Status of Positron Emission Tomography in Japan

In 1997, 11,040 PET examinations were estimated to have been performed on humans in 24 PET facilities in Japan. PET procedures were used for the studies of the brain (45.0%), tumors (31.3%), and heart (22.9%). (18)F labeled tracers are most frequently utilized followed by (15)O, (13)N, and (11)C labeled tracers in that order. Instrumentations used for PET including cyclotrons and PET scanners are listed. Status of clinical PET and future strategy in our national health insurance system is described. PET examinations performed for clinical oncology and research in our institute are discussed.     

Obesity and Brain Positron Emission Tomography

Obesity, an increasingly common problem in modern societies, results from energy intake chronically exceeding energy expenditure. This imbalance of energy can be triggered by the internal state of the caloric equation (homeostasis) and non-homeostatic factors, such as social, cultural, psychological, environmental factors or food itself. Nowadays, positron emission tomography (PET) radiopharmaceuticals have been examined to understand the cerebral control of food intake in humans. Using ¹⁵O–H₂ PET, changes in regional cerebral blood flow (rCBF) coupled to neuronal activity were reported in states of fasting, satiation after feeding, and sensory stimulation. In addition, rCBF in obese subjects showed a greater increase in insula, the primary gustatory cortex. ¹⁸F–fluorodeoxyglucose PET showed higher metabolic activity in postcentral gyrus of the parietal cortex and lower in prefrontal cortex and anterior cingulate cortex in obese subjects. In addition, dopamine receptor (DR) PET demonstrated lower DR availability in obese subjects, which might lead to overeating to compensate. Brain PET has been utilized to reveal the connectivity between obesity and brain. This could improve understanding of obesity and help develop a new treatment for obesity.     

Positron Emission Tomography in Grading Soft Tissue Sarcomas

Soft tissue sarcomas present with varied radiological appearances. Positron imaging with [F-18] fluorodeoxyglucose (FDG PET) has recently made promising contributions to management of patients by providing a noninvasive means for evaluating tumor metabolism and providing important biological information about soft tissue malignant tumors. PET imaging not only gives quantitative data on metabolic rates of tumors but can also readily provide semiquantitative data of uptake of tumors by measuring uptake ratios. These values have been helpful for noninvasively grading tumors. This value is called the tumor standard uptake value (SUV). The tumor grades (low, intermediate, high) mean SUV values show a high level of significance in discrimination among tumor grade groups.     

Positron Emission Tomography for Radiation Treatment Planning

Purpose:  

To evaluate the impact of positron emission tomography (PET) on target volume delineation for radiation treatment planning.     

68Ga-Labeled Radiopharmaceuticals for Positron Emission Tomography

⁶⁸Ga is a promising emerging radionuclide for positron emission tomography (PET). It is produced using a ⁶⁸Ge/⁶⁸Ga-generator, and thus, would enable the cyclotron-independent distribution of PET. However, new ⁶⁸Ga-labeled radiopharmaceuticals that can replace ¹⁸F-labeled agents like [¹⁸F]fluorodeoxyglucose (FDG) are needed. Most of the ⁶⁸Ga-labeled derivatives currently used are peptide agents, but the developments of other agents, such as amino acid derivatives, nitroimidazole derivatives, and glycosylated human serum albumin, are being actively pursued in many laboratories. Thus, appearance of new ⁶⁸Ga-labeled radiopharmaceuticals with high impact are expected in the near future. Here, we present an overview of ⁶⁸Ga-labeled agents in terms of their clinical significances and relevances to the management of certain tumors, and pertinent pre-clinical developments.     

The Role of the Practice of Nuclear Pharmacy in Positron Emission Tomography

As nuclear medicine evolved from an obscure research tool to a mainstream clinical diagnostic and therapeutic modality, so has the role of the practice of pharmacy in nuclear medicine also evolved. A similar evolution is unfolding today in the practice of positron emission tomography (PET). The skills of many diverse professionals, including pharmacists, are essential for the safe and efficient operation of a modern PET facility. The importance of the role of pharmacists in PET has been increasing as the use of PET radiopharmaceuticals has matured from research to clinical to commercial arenas. While it is clear that pharmacists can contribute clinical and technical skills to the operation of a PET center, perhaps one of the most important factors influencing the increased role of pharmacists in PET is their expertise and experience in the drug regulatory process. The commercial distribution of PET radiopharmaceuticals, primarily [18F]2-fluorodeoxyglucose (FDG), is currently being performed by a variety of corporate and institutional facility partnerships, with the likelihood of several new players entering the marketplace in the near future. This factor has served to dramatically increase the role for nuclear pharmacy in PET. The practice of nuclear pharmacy is a well-established component of PET. The role of nuclear pharmacists in PET is complementary to the many other professionals currently practicing in this specialty. With the rapidly increasing clinical demand for FDG imaging, it is likely that the number of facilities and institutions entering into the commercial distribution of PET radiopharmaceuticals will also increase. Such growth will also serve to solidify and expand the role for the practice of nuclear pharmacy in PET.