Many neurological illnesses such as, Alzheimer, ischemic strokes and cerebral neoplasms are associated with abnormal blood flow and volume. Different imaging modalities are used in combination with indicator dilution techniques to quantify vascular-specific parameters such as mean transit time, blood volume, blood flow and vascular permeability.
In this work, I have focused on dynamic susceptibility-weighted, contrast-enhanced magnetic resonance imaging (DSC MRI) of gliomas. DSC MRI involves injection of a tracer bolus, a paramagnetic contrast agent such as gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA). As the bolus passes through the vasculature of a region of interest, inhomogeneities in the local magnetic field are created. This results in a transient T2 signal loss that can be measured by rapid imaging. From the intensity of this signal loss, Gd-DTPA concentration can be estimated using previously defined formulas. GD-DTPA concentration is in turn related to vascular parameters via indicator dilution techniques.
These techniques have been at the heart of diagnostics for vascular diseases. The conventional approach only allows us to analyze the first pass of the tracer and cannot account for recirculating boluses, which has remained an unresolved problem. Practically, these boluses overlap the first bolus, and it has been a challenge to identify them. In this work, I solve this problem by providing a global approach to tracer circulation within the organism, and I find an exact solution for the global tracer dynamics. Technically, I express the problem in the frequency domain which simplifies the problem conceptually. This representation allows us to map different features of tracer dynamics–its different passes and its decaying long-time tail–to singularities in the complex plane of the frequency. From here, using methods of complex integration, the time domain dynamics can be exactly solved for.
This framework also provides us with the arterial input function (AIF), without the need to directly measure it, and a practical way to map local cerebral blood volume (CBV).
|Advisor:||Johnson, Glyn, Novikov, Dmitry S.|
|Commitee:||Gonen, Oded, Sodickson, Daniel K., Turnball, Daniel H.|
|School:||New York University|
|Department:||Basic Medical Science|
|School Location:||United States -- New York|
|Source:||DAI-B 78/01(E), Dissertation Abstracts International|
|Subjects:||Neurosciences, Biomedical engineering, Biophysics|
|Keywords:||Arterial input function, Central volume principle, Cerebral blood volume, Indicator dilution theory, Perfusion dynamic susceptibility-weighted, contrast-enhanced magnetic resonance imaging, Pharmacokinetic modeling|
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