A combined X-ray CT-scintillation camera system for measuring radionuclide uptake in tumors

Absolute measurement of radiolabeled pharmaceutical uptake in nuclear medicine allows for the improved differentiation between diseased and normal tissues by estimating the pharmaceutical delivery to specific target sites. While established measurement techniques in nuclear medicine are useful under the correct circumstances, they are not always accurate or precise in practice. To develop better methods for radionuclide activity measurement, an imaging system that combines an X-ray CT scanner with a scintillation camera using a common patient table has been developed. With the combined imaging system, the registered X-ray CT images provide physical information that can be used to overcome the quantitative errors in nuclear imaging due to attenuation and limited spatial resolution.;Because the prototype imaging system is composed of separate systems, a registration technique for correlating the three-dimensional data sets using liquid-filled markers was first developed and validated. Preliminary scans suggest that the registration techniques developed for phantom studies are still applicable to patient studies. To help account for measurement errors due to photon attenuation, techniques to convert the registered X-ray CT images to a patient-specific attenuation distribution using calibrated data were developed and further extended to account for the presence of iodinated contrast agents, a potential source of error in estimating the attenuation distribution. To overcome the low spatial resolution in nuclear images, volumes of interest (VOI's) were defined on the registered, high-resolution X-ray CT images and transferred to nuclear images. Analysis methods developed to estimate activity from reconstructed emission images and planar images using registered VOI's provided similar or better accuracy and precision than current standard methods in nuclear medicine. Finally, localization and measurements of 131 I-MIBG uptake in neuroblastoma patients have been undertaken to determine the differences between the new estimation techniques and standard clinically practiced techniques.;In summary, this dissertation describes the tools and techniques that have been developed for a prototype imaging system and demonstrates the differences between measurements made with this system and measurements made with current standard methods in both experimental phantoms and patients.