Dissertation Abstract

Methods used in quality assurance and optimization in nuclear medicine imaging and imaging systems

The overall aim of this study was to develop and apply new and existing phantoms for use in quality assurance and optimization in nuclear medicine imaging and imaging systems.

A slice phantom with a 1 mm thin slice was designed for measuring transfer functions for different organ thicknesses and depths. The slice phantom was filled with a radioactive solution to heights that corresponded to certain organ thickness, and was placed in a water tank at depths corresponding to simulated organ depths.

Effective attenuation coefficients µ _eff for ^99m Tc, ¹¹¹ In and ²⁰¹ Tl were determined with transfer function measurements with the slice phantom and a line source. The effective attenuation coefficient µ _eff for ¹¹¹ In reached lower values with increasing depth in the phantom, while the effective attenuation coefficient µ _eff for ²⁰¹ Tl reached lower values with increasing height of activity.

A line source and a plane source filled with ^99m Tc were used to calculate the detective quantum efficiency (DQE) of two gamma camera systems. DQE was calculated and compared for different measuring depths, energy window settings, collimators and crystal thicknesses. For examinations at larger depths, a 15% energy window is preferable with an all purpose collimator except for examinations of fine details. A 5/8 inches crystal has advantages over a 3/8 inches crystal at larger depths. A transmission bone phantom was used with ROC analysis to evaluate different digital filters. The results showed that digital filtering increased the area under the ROC curve significantly compared to unfiltered images. The results also showed that more uptakes having low contrast were detected in filtered than in unfiltered images.

Patient examinations were used together with visual grading analysis for evaluating different reconstruction techniques in bone SPECT of the spine. Using visual grading analysis it was shown that the iterative reconstruction with a Metz filter without scatter correction was significantly better than filtered back projection and reconstruction techniques which include scatter correction.

This dissertation citation and abstract are published with permission of ProQuest Information and Learning. Further reproduction is prohibited without permission.