent. I demonstrated its utility in several experimental settings, including single-shot acquisition, multi-shot acquisition, and detection of cerebral blood flow (CBF) changes. Next, I worked on the analysis strategies of perfusion MRI data. I developed a cloud-based tool for ASL data processing that is free from any software installation, compatible with file formats from all major MRI manufacturers, and publicly accessible. Quantitative CBF maps and region-specific reports are available for download within minutes. I have launched this cloud service recently and received initial feedback from researchers around the world. Finally, I developed a technique to measure vascular compliance in larger cerebral arteries. I used a time-resolved vascular-space-occupancy technique to obtain 3D maps of cerebral arterial compliance and then applied the technique to study arterial stiffness in aging.
Disorders of consciousness and neuroethics: why rights must come to mind (The Daniel W. Foster, M.D., Visiting Lectureship in Medical Ethics)
(2016-09-13) Fins, Joseph J.
[Note: The slide presentation and video are not available from this event.] Over the past two decades neuroimaging has revealed the possibility of covert consciousness in patients once thought vegetative. This knowledge coupled with the ability of drugs, devices and neuroprosthetics to restore functional communication in patients with disorders of consciousness has the potential to reintegrate patients into the nexus of family and community. A worthy scientific pursuit, I will argue that this effort is a moral imperative which links respect for persons with the reemergence of voice out of covert consciousness. As I describe in my recently published book, "Rights Come to Mind: Brain Injury, Ethics and the Struggle for Consciousness" (Cambridge University Press, 2015), this is a human rights issue for a population too long marginalized. For rights to come to mind, patients will need greater access to medical care and research, the skilled engagement of the clinical community, and fuller protections under of the law.
Magnetic Resonance Imaging of Cerebral Venous Oxygenation
(2017-05-02) Mao, Deng; Mason, Ralph P.; Madhuranthakam‎, Ananth; Takahashi, Masaya; Lu, Hanzhang
Cerebral venous oxygenation (Yᵥ) is an important biomarker for brain diseases. My dissertation consisted of two studies. The first study aims to investigate the regional Yᵥ in hypertension. Hypertension is known to cause cerebral hypoperfusion and cortical atrophy but its impact on Yᵥ is not yet clear. A 2D venous oxygenation mapping technique, TRUPC was applied to an elderly cohort from Dallas Heart Study. The Yᵥ in internal cerebral veins (ICV), anterior and posterior superior sagittal sinus (SSS) and anatomical data was obtained. It was found lower relative venous oxygenation in the ICV and anterior SSS are associated with high systolic pressure. Such trend is also observed in hypertensive group alone. Moreover, the volume reduction in hippocampus and thalamus is correlated with decreased regional Yᵥ. The findings presented are consistent with previous literature on the targeted hypofusion and volume reduction in these regions. Imaging marker Yᵥ reported here may prove valuable in the understanding of hypoxia effect, hypoperfusion and cortical volume reduction caused by hypertension. The second study aims to develop an R2*-based MR oximetry that can measure cerebral Yᵥ in 3D. This technique separates blood signal from tissue by velocity-encoding phase contrast and measures the R2* of pure blood by multi-gradient-echo acquisition. The blood R2* was converted to Yᵥ using an R2*-vs-oxygenation (Y) calibration curve, which was obtained by in vitro bovine blood experiments. Reproducibility, sensitivity, validity, and resolution dependence of the technique were evaluated. In vitro R2*-Y calibration plot revealed a strong dependence of blood R2* on oxygenation, with additional dependence on hematocrit. In vivo results demonstrated that the technique can provide a 3D venous oxygenation map that depicts both large sinuses and smaller cortical veins, with venous oxygenation ranging from 57% to 72%. Intra-session coefficient-of-variation of the measurement was 3.0%. The technique detected an average Yᵥ increase of 10.8% due to hyperoxia, which was validated by global oxygenation measurement from TRUST. Two spatial resolutions, one with an isotropic voxel dimension and the other with a non-isotropic dimension, were tested for full brain coverage. This study demonstrated the feasibility of 3D brain oxygenation mapping without using contrast agent.
[News]
(1976-04-01) Taylor, Silvi
[News]
(1984-08-09) Williams, Ann; Floyd, Carol
Pre-Surgical fMRI Mapping of Language: Accuracy of Mapping Language Regions in Patients with Mass Lesions
(2017-01-17) Thrikutam, Nikhitha; O'Neill, Thomas; Yetkin, Zerrin; Patel, Toral
OBJECTIVES: (1) To introduce a novel methodology for co-registration of pre- and post-surgical clinical imaging. (2) To document prognostic imaging correlates of functional imaging/tractography to post-surgical outcome. BACKGROUND: The accuracy, reproducibility, and clinical applicability of pre-surgical imaging evaluation of language in patients with mass lesions near language areas has been previously demonstrated by this group. The accuracy and clinical applicability of pre-surgical mapping can be confirmed by correlating pre-surgical imaging to post-surgical imaging and then to any related language deficits. It is hypothesized that if the surgical resection cavity includes areas of language activation language deficits will result. Correlation of outcomes with language mapping and post-surgical imaging has not been documented in the literature. MATERIALS AND METHODS: Pre-surgical functional maps and diffusion tensor tracts were created utilizing AFNI and DynaSuite software following fMRI/DTI tractography protocol to evaluate language regions. Post-surgical follow-up of speech deficits was obtained from the medical charts. A computerized method was used to co-register pre- and post-surgical images. Multiple variables including structural, functional, and clinical findings were documented and analyzed for correlation to outcome. RESULTS: 13 patients with left-sided mass lesions with complete pre- and post-surgical clinical imaging and clinical evaluation were included in this retrospective study. Of the 13 patients only 1 patient was noted to have a severe post-operative language deficit and 4 patients were noted to have moderate post-operative laguage deficits. Accurate co-registration was achieved in all cases. Prognostic indicators of language deficits included proximity of activation to the resection cavity, the level of resection, and involvement of the adjacent trajectory of arcuate fasciculus. CONCLUSIONS: (1) Pre-surgical fMRI was accurately co-registered with post-surgical images. (2) Structural, functional, and DTI images were shown to have prognostic value for post-surgical language deficits.
[Southwestern News]
(2005-04-21) Siegfried, Amanda