Biomedical Imaging with Combined X-ray Transmission and Radionuclide Emission Detection Techniques
Bruce Hasegawa, Ph.D.
UCSF Physics Research Laboratory
September 23, 2003
11:00 AM
Building 151, Room 1209 (Stevenson Conference Room)

Abstract:
Radiation detection plays a central role in modern biomedical imaging. Specifically, x-ray imaging using plain-film radiography, x-ray angiography, and computed tomography (CT) allows a patient's anatomical structure to be visualized with millimeter or submillimeter spatial resolution. In comparison, radionuclide imaging using scintigraphy, positron emission tomography (PET), or single-photon emission computed tomography (SPECT) measures physiological function at millimeter or centimeter length scales with high sensitivity. In practice, these procedures generally are performed using different systems on different days, forcing the physician to mentally extract and correlate the relevant diagnostic information from the resulting data sets. Over the past decade, a new generation of medical imaging techniques has emerged that records both x-ray transmission and radionuclide emission data so that structure and function can be correlated in a single imaging procedure. The goal of designing a truly simultaneous emission-transmission imaging system is complicated by significant differences between the inherent properties of the x-ray and radionuclide data. For this reason, practical emission-transmission imaging systems that combine CT with PET or SPECT currently use two separate detectors, one for x-ray imaging and the other for radionuclide imaging. Nevertheless, over the past 2-3 years, these dual-modality imaging systems have received significant attention from the medical community and now are being incorporated into clinical practice for diagnosis of cancer, heart disease, and other disorders. In addition, dual-modality imaging systems now are being developed for high resolution imaging of mice and other small animals for biomedical research and drug discovery. These applications demonstrate how radiation detection techniques can play a crucial role in medical imaging, and have expanded their use for biological and pharmaceutical research.