Abstract

Osteoarthritis (OA) is one of the leading causes of disability world-wide. It affects 12% of all Americans ages 25-74 [1]. One of the challenges with OA, is that there are currently no clinically viable methods to measure the health of the cartilage before cartilage loss. There are no ways to replace or heal the cartilage after it has been lost. It is known that the early stages of OA involve a decrease in the amount of glycosaminoglycans (GAG), one of the main molecules in cartilage. This decrease in GAG leads to a change in the fixed charge density of the cartilage and a higher water content with higher diffusivity. The development of techniques to measure the PG content in the cartilage could lead to early diagnosis and the development of effective preventative treatments.One of the suggested methods for measuring the PG content is through quantitative magnetic resonance imaging (MRI). MRI is a non-invasive medical imaging technique known for it's ability to image soft tissue. MRI measures the reaction of the nuclear spin in a magnetic field to a radio frequency (RF) pulse. These spins, and the signal they produce, are sensitive to magnetic fields. This makes it possible to measure small changes in anatomical structure, like a decrease in PG content, because the magnetic spins are sensitive to the local magnetic environment. There are several MRI techniques that are able to measure the PG content in the cartilage.The behavior of the MR signal can be affected by changes in the molecular environment. This effect can by measured through changes in the MR signal parameters T1r and T2. More complex MRI techniques such as chemical exchange saturation transfer (CEST) can be used to directly measure the amount of GAG by taking advantage of the transfer of proton magnetization between the GAG molecules and the surrounding fluids. There are even MRI techniques such as balanced steady state free precession (bSSFP) which makes it possible to measure high resolution morphological images, making it easier to interpret the quantitative scans.This thesis will describe methods employed to improve MRI imaging of cartilage. One method is the developing and testing a new technique for creating maps of the local magnetic field. These field maps can help scans that are particularly sensitive to non-homogeneities in the field. Another method is improving the parameter estimation algorithms which make it easier to more accurately predict values of signal parameters like T1r and T2. This thesis will also describe ongoing efforts to create, and optimize a clinically viable whole-joint cartilage imaging protocol that can be used for early OA detection and diagnosis.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Electrical and Computer Engineering

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