Ira Blevis

Philips | Philips · Diagnostic Imaging Research Area

In medical X-ray imaging using semiconductor detectors, small pixels are employed to increase image resolution and count rate capability. However, the use of small pixels increases the occurrence of imaging signals that are split between neighboring pixels or even lost in the gap regions between pixels. To assess this problem monolithic pixelated C...

The possibility of influencing nuclear beta decay with high intensity optical lasers is examined numerically with the appropriate exact wave functions of a Dirac electron in a plane-wave field, as in previous literature. The total β-decay rate for 3H is found to be unaffected by the laser field for a 2-eV laser with intensities in the range 1018–10...

A large-area flat-panel detector for digital radiology is being developed. The detector uses an array of dual-gate thin-film transistors (TFTs) to read out X-ray-generated charge produced in an amorphous selenium (a-Se) layer. The TFTs use CdSe as the semiconductor and use the bottom gate for row selection. The top gate can be divided into a "delib...

Calibration and quality control (QC) of gamma cameras with fixed pinhole collimators presents unique challenges since the usual assumption of uniform flood intensity at the surface of the detector is violated. For the GE Discovery NM 530c∗, a fast cardiac SPECT system with multiple pinholes and CZT detectors focused on the heart, the problem is fur...

The goal of this study is to present the Discovery NM 530c (DNM), a cardiac SPECT camera, interfacing multi-pinhole collimators with solid-state modules, aiming at slashing acquisition time without jeopardizing quality. DNM resembles PET since it enables 3-D SPECT without detector motion. We further envision how these novel capabilities may help wi...

The goal of this study was to evaluate the effect of the detector energy response on the quality of ^99mTc myocardial perfusion SPECT images. A Data Spectrum torso phantom was prepared to model the low-dose rest portion of a standard one-day myocardial perfusion protocol. Projection data were acquired with a recently developed Ultra-Fast...

To date, CZT has been investigated for a variety of nuclear imaging applications using mostly parallel hole collimators. The image quality realized has evolved to make these configurations competitive with the mature conventional configurations using scintillators such as NaI. However the full potential of CZT detectors is still evolving. In our in...

Myocardial perfusion imaging is currently the most frequently used nuclear medicine test. Recently, several alternative approaches to myocardial perfusion SPECT imaging have been evaluated. In this study, we compare imaging capabilities of the new ultra-fast cardiac (UFC) system developed by GE Healthcare to a conventional cardiac SPECT camera (Ven...

We tested the capacity of a newly developed portable gamma camera to precisely locate sentinel nodes by injecting a radiotracer. Two sets of experiments were performed on eight pigs under general anesthesia. 99mTc-Nanocolloid and dye complex was injected in the submuscular layer of the small bowel in the first set and subcutaneously in the knee reg...

This article provides the complete description of results from the Phase I data set of the Sudbury Neutrino Observatory (SNO). The Phase I data set is based on a 0.65 kiloton-year exposure of 2H2O (in the following denoted as D2O) to the solar 8B neutrino flux. Included here are details of the SNO physics and detector model, evaluations of systemat...

This article provides the complete description of resultsfrom the Phase I data set of the Sudbury Neutrino Observatory (SNO). ThePhase I data set is based on a 0.65 kt-year exposure of heavy water tothe solar 8B neutrino flux. Included here are details of the SNO physicsand detector model, evaluations of systematic uncertainties, andestimates of ba...

A high performance prototype gamma camera based on the semiconductor radiation detector Cd(Zn)Te is described. The camera features high spatial resolution, high-energy resolution, a reduced dead space on the edge of the field of view, and a compact format. The camera performance was first examined by comparison of small field of view examinations w...

Radioguided surgery depends on the intra-operative detection of radiolabelled tissues. This is currently accomplished with hand tools capable of providing a tone signal, depending on the proximity and direction of a radioactive source in relation to the probe. The advantages of visual images of radiolabelled tissues are well recognised, but satisfa...

An experimental imaging probe with a 4 cm×4 cm field of view and utilizing CZT (cadmium zinc telluride) technology has been constructed and evaluated for intra-operative applications. CZT is well suited to the application because of its compact size and good spatial and energy resolution as compared to other technologies. The CZT is instrumented to...

Monolithic CZT with multiple anode pads and a common cathode has been used in a number of gamma camera prototypes. The pixelation of the anode pads has been shown to result in high intrinsic resolution that in turn has been shown to yield advantages in both close subject planar imaging and in Single Photon Emission Computed Tomography. A major prob...

The technique used at the Sudbury Neutrino Observatory (SNO) to measure the concentration of in water is described. Water from the SNO detector is passed through a vacuum degasser (in the light water system) or a membrane contact degasser (in the heavy water system) where dissolved gases, including radon, are liberated. The degasser is connected to...

The technique used at the Sudbury Neutrino Observatory (SNO) to measure the concentration of 222Rn in water is described. Water from the SNO detector is passed through a vacuum degasser (in the light water system) or a membrane contact degasser (in the heavy water system) where dissolved gases, including radon, are liberated. The degasser is connec...

The purpose of this study was to evaluate a small semiconductor-based gamma camera that may have applications in scintimammography. A small cadmium zinc telluride (CZT) detector was evaluated. The detector had a field of view of 20 x 20 cm with detector elements of 2.5 x 2.5 mm in size. Both short-bore (35 mm) and long-bore (50 mm) collimators, mat...

We describe a method to measure the concentration of and in the heavy water target used to detect solar neutrinos at the Sudbury Neutrino Observatory and in the surrounding light water shielding. A water volume of 50– from the detector is passed through columns which contain beads coated with a compound of manganese oxide onto which the Ra dissolve...

As photodisintegration of deuterons mimics the disintegration of deuterons by neutrinos, the accurate measurement of the radioactivity from thorium and uranium decay chains in the heavy water in the Sudbury Neutrino Observatory (SNO) is essential for the determination of the total solar neutrino flux. A radium assay technique of the required sensit...

The Sudbury Neutrino Observatory (SNO) is a 1,000 tonne heavy water Cerenkov-based neutrino detector situated 2,000 meters underground in INCO's Creighton Mine near Sudbury, Ontario, Canada. For the neutrinos from 8B decay in the Sun SNO observes the Charged Current neutrino reaction sensitive only to electron neutrinos and others (Neutral Current...

Observations of neutral-current nu interactions on deuterium in the Sudbury Neutrino Observatory are reported. Using the neutral current (NC), elastic scattering, and charged current reactions and assuming the standard 8B shape, the nu(e) component of the 8B solar flux is phis(e) = 1.76(+0.05)(-0.05)(stat)(+0.09)(-0.09)(syst) x 10(6) cm(-2) s(-1) f...

The Sudbury Neutrino Observatory (SNO) has measured day and night solar neutrino energy spectra and rates. For charged current events, assuming an undistorted 8B spectrum, the night minus day rate is 14.0%+/-6.3%(+1.5%)(-1.4%) of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymmetry, the nu(e) asym...

The Sudbury Neutrino Observatory (SNO) has measured day and night solar neutrino energy spectra and rates. For charged current events, assuming an undistorted (sup 8)B spectrum, the night minus day rate is 14.0%[plus-or-minus]6.3%(sup +1.5)-1.4 % of the average rate. If the total flux of active neutrinos is additionally constrained to have no asymm...

Observations of neutral current neutrino interactions on deuterium in the Sudbury Neutrino Observatory are reported. Using the neutral current, elastic scattering, and charged current reactions and assuming the standard 8B shape, the electron-neutrino component of the 8B solar flux is 1.76 +/-0.05(stat.)+/-0.09(syst.) x10^6/(cm^2 s), for a kinetic...

Solar neutrinos from (8)B decay have been detected at the Sudbury Neutrino Observatory via the charged current (CC) reaction on deuterium and the elastic scattering (ES) of electrons. The flux of nu(e)'s is measured by the CC reaction rate to be straight phi(CC)(nu(e)) = 1.75 +/- 0.07(stat)(+0.12)(-0.11)(syst) +/- 0.05(theor) x 10(6) cm(-2) s(-1)....

The first neutrino observations from the Sudbury Neutrino Observatory are presented from preliminary analyses. Based on energy, direction and location, the data in the region of interest appear to be dominated by 8B solar neutrinos, detected by the charged current reaction on deuterium and elastic scattering from electrons, with very little backgro...

The technique of extracting electron energy spectra from measured distributions of dose along the central axis of clinical electron beams is explored in detail. Clinical spectra measured with this simple spectroscopy tool are shown to be sufficient in accuracy and resolution for use in Monte Carlo treatment planning. A set of monoenergetic depth do...

The commonly use Anger camera provides a relatively simple, large-scale solution to nuclear medicine imaging. However it has some disadvantages: count-rate limitation, nonlinear spatial resolution and relatively poor energy contrast. Many efforts have been invested over the past few years aiming at replacing the current Anger technology with variou...

The Sudbury Neutrino Observatory is a second-generation water Cherenkov detector designed to determine whether the currently observed solar neutrino deficit is a result of neutrino oscillations. The detector is unique in its use of D2O as a detection medium, permitting it to make a solar model-independent test of the neutrino oscillation hypothesis...

The use of low-mobility photoconductors in x-ray imaging, especially amorphous selenium (a-Se), is currently of great interest. Detailed measurements of the photoconversion gain factor W± and gain fluctuations σ have been obtained to facilitate applications using a-Se and to provide a better understanding of the charge formation process. The measur...

New radiological imaging techniques have to be capable of high image quality, high acquisition speed, compactness, and versatility in operation. We have been investigating a flat panel imager based on the direct conversion of x-ray energy to an electric charge signal in a layer of amorphous selenium (a- Se) and an active matrix real-time self scann...

The use of photoconductors, especially amorphous selenium (a-Se), in x-ray imaging is currently of interest. A critical performance parameter of an imaging detector is the Swank factor for degradation of the signal to noise ratio, or DQE(0), due to variations in the detector response. The Swank factor is evaluated from measured pulse height spectra...

The goal of the present work is to develop a large area, flat-panel solid-state detector for both digital radiography and fluoroscopy. The proposed detector employs a photoconductive layer of amorphous selenium (a-Se) to convert x rays into charge. The charge image formed by the a-Se layer is electronically read out in situ using a two dimensional...

Future imaging techniques will be capable of high image quality, fast acquisition, compactness, and versatile operation. A flat-panel imager that is expected to achieve these goals is under development. It consists of a thin layer of amorphous selenium that converts x rays directly to an electric charge and a thin-film electronic circuit, or active...

We report on the production ofe ± μ∓ pairs in 450 GeV/c pBe collisions at the CERN SPS. Theeμ signal, which has average missing energy of 21 GeV, is shown to be consistent with expectations from charm decay, and implies a σ ×B for\(c\bar c\) production in p-nucleon collisions of 0.63 ± 0.35μb. Alternatively, using an estimate of charm production fr...

Our goal is to develop a large area, flat panel, solid-state detector for both digital radiography and fluoroscopy. The proposed detector employs a photoconductive layer of amorphous selenium (a-Se) to convert x rays into charge. The charge image formed on the a-Se is electronically read out in situ using a two dimensional array of thin film transi...

We report on the production of $e^{\pm}\mu^{\mp}$ pairs in $450\GeVc$ {\em pBe} collisions at the CERN SPS. The $e\mu$ signal, which has average missing energy of 21~GeV, is shown to be consistent with expectations from charm decay, and implies a $\sigma\times B$ for $çbar$ production in p-nucleon collisions of $0.63\pm 0.28 \mu b$. Alternatively,...

The Sudbury Neutrino Observatory (SNO) will observe solar neutrino interactions in D2O. Photomultiplier tubes (PMT) surrounding the D2O will detect Cherenkov light from these interactions. The neutral current (NC) interactions of the neutrinos disintegrate the deuterons producing neutrons. Cherenkov light from the subsequent capture-gamma-ray showe...

We report on the production of low-mass electron pairs and muon pairs in p-Be collisions at 450 GeV/c at the CERN SPS. For both electron and muon pairs the low-mass spectrum can be explained satisfactorily by lepton pairs from hadronic decays, and there is no need to invoke any unconventional source. The normalisation of the major hadronic sources...

We present the results of a search for exotic bosons produced in the decay π0-->Xγ. A low energy π- beam at TRIUMF was stopped in a liquid hydrogen target to produce the reactions π-p-->nγ and π-p-->nπ0,π0-->γγ. The γ rays from these reactions were detected in a sodium iodide crystal. From the energy distributions we extract a branching ratio limit...

The results of two sets of transverse energy measurements, performed with incident proton beams of 200 and 450 GeV/c momentum on several nuclear targets, are presented. The transverse energy cross sections d/dE T are measured in a pseudorapidity range including the target fragmentation region (–0.1 region. We find that the mean value of pseudorapi...

Results from the HELIOS External Spectrometer on kaon production in 200 GeV/A S + W and p + W collisions are presented. The ratios are compared with results from a lower beam energy and are found to be remarkably similar. Evidence for secondary production of K+ by meson-baryon rescattering is reviewed. Our results at y = 1.0–1.5 are compared with n...

We have measured the slope parameter of the π0 electromagnetic form factor by measuring the partial branching ratio of the Dalitz decay π0→γe+e− into high-invariant-mass electron-positron pairs. We obtain a value a=0.026 with a total (statistical and systematic) error of ±0.054, in agreement with vector dominance and quark loop calculations.

We present measurements of the rapidity and transverse-momentum distributions of the protons emitted in S+W, O+W, andp+W reactions at 200 GeV/A around the target rapidity (y=1). The rapidity density rises linearly with the transverse energy for all three systems, but the slope forp+W is much steeper than for O+W and S+W. The rapidity density forp+W...

Diffractive dissociation of nuclei (Be, Al, W) in collisions with 450 GeV/c protons,pApX, has been measured with the HELIOS spectrometer at the CERN Super Proton synchrotron. The dependence of the single-diffraction cross-section on the nuclear massA can be parametrized as SD mbA 0.350.02, showing the peripheral nature of the process. The different...

We have measured the inclusive cross-section as a function of missing energy, due to the production of neutrinos or new weakly interacting neutral particles in 450 GeV/c proton-nucleus collisions, using calorimetric measurements of visible event energy. Upper limits are placed on the production of new particles as a function of their energy. These...

The transverse energy distributions have been measured for interactions of 32S nuclei with Al, Ag, W, Pt, Pb, and U targets, at an incident energy of 200 GeV per nucleon in the pseudorapidity region −0.1 < νlab < 5.5. These distributions are compared with those for 16OW interactions in the same pseudorapidity region and with earlier measurements p...

Diffractive dissociation of nuclei (Be, Al, W) in collisions with 450 GeV/c protons,pA?pX, has been measured with the HELIOS spectrometer at the CERN Super Proton synchrotron. The dependence of the single-diffraction cross-section on the nuclear massA can be parametrized as sSD mb×A0.35±0.02, showing the peripheral nature of the process. The differ...

A search for non-statistical fluctuations was performed in 200 GeV per nucleon oxygen and sulphur ion-emulsion interactions selected by a high transverse energy trigger. No clear signal of dynamical correlations or of unusual fluctuations was found.

Interactions of 16O and 32S at 200 GeV per nucleon in emulsion and in emulsion-tungsten chamber targets were tagged by transverse energy and multiplicity triggers in the HELIOS apparatus at CERN. As a first sample, 375 events, covering a wide range of transverse energies, were located and studied in emulsion. Results are reported in this paper. The...

Multiplicity distributions of charged particles produced in the pseudorapidity range 0.9 < ηlab < 5.5 were measured in oxygen-nucleus collisions for Al, Ag, and W target nuclei at incident energies of 60 and 200 GeV per nucleon. The multiplicity differential cross sections and the pseudorapidity distributions as a function of transverse energy are...

Inclusive photonp ⊥ spectra were measured with 200 GeV/u proton,16O and32S beams on W and Pt targets, using a conversion method. The measurement of charged pions in the same apparatus allows a comparison of the γ data with the expected γ's from hadronic decays π0, η, η', ω). In all data sets, no deviation from the expected shape is observed in the...

The HELIOS experiment has measured inclusivep spectra of negative particles in the rapidity region 1.0yp spectra in p +W, O+W and S+W is similar, but cannot be described by a single exponential. Compared to p+p collisions, an excess is observed for low and highp . This effect increases with the projectile mass. Except for very lowE , the average tr...

Transverse-energy distributions have been measured for the collisions of the 32S nucleus with Al, Ag, W, Pt, Pb, and U target nuclei, at an incident energy of 200 GeV per nucleon. The shapes of these distribution reflect the geometry of the collisions, including the deformation effects. For central collisions, the transverse-energy production in th...

Transverse-energy distributions have been measured in the pseudorapidity region −0.1<η lab<2.9 for oxygen-nucleus collisions at incident energies of 60 and 200 GeV per nucleon for Al, Ag, and W target nuclei. The cross-section for the heaviest target nuclei at the highest incident energy is measured over 5 orders of magnitude and out to a maximumE...

Transverse-energy distributions have been measured in the pseudo-rapidity region –0.1 > lab

Transverse-energy distributions have been measured in the pseudorapidity region -0.1?labET of 200 GeV. Measurements of the differential densitydET/d?lab as a function of?lab are presented. In the pseudorapidity region -0.1?labA0.5, while the fraction of the total transverse energy measured in an extended region of?lab>2.9 decreases with increasingA...