Date of Award
1993
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
A dynamic computed-tomography (CT) scanner has been developed for imaging objects undergoing periodic motion. The scanner has high spatial resolution and sufficiently high temporal resolution to produce quantitative tomographic images of objects, such as excised arterial samples perfused under physiological pressure conditions.;The dynamic CT scanner is comprised of a modified x-ray image intensifier (XRII) coupled to a 1024-element linear photo-diode-array detector. The XRII was modified to allow continuous electro-optical magnification of the field-of-view, thereby increasing the system's limiting resolution. High-resolution gated projection radiographs of a single slice are acquired at the rate of 60 Hz, as the object undergoes periodic motion. If the moving object is rotated through 180{dollar}\sp\circ{dollar}, and projections are obtained at many view angles, tomographic images at different phases of the object's motion cycle can be reconstructed. Performance evaluation of the scanner showed that tomographic images can be obtained with resolution as high as 3.2 mm{dollar}\sp{lcub}-1{rcub}{dollar}, with only a 9% decrease in the resolution limit for objects moving at 1 cm s{dollar}\sp{lcub}-1{rcub}{dollar}. Quantitative measurements of attenuation coefficient are obtained with an accuracy of {dollar}\pm{dollar}0.02 cm{dollar}\sp{lcub}-1{rcub}{dollar}, and the accuracy in geometrical measurements of perimeter is {dollar}\pm{dollar}0.3 mm.;To evaluate the application of the system for imaging of intact excised vascular specimens under simulated physiological conditions, a computer-controlled flow simulator was built and used in the measurement of dynamic arterial distensibility. The flow simulator can reproduce physiological flow waveforms (including waveforms with reverse components) with a precision of {dollar}\pm{dollar}0.1 ml s{dollar}\sp{lcub}-1{rcub}{dollar}.;Existing techniques for the measurement of the static and dynamic elastic properties of excised vessels were adapted to take advantage of the additional data from the CT images and were used to demonstrate the utility of the CT scanner for applications in vascular research. Using these techniques, the local static and dynamic circumferential modulus of elasticity can be measured in intact arterial samples. Since the imaging technique is non-destructive, the mechanical properties of these vessels can be correlated directly with the composition of the vascular wail. This new system, together with the described techniques, offers a unique opportunity for studying dynamic events in vitro.
Recommended Citation
Drangova, Maria, "Computed Tomography Scanner For Dynamic Vascular Imaging In Vitro" (1993). Digitized Theses. 2309.
https://ir.lib.uwo.ca/digitizedtheses/2309