Cancer cells are known to show increased rates of glycolysis metabolism. Based on this, PET studies using F-18-fluorodeoxyglucose have been used for the detection of primary and metastatic tumors. To account for this increased glucose uptake, a variety of mechanisms has been proposed. Glucose influx across the cell membrane is mediated by a family of structurally related proteins known as glucose transporters (Gluts). Among 6 isoforms of Gluts, Glut-1 and/or Glut-3 have been reported to show increased expression in various tumors. Increased level of Glut mRNA transcription is supposed to be the basic mechanism of Glut overexpression at the protein level. Some oncogens such as src or ras intensely stimulate Glut-1 by means of increased Glut-1 mRNA levels. Hexokinase activity is another important factor in glucose uptake in cancer cells. Especially hexokinase type II is considered to be involved in glycolysis of cancer cells. Much of the hexokinase of tumor cells is bound to outer membrane of mitochondria by the porin, a hexokinase receptor. Through this interaction, hexokinase may gain preferred access to ATP synthesized via oxidative phosphorylation in the inner mitochondria compartment. Other biologic factors such as tumor blood flow, blood volume, hypoxia, and infiltrating cells in tumor tissue are involved. Relative hypoxia may activate the anaerobic glycolytic pathway. Surrounding macrophages and newly formed granulation tisssue in tumor showed greater glucose uptake than did viable cancer cells. To expand the application of FDG PET in oncology, it is important for nuclear medicine physicians to understand the related mechanisms of glucose uptake in cancer tissue.
Adenosine Triphosphate ; Anoxia ; Biological Factors ; Blood Volume ; Carcinogens ; Cell Membrane ; Glucose* ; Glycolysis ; Hexokinase ; Humans ; Macrophages ; Membranes ; Metabolism ; Mitochondria ; Nuclear Medicine ; Oxidative Phosphorylation ; Protein Isoforms ; RNA, Messenger

Positron Emission Tomography(PET) is a new imaging modality to make biochemical metabolic images. Because biochemical changes precede anatomical changes in most of diseases including cancer, PET can detect earlier changes of diseases than conventional anatomical imaging modalities. PET can also characterize biochemical property of diseases. A PET center is composed of a medical cyclotron, synthesis system of radiopharmaceuticals and scanner. For PET oncology, several positron-emitting radiopharmaceuticals have been developed. Among them, F-18-fluorodeoxyglucose (FDG) is most frequently used. Higher rate of glucose metabolism has been observed in cancer cells. Like glucose, FDG is transported into the cancer cells and converted to FDG-6-phosphate by hexokinase. FDG-6-phosphate is trapped in the cytoplasm, and emits gamma rays to make PET images. The current application of FDG PET in oncology is in detection, differentiation, and staging of the primary tumors, grading malignancy, monitoring therapeutic response, and early detection of recurrence. Nowadays, PET is an established procedure for staging the diseases and detecting the recurrence in many cancers, especially the lung, colorectal, and head and neck cancers, melanoma, and lymphoma. PET is a regular part of medical insurance reimbursement in many developed countries, and becomes a valuable research tool in oncology as well as an important imaging modality in managing cancer patients.
Cyclotrons ; Cytoplasm ; Developed Countries ; Electrons* ; Gamma Rays ; Glucose ; Head ; Hexokinase ; Humans ; Insurance ; Lung ; Lymphoma ; Melanoma ; Metabolism ; Neck ; Radiopharmaceuticals ; Recurrence

No abstract available.
Brain Neoplasms* ; Brain*

No abstract available.
Brain Neoplasms* ; Brain*

No abstract available.
Electrons* ; Positron-Emission Tomography*

No abstract available.
Thyroid Gland* ; Thyroid Neoplasms*

PURPOSE: We investigated the statistical methods to compose the functional brain map of human working memory and the principal factors that have an effect on the methods for localization. MATERIALS AND METHODS: Repeated PET scans with successive four tasks, which consist of one control and three different activation tasks, were performed on six right-handed normal volunteers for 2 minutes after bolus injections of 925 MBq H0 at the intervals of 30 minutes. Irnage data were analyzed using SPM96 (Statistical Parametric Mapping) imple-mented with Matlab (Mathworks Inc., U.S.A.). Images from the same subject were spatially registered and were normalized using linear and nonlinear transformation methods. Significant difference between control and each activation state was estimated at every voxel based on the general linear model. Differences of global counts were removed using analysis of covariance (ANCOVA) with global activity as covariate. Using the mean and variance for each condition which was adjusted using ANCOVA, t-statistics was performed on every voxel To interpret the results more easily, t-values were transformed to the standard (saussian distri-bution (Z-score). RESULTS: All the subjects carried out the activation and control tests successfully. Average rate of correct answers was 95%. The numbers of activated blobs were 4 for verbal memory I, 9 for verbal memory II, 9 for visual memory, and 6 for canjunctive activation of these three tasks. The verbal working memory activates predominantly left-sided slruetures, and the visual memory activates the right hernisphere. CONCLUSION: We conclude that rCBF PET imaging and statistical parametric mapping method were useful in the localization of the brain regions for verbal and visual working memory.
Brain Mapping* ; Brain* ; Electrons* ; Healthy Volunteers ; Humans ; Linear Models ; Memory ; Memory, Short-Term ; Positron-Emission Tomography*

PURPOSE: We investigated whether myocardial SPECT had additional usefulness to clinical, functional or surgical indices for the preoperative evaluation of cardiac risks in noncardiac surgery. MATERIALS AND METHODS: 118 patients (M: F=66:52, 62.7+/-10.5 years) were studied retrospectively. Eighteen underwent vascular surgeries and 100 nonvascular surgeries. Rest T1-201/stress Tc-99m-MIBI SPECT was performed before operation and cardiac events (hard event: cardiac death and myocardial infarction; soft event: ischemic ECG change, congestive heart failure and unstable angina) were surveyed through perioperative periods (14.6+/-5.6 days). Clinical risk indices, functional capacity, surgery procedures and SPECT findings were tested for their predictive values of perioperative cardiac events. RESULTS: Peri-operative cardiac events occurred in 25 patients (3 hard events and 22 soft events). Clinical risk indices, surgical procedure risks and SPECT findings but functional capacity were predictive of cardiac events. Reversible perfusion decrease was a better predictor than persistent decrease. Multivariate analysis sorted` out surgical procedure risk (p=0.0018) and SPECT findings (p=0.0001) as significant risk factors. SPECT could re-stratify perioperative cardiac risks in patients ranked with surgical procedures. CONCLUSION:: We conclude that myocardial SPECT provides additional predictive value to surgical type risks as well as clinical indexes or functional capacity for the prediction of preoperative cardiac events in noncardiac surgery.
Death ; Electrocardiography ; Heart Failure ; Humans ; Multivariate Analysis ; Myocardial Infarction ; Myocardial Ischemia ; Perfusion ; Perioperative Period ; Retrospective Studies ; Risk Factors ; Tomography, Emission-Computed, Single-Photon*

No abstract available.
Animals ; Dopamine* ; Nucleus Accumbens* ; Panax* ; Rats* ; Saponins*

No abstract available.
Thyroid Gland* ; Thyroid Neoplasms*