Research Involving PET

Brain Mechanisms in Classical Conditioning

Here PET imaging has been used to study the brain mechanisms that underlie human classical conditioning. This was done was by measuring the blood flow distribution in the brain. The experiment consisted of three phases, pre- conditioning, conditioning, and postconditioning. PET scanning was performed during the first and third phases. The conditioning phase was used to send slight electrical shocks to the subjects. Thru viewing the first and third stage it was seen that the conditioning stage resulted in increased activation in frontal and temporal regions of the brain especially in the right cerebral hemisphere. [16]

Brain Mechanisms in Memory Retrieval

Retrieval of information from a person's memory involves not only the successful retrieval of stored information (cephory), but also the processes invoked by the attempt to remember. Recent PET studies of human memory retrieval show that retrieval of stored information engages a network of brain regions. These regions include the right prefrontal cortex together with posterior cortical regions. This study was able to show that the activation of these regions is associated with the attempt to retrieve this information, not necessarily to their successful retrieval. [17]

Brain Mechanisms and the Perceptual Maze Test

PET was used in this situation to examine the cerebral activation pattern elicited by the perceptual maze test (PTM). The PTM is a neuropsychological test used to evaluate organic brain injury. This test examines general intelligence, visuospatial skill, visually guided motor planning, and the ability to obey rules. [18]

The Evolution of Abnormal Metabolic Networks in the Brain

To visualize the complex information provided by PET data, we have combined standard PET methods with statistical modeling approaches and visualization techniques to best demonstrate the results of analysis. Topographic profiles represent underlying functional networks of metabolically covarying regions that are not discernible by conventional image processing and statistical techniques because of their small magnitude compared to global effects. By quantifying, identifying, and illustrating the existence of such underlying functional networks, independent neuroimaging markers are provided for differentiating between clinically similar neurogenerative disorders as well as insights into the physiological mechanisms of these diseases. [20]

PET Imaging of Malignant Melanoma

PET imaging with Carbon-11-methionine has proven an effective method for visualizing melanoma, and may also be useful in measuring tumor metabolic activity in vivo. [21]

Estrogen Receptors in Breast Cancer

PET has been used to study several aspects of breast cancer pathophysiology. FDG has been broadly applied in PET studies of cancer because of observations that nearly all malignant tumors exhibit increased uptake of FDG, presumably reflecting an increased rate of glycolysis in tumor tissue. FDG-PET has shown in clinical studies to be a reliable means for distinguishing benign from malignant breast masses and for evaluating the locoregional extent of tumor. [22]

Presurgical Visualization of Primary Breast Carcinoma

Reconstructed PET images are provided as a series of two-dimensional transaxial cuts. PET's ability to indicate the locoregional extent of a malignant tumor has proven to be a useful presurgical aid. However, these images are often difficult to evaluate because abnormalities are normally scattered across a large volume with quite variable intensities. [23]

Attenuation Correction in Whole-Body PET

Attenuation correction is a routine procedure in PET by use of attenuation factors derived from a transmission scan or by assuming constant tissue density. Whole-body PET imaging is however, a notable exception to this. Whole-body imaging extends the axial field of view of the PET scanner by moving the bed in steps through the tomograph. Data are acquired for typically 4 to 10 minute periods at each position. Because of this, accurate quantification is not possible and reconstructed images include artifacts, such as an apparent decrease in tracer accumulation towards the center of the body. [24]

PET Imaging in Renal Disease

The kidneys are distinguished by high levels of metabolism and high blood flow. This study proves that excellent images of the kidneys can be obtained with Carbon-11-acetate and PET imaging. Because of the high blood flow in the kidneys a high target-to-background ratio is almost expected. Even when there is greatly reduced blood flow due to renal disease, the corresponding reduction in tracer accumulation does not preclude visualization of the kidneys or sufficient tissue tracer activity for tracer kinetic analysis. Excellent images of the kidneys in human subjects can be obtained when using PET with the tracer Carbon-11-acetate. [25]

Back to PET Home Page