[en] The laboratory condition where charged particle fusion reactions have been studied is not exactly the same as stellar condition. To probe details of solar fusion and to test the prediction of standard solar model, we need more precise data for charged particle fusion reactions in the laboratory. We propose several experimental approaches to reduce the ambiguity of the estimation of screening potential value which is crucial for obtaining the astrophysical S-factor. The laboratory experiments of reactions with bare target and bare beam will be achieved by using proposed Electron Beam Ion Trap Apparatus (NARITA). (author)

[en] Accurate μ maps are important for quantitative image reconstruction in SPECT. The Compton scatter energy window (CSW) technique has been proposed to define the outline of objects. In this technique, a lower energy window image is acquired in addition to the main photo-peak energy window. The image of the lower energy window is used to estimate the edge of the scanned object to produce a constant attenuation map. The aim of this study was to investigate the dependency of CSW on the spatial and energy distribution of radioisotope to predict the edges of objects. Two particular cases of brain study were considered, namely uniform distribution and non-uniform distribution using Monte Carlo simulation and experiments with uniform cylindrical phantom and hotspot phantom. The phantoms were filled with water and a radioactive solution of ^99mTc. For each phantom, 20%, 30%, 40% and 50% thresholds of the mean profile were applied to estimate E_wt, the energy window for minimum difference between the estimated and true edge of objects. The E_wt's were 100-120 keV with a 40% threshold and 92-114 keV with a 30% threshold for uniform and hotspot phantoms, respectively. Edge of the objects with CSW technique varies with energy window and thresholds. Careful setting of the energy window is required to use the CSW technique. (author)

[en] Cerebral blood flow (CBF), oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO₂) provide us important clinical indices and are used for assessing ischemic degree in cerebrovascular disorders. These quantitative images can be measured by positron emission tomography (PET) using ¹⁵O-labelled tracers such as C¹⁵O, C¹⁵O₂ and ¹⁵O₂. To reduce the time of scan, one possibility is to omit the use of cerebral blood volume (CBV) data. The present study investigated the influence of fixing the CBV to OEF and CMRO₂ values on subjects with and without cerebrovascular disorders. The study consisted of three groups, namely, GROUP-0 (n=10), GROUP-1 (n=9), and GROUP-2 (n=10), corresponding to- without significant disorder, with elevated CBV, and with reduced CBF and elevated OEF, respectively. All subjects received PET examination and using the PET data OEF and CMRO₂ images were computed by fixing CBV and with CBV data. The computed OEF and CMRO₂ values were compared between the methods. The OEF and CMRO₂ values obtained by fixing the CBV were around 10% underestimation against that with CBV data. The regression analysis showed that these values were comparable (r=0.93-0.98, P<0.001). The simulation showed that fixing of the CBV would not derive significant error in either OEF or CMRO₂ values, when changed from 0 to 0.08 ml/g. This study shows the feasibility of fixing the CBV value for computing OEF and CMRO₂ values in the PET examination, suggesting the CO scan could be eliminated. (author)

[en] A compact low energy and high current accelerator is designed for a study of fusion reaction in a nuclear astrophysics. The accelerator can produce an intense beam of several ion species such as proton, deuteron and helium isotopes more than 1 mA. To provide extremely fine cross sectional measurement for fusion reactions ion beam production, extraction, transport to a windowless gas target is made using the GIOS and FUGUN computer codes. Multielectrodes for the ion extraction applied to the NANOGUN ion source can be expected to improve the beam quality and to raise a luminosity for beam to gas target interaction. To study the electron screening effects, an experimental apparatus is proposed and constructed. A combination of FBIS type plasma source as a target with a high current ECR ion source is also proposed. The present state of these design consideration and its development are described. (author)

[en] ¹⁵O-labled gases like O₂, CO₂ and CO are used for PET diagnosis of brain vascular diseases. Since the half life of ¹⁵O is about 2 min, for more popular practice of the diagnosis, an easily operable compact cyclotron is needed and thus under development. This paper describes its outline. Improvement of diagnostic methods and of synthesis of medicals has been also discussed. For miniaturization of the cyclotron, the accelerator of low energy deuterium alone is planned for the reaction ¹⁴N(d, n)¹⁵O, where nitrogen gas is economical. The compact accelerator is to be of a coil cavity, smaller magnetic diameter, self-shield and compact high frequency system. Here, the generated neutron is important in shielding and an experiment is performed to measure its dose with a tandem van de Graff accelerator in Kyoto University. Energy of deuterium is 3.5 MeV, the maximum in the planned cyclotron, and dose is measured by the Aloka neutron dosimeter suitable for 0.025-15 MeV neutrons. The target atomic number is the larger, the dose equivalent rate is found the smaller: use of materials like Ta and W can reduce the shield mass quantity. Findings are useful for the optimal development. (S.I.)

[en] Cerebral metabolic rate of oxygen (CMRO₂), oxygen extraction fraction (OEF) and cerebral blood flow (CBF) images can be quantified using positron emission tomography (PET) by administrating ¹⁵O-labelled water (H¹⁵₂O) and oxygen (¹⁵O₂). Conventionally, those images are measured with separate scans for three tracers C¹⁵O for CBV, H¹⁵₂O for CBF and ¹⁵O₂ for CMRO₂, and there are additional waiting times between the scans in order to minimize the influence of the radioactivity from the previous tracers, which results in a relatively long study period. We have proposed a dual tracer autoradiographic (DARG) approach (Kudomi et al 2005), which enabled us to measure CBF, OEF and CMRO₂ rapidly by sequentially administrating H¹⁵₂O and ¹⁵O₂ within a short time. Because quantitative CBF and CMRO₂ values are sensitive to arterial input function, it is necessary to obtain accurate input function and a drawback of this approach is to require separation of the measured arterial blood time-activity curve (TAC) into pure water and oxygen input functions under the existence of residual radioactivity from the first injected tracer. For this separation, frequent manual sampling was required. The present paper describes two calculation methods: namely a linear and a model-based method, to separate the measured arterial TAC into its water and oxygen components. In order to validate these methods, we first generated a blood TAC for the DARG approach by combining the water and oxygen input functions obtained in a series of PET studies on normal human subjects. The combined data were then separated into water and oxygen components by the present methods. CBF and CMRO₂ were calculated using those separated input functions and tissue TAC. The quantitative accuracy in the CBF and CMRO₂ values by the DARG approach did not exceed the acceptable range, i.e., errors in those values were within 5%, when the area under the curve in the input function of the second tracer was larger than half of the first one. Bias and deviation in those values were also compatible to that of the conventional method, when noise was imposed on the arterial TAC. We concluded that the present calculation based methods could be of use for quantitatively calculating CBF and CMRO₂ with the DARG approach

[en] The nucleoside analog 3'-deoxy-3'-¹⁸F-fluorothymidine (FLT) has been investigated for evaluating tumor proliferating activity in brain tumors. We evaluated FLT uptake heterogeneity using textural features from the histogram analysis in patients with newly diagnosed gliomas and examined correlation of the results with proliferative activity and patient prognosis, in comparison with the conventional PET parameters. FLT PET was investigated in 37 patients with newly diagnosed gliomas. The conventional parameters [tumor-to-contralateral normal brain tissue (T/N) ratio and metabolic tumor volume (MTV)] and textural parameters (standard deviation, skewness, kurtosis, entropy, and uniformity) were derived from FLT PET images. Linear regression analysis was used to compare PET parameters and the proliferative activity as indicated by the Ki-67 index. The associations between parameters and overall survival (OS) were tested by Cox regression analysis. Median OS was 662 days. For the conventional parameters, linear regression analysis indicated a significant correlation between T/N ratio and Ki-67 index (p = 0.02) and MTV and Ki-67 index (p = 0.02). Among textural parameters, linear regression analysis indicated a significant correlation for kurtosis (p = 0.003), entropy (p < 0.001), and uniformity (p < 0.001) as compared to Ki-67 index, exceeding those of the conventional parameters. The results of univariate analysis suggested that skewness and kurtosis were associated with OS (p = 0.03 and 0.02, respectively). Mean survival for patients with skewness values less than 0.65 was 1462 days, compared with 917 days for those with values greater than 0.65 (p = 0.02). Mean survival for patients with kurtosis values less than 6.16 was 1616 days, compared with 882 days for those with values greater than 6.16 (p = 0.006). Based on the results of this preliminary study in a small patient population, textural features reflecting heterogeneity on FLT PET images seem to be useful for the assessment of proliferation and for the potential prediction of survival in newly diagnosed gliomas. (author)

[en] Glioblastoma multiforme (GBM) is characterized by tissue hypoxia associated with resistance to radiotherapy and chemotherapy. To clarify the biological link between hypoxia and tumour-induced neovascularization and tumour aggressiveness, we analysed detailed volumetric and spatial information of viable hypoxic tissue assessed by ¹⁸F-fluoromisonidazole (FMISO) PET relative to neovascularization in Gd-enhanced MRI and tumour aggressiveness by L-methyl-¹¹C-methionine (MET) PET in newly diagnosed GBMs. Ten patients with newly diagnosed GBMs were investigated with FMISO PET, MET PET and Gd-enhanced MRI before surgery. Tumour volumes were calculated by performing a three-dimensional threshold-based volume of interest (VOI) analysis for metabolically active volume on MET PET (MET uptake indices of ≥1.3 and ≥1.5) and Gd-enhanced volume on MRI. FMISO PET was scaled to the blood FMISO activity to create tumour to blood (T/B) images. The hypoxic volume (HV) was defined as the region with T/B greater than 1.2. PET and MR images of each patient were coregistered to analyse the spatial location of viable hypoxic tissue relative to neovascularization and active tumour extension. Metabolically active tumour volumes defined using MET uptake indices of ≥1.3 and ≥1.5 and the volumes of Gd enhancement showed a strong correlation (r = 0.86, p < 0.01 for an index of ≥1.3 and r = 0.77, p < 0.05 for an index of ≥1.5). The HVs were also excellently correlated with the volumes of Gd enhancement (r = 0.94, p < 0.01). The metabolically active tumour volumes as defined by a MET uptake index of ≥1.3 and the HVs exhibited a strong correlation (r = 0.87, p < 0.01). On superimposed images, the metabolically active area on MET PET defined by a MET uptake index of ≥1.3 was usually larger than the area of the Gd enhancement and about 20-30% of the MET area extended outside the area of the enhancement. On the other hand, the surface area of viable hypoxic tissue with a T/B cutoff of ≥1.2 on FMISO PET did not substantially differ from the area of the Gd enhancement. The volumetric analysis demonstrates that the viable hypoxic tissue assessed by FMISO PET is related to the neovascularization in Gd-enhanced MRI and the tumour aggressiveness by MET PET in newly diagnosed GBMs. The spatial analysis shows that the metabolically active tumour may be substantially underestimated by Gd-enhanced MRI. Complementary use of MET and FMISO to Gd-enhanced MRI may improve the understanding of tumour biology and lead to the most efficient delineation of tumour volume and treatment strategy. (orig.)

No abstract available

[en] Quantification of cerebral blood flow (CBF) is important for the understanding of normal and pathologic brain physiology. When CBF is assessed using PET with ${\text{H}}_2$ ¹⁵O or C¹⁵O₂, its calculation requires an arterial input function, which generally requires invasive arterial blood sampling. The aim of the present study was to develop a new technique to reconstruct an image derived input function (IDIF) from a dynamic ${\text{H}}_2$ ¹⁵O PET image as a completely non-invasive approach.

Our technique consisted of using a formula to express the input using tissue curve with rate constant parameter. For multiple tissue curves extracted from the dynamic image, the rate constants were estimated so as to minimize the sum of the differences of the reproduced inputs expressed by the extracted tissue curves. The estimated rates were used to express the inputs and the mean of the estimated inputs was used as an IDIF. The method was tested in human subjects (n  =  29) and was compared to the blood sampling method. Simulation studies were performed to examine the magnitude of potential biases in CBF and to optimize the number of multiple tissue curves used for the input reconstruction.

In the PET study, the estimated IDIFs were well reproduced against the measured ones. The difference between the calculated CBF values obtained using the two methods was small as around  <8% and the calculated CBF values showed a tight correlation (r  =  0.97). The simulation showed that errors associated with the assumed parameters were  <10%, and that the optimal number of tissue curves to be used was around 500.

Our results demonstrate that IDIF can be reconstructed directly from tissue curves obtained through ${\text{H}}_2$ ¹⁵O PET imaging. This suggests the possibility of using a completely non-invasive technique to assess CBF in patho-physiological studies. (paper)