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We have designed and tested a large-area (0.15~m$^2$) neutron detector based on neutron capture on \ce{^{6}Li}. The neutron detector design has been optimized for the purpose of tagging the scattering angle of keV-scale neutrons. These neutron detectors would be employed to calibrate the low-energy ($, Comment: 25 pages, 14 figures, and 2 tables

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Accurate prediction of fracture toughness from Charpy energy is challenging due to the differences between fracture toughness tests and Charpy tests, such as geometry (deep sharp crack vs. shallow blunt V-notch) and loading rate (quasi-static vs. dynamic). This paper uses experimental and numerical approaches to investigate whether the Weibull stress can be used to scale Charpy energy to fracture toughness in the lower transition region. A Weibull-stress based energy scaling model is proposed which is shown to accurately predict cleavage fracture at quasi-static loading rates. An extension of the energy scaling approach to dynamic loading conditions indicates that the Weibull modulus is independent of strain rate, and that quasi-statically derived moduli can be used to predict fracture toughness from a dynamically tested Charpy specimen. The paper concludes that the proposed energy scaling approach, and its extension to dynamic loading conditions, provides a suitable basis for relating Charpy energy to fracture toughness in the lower transition region.

(ABRIDGED) We present a power spectrum analysis of the 10K catalogue from the 2dF QSO Redshift Survey. We compare the redshift-space power spectra of QSOs to those measured for galaxies and Abell clusters at low redshift and find that they show similar shapes in their overlap range, 50-150h^{-1}Mpc, with P_QSO(k)\propto k^{-1.4}. The amplitude of the QSO power spectrum at z~1.4 is almost comparable to that of galaxies at the present day if Omega_m=0.3 and Omega_Lambda=0.7 (the Lambda cosmology), and a factor of ~3 lower if Omega_m=1 (the EdS cosmology) is assumed. The amplitude of the QSO power spectrum is a factor of ~10 lower than that measured for Abell clusters at the present day. At larger scales, the QSO power spectra continue to rise robustly to ~400 h^{-1}Mpc, implying more power at large scales than in the APM galaxy power spectrum measured by Baugh & Efstathiou. We split the QSO sample into two redshift bins and find little evolution in the amplitude of the power spectrum. The QSO power spectrum may show a spike feature at ~90h^{-1}Mpc assuming the Lambda cosmology or ~65 h^{-1}Mpc assuming an EdS cosmology. Although the spike appears to reproduce in both the North and South strips and in two independent redshift ranges, its statistical significance is still marginal and more data is needed to test further its reality. We compare the QSO power spectra to CDM models to obtain a constraint on the shape parameter, Gamma. For two choices of cosmology (Omega_m=1, Omega_Lambda=0 and Omega_m=0.3, Omega_Lambda=0.7), we find the best fit model has Gamma~0.1 +-0.1., MNRAS Accepted

A 67-year-old man presented with neck cellulitis following acupuncture for cervical spondylosis. Blood cultures were positive for methicillin-sensitive Staphylococcus aureus. Increased neck pain and bacteraemia prompted MRI, which showed atlanto-axial septic arthritis without signs of infection of the tissues between the superficial cellulitic area and the atlanto-axial joint, thus making direct extension of infection unlikely. It is more likely that haematogenous spread of infection resulted in seeding in the atlanto-axial joint, with the proximity of the arthritis and acupuncture site being coincidental. Acupuncture is a treatment option for some indolent pain conditions. As such, acupuncture services are likely to be more frequently utilised. A history of acupuncture is rarely requested by the admitting doctor and seldom offered voluntarily by the patient, especially where the site of infection due to haematogenous spread is distant from the needling location. Awareness of infectious complications following acupuncture can reduce morbidity through early intervention.

Fourteen bacteriophages of Erwinia carotovora subsp. carotovora, the causal agent of bacterial soft rot, were isolated from samples of fertilizer solutions taken from a greenhouse producing calla lily (Zantedeschia spp.). To avoid a single-host selection bias, a mixture of four bacterial hosts was used to enrich bacteriophages. Molecular characterization of the phages with restriction endonuclease digestions indicated that two distinct types had been isolated. Representatives from both molecular groups were studied by electron microscopy to determine their morphology. The phages possessed icosahedral heads with long, flexible tails. On the basis of morphotypes, the bacteriophages of E. carotovora subsp. carotovora were placed in the order Caudovirales. Limited host-range studies revealed that both phage groups would lyse only E. carotovora subsp. carotovora isolates taken from calla tubers infected with bacterial soft rot. When assayed for persistence in fertilizer solutions for calla lilies, phage titres...

The 2 m robotic Liverpool Telescope reacted promptly to the gamma-ray burst GRB 050502a, discovered by INTEGRAL, and started observing 3 minutes after the onset of the burst. The automatic identification of a bright afterglow with r' ~ 15.8 mag triggered, for the first time, an observation sequence in the BVr'i' filters during the first hour after a GRB. Observations continued for ~1 day using the RoboNet-1.0 network of 2 m robotic telescopes. The light curve in all filters can be described by a simple power law with index of 1.2 ± 0.1. We find evidence for a bump rising at t ~ 0.02 days in all filters. From the spectrum and the light curve, we investigate different scenarios and find possible evidence for a uniform circumburst medium with clumps in density, as in the case of GRB 021004. Other interpretations of such bumps, such as the effect of energy injection through refreshed shocks or the result of a variable energy profile, are less favored. The optical afterglow of GRB 050502a is likely to be the result of slow electron cooling, with the optical bands lying between the synchrotron peak frequency and the cooling frequency.

atura poisoning of horses is extensively reviewed. An outbreak of intractable impaction colic affecting 18 of 83 horses was stopped by withdrawing dried tef hay contaminated with young Datura plants. The dried, botanically identified Datura stramonium and D. ferox contained respectively 0.15 % mass/mass (m/m) hyoscyamine as well as 0.16 % m/m hyoscine (scopolamine) and only hyoscine at a concentration of 0.11 % m/m. Immature, unidentifiable plants resembling D. stramonium, contained 0.14 % m/m and 0.12 % m/m of the 2 respective tropane alkaloids. The outbreak was characterised by protracted and repeated colic attacks due to impaction of the large colon and/or caecum without any other anti-muscarinic signs. Comparative analyses of single specimens of dried seed of the 2 species collected from both fertilised and waste areas revealed that young South African Datura spp. had levels of tropane alkaloids comparable to those in the well-known toxic seed and were, consequently, equally toxic. The inherent danger of tef hay being contaminated with Datura is emphasised. To our knowledge this is the 1st field case of poisoning in horses ascribed to the vegetative parts of Datura spp.

Intrahippocamal injections of kainic acid (KA) significantly increase the expression of monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-2 (MIP-2) in the ipsilateral hippocampus at 2-4 h and 21-45 days post-administration, suggesting the possible involvement of these chemokines in both neurodegenerative and regenerative processes. To examine the possible role of these chemokines on neuronal cell death, hippocampal neurons were incubated with either MCP-1 or MIP-2 in vitro and examined to assess the effects on neuronal cell viability. These treatments resulted in significant neuronal apoptosis that could be abrogated by prior treatment with the caspase-1 inhibitor, Z-VAD-FMK, the caspase-3 inhibitor, Z-DEVD-FMK, the Galphai inhibitor, pertussis toxin, or the MAO-B inhibitor, (-)deprenyl. Furthermore, this chemokine apoptotic effect could also be observed in vivo as intrahippocampal injections of MCP-1 or MIP-2 resulted in the apoptosis of hippocampal neurons, thus supporting a direct role of these chemokines in neuronal death. In contrast, immunohistological analysis of kainic acid lesions on days 21-45 revealed significant expression of MCP-1 and MIP-2 associated with reactive astrocytes and macrophages, respectively, with no apoptotic populations being observed. These results suggested that these chemokines might also mediate distinct biological effects on local microenvironmental cell populations at various stages post truama and during cellular repair. To address this possibility, astrocyte were cultured in the presence or absence of these chemokines and examined by microarray analysis for effects on astrocytes gene expression. A number of genes encoding proteins associated with inflammation, cellular signaling, differentiation, and repair were directly modulated by chemokine treatment. More specifically, the RNA and protein expression of the neurotrophic factor, basic fibroblast growth factor (bFGF), was found to be significantly increased upon culture with MCP-1 and MIP-2. Conditioned media derived from chemokine-stimulated astrocytes also facilitated bFGF-dependent neuronal cell differentiation and promoted survival of H19-7 neurons in vitro, suggesting a possible role for chemokine-activated astrocytes as a source of trophic support. Taken together, these data support possible autocrine and paracrine roles for MCP-1 and MIP-2 in both the "death and life" of hippocampal neurons following CNS injury.

Contamination issues are increasingly causing pumping equipment reliability concerns, as the upstream sector pushes for production in ever more marginal fields. Seal designers are frequently in a position where design requirements conflict. Increasing contamination, industry trends for high barrier fluid pressures, coupled with larger shaft diameters and high shaft speeds only serve to exacerbate these issues. The paper discusses the three different recognised dual seal configurations and some of the advantages and disadvantages. Choices and execution barrier fluid system also impact on design choice. A case study is presented where contamination caused high levels of leakage from a traditional dual seal and where alternative configuration proved more reliable.

Since the development of the Nimonic1 alloys for Sir Frank Whittle’s first jet engine, Henry Wiggin Ltd, now part of Special Metals Corporation, has been involved with the design and improvement of nickel alloys for aerospace engineering. Whilst much of this work continues to be in relation to alloys for the high strength/high temperature applications of turbine blades, discs, seals, rings and casings of aero engines, nickel alloys are being utilised for other key aerospace engineering areas such as tooling for composite manufacture. The focus of this paper is on four recent developments in nickel alloys for aerospace engineering, namely: disc alloys; low expansion superalloys; Inconel alloy 718SPF – a nickel base superalloy capable of being superplastically formed; Nilo (low expansion alloys) for composite tooling.

A Bruker model IFS 125HR Fourier transform interferometer has been installed and its performance tested using high-brightness, far-infrared synchrotron radiation. Results of absorption measurements for the rotational modes of water vapor demonstrate a nearly 10-fold improvement in signal-to-noise when compared with the instrument’s internal high-pressure Hg arc lamp source.

Members of two barley gene families, blt 4 and blt 101, previously shown to be upregulated in winter cultivar Igri by a period of low temperature treatment, responded to challenge and infection by Erysiphe graminis f.sp. hordei . There was at normal temperature a transient and modest increase in transcript accumulation of blt 4 genes in shoots and leaves within hours of inoculation. When plants with established infections were transferred to low temperature, transcription of blt 4 and blt 101, in leaves and shoots, was less than that in uninfected plants. The degree of inhibition of transcript accumulation in both leaves and shoots was positively related to the area of leaf inoculated and was weakest, but detectable, in uninoculated tissues. Infected plants subject to a freezing and regrowth test showed no significantly increased susceptibility to freezing injury compared to non-infected plants. Survivors and non survivors of this test showed no significant difference in transcript accumulation of these genes in leaves harvested immediately prior to the test.

Refinement of the crystallographic structure of (1:1) CdII3[(FeIII/CoIII)(CN)6]2·14H2O (I) has been carried out by means of three-dimensional single-crystal X-ray diffractometry. This novel disordered mixed anionic complex crystallizes in the cubic space groupFm 3 m(Z=11/3) witha0=10.638(1) A. Based on 166 unique reflections, the employed full-matrix least-squares method yielded a final reliability factor ofR=0.041 (Rw=0.047) and a goodness-of-fit value (Σ2) of 1.79. Indexed power diffraction data are reported and evaluated according to the quantitative figures-of-meritF21=114 (0.007, 25) andM20=154.9. A thermal gravimetric analysis revealed 14 water molecules per formula unit and the experimental density is 1.93(5) Mg m−3[calc., 1.87(1) Mg m−3]. The divalent Cd atoms are linked to the (1:1) mixed metal atoms by linear cyanide bridging. The disordered structure I is isomorphous with the hydrated cobalticyanides of Mn and Cd. A hydrogen-bonding network is set up within cavities of the crystal lattice created by the molecular disorder. Selective geometric parameters as well as conoscopic and IR spectral results are presented.

The authors report on methods developed to reliably perform attenuation correction by post-injection transmission in a volume imaging PET scanner. The method directly measures the emission contamination during the transmission study, using a virtual transmission source position offset by 200 from the actual /sup 68/Ge transition source. Events are recorded only if they meet a co-linearity requirement with either the real or virtual source position. The simultaneous measurements of the emission contamination and transmission data remove the need for complex corrections to the emission data and are not subject to activity redistributions between emission and transmission scans performed sequentially. Correction is, necessary, however, for the extra deadtime that varies with the amount of emission activity in the FOV. The extra deadtime is determined from a lookup table of deadtime as a function of detector countrates, which are recorded during the study. The lookup table is based upon phantom measurements. Using patient and phantom data, with both preand post-injection transmission measurements, this method is shown to be reliable for attenuation correction in the body. In addition, it enables the calculation of Standardised Uptake Values for analyzing tumor activity.

The production of coat protein is necessary for cell-to-cell transport of potexviruses in plants. To investigate the role of coat protein in the movement process, the intracellular distribution of coat protein in tissues infected with either of two potexviruses was studied using immunocytochemical procedures. We report that coat protein antigens are associated with the plasmodesmata of infected cells.

Chiral separations of related compounds within a series of potassium channel activator (KCA) analogues were compared by supercritical fluid chromatography (SFC) and high-performance liquid chromatography (HPLC) at several temperatures between 0° and 52°C. Mobile phases as close as possible in performance were selected for the two modes of analysis, and the same chiral stationary phase (CSP) was used, namely, cellulose tris(3,5-dimethylphenyl-carbamate) (Chiralcel-OD). Two of the compounds, which differed only by replacement of a benzoyl group by a n-pentanoyl group, showed quite strikingly different temperature dependencies. These indicate that one compound is above, and the other below, its isoenantioselective temperature (Tiso), at which separation of enantiomers is not possible. The thermodynamic parameters for these chiral discriminations support the conclusion that, in spite of their very similar structures, quite different chiral recognition factors operate for these two racemic mixtures.

A chiral anthrylamine derivative was prepared and adsorbed on the surface of pre-packed porous graphitic carbon, and was evaluated as a chiral stationary phase in packed-column supercritical (and sub-critical) fluid chromatography. It successfully separated the enantiomers of two commercial anti-inflammatory agents and also a series of racemic tropic acid derivatives.

The open reading frame 2 (ORF2) of the potexviral genome encodes a 24- to 26-kDa protein which is part of the "triple gene block," a group of overlapping ORFs also present in the genomes of the carla-, hordei-, and furoviruses. The product of these ORFs is believed to play a role in the cell-to-cell movement of the viruses in host plants. The amino acid sequences of the homologous ORF2 products encoded by these related viruses suggest that they specify NTP binding and possibly helicase activities. We have used an Escherichia coli expression system to produce significant amounts of the 26-kDa protein (p26) encoded by foxtail mosaic potexvirus ORF2. p28 was purified to near homogeneity by conventional purification methods and some of its biochemical properties were determined. We present evidence that p26 is an ATP, CTP, and RNA binding protein with apparent ATPase activity. Western blot analysis of infected plant extracts using a polyclonal antiserum produced against p26 indicates that it is a relatively stable protein maintained at high levels for at least 6 days following its peak level of expression. Moreover, it is found predominantly in the soluble fraction of infected tissues. An immunocytochemical analysis of infected Chenopodium quinoa leaves reveals that p26 is exclusively associated with cytoplasmic inclusions in proximity to but distinct from aggregates of viral particles.

Using classical trajectory calculations the translational energy ratio of the final and initial energy ( E f E i ) for Ar inelastically scattered from a Pt(111) surface has been investigated for thermal and hyperthermal energies up to 30 eV. The Ar Pt (111) potential is based on a Hartree-Fock-Slater calculation for an Ar atom with a Pt4-cluster. The energy ratio varies strongly across the surface unit cell. There is a most unusual energy dependence: for energies below 16 eV the atop site shows the larger loss than the bridge and centre sites, whereas for higher energies the situation is reversed. This reversal can be understood in terms of a simple analytical model. The calculations show a site dependent onset for trapping and implantation.

A molecular dynamics simulation has been developed to study the trapping and scattering of rare gases at metal surfaces. We have carried out deterministic trajectory calculations of the interaction of Ar with a Pt(111) surface. We do not use the generalized Langevin method with periodic boundaries but instead use a crystal containing a relatively large number of atoms. The sandbag method is used to thermostat the surface. The interaction can be divided into two distinct channels; a trapping channel and a direct scattering channel. Trapping probabilities were calculated for different incident energies and angles for a range of surface temperatures (0 to 190 K). For low surface temperatures, the trapping scales with the normal kinetic energy of the Ar. The reported change in this energy scaling with surface temperature is shown to be due to atoms which trap but leave the surface after a short residence time. For the trapping channel, energy exchange with the surface was found to have greater efficiency for the perpendicular direction. Scattering has also been studied and the results are compared for high and low surface temperatures (80 and 500 K). The key issue addressed here is how the initial energy partitioning is changed as a consequence of interacting with the moving surface.

A molecular dynamics simulation using a large number of atoms has been developed to study scattering and trapping of heavy rare gases on metal surfaces. Trapping probabilities were calculated for different incident energies and angles for a range of surfaces temperatures for the Ar/Pt(111) system. At T s = 0 and 80 K trapping is strongly dependent upon the incident normal energy component and we observe near-normal energy scaling. At higher surface temperatures indirect inelastic scattering is observed. This fraction of the trajectories “desorbs” after a few bounces on the surface. During their encounters with the surface, these atoms begin to loose memory and as a consequence they overturn the normal energy scaling relationship.

The thermal disordering of Al(110) and Al(111) surfaces was studied up to temperatures of 0.5 and 1.2 K below the bulk melting point Tm, respectively. With the use of medium energy ion scattering it was found that surface melting is present on the (110) face but not on the (111) face. The (110) disordered layer thickness increases with temperature as ln[Tm(T>m − T)]. The result in terms of a thermodynamic model that was presented earlier to explain the melting of Pb surfaces.

The passivation behavior of nickel in 0.15 N Na2SO4 chloride-free solution is compared with that which occurs in a chloride-containing electrolyte. Insitu techniques, such as differential reflectometry and electrochemical polarization, are utilized in this study. The presence of Cl- ions did not alter the composition of the passivating film nor does Cl- alter the mechanisms by which passive film formation occurs. However, Cl− ions delay the growth of a passivating film at pH values of 4 and 8. In these solutions, film breakdown as well as severe pitting occurs subsequent to passivation. In contrast, in solutions of pH 12, the chlorides affect neither the film formation process nor film stability.

Observations that radio-quiet QSOs exist in average galaxy cluster environments (Smith et al. 1995 and references therein) demonstrate that QSOs can be used to derive important information on the structure of the Universe at the largest scales. Previous studies of QSO clustering have been frustrated by the lack of large QSO redshift surveys. Although QSO clustering is detected in the largest existing QSO catalogues (see Shanks & Boyle 1994), it is difficult to place strong limits on the cosmological evolution of QSO clustering or the level of clustering at large scales (> 10h–1 Mpc) with current QSO catalogues.

The discovery of a diminutive, small-brained hominin skeleton (LB1) from the Pleistocene of Flores, Indonesia, seems to present a paradox concerning the interpretation of overall brain size in an evolutionary context. This specimen forms the holotype of a purportedly new hominin species, Homo floresiensis. As inferred from the archaeological record, it has been suggested that this species of Homo, existing as recently as 12,000 years ago, engaged in sophisticated cultural behaviors with an adult brain size equivalent to that seen in modern chimpanzees and one that in modern humans would be defined as "high degree microcephaly" and "always associated with idiocy". The alternative explanation for these behaviors at the observed brain size would require that H. floresiensis deviate from existing patterns of primate brain scaling at either a macroscopic or microscopic level. Here we develop predictive equations and confidence intervals for estimating the size of various brain components in the human evolutionary lineage by calculating scaling relationships among overall brain size and 11 components of the primate brain using phylogenetically independent contrasts (PIC) methods. Using these equations, paleoanthropologists can: (a) estimate brain component size (and confidence intervals) for any primate in the fossil record if overall brain size is known; and (b) calculate some reasonable outside limits as to how far species-specific departures from allometric constraints (i.e., brain "reorganization") can be taken in assessing human brain evolution. We conclude that if the original assessment of LB1 is correct, i.e., that it samples a population from a new species of Homo, H. floresiensis, that was capable of Homo sapiens-like cultural attributes (fire, blade manufacturing, etc.), while having a chimpanzee-sized brain, then we are faced with the paradox that 1 cm(3) of H. floresiensis brain could not be functionally equivalent to 1cm(3) of a modern human or modern chimpanzee brain.

Experiments to compare the performance of several widely-used interconnection routing algorithms are described. Examples of the experimental results are given and their implications discussed.

Pulse power technology is a major engineering challenge for any particle accelerator. It is employed at Daresbury Laboratory on the existing synchrotron radiation source (SRS) for injecting and extracting electron beams and on the energy recovery linac prototype (ERLP) for thermionic valve protection. The proposed new 4th generation light source (4GLS) has a conceptual design that requires significant advances on the current pulse power technology operating at Daresbury Laboratory. (4 pages)

Abstract This paper describes Imperial Oil's success in identifying and remediating poor steam conformance in a horizontal well used in Cyclic Steam Stimulation operations. Imperial Oil is conducting Horizontal Well Cyclic Steam Stimulation (HWCSS) at nine horizontal wells located at two pads in Cold Lake. Steam conformance along horizontal wells is a significant issue in these types of thermal applications. The horizontal wells are completed with Limited Entry Perforations (LEP) to improve distribution of steam along the liner. One of the HWCSS pads, D36, has been the subject of both 4D seismic and injectivity analyses to characterize steam conformance along the horizontal section over the fi rst three cycles. These analysis techniques showed that four out of the five wells on the pad had excellent steam distribution along the horizontal liners. However, one of the wells, D36-H1, showed little or no steam conformance along the last half of the liner. This lack of horizontal steam conformance put the recovery expectations of this well at risk. A workover conducted on D36-H1 successfully removed sand that had been obstructing the liner. Steam injection subsequent to the clean-out showed steam distributed across the majority of the liner (most of the LEPs accepting steam). Introduction Imperial Oil has been conducting commercial operations at Cold Lake using Cyclic Steam Stimulation (CSS) since the mid- 1980s. CSS involves injecting steam at fracture pressure (>10 MPa) and producing a mixture of water, bitumen, and gas from the same wells. Approximately 3,000 wells are in operation at Cold Lake, the vast majority of which are deviated vertical wells. These wells are drilled from common surface pads, typically in groups of 20. As an enhancement to the CSS process, Imperial has been piloting Horizontal Well CSS (HWCSS) at nine 500 m long wells located at two pads. One of the main challenges of the HWCSS process is the control of steam conformance in the reservoir. To aximize recovery, it is necessary to contact as much of the reservoir as possible with steam. This becomes more difficult with advancing cycles because steam preferentially accesses channels that have already been heated and depleted of oil. Horizontal wells with conventional perforations or slotted liners could be further compromised by preferential steam injection into the heel of the well. To overcome this problem, Imperial Oil uses its patented Limited Entry Perforation (LEP) design to control the distribution of steam along the horizontal well liners(1). A schematic of the well completion and LEP design is shown in Figure 1. A previous publication has described the use of 4D seismicnd injectivity analyses to evaluate the effectiveness of LEPs at a 1,000 m infill horizontal well injector(2). This paper follows a similar analysis technique for D36 pad, one of the HWCSS pads at Cold Lake. Excellent steam conformance over the first four cycles is inferred from this analysis at four of the five wells on the pad. However, the analysis identified a steam conformance problem atne of the wells designated as D36-H1.

An optimized FDG PET survey of the human body should acquire data near peak camera performance. This is achieved by a knowledge of patient activity distributions and tumor uptake as well as camera performance characteristics. The C-PET camera has been used to perform both patient-matched phantom and clinical measurements. Phantom measurements of camera resolution, countrates, noise, signal-to-noise ratio (SNR) and contrast have been performed as a function of activity and scan duration. Measurements of body countrates and normal organ, whole body and tumor activity have been performed on patient data as a function of dose, uptake period and volume in the FOV. Peak NEC is reached at a singles countrate of 5 Mcps. However, image nonuniformity, contrast and SNR are optimal at 3 Mcps. At this countrate camera resolution is not significantly degraded while measured SNR and contrast for a torso-sized phantom are near their optimal values. Noise for head and leg matched phantoms are lower due to the reduced attenuation and scatter for these objects. Emission scan durations of 4 mins for the head and torso and 2 min for the legs result in only moderately reduced SNR compared to 10 min scans. Torso SUVs are constant across patients and uptake periods. Normal lung, liver, heart and kidney uptake remain constant to /spl plusmn/10% between 70 and 120 mins post-injection, while tumor uptakes increase by 30% over this period, showing the value of delayed imaging. In conclusion, an optimized FDG PET survey requires injection of 2.6 MBq/kg of /sup 18/F, a 60 minute uptake period and survey from knees to head (140 cm axially) within 60 minutes. In this way overall activities, countrates and SNRs are optimized. At the same time tumor uptakes are sampled near their peak while background activities are saturated or declining.

Post-injection singles transmission scanning has been implemented in the septumless PENN PET 240H scanner (prototype of the GE QUEST). The method uses a 6 mCi point transmission source of /sup 137/Cs at the axial center and 37 cm off transaxial center of the camera field of view. Singles transmission scans of 1.8 minutes per bed axial position provide similar scan count densities to 15 minute coincidence transmission scans with a 0.5 mCi /sup 68/Ge rod transmission source. Scatter and emission contamination suppression are achieved by applying a narrow 662 keV transmission photopeak energy window. The residual 511 keV emission contamination constitutes a background of uniform spatial distribution. Accurate and low noise attenuation correction is achieved by segmenting the singles transmission images into lung and soft tissue volumes. Established 511 keV gamma ray attenuation coefficients are then applied and these images are forward projected for attenuation correction. Expectation maximisation or OS-EM reconstruction of the transmission and emission images is used to improve image quality. Both the segmentation and OS-EM reconstruction maintain quantitative accuracy in the fully corrected emission images compared to measured coincidence transmission correction. Thus, a clinical protocol involving 40 minutes of emission scans followed by 20 minutes of singles transmission scans allow the 60 cm of the human torso to be fully scanned within 60 minutes. These quantitative whole body FDG PET images may then be used for tumor grading and assessment of tumor response to treatment.

The purpose of this study was to evaluate factors affecting the quality of the measured attenuation map and nonuniform attenuation compensation (AC) for SPECT myocardial perfusion imaging. Acquiring this map with low noise and accurate attenuation coefficients is important for simultaneous transmission-emission (STE) systems using fan beam geometry. The authors have investigated several factors affecting the measured attenuation map and AC using phantom and patient data. Myocardial uniformity decreased as extent of truncation increased. Finer sampling (128/spl times/128) in acquisition and reconstruction provided more accurate myocardial wall thickness and better contrast compared to 64/spl times/64 matrix. Downscatter correction improved accuracy of attenuation coefficients and myocardial uniformity. Reliable myocardial uniformity required scan durations of at least 14 minutes for myocardial activity of 350 /spl mu/Ci. Over a broad range of ML-EM iterations (20 to 50) in transmission (TCT) reconstruction measured attenuation coefficients for water were similar. Scatter correction improved normal myocardial wall contrast and moderate or severe defect contrast. In conclusion, methods to achieve accurate and low noise AC in myocardial imaging should use the best affordable sampling and scan duration, adequate activity of Gd-153 TCT source, proper positioning of patients and scatter correction.

The NEMA and IEC performance tests of PET cameras provide standard measurements of their intrinsic physical characteristics and the accuracy of corrections applied to them. However the clinical performance of PET cameras are more clearly defined by using patient data with clinical acquisition and processing parameters. Thus, a series of simple patient measurements are proposed to supplement the standard performance measurements. NEMA and clinical measurements are reported here for 3 PET cameras: the UGM 240 H, UGM CPET and HEAD PENN PET cameras. Totals and trues countrates and scatter fractions are compared to 6 liter (20 cm long) and 22 liter (70 cm) cylinder data, while tumor detectability data is used to illustrate the effects of camera resolution and sensitivity. Typical patient images with small tumors are compared to proposed NEMA image quality tests. The accuracy of corrections to the data are assessed from normal organ SUVs and from whole brain blood flow and metabolism measurements. Patient countrates are well reproduced by the 6 liter (brain) and 22 liter (body) cylinder data. However patient activities are typically 40-70% of the activities for peak trues countrates. The patient scatter fractions subtracted are 20% higher than NEMA measurements and patient volumes in the FOV are more than twice that of the 20 cm diameter cylinders. The sensitivity for typical patient studies is indicative of study noise per unit activity in the FOV. Superimposing measured hot sphere contrasts (for 4, 7 and 10:1 data) on a plot of tumor SUV against diameter the authors see the effects of partial volume and tumor metabolism on tumor detectability. These examples illustrate the value of patient measurements in defining clinical PET camera performance.

Single photon transmission scans, using /sup 137/Cs (662 keV gamma rays), are performed post-injection for clinical whole body PET studies. Two methods of processing the transmission data are investigated. The first method segments the transmission image into lung and soft tissue volumes. Average attenuation coefficients for 511 keV are applied and this transmission image is forward projected for attenuation correction. In the second method short emission contamination (EC) scans are performed after the singles transmission scans. These are singles transmission scans without a /sup 137/Cs transmission source. These EC scans are then subtracted from the transmission scans to remove contamination of the 662 keV energy window by 511 keV emission gamma rays. From ten patients studied by this method, the EC subtracted transmission images have average soft tissue attenuation coefficients of 0.074/cm, compared to the expected value of 0.086/cm for 662 keV gamma rays. Simple scaling of these transmission images to 511 keV values (0.095/cm) results in quantitative attenuation correction. A comparison of the two methods is made for these ten patient studies. Both methods result in accurate attenuation correction. The segmentation method performs low noise attenuation correction but is more limited to torso studies with the limbs out of the FOV. The EC subtraction method is more versatile and is applicable to the entire body but results in some more noise in the fully corrected images.