Background
A brain single-photon emission computed tomography (SPECT) system using cadmium telluride (CdTe) solid-state detectors was previously developed. This CdTe-SPECT system is suitable for ...simultaneous dual-radionuclide imaging due to its fine energy resolution (6.6 %). However, the problems of down-scatter and low-energy tail due to the spectral characteristics of a pixelated solid-state detector should be addressed. The objective of this work was to develop a system for simultaneous Tc-99m and I-123 brain studies and evaluate its accuracy.
Methods
A scatter correction method using five energy windows (FiveEWs) was developed. The windows are Tc-lower, Tc-main, shared sub-window of Tc-upper and I-lower, I-main, and I-upper. This FiveEW method uses pre-measured responses for primary gamma rays from each radionuclide to compensate for the overestimation of scatter by the triple-energy window method that is used. Two phantom experiments and a healthy volunteer experiment were conducted using the CdTe-SPECT system. A cylindrical phantom and a six-compartment phantom with five different mixtures of Tc-99m and I-123 and a cold one were scanned. The quantitative accuracy was evaluated using 18 regions of interest for each phantom. In the volunteer study, five healthy volunteers were injected with Tc-99m human serum albumin diethylene triamine pentaacetic acid (HSA-D) and scanned (single acquisition). They were then injected with I-123
N
-isopropyl-4-iodoamphetamine hydrochloride (IMP) and scanned again (dual acquisition). The counts of the Tc-99m images for the single and dual acquisitions were compared.
Results
In the cylindrical phantom experiments, the percentage difference (PD) between the single and dual acquisitions was 5.7 ± 4.0 % (mean ± standard deviation). In the six-compartment phantom experiment, the PDs between measured and injected activity for Tc-99m and I-123 were 14.4 ± 11.0 and 2.3 ± 1.8 %, respectively. In the volunteer study, the PD between the single and dual acquisitions was 4.5 ± 3.4 %.
Conclusions
This CdTe-SPECT system using the FiveEW method can provide accurate simultaneous dual-radionuclide imaging. A solid-state detector SPECT system using the FiveEW method will permit quantitative simultaneous Tc-99m and I-123 study to become clinically applicable.
Our previous study demonstrated that a cadmium telluride (CdTe)-based single-photon emission computed tomography (SPECT) system with good energy resolution could provide dual-radioisotope SPECT ...images of a patient who had been administered with two kinds of radioisotope simultaneously. To obtain two quantitative physiological parametric images from these radioisotope images by using compartment model analysis, the concentrations of the dual-radioisotope in the blood sample need to be measured. In this paper, a CdTe-based well counter was developed to measure the concentrations of a dual-radioisotope of 99m Tc and 123 I, and its performance was evaluated. The counter consists of four detector panels. Each detector panel consists of two detector modules, and each module has 16 × 16 CdTe detector pixels with a pitch of 2.5 mm; the eight detector modules give our system a field of view (x × y × z) of 4 × 4 × 8 cm 3 . The crosstalk correction coefficient α, which is the ratio of the count rate in the 99m Tc-energy window to that in the 123 I-energy window, was obtained by measuring the single-radioisotope solution of 123 I. When the dual-radioisotope of 99m Tc and 123 I was measured, the true count rate of 99m Tc was obtained by subtracting the crosstalk count rate (α × the count rate of 123 I) from the uncorrected count rate of 99m Tc. To evaluate the measurement accuracy, dual- and single-radioisotope solutions were measured, and the mean percentage error of the measured count rate of dual-radioisotope solutions to that of the single-radioisotope solution was obtained. The energy resolutions full width at half maximum of the CdTe-based well counter were 6.95% and 6.93% at 140.5 keV and 159 keV, respectively, and were higher than that of a conventional NaI (Tl) scintillation detector (10% at 140.5 keV). The count loss in the CdTe detector was 1.7% at 44 kcps. For the dual-radioisotope measurement, the percentage errors (mean percentage% ± standard deviation%, N = 3) of the count rate of 99m Tc and 123 I at a high count rate ( 99m Tc: 44 kcps, 123 I: 28 kcps) were -1.9% ± 0.0% and -3.5% ± 1.1%, respectively. On the other hand, the percentage errors of the count rate of 99m Tc and 123 I at a low count rate ( 99m Tc: 3 kcps, 123 I: 4 kcps) were -0.4% ± 0.3% and 0.2% ± 0.6%, respectively. The CdTe-based well counter measured each concentration of 99m Tc and 123 I in mixed solutions with high accuracy.
In this paper, the authors propose a sophisticated analysis method to determine possible maximum generator capacity and to evaluate the generator's potential ability. The method surveys generator ...design parameters on a large scale efficiently and objectively. The possible maximum generator capacity acquired by the proposed method satisfies the specifications of short-circuit ratio, power factor, and temperature limitations of armature and field windings. Armature voltage, armature current, and field current are adjusted to satisfy the above specifications simultaneously. An example adopting the proposed method is shown which clarifies the method's effectiveness in the research and design phase. The specific results obtained demonstrate the sensitivities of the calculated possible maximum generator capacity and the calculated loss for various development factors.
A new approach to simulate flow-induced vibrations in piping systems and circular cylindrical structures is introduced. In the developed method, three-dimensional unsteady flow is solved by a direct ...simulation method. Based on the fluid dynamic calculation, fluid forces on structure surfaces(piping inner wall or cylinder surface)are estimated by integrating fluid pressure and shear stress. The calculated fluid forces are translated to finite element nodes in structure surfaces and treated as external forces acting on these surfaces. Then dynamic response of the structures is calculated by using modal analysis or the Newmark-β method. For a full coupling analysis, the moved surfaces become the new coordinate boundaries at the next time step. As an application of the developed method, flow-induced vibrations in an elbow and an array of tubes were evaluated. Turbulent intensity agreed well with experimental data in the unsteady flow analysis and vibration of the elbow was successfully simulated in the dynamic response analysis. For a 3×3 square array, the occurrence of fluid elastic instability could be simulated.
The finite element analysis of framed structures by the Adaptively Shifted Integration technique is improved for higher accuracy in the present study. The bending moment distribution on the cubic ...element based on Bernoulli-Euler hypothesis is interpolated in a cubic form by using shear forces determined by nodal forces. This treatment makes it possible to evaluate the maximum value of the bending moment and to form a plastic hinge at an arbitrary location in the element. Several numerical studies have been carried out in order to show the effectiveness of the present method.
The Shifted Integration technique, which has been developed for the efficient nonlinear finite element analysis of framed structures, is extended to the plastic collapse analysis of frames with ...semi-rigid joints. By using the SI technique in short cubic elements inserted at member ends, both of the nonlinear characteristic of joints and the elastoplastic property of member ends can be independently taken into account in these short elements. The highly accurate analysis of semi-rigid frames is made possible in the framework of displacement-type finite element method using only standard cubic beam elements. Several numerical studies are conducted in order to illustrate the validity of the proposed method.
A rotating machine experiences various losses, such as copper loss, iron loss, and mechanical loss, while operating in various modes and these losses raise the temperatures of its components. A ...rotating machine must also be designed so that the temperatures of its conductors remain below the temperature tolerance limit of their insulation. The necessary cooling design is one of the critical design factors that determines the dimensions and efficiency of the machine. The aim of this study was to apply quality engiheering to air-cooling parameter design for the rotor of a rotating machine. This was done in two steps: in the first step, the main factors affecting the air cooling of the rotor were extracted using network analysis; in the second step, the effects of the main factors were evaluated quantitatively by model test analysis. As a result of this study, a 28% increase in complete flow around the rotor was confirmed and the flow was distributed more uniformly.
The aim of the present study is to clarify the mechanical behavlor of a bridge girder during hot galvanizing. The mechanical behavior is analyzed using finite element method (FEM) analysis in which ...the constitutive equation is given by Bodner's viscoplastic model. The mechanism of zinc induced cracking is also discussed in detall. A shape and size parameter, Rσmax. is proposed and discussed. Rσmax is the ratio of the maximum compressive thermal stress to the elastic buckling stress of the panel and is related to zinc induced cracking. The parameter Rσmax correlates well with the final tensile strain calculated by FEM analysis. Critical strain for crack initiation, εc, was obtained from bending tests and from FEM analysis for several steels. Each value of Rσmax at crack initiation was estimated from comparison with the final tensile strain and εc. The estimated critical value of Rσmax is nearly the same as the critical value of Rσmaxobtained by calculation of the transition from non-cracking to cracking behavior of bridge girders.
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