Scatter and attenuation correction for brain SPECT.

摘要

Single Photon Emission Computed Tomography (SPECT) is a three-dimensional imaging technology that measures the functional state of an organ. It is often used in an attempt to diagnose brain diseases, such as dementia and stroke. If brain SPECT could be made quantitatively accurate, then it would have the potential to objectively diagnose these brain diseases. It is conceived that objective diagnosis would improve the ability of SPECT to detect the onset of disease, establish differential diagnosis between dementia subtypes, and evaluate therapeutic intervention.; The discriminating power of SPECT is, unfortunately, confounded by large degrees of overlap between dementia patients and normal controls. In this thesis, I show that a significant component of this overlap originates from the measurement process of SPECT, and thus represents an artifactual misrepresentation of physiological parameters.; Photon scatter and attenuation are the greatest confounds to quantitatively accurate emission tomography. I characterize these physical processes in the context of brain imaging, and develop methods to compensate for their effects. More specifically, I demonstrate, using high-resolution X-ray computed tomography (CT), that attenuation is a non-uniform phenomenon at the 140 keV energy of 99mTc. Moreover, attenuation correction should be used in conjunction with scatter correction. The latter markedly improved the accuracy of relative quantification, while simultaneously improving contrast-recovery and bias. However, implementations of non-uniform scatter and attenuation corrections were found to provide for only small incremental benefits over their uniform counterparts.; Finally, I present a method to apply non-uniform scatter and attenuation correction without CT transmission imaging. This technology, termed Inferred Anatomy, has the potential to replace transmission imaging; thereby shortening patient imaging time and decreasing costs associated with hardware purchase and maintenance. Additionally, Inferred Anatomy can be retrospectively applied to existing brain SPECT scans, thereby improving longitudinal and inter-institutional standardization.