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The purpose of this study is to evaluate the effect of a lead radiation shield on the ability of a beam imaging device consist of an imaging plate (IP) and a collimator by Monte Carlo simulations. Simulations were performed using PHITS. A carbon-ion beam was injected to an acrylic target. A tungsten collimator having a pinhole was placed at the distance of 31.2 cm from the beam. A lead radiation shield was placed on the tungsten collimator. An IP was placed under the collimator. Beam images were acquired by recording the position distribution of energy deposition on the IP. We confirmed that therapeutic carbon-ion beam images could be acquired using the imaging device combining the IP and collimator. It was found that removal of the lead shield had no effect on the imaging results.

In nuclear medicine, the development of portable imaging devices that provide high imaging resolution and sensitivity, capable of imaging gamma rays with a wide energy range and multiple radioisotopes tracing capabilities, is so important. These goals have been possible thanks to developing a compact Compton camera, a collimatorless detector coupled to compact silicon photomultiplier(SiPM) array, using scintillator crystal. In this study, the portable segmented GAGG:Ce scintillator-based Compton camera (CC) is optimized with the GATE, a Monte Carlo simulation toolkit based on Geant4, to maximize its performance for a wide range of gamma-ray energy (364–1000 keV). The geometrical parameters are selected as optimization parameters to investigate their effects on CC's performance, including imaging resolution and absolute detection efficiency (DE a ). The geometry parameters of CC include the planner area of scatterer and absorber detectors, their thicknesses, and the distance between them. The results for the energy range of 364–1000 keV show that the most important contributions to the spatial resolution and DE a of the camera are SAD (scatterer to absorber distance) and the scatterer area while changing absorber area (AA ) showed the most negligible impact. In the short SADs, imaging resolution and DE a are significantly affected by the detector's size and thickness. On the other hand, in the long SADs (> 4 cm), both spatial resolution and DE a are significantly affected by the detector's area but less affected by the detector's thickness. Decreasing the scatterer's thickness and the absorber's size or thickness improves imaging resolution without significantly reducing DE a . The simulation study's findings presented here will provide valuable guidelines for researchers choosing a desired CC's design according to particular objectives, manufacturing limitations in scintillator growth, cost, etc.

Astatine-211 is one of the promising radioisotopes for targeted alpha therapy. Optimising treatment strategies as well as determining the suitability of a given agent for a particular patient requires to image the time-dependent distribution of the targeted radiotherapeutic agent both in tumours and in normal tissues. Since the biodistribution of astatine is different from that of iodine, imaging astatine-211 directly is essential. In the previous study of astatine-211 Compton imaging, random coincidence events due to polonium K-shell X-rays were dominant and seemed to cause saturation of counts. Thus optimisation of the coincidence time windows is important to reduce random coincidence events. In this study, we have optimised the coincidence time windows of a Compton camera and improved the sensitivity, noise and spatial resolution of astatine-211 imaging.

We aimed to determine whether high-resolution specimen-positron emission mammography (PEM) using fluorodeoxyglucose (18F-FDG) can reveal extension of breast cancer in breast-conserving surgery (BCS), and assess the safety of radiation exposure to medical staff. Sixteen patients underwent positron emission tomography, and then BCS with intraoperative frozen section analysis on the same day. Resected specimens with remaining 18F-FDG accumulation were scanned by high-resolution PEM. At least 1 day after surgery, tumour extension was evaluated by three independent experienced readers and by binarized images from the specimen-PEM data. Intraoperative exposure of medical staff to 18F-FDG was measured. Specimen-PEM evaluations of binarized images and the three investigators detected all (100 %, 12/12) invasive lesions and 94.4 % (17/18) of in situ lesions using both methods. The positive predictive value of the accumulated lesions was 74.4 % (29/39) for the binarized images and 82.9 % (29/35) for the three investigators. Analysis of intraoperative frozen sections detected 100 % (2/2) of the margin-positive cases, also detected by both specimen-PEM evaluation methods with no false-positive margin cases. The mean exposure of the medical staff to 18F was 18 μSv. Specimen-PEM detected invasive and in situ lesions with high accuracy and allowable radiation exposure. • Specimen-PEM detected invasive and in situ lesions with high accuracy. • Specimen-PEM predicted complete resection with the same accuracy as frozen section analysis. • Breast-conserving surgery after fluorodeoxyglucose injection was performed with low medical staff exposure.

Allozyme electrophoresis and three different DNA sequences (ATOC180 satellite DNA, 5SrDNA repeats, and parts of the Adh gene) were used to compare the two closely related East Asian sibling species Drosophila sinobscura and D. hubeiensis producing fertile hybrids in the laboratory. The data were also applied to establish their phylogenetic relationships to the other species of the D. obscura group. Genetic divergence in 5SrDNA repeats and specifically in the Adh gene separate the two species clearly from each other and justify their species status. Both species are related to the European species of the D. obscura group but the presence of members of the ATOC 180 satellite DNA family, specific and common to the species triad D. ambigua, D. tristis and D. obscura, in the genomic DNA of D. sinobscura and D. hubeiensis put the two sibling species in their close neighbourhood.

Transmission-dependent convolution subtraction (TDCS) is a promising technique in quantitative SPECT for subtracting the scatter components from emission images. Usually, a 20% photopeak energy window is used in SPECT acquisitions. To date, no investigation has assessed the effects of energy windows in the subtraction of scatter components from emission images with the TDCS technique. To evaluate the energy dependence of the TDCS technique, we analyzed photopeak energy windows of 5%, 10%, 15%, 20%, 25%, 30%, and 35% using /sup 99m/Tc radionuclide. The scatter fractions for a point source placed in a water phantom were estimated using the triple-energy-window (TEW) technique. These estimates were used to establish the parameters of the TDCS equation as a function of transmission. The estimated parameters were applied to the TDCS technique to subtract the scatter components from data of corresponding energy windows using nonuniform and uniform phantoms. All data were reconstructed with the OSEM algorithm. The energy window dependence of the TDCS technique was verified by comparing the coefficients of variance (COV) of the data from the uniform phantom of each energy window. Ten Poisson deviates were generated from each projection's data from the uniform phantom. The nonuniform phantom results showed that the estimated parameters effectively estimated the scatter component from the projection image for each energy window. The COV for the 5%, 10%, 15%, 20%, 25%, 30%, and 35% windows were 2.10%, 1.76%, 1.44 %, 1.39%, 1.34%, 1.37%, and 1.61%, respectively. In the TDCS technique, any photopeak energy window from 15% to 30% may work almost as well as judged by the COV measured for a uniform phantom in this study. The best window by that measure was the 25% window.

Motion of the head during brain positron emission tomography (PET) acquisitions has been identified as a source of artifact in the reconstructed image. A number of techniques have been proposed to correct for this motion artifact, but they are unable to correct for a motion during an acquisition. The aim of this study was to develop a sinogram-based motion correction (SBMC) technique to correct directly the head motion during a PET scan using a motion tracking system and list-mode data acquisition. This method uses a rebinning procedure whereby the lines of response (LOR) are geometrically transformed according to the current values of six-dimensional motion data. A Michelogram was recomposed using the rebinned LOR, and the motion-corrected sinogram was generated. In the motion corrected image, the blurring artifact due to the motion was reduced by the SBMC technique. This technique was applied to actual PET data acquired in the list-mode, and demonstrated the potential for real-time motion correction of head movements during a PET acquisition.

We investigated the effects of attenuation correction and scatter correction on rCBF values with /sup 99m/Tc-ECD SPECT imaging. Scans were performed on seven subjects, in the presence of /sup 99m/Tc-ECD. Quantitative K/sub 1/ images were computed using the reconstructed images and the input function obtained with the frequent arterial blood sampling method. The images were reconstructed by the ordered subset expectation maximization (OSEM) reconstruction in which uniform and segmented /spl mu/ maps were used for attenuation correction with and without scatter correction. The transmission-dependent convolution subtraction technique was utilized for scatter correction. Segmented and uniform /spl mu/ maps were generated from magnetic resonance (MR) images. We also produced uniform /spl mu/ maps using ECD images obtained at various threshold levels and /spl mu/ values (0.11, 0.15, and 0.172 cm/sup -1/). Scatter correction improved the image contrast dramatically. There were no significant differences between K/sub 1/ images with attenuation and scatter corrections assuming a uniform /spl mu/ map (not 0.15 but 0.172 cm/sup -1/) and those corrected with segmented /spl mu/ maps for most regions. However, in the former images, values were overestimated for deep structures (e.g., overestimation of 9.5% in the striatum and 7.3% in the central semi oval). This small but significant error was also observed in phantom studies and Monte Carlo simulations. We show that the overestimation using uniform /spl mu/ maps is due to the weight of the path length in the bone. Absolute K/sub 1/ values were sensitive to the threshold level when the edge of the brain was determined from the ECD images, but the variation of the estimated K/sub 1/ was /spl plusmn/9.0% when the optimal threshold level was selected. This study suggests that the use of uniform attenuation /spl mu/ maps provides reasonable accuracy, despite a small but significant error in deep structure regions, and that uniform /spl mu/ maps may be provided from the emission data alone in this patient population.

Emission from individual InAs quantum dots by tunneling current injection using a scanning tunneling microscope (STM) is reported. By scanning the STM tip above the self-assembled InAs quantum dot structures, a spatially resolved scanning tunneling luminescence (STL) image was measured, which contained some peaks originating from InAs quantum dots. The width of these peaks are of the same size as the average dot size, suggesting that the resolution of this method is much higher than 20 nm.

We demonstrate visualization of electron flow from a point contact by using a micro-photoluminescence measurement technique. It was found that the photoluminescence intensity at the exit of the point contact was strongly reduced by the majority electron flow from the point contact. This is considered to be caused from that the majority electrons with large wave number reduce radiative recombination of the electron-hole pairs generated by the laser illumination, which was also supported by the time and spatial resolved measurement.

This study proposes a new method for the pixel-by-pixel quantification of regional CBF (rCBF) with positron emission tomography and H215O by using a reference tissue region. No arterial blood is required. Simulation studies revealed that the calculation of rCBF was fairly stable provided that the frame time was relatively short compared with total scan time. In practice, calculated CBF images correlated significantly with those obtained with the dynamic/integral method. Because the method accurately detects changes in CBF, it is particularly suitable for brain activation studies.

We discuss experimental results on the spatial and time resolved photoluminescence in quantum wires and dots using a micro-photoluminescence technique. Particularly, we succeeded in measuring time resolved photoluminescence from a single quantum dot. Very fast diffusion dynamics of excitons in the quantum wires were observed as well as long photoluminescence decay times in a single quantum dot. These results demonstrate the one-dimensional and zero-dimensional characters of excitons in the quantum nanostructures.

The objective of this study was to evaluate a resolution recovery (RR) method using a variety of simulated human brain [¹¹C]raclopride positron emission tomography (PET) images. Simulated datasets of 15 numerical human phantoms were processed by a wavelet-based RR method using an anatomical prior. The anatomical prior was in the form of a hybrid segmented atlas, which combined an atlas for anatomical labelling and a PET image for functional labelling of each anatomical structure. We applied RR to both 60 min static and dynamic PET images. Recovery was quantified in 84 regions, comparing the typical 'true' value for the simulation, as obtained in normal subjects, simulated and RR PET images. The radioactivity concentration in the white matter, striatum and other cortical regions was successfully recovered for the 60 min static image of all 15 human phantoms; the dependence of the solution on accurate anatomical information was demonstrated by the difficulty of the technique to retrieve the subthalamic nuclei due to mismatch between the two atlases used for data simulation and recovery. Structural and functional synergy for resolution recovery (SFS-RR) improved quantification in the caudate and putamen, the main regions of interest, from -30.1% and -26.2% to -17.6% and -15.1%, respectively, for the 60 min static image and from -51.4% and -38.3% to -27.6% and -20.3% for the binding potential (BP(ND)) image, respectively. The proposed methodology proved effective in the RR of small structures from brain [¹¹C]raclopride PET images. The improvement is consistent across the anatomical variability of a simulated population as long as accurate anatomical segmentations are provided.

In small animal imaging using a single photon emitting radionuclide, a high resolution gamma camera is required. Recently, position sensitive photomultiplier tubes (PSPMTs) with high quantum efficiency have been developed. By combining these with nonhygroscopic scintillators with a relatively low light output, a high resolution gamma camera can become useful for low energy gamma photons. Therefore, the authors developed a gamma camera by combining a pixelated Ce-doped Gd(2)SiO(5) (GSO) block with a high quantum efficiency PSPMT.GSO was selected for the scintillator, because it is not hygroscopic and does not contain any natural radioactivity. An array of 1.9 mm × 1.9 mm × 7 mm individual GSO crystal elements was constructed. These GSOs were combined with a 0.1-mm thick reflector to form a 22 × 22 matrix and optically coupled to a high quantum efficiency PSPMT (H8500C-100 MOD8). The GSO gamma camera was encased in a tungsten gamma-ray shield with tungsten pixelated parallel hole collimator, and the basic performance was measured for Co-57 gamma photons (122 keV).In a two-dimensional position histogram, all pixels were clearly resolved. The energy resolution was ∼15% FWHM. With the 20-mm thick tungsten pixelated collimator, the spatial resolution was 4.4-mm FWHM 40 mm from the collimator surface, and the sensitivity was ∼0.05%. Phantom and small animal images were successfully obtained with our developed gamma camera.These results confirmed that the developed pixelated GSO gamma camera has potential as an effective instrument for low energy gamma photon imaging.

It is unclear how bone cells at different sites detect mechanical loading and how site-specific mechanotransduction affects bone homeostasis. To differentiate the anabolic mechanical responses of mandibular cells from those of calvarial and long bone cells, we isolated osteoblasts from C57B6J mouse bones, cultured them for 1week, and subjected them to therapeutic low intensity pulsed ultrasound (LIPUS). While the expression of the marker proteins of osteoblasts and osteocytes such as alkaline phosphatase and FGF23, as well as Wnt1 and β-catenin, was equally upregulated, the expression of mandibular osteoblast messages related to bone remodeling and apoptosis differed from that of messages of other osteoblasts, in that the messages encoding the pro-remodeling protein RANKL and the anti-apoptotic protein Bcl-2 were markedly upregulated from the very low baseline levels. Blockage of the PI3K and α(5)β(1) integrin pathways showed that the mandibular osteoblast required mechanotransduction downstream of α(5)β(1) integrin to upregulate expression of the proteins β-catenin, p-Akt, Bcl-2, and RANKL. Mandibular osteoblasts thus must be mechanically loaded to preserve their capability to promote remodeling and to insure osteoblast survival, both of which maintain intact mandibular bone tissue. In contrast, calvarial Bcl-2 is fully expressed, together with ILK and phosphorylated mTOR, in the absence of LIPUS. The antibody blocking α(5)β(1) integrin suppressed both the baseline expression of all calvarial proteins examined and the LIPUS-induced expression of all mandibular proteins examined. These findings indicate that the cellular environment, in addition to the tridermic origin, determines site-specific bone homeostasis through the remodeling and survival of osteoblastic cells. Differentiated cells of the osteoblastic lineage at different sites transmit signals through transmembrane integrins such as α(5)β(1) integrin in mandibular osteoblasts, whose signaling may play a major role in controlling bone homeostasis.

The intravenous glucose tolerance test, IVGTT, has been used to evaluate patients in whom abnormalities in carbohydrate metabolism and diabetes mellitus are suspected. IVGTT, if analyzed using “minimal models”, or discrete-time methods, provides information on the sensitivity of glucose disappearance to insulin and on pancreatic sensitivity to glucose, information that cannot be obtained from direct analysis of the dynamic response alone. In a preliminary study, data obtained by intravenously injecting 18-FDG in four subjects was analyzed using a discrete-time model. The experimental details, the results and their implications will be discussed.

The digital pitting scar is a common clinical feature in patients with progressive systemic sclerosis (PSS). Its pathogenesis is unclear, but it may result in small ulcerations. The clinical and histological features of these lesions are poorly understood. Eighty-seven patients with PSS were examined at least once per year. Pitting scars were defined as pinhole-sized digital concave depressions with hyperkeratosis. They were seen in 34 cases (39%) and were located not only on the tips of the fingers, but also on the sides, especially on the radial border of the index and middle finger and the ulnar side of the thumb, where they had a linear arrangement. Additional pitting scars were noticed on the dorsal surface of the proximal interphalangeal and metacarpophalangeal joints. Pitting was closely associated with several signs of PSS, e.g. Raynaud's phenomenon, skin thickening or articular involvement (e.g. stiffness, swelling, pain). There was no relationship between the number of pitting scars and the duration of PSS. Biopsy samples were taken of the lesions on the lateral sides of fingers in 3 patients. Histologically, there was a plug-like hyperkeratosis with parakeratosis, homogenized collagen fibers and slight perivascular mononuclear cell infiltration. Calcification and altered collagen fibers were observed in the deep dermis. Although pitting scars of the fingertips may be different from those of the lateral sides of the fingers, both histologically and pathogenetically, they were similar clinically. The scar locations on the fingertips and finger joints (proximal interphalangeal and metacarpophalangeal) suggest that exogenous trauma, vibration injury and/or cold exposure may play a role in their pathogenesis.

Regular monitoring of PET scanner performance is mandatory to assure quality of acquired data. While extensive performance measurements include many scanner characteristics such as resolution, count rate, uniformity, sensitivity, and scatter fraction (SF), most daily QC protocols are limited to uniformity and sensitivity measurements. These measurements may be too insensitive to detect more subtle drifts in detector gains that could lead to reduced detection of primary and increased detection of scattered events. Current methods to measure SF, such as those prescribed by the NEMA protocols (SF-NEMA), however, require specially designed phantoms and are too cumbersome to be performed on a daily basis.In this study, a simple and versatile method to determine SF is described. This method (SF-DAILY) does not require additional measurements, making it suitable for daily QC. The method was validated for four different scanners by comparing results with those obtained with the NEMA 1994 protocol.For all scanner types and acquisition modes, excellent agreement was found between SF-NEMA and SF-DAILY.The proposed method is a very practical and valuable addition to current daily QC protocols. In addition, the method can be used to accurately measure SF in phantoms with other dimensions than the NEMA phantom.

Henoch-Schönlein purpura (HSP) is a small-vessel vasculitis characterized by palpable purpura on the lower extremities and IgA-dominant immune complex deposition within the wall and lumen of dermal vessels in the lesions. This disorder is associated, to varying degrees, with joint, gastrointestinal and renal involvement. Antiphospholipid antibodies, including anticardiolipin antibodies (aCL Abs), are a heterogeneous group of circulating autoantibodies found in patients with autoimmune and infectious diseases.To investigate the possible role of aCL Abs in adult HSP, we measured levels of serum IgA, C-reactive protein (CRP), aCL Abs of the IgG, IgM and IgA isotypes and anti-beta(2)-glycoprotein I (beta(2)GPI)-dependent aCL Abs in adult patients with HSP. We evaluated the correlation between these biological parameters and the clinical manifestations.Adult patients with HSP with an initial cutaneous manifestation of palpable purpura on their lower extremities seen between 2001 and 2005 in our department were retrospectively reviewed. Patients with known connective tissue diseases were not included in the study. Histological examination of all patient skin biopsy specimens revealed leucocytoclastic vasculitis in the upper and mid-dermis. Direct immunofluorescence analysis showed prominent deposits of IgA in the capillary walls of all patients. Blood samples were taken at the time that the patient presented. Serum levels of aCL Abs and anti-beta(2)GPI-dependent aCL Abs were measured by enzyme-linked immunosorbent assay.Twenty adult patients with HSP (12 men and eight women), mean age 62.2 years (range 23-81) were enrolled. IgA aCL Abs were found in 15 of the 20 patients (75%). All were negative for IgG aCL Abs, IgM aCL Abs and anti-beta(2)GPI-dependent aCL Abs. The elevation of serum IgA aCL Abs in the 15 patients showed a significant correlation with serum IgA and CRP levels (r(s) = 0.91, P = 0.0007; r(s) = 0.80, P = 0.0026, respectively). Levels of serum IgA aCL Abs were also significantly associated with arthralgia (P = 0.022) and proteinuria according to urinalysis (P = 0.013).Serum levels of IgA aCL Abs are elevated in the initial active stage of adult HSP, suggesting that serum IgA aCL Abs may play some role in the onset of adult HSP. We believe that serum IgA aCL Abs might be an indicator of adult HSP activity.

Regional myocardial blood flow (MBF) can be measured with I5O-water and PET using the one-tissue compartment model (IT model) with perfusable tissue fraction (PTF), which provides MBF value that is free from the partial volume effect (PVE). Study with I5O-water has several advantages such as the ability of repeated scan. However, the image quality of 15O-water is limited, which impedes the computation of MBF and PTF values at the voxel level. We implemented the basis function method (BFM) for generating parametric images of MBF, PTF and arterial blood volume (Va) with 15O-water and PET. The BFM is to linearize the solution of IT model, which results in a computationally much faster method than the conventional non-linear least squares fitting method (NLM) in estimating the parameters. In order to fully automate the process of the BFM, PET images were realigned to a reference image using Affine transformation. Arterial input function with PVE correction was derived from the realigned PET images using templates of regions of left ventricle and myocardium. In order to validate the BFM, series of PET studies were performed on infarction model pigs (n=4). PET scans with 15O-water were performed with varying doses of adenosine (5-7 scans for each pig). The results by the BFM were well correlated to ones by the NLM. The method automatically generated functional maps computationally fast enough for clinical application.

The acquisition of 3D septa-less data in PET is gaining increasing acceptance but is still hampered by large data volumes and relatively long data transfer times. These problems are compounded by the desire for multiple time frames of data so that the increased efficiency of 3D can be fully utilised to define dynamic physiological processes. The tracer kinetics of /sup 11/C-diprenorphine and /sup 11/C-flumazenil (opiate and benzodiazepine receptor ligands respectively) have been studied using up to 20 time frames of 3D data. If the maximum number of projections (192) plus dual energy window data (for scatter correction) are acquired (32 MBytes per frame), the minimum frame duration in the authors' system is 3 min. This limit is imposed by the available sorter buffer memory (128 MBytes) and the disk transfer time (0.2 to 0.4 MBytes per sec). Although adequate for the measurement of volume of distribution (V/sub D/), for instance, this minimum time frame would not be so for many other dynamic studies. The effects of reducing the volume of data, by (i) averaging of projections and (ii) spatial averaging of the lower energy window, on resolution, scatter correction and V/sub D/ have been investigated. Preliminary findings indicate that there is considerable scope for data reduction without significantly affecting the final result. >

Attenuation correction (AC) is essential in order to get quantitative data with positron emission tomography (PET). AC is normally carried out using transmission scan, which is obtained by scanning a subject with external radiation source before the administration of radiopharmaceuticals. The transmission scan makes longer time of PET study and additional radiation exposure to the subject. To avoid these inconveniences, we have aimed to develop a technique to generate attenuation map without the transmission scan for brain PET study. In the procedure, a special cap was designed to put on the head of the subject to be scanned for brain PET study. The surface of the cap has 22 points of markers. An optical tracking system was utilized to determine positions of these 22 markers. In order to obtain the reference attenuation map and positions of 22 markers, the cap was put on the head of a reference subject and the transmission scan was performed. In order to generate a subject's attenuation map, the subject put on the cap and the positions of 22 markers were determined by the optical tracking system. The thin plate spline (TPS) technique was employed to transform from the reference attenuation map to a target subject's attenuation map using 22 markers as control points. Preliminary experiment showed good agreement between the attenuation map computed by the present method and the actual attenuation map by the transmission scan. The present method has potential to shorten brain PET study and reduce the exposure of radiation to the subject. The method might provide an accurate attenuation map for single-photon emission computed tomography (SPECT) study.

A vertical microcavity laser structure with an active layer of Stranski-Krastanow quantum dots was fabricated for the first time. The microcavity consists of an InGaAs quantum dot layer grown by MOCVD, located between two AlAs/Al0.2Ga0.8As distributed Bragg-reflector mirrors. The length of the microcavity was 4λ(λ = 884 nm). The cavity effect was evidenced by the difference of the PL linewidths of samples with and without the cavity.

A flying height tester has been developed for measuring low disk-to-media gap and high disk rotation speeds. The tester can obtain two-dimensional measurement data for a flying head, using an adaptive detection algorithm and signals from a color television camera. A depolarizing unit is used to suppress measurement errors caused by the photoelastic effect of the glass disk at high rotation speeds.

Measurements of the oxygen consumption in brain have been studied by PET. Autoradiographic method(ARG) was suggested (Mintum et al.) to yield CMRO2. This method required separately obtained information about CBF, CBV, thus time of 30-60 min. is required for three separate scans. We developed a rapid dual table method, in which water and oxygen are continuously administrated with the 90-180 sec of water and 180 sec of oxygen scan. In order to derive the quantitative CMRO2 in PET scan, it is necessary to obtain the arterial blood time activity curve. In this study, a method to estimate the input functions corresponds to [/sup 15/O] water injection and [/sup 15/O] oxygen inhalation, in a continuously administration study, was developed. A method developed was model-based, employing a fitting method. In order to estimate the reliability of developed method, input functions of [/sup 15/O] water injection and [/sup 15/O]oxygen inhalation obtained separately in a clinical study was combined with time lag of 90 seconds and 180 seconds. The reproducibility was examined by comparing the blood input functions obtained from present method and from original input functions obtained in clinical study. After fitting the combined input function with model function, each input function of [/sup 15/O] water injection and [/sup 15/O] oxygen inhalation was derived. The whole shapes were in agreement with each other. This method could be used for estimation of each input function in continuously water and oxygen administrated study.

Measurements of the oxygen consumption in brain have been studied by PET. Autoradiographic method(ARG) was suggested (Mintum et al.) to yield CMRO/sub 2/. This method required separately obtained information about CBF, CBV, thus time of 30-60 min. is required for three separate scans. To decrease the scan time, a new protocol was suggested as a rapid dual table method(ARG-D), in which [/sup 15/O]water injection scan and [/sup 15/O]O/sub 2/ inhalation scan are continuously carried out. Another method of weighted integration(WI) method with single 3 min. /sup 15/O/sub 2/ inhalation scan was suggested (Ohta et W.). We modified this method by taking into account the water re-circulation(WI-WR). In this study, the statistical noise properties and effects of error propagated from dispersion, delay and volume of distribution on CMRO/sub 2/ image, derived by these methods were evaluated. Tissue time activity curves was generated from typical blood time activity curves. A 80% of noise at a peak in [/sup 15/O]water tissue time activity curve was added to study the noise propagation and accuracy in CMRO/sub 2/ image. Also dispersion, delay, and volume of distribution was varied and evaluated the error propagation. Methods of ARG, WI-WR and ARG-D, reproduce the given CMRO/sub 2/ within 2% accuracy, while method WI gives CMRO/sub 2/ 5-15 The effect of noise in unit of %SD was 12 % for ARG, 25 % for WI and WI-WR, and 17 % for ARG-D method. On the basis of simulation study suggests that the ARG-D method developed could be used to estimate the CMRO/sub 2/ values in clinic.

Recently list mode (event-by-event) data acquisition with positron emission tomography (PET) has been widely noticed because the list mode acquisition is superior to the conventional frame mode data acquisition in terms of (1) higher efficiency of data storage, (2) higher temporal resolution and (3) higher flexibility of data manipulation. The aim of this study is to investigate the performance of list mode data acquisition with ECAT HR and HR + PET scanners(CTI PET Systems). The cylindrical phantom (16 cm diameter and 16 cm long) filled with /sup 11/C solution for HR and /sup 15/O solution for HR+ was scanned several times varying the radioactivity with list mode and frame mode acquisitions. The scans with the septa (2D mode) and without the septa (3D mode) were also carried out in order to evaluate the effect of interplane septa on quality of the list mode data. The acquired list mode data were sorted to sinogram and reconstructed using filtered back-projection algorithm. The count rate performance of the list mode data was comparable to the frame mode data. However list mode acquisition could not be performed if radioactivity in the field-of-view was high (more than 3 mCi for 3D mode) due to lack of transfer speed for sending data from memory to hard disk. 10 replicated data set from one list mode data were generated to estimate the noise in the reconstructed image. The reconstructed images with 3D mode has more than 60% better signal-to-noise ratio compared to the image with 2D mode. Generated file size of list mode was also evaluated. In the case of HR+ with 3D list mode, list mode data with 2.31 MBytes/s for 1mCi injection were generated. Out results suggest that careful attention must be paid for protocol of the list mode data acquisition in order to obtain the highest performance of the PET scanner.

Dietary diacylglycerol (DAG) oil is an edible oil enriched in DAG (more than 80%). A recent investigation indicated that DAG oil or its components may have beneficial effects on the prevention and management of obesity. We evaluated the genotoxic potential of DAG oil using standard genotoxicity tests. Bacterial reverse mutation assay (Ames test), the chromosomal aberration assay in cultured Chinese hamster lung cells (CHL/IU), and a bone marrow micronucleus assay in ICR CD mice were employed in the present study. In addition we have tested the possibility that genotoxic substances may be formed during cooking, heated DAG oil (HDG) was prepared by batch frying potato slices in the oil at 180 degrees C for 8 h/day for three consecutive days. Therefore, genotoxicity tests were also performed on HDG. Results obtained did not show any genotoxic effect on either unheated DAG oil (UDG) or HDG. We conclude that there are no safety concerns on the genotoxicity of DAG oil under the conditions for normal use.

We observed a very sharp photoluminescence peak from a single GaAs/AlGaAs quantum dot structure by using a microphotoluminescence measurement technique. The spectral linewidth was more suppressed by decreasing the excitation laser power, which is mainly due to reduction of the filling effect of quantized energy levels. The minimal spectral linewidth with low excitation laser power was 0.9 meV.

One‐dimensional diffusion of excitons in GaAs quantum wires was observed by using microphotoluminescence measurements at low temperature. The observed diffusion length increased with decreasing wire width from 30 to 15 nm, and decreased from 15 to 7 nm, where maximum diffusion length was about 4 μm for the 15 nm quantum wire, which is the largest value so far reported. It is considered that the change of diffusion length versus wire width is caused by the competition between one‐dimensional character and the interface fluctuation.

For the application of a kinetic model to PET data, it is necessary to obtain the arterial input function. Since arterial blood sampling is invasive and labor intensive, a method to evaluate the input function without arterial blood sampling is important. In case of the [/sup 15/O] water injection study, because of the noise in the time activity curve obtained from the PET reconstructed image round the carotid artery region, a model based evaluation method might be promised. In this study, a model function is composed or combination of blood time activity curve function and tissue time activity curve function which is generated from blood activity curve function. The present method was applied to 15 of dynamic PET scans or /sup 15/O water (10 normal subjects, 10 : Rest, and 5 : Diamox) for normal volunteers. The time activity curve obtained was fitted with the above model function. The shapes or input function obtained was in agreement with that by arterial blood sampling. The accuracy of height of the peak was 14 % and the accuracy of area under the curve was 10 %. This study supposed that present method could be used for direct extraction of the carotid artery input function from the dynamic PET image, and could be used in a quantitative CBF study using /sup 15/O water PET.

A new type of nonlinear image processing filters for multimedia applications is proposed. The filters remove small-amplitude fluctuations while keeping edges sharp. The filter algorithm is simply realized by combination of a usual linear filter and a comparator, which is suitable for hardware implementation. Here, two types of multimedia applications are considered, one is to post-process block-based encoded images which contain blocking artifacts, and the other to remove undesirable skin components in facial images, which is useful for facial beautification. Computer simulations verify the high performance of the proposed methods.

Thermal stability has been investigated for the structure and the perpendicular anisotropy Ku of Nd44Gd56/Fe89Co11 multilayer films with the bilayer period of 1 nm, where Ku becomes the maximum. From the results of isothermal annealing at temperature Ta, it has been found that the saturation magnetization Ms scarcely changes up to Ta=400 °C, while Ku is almost constant up to Ta=200 °C but decreases rather quickly for Ta above 200 °C. The decrease in Ku for Ta≳260 °C is accompanied by the decrease in the peak intensity of low angle x‐ray diffraction, namely by the deterioration of the layered structure.

We describe the case of 55-year old male with antiphospholipid syndrome (APS) who developed pulmonary hypertension without any thromboembolic episode. Multiple pulmonary perfusion defects suggestive of in situ thrombosis were observed. Hematological findings revealed microangiopathic hemolytic anemia and thrombocytopenia. These findings were improved by anticoagulant therapy. We monitored mean pressure of pulmonary artery (mPAP) and total pulmonary vascular resistance (TPR) before and after using vasodilator agents by Swan-Ganz catheter. mPAP and TPR showed improvement on treatment with oxygen supplementation therapy and Isosorbide administration. Previously 11 cases with APS complicated with pulmonary hypertension were reported. Majority of these patients have had recurrent venous thrombosis, particularly deep vein thrombosis often accompanied by pulmonary thromboembolism (8/11 cases, 72%). However in this case pulmonary hypertension with APS may be induced by in situ thrombosis in pulmonary micro vessels.

Quantitative measurement of tumor blood flow with [15O]water can be used to evaluate the effects of tumor treatment over time. Since quantitative flow measurements require an input function, we developed the profile fitting method (PFM) to measure the input function from positron emission tomography images of the aorta. First, a [11C]CO scan was acquired and the aorta region was analyzed. The aorta diameter was determined by fitting the image data with a model that includes scanner resolution, the measured venous blood radioactivity concentration, and the spillover of counts from the background. The diameter was used in subsequent fitting of [15O]water dynamic images to estimate the aorta and background radioactivity concentrations. Phantom experiments were performed to test the model. Image quantification biases (up to 15%) were found for small objects, particularly for those in a large elliptical phantom. However, the bias in the PFM concentration estimates was much smaller (2%-6%). A simulation study showed that PFM had less bias and/or variability in flow parameter estimates than an ROI method. PFM was applied to human [11C]CO and [15O]water dynamic studies with left ventricle input functions used as the gold standard. PFM parameter estimates had higher variability than found in the simulation but with minimal bias. These studies suggest that PFM is a promising technique for the noninvasive measurement of the aorta [15O]water input function.

We report a 39-year-old man with unilateral dermatomal cavernous haemangiomatosis (UDCH). Clinically, three haemangiomas were unilaterally distributed in the C6 dermatome. Histologically, these haemangiomas were distinct from routine cavernous haemangioma in that hyperplasia of smooth muscle cells on the vascular wall was observed, and electron microscopy showed that smooth muscle cells contained myofilaments and a crystal-like structure in the endothelial cells. This is distinct from Weibel-Palade bodies, which are rod-shaped cytoplasmic organelles measuring approximately 0.1 microm in diameter with a parallel linear structure. In UDCH, the haemangiomas occur only in the skin. They are clinically and histologically similar to those of blue rubber bleb naevus syndrome (BRBNS), but in BRBNS there are multiple haemangiomas in the digestive tract and other organs. UDCH is distinct from Maffucci syndrome in that enchondromata and malignant tumours are absent. To our knowledge, this is the second case of UDCH reported in the literature.

PET studies with [11C]raclopride provide an indirect measure of changes in synaptic dopamine. Previously, we used the bolus-plus-infusion (B/I) method to assess dopamine response from the percentage change in binding potential (deltaBP) before and after administration of amphetamine. The goal of this work is to optimize the measurement of changes in neurotransmitter with the B/I method by choosing the optimal timing for pre- and poststimulus scanning.Two sources of variability in deltaBP were considered: within-subject and between-subject noise. A noise model based on a phantom study and human data was used to evaluate the within-subject noise. For between-subject noise, simulated time--activity curves were generated from measured [11C]raclopride input functions. Optimal timing to measure deltaBP was determined and applied to human data.According to the simulation study, the optimal scan times for pre-and poststimulus scans were 39-50 and 58-100 min, respectively. The optimal timing resulted in a 28% noise reduction compared with the original timing. By applying the optimal timing to human studies, the statistical significance of the difference in deltaBP between patients with schizophrenia and healthy volunteers increased from P = 0.038 to 0.012.Careful assessment of the sources of noise in receptor imaging studies can increase the sensitivity of the B/I method for the detection of biologic signals.

We have developed a method for obtaining the cumulated activities in organs from radionuclides, which are injected into the patient in nuclear medicine procedures, by external exposure measurement with thermoluminescent dosimeters (TLDs) which are attached to the patient's body surface close to source organs to obtain information on body-surface doses. As the surface dose is connected to the cumulated activities in source organs through radiation transmission in the human body which can be estimated with the aid of a mathematical phantom, the organ cumulated activities can be obtained by the inverse transform method. The accuracy of this method was investigated by using a water phantom in which several gamma-ray volume sources of known activity were placed to simulate source organs. We then estimated by external measurements the organ cumulated activities and absorbed doses in subjects to whom the radiopharmaceuticals 11C-labelled Doxepin, 11C-labelled YM09151-2 and 11C-labelled Benzotropin were administered in clinical nuclear medicine procedures. The cumulated activities in the brain obtained with TLDs for Doxepin and YM09151-2 are 63.6 +/- 6.2 and 32.1 +/- 12.0 kBq h MBq-1 respectively, which are compared with the respective values of 33.3 +/- 9.9 and 23.9 +/- 6.2 kBq h MBq-1 with direct PET (positron emission tomography) measurements. The agreement between the two methods is within a factor of two. The effective doses of Doxepin, YM09151-2 and Benzotropin are determined as 6.92 x 10(-3), 7.08 x 10(-3) and 7.65 x 10(-3) mSv MBq-1 respectively with the TLD method. This method has great advantages, in that cumulated activities in several organs can be obtained easily with a single procedure, and the measurements of body surface doses are performed simultaneously with the nuclear medicine procedure, as TLDs are too small to interfere with other medical measurements.