Treatments delivered by proton therapy are affected by uncertainties on the range of the beam within the patient. To reduce these margins and improve feedback on treatment delivery, different ...projects are investigating real-time range control by imaging prompt gammas emitted along the proton tracks in the patient. This study supports the development of a prompt gamma camera using a knife-edge slit collimator to produce a reversed 1-dimensional projection of the beam path on a scintillation detector for treatments delivered in pencil beam scanning mode. The ability of this camera design to detect modifications of the beam penetration depth in a PMMA target was already demonstrated down to 1 mm accuracy for doses compatible with single pencil beams at low proton beam currents thanks to the HiCam photo-detection system. In order to fulfill the very demanding count rate capability required for prompt gamma imaging at clinical beam currents, a new, dedicated, cost-effective photo-detection system was designed. This 1-dimensional, high-energy gamma imaging device relies on two rows of 20 LYSO crystal slabs, directly coupled to SiPMs' arrays and readout by 40 independent acquisition channels in fast counting mode. A first prototype limited to 20 channels was implemented to benchmark the performances of various components and validate the adequate combination of crystal material, surface treatment, optical coupling and SiPMs. This prototype was tested during proton irradiation at the West German Proton Therapy Centre in Essen at clinical beam currents of several nA at nozzle exit.
This paper reports on the use of PIXE and RBS (resonant and non-resonant RBS) implemented with proton beams to simultaneously analyse light and heavy elements in materials of cultural heritage ...significance, as exemplified by Russian icons or in lead seals. It is shown that in spite of its poor mass resolution RBS with protons can provide useful information when combined with PIXE. In the case of Russian icons, it is possible to discriminate between an Au–Ag bilayer and an alloy of these metals in the gilds. However, when applied to lead seals RBS with protons encounters a significant limitation due to some deficiency in the available computer programs used for spectrum processing.
Human recombinant myeloperoxidase was evaluated in a cell-free system for its inactivation properties on the replication of human immunodeficiency virus, HTLV-III
B. In the presence of a hydrogen ...peroxide generating system (glucose and glucose oxidase) and sodium thiocyanate, the recombinant enzyme inhibited virus-induced syncytium formation and viral replication without causing any cytopathic effects on SupT1 reporter cells. In addition, U937 monocytoid cells, chronically infected with HIV1, were exposed to recombinant myeloperoxidase (10 U/ml) and monitored during 48 h for the accumulation of intracellular p24 viral antigen. Under these conditions, the recombinant enzyme significantly reduced intracellular viral replication without affecting cell viability.
The HICAM gamma camera is an imaging device recently developed in the framework of a European project, based on Silicon Drift Detectors (SDDs) as photodetectors. Although originally designed for ...low-energy gamma-ray imaging in nuclear medicine (140 keV of 99m Tc), in this work we attempt to use the camera, suitably modified, to image high energy prompt gamma rays (2 to 7 MeV) emitted by a target irradiated by protons. The final objective of our experiment is to assess the feasibility of proton beam range measurements by prompt gamma imaging with a slit camera, and the HICAM camera was chosen for a first prototype. Although a SDD-based camera would not be fast enough for real treatment conditions, the prototype here employed benefited from the camera modularity, compactness, high resolution and low noise. The camera here employed is composed of 25 SDDs of 1 cm 2 active area each, arranged in a 5×5 format, already used in clinical and research environments with a high intrinsic spatial resolution (~1 mm). The SDD matrix has been coupled to a LYSO crystal (1cm thickness), to improve efficiency with high-energy gammas, and has been characterized preliminarily with a 60 Co source. Good imaging performances have been obtained in this test. Moreover, results of a first test of the camera to detect prompt gammas emitted with a proton beam impinging on a plastic target are presented in this work.
The development of a vaccine for tuberculosis requires a combination of antigens and adjuvants capable of inducing appropriate and long-lasting T cell immunity. We evaluated Mtb72F formulated in ...ASO2A in the cynomolgus monkey model. The vaccine was immunogenic and caused no adverse reactions. When monkeys were immunized with bacillus Calmette-Guérin (BCG) and then boosted with Mtb72F in ASO2A, protection superior to that afforded by using BCG alone was achieved, as measured by clinical parameters, pathology, and survival. We observed long-term survival and evidence of reversal of disease progression in monkeys immunized with the primeboost regimen. Antigen-specific responses from protected monkeys receiving BCG and Mtb72F/ASO2A had a distinctive cytokine profile characterized by an increased ratio between 3 Th1 cytokines, IFN-y, TNF, and IL-2 and an innate cytokine, IL-6. To our knowledge, this is an initial report of a vaccine capable of inducing long-term protection against tuberculosis in a nonhuman primate model, as determined by protection against severe disease and death, and by other clinical and histopathological parameters.
Treatments delivered by proton therapy are affected by uncertainties on the range of the beam within the patient. To reduce these margins and deliver safer treatments, different projects are ...currently investigating real-time range control by imaging prompt gammas emitted along the proton tracks in the patient. This study reports on the development and test of a prompt gamma camera using a slit collimator to obtain a 1-dimensional projection of the beam path on a scintillator detector. A first prototype slit camera using the HICAM gamma detector, originally developed for low-energy gamma-ray imaging in nuclear medicine and modified for this purpose, was tested successfully up to 230 MeV beam energy. Results now confirm the potential of this concept for real-time range monitoring with millimeter accuracy in pencil beam scanning mode for the whole range of clinical energies. With the experience gained, a new prototype is under study for clinical beam currents. In this work, we present both the profiles obtained at 230 MeV using HICAM and the description of the new gamma camera prototype design.
A precision measurement of the 277 keV
γ ray produced by capturing muons in gaseous oxygen was performed using high-resolution HPGe detectors. The Doppler-broadened shape of this line is sensitive to ...the possible admixture into muon capture of genuine scalar interaction. This experiment complements, in the muon sector, in principle, similar ones undertaken recently in nuclear
β decay.
Using a procedure discussed in earlier papers, a fit to the experimental line-shape allowed us to obtain for the recoil–gamma correlation coefficient the value of
a
1
2=0.096±0.041 (95% CL). The available evaluations of the contributing nuclear matrix elements, performed in the impulse approximation in the absence of scalar interaction, produce correlation coefficients in disagreement with our result. These evaluations are independent of the induced pseudoscalar coupling and so of the validity of the PCAC hypothesis, but their reliability and model dependence remain to be investigated.
Six purified glycosyltransferase (a beta-galactoside alpha 2 leads to 6 sialyltransferase, a beta-galactoside alpha 2 leads
to 3 sialyltransferase, an alpha-N-acetylgalactosaminide alpha 2 leads to 6 ...sialyltransferase, a beta-galactoside alpha 1
leads to 2 fucosyltransferase, a beta-N-acetylglucosaminide alpha 1 leads to 3 fucosyltransferase, and a (fucosyl alpha 1
leads to 2) galactoside alpha 1 leads to 3 N-acetyl-galactosaminyltransferase) have been used to study the biosynthetic pathways
for formation of the nonreducing terminal oligosaccharide sequences in mammalian glycoproteins. The two glycoproteins used
as model acceptor substrates in this study were human asialotransferrin, which contains the nonreducing terminal oligosaccharide
sequence Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man, and antifreeze glycoprotein, which contains oligosaccarides with
the structure, Gal beta 1 leads to 3GalNAc alph 1 leads O-Thr. Sequential action of the six glycosyltransferases on these
model substrates led to the formation of previously described oligosaccharide structures. The studies reported here indicate
that the substrate specificities of the individual enzymes dictate the structures that can be synthesized and the pathways
by which they may be formed. The actions of a number of the transferasesare mutually exclusive, thereby prohibiting the formation
of theoretically possible oligosaccharide structures. Oligosaccharides with the terminal sequence NeuAc alpha 2 leads to 3(Fuc
alpha 1 leads to 2)Gal beta 1 leads to 3GalNAc and NeuAc alpha 2 leads to 6Gal beta 1 leads to 4(Fuc alpha 1 leads to 3)GlcNAc
cannot be formed because the prior incorporation of sialic acid by the sialyltransferases yields products that are not acceptor
substrates for the fucosyltransferases, and vice versa. Synthesis of other products requires that the enzymes act sequentially
in a specific order. The structures NeuAc alpha 2 leads to 6(Fuc alpha 1 leads to 2)Gal beta 1 leads to 4GlcNAc, Fuc alpha
1 leads to 2Gal beta 1 leads to 4(Fuc alpha 1 leads to 3)GlcNAc, GalNAc alpha 1 leads to 3(Fuc alpha 1 leads to 2)Gal beta
1 leads to 4GlcNAc, and GalNAc alpha 1 leads to 3(Fuc alpha 1 leads to 2)Gal beta 1 leads to 3GalNAc can only be synthesized
if the fucosyl alpha 1 leads to 2 galactose linkage is formed first. Synthesis of the pentasaccharide sequences GalNAc alpha
1 leads to 3(Fuc alpha 1 leads to 2)Gal beta 1 leads to 3(NeuAc alpha 2 leads to 6)GalNAc and GalNAc alpha 1 leads to 3(Fuc
alpha 1 leads to 2)Gal beta 1 leads to 4(Fuc alpha 1 leads to 3)GlcNAc requires that the N-acetylgalactosaminyltransferase
act last on the former structure and that the alpha 1 leads to 3 fucosyltransferase act last on the latter. In those instances
where a product can be formed by one of two possible pathways, the comparisons of reaction rates indicate that one pathway
is usually preferred...
This work was carried out as part of a project aiming at a greatly improved measurement of the muon capture rate from the singlet state of the μp atom. The experiment will be performed at the intense ...muon beam of PSI using a new experimental method allowing high precision measurements of the lifetime of muons stopped in ultra-pure deuterium-depleted hydrogen (protium). The basic element of the detector is a time projection chamber operating in hydrogen gas at
10
bar
pressure. The arrival times and trajectories of the incoming muons and the outgoing decay electrons are measured with this device providing effective suppression of background. The system of chambers and electronics is designed for the large muon stop rates required for attaining high statistical accuracy. During four beam periods at PSI, data were taken. Also, various studies of the MWPC performance in hydrogen were made including ageing studies of the chambers under irradiation with stopped muons and with alpha and beta sources. It was demonstrated that the MWPCs can operate in pure hydrogen under 10 bar pressure with gas gains up to 5000, which is sufficient for the detection of relativistic electrons.
PDF
