151 research outputs found
A new nanocomposite packaging based on lasis-generated agnps for the preservation of apple juice
Designing bioactive materials, with controlled metal ion release, exerting a significant biological action and associated to low toxicity for humans, is nowadays one of the most important challenges for our community. The most looked-for nanoantimicrobials are capable of releasing metal species with defined kinetic profiles, either by slowing down or inhibiting bacterial growth and pathogenic microorganism diffusion. In this study, laser ablation synthesis in solution (LASiS) has been used to produce bioactive Ag-based nanocolloids, in isopropyl alcohol, which can be used as water-insoluble nano-reservoirs in composite materials like poly(3-hydroxybutyrate-co-3-hydroxyvalerate). Infrared spectroscopy was used to evaluate the chemical state of pristine polymer and final composite material, thus providing useful information about synthesis processes, as well as storage and processing conditions. Transmission electron microscopy was exploited to study the morphology of nano-colloids, along with UV-Vis for bulk chemical characterization, highlighting the presence of spheroidal particles with average diameter around 12 nm. Electro-thermal atomic absorption spectroscopy was used to investigate metal ion release from Ag-modified products, showing a maximum release around 60 ppb, which ensures an efficient antimicrobial activity, being much lower than what recommended by health institutions. Analytical spectroscopy results were matched with bioactivity tests carried out on target microorganisms of food spoilage
Analysis of time-profiles with in-beam PET monitoring in charged particle therapy
Background: Treatment verification with PET imaging in charged particle
therapy is conventionally done by comparing measurements of spatial
distributions with Monte Carlo (MC) predictions. However, decay curves can
provide additional independent information about the treatment and the
irradiated tissue. Most studies performed so far focus on long time intervals.
Here we investigate the reliability of MC predictions of space and time (decay
rate) profiles shortly after irradiation, and we show how the decay rates can
give an indication about the elements of which the phantom is made up.
Methods and Materials: Various phantoms were irradiated in clinical and
near-clinical conditions at the Cyclotron Centre of the Bronowice proton
therapy centre. PET data were acquired with a planar 16x16 cm PET system.
MC simulations of particle interactions and photon propagation in the phantoms
were performed using the FLUKA code. The analysis included a comparison between
experimental data and MC simulations of space and time profiles, as well as a
fitting procedure to obtain the various isotope contributions in the phantoms.
Results and conclusions: There was a good agreement between data and MC
predictions in 1-dimensional space and decay rate distributions. The fractions
of C, O and C that were obtained by fitting the decay
rates with multiple simple exponentials generally agreed well with the MC
expectations. We found a small excess of C in data compared to what was
predicted in MC, which was clear especially in the PE phantom.Comment: 9 pages, 5 figures, 1 table. Proceedings of the 20th International
Workshop on Radiation Imaging Detectors (iWorid2018), 24-28 June 2018,
Sundsvall, Swede
Comparison of Travoprost and Bimatoprost plus timolol fixed combinations in open-angle glaucoma patients previously treated with latanoprost plus timolol fixed combination
To compare the ocular hypotensive effect of bimatoprost plus timolol and travoprost plus timolol fixed combinations in glaucoma patients whose disease was controlled but had not reached their target intraocular pressure (IOP) with the fixed combination of latanoprost plus timolol
Risk factors for infections due to carbapenem-resistant Klebsiella pneumoniae after cardiac surgery
Analysis methods for in-beam PET images in proton therapy treatment verification: a comparison based on Monte Carlo simulations
Background and purpose: In-beam Positron Emission Tomography (PET) is one of
the modalities that can be used for in-vivo non-invasive treatment monitoring
in proton therapy. PET distributions obtained during various treatment sessions
can be compared in order to identify regions that have anatomical changes. The
purpose of this work is to test and compare different analysis methods in the
context of inter-fractional PET image comparison for proton treatment
verification.
Methods: For our study we used the FLUKA Monte Carlo code and artificially
generated CT scans to simulate in-beam PET distributions at different stages
during proton therapy treatment. We compared the Beam-Eye-View method, the
Most-Likely-Shift method, the Voxel-Based-Morphology method and the gamma
evaluation method to compare PET images at the start of treatment, and after a
few weeks of treatment. The results were compared to the CT scan.
Results and conclusions: Three-dimensional methods like VBM and gamma are
preferred above two-dimensional methods like MLS and BEV if much statistics is
available, since the these methods allow to identify the regions with anomalous
activity. The VBM approach has as disadvantage that a larger number of MC
simulations is needed. The gamma analysis has the disadvantage that no clinical
indication exist on tolerance criteria. In terms of calculation time, the BEV
and MLS method are preferred. We recommend to use the four methods together, in
order to best identify the location and cause of the activity changes.Comment: 9 pages, 5 figure
Full-beam performances of a PET detector with synchrotron therapeutic proton beams
Treatment quality assessment is a crucial feature for both present and nextgeneration ion therapy facilities. Several approaches are being explored, based on prompt radiation emission or on PET signals by β+;-decaying isotopes generated by beam interactions with the body. In-beam PET monitoring at synchrotron-based ion therapy facilities has already been performed, either based on inter-spill data only, to avoid the influence of the prompt radiation, or including both in-spill and inter-spill data. However, the PET images either suffer of poor statistics (inter-spill) or are more influenced by the background induced by prompt radiation (in-spill). Both those problems are expected to worsen for accelerators with improved duty cycle where the inter-spill interval is reduced to shorten the treatment time. With the aim of assessing the detector performance and developing techniques for background reduction, a test of an in-beam PET detector prototype was performed at the CNAO synchrotron-based ion therapy facility in full-beam acquisition modality. Data taken with proton beams impinging on PMMA phantoms showed the system acquisition capability and the resulting activity distribution, separately reconstructed for the in-spill and the inter-spill data. The coincidence time resolution for in-spill and inter-spill data shows a good agreement, with a slight deterioration during the spill. The data selection technique allows the identification and rejection of most of the background originated during the beam delivery. The activity range difference between two different proton beam energies (68 and 72 MeV) was measured and found to be in submillimeter agreement with the expected result. However, a slightly longer (2 mm) absolute profile length is obtained for in-spill data when compared to inter-spill data
Proton range monitoring with in-beam PET: Monte Carlo activity predictions and comparison with cyclotron data
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First tests for an online treatment monitoring system with in-beam PET for proton therapy
PET imaging is a non-invasive technique for particle range verification in
proton therapy. It is based on measuring the beta+ annihilations caused by
nuclear interactions of the protons in the patient. In this work we present
measurements for proton range verification in phantoms, performed at the CNAO
particle therapy treatment center in Pavia, Italy, with our 10 x 10 cm^2 planar
PET prototype DoPET. PMMA phantoms were irradiated with mono-energetic proton
beams and clinical treatment plans, and PET data were acquired during and
shortly after proton irradiation. We created 1-D profiles of the beta+ activity
along the proton beam-axis, and evaluated the difference between the proximal
rise and the distal fall-off position of the activity distribution. A good
agreement with FLUKA Monte Carlo predictions was obtained. We also assessed the
system response when the PMMA phantom contained an air cavity. The system was
able to detect these cavities quickly after irradiation.Comment: 11 pages, 6 figures, Proceedings for International Workshop on
Radiation Imaging Detectors, 201
A new PET prototype for proton therapy: comparison of data and Monte Carlo simulations
Ion beam therapy is a valuable method for the treatment of deep-seated and radio-resistant tumors thanks to the favorable depth-dose distribution characterized by the Bragg peak. Hadrontherapy facilities take advantage of the specific ion range, resulting in a highly conformal dose in the target volume, while the dose in critical organs is reduced as compared to photon therapy. The necessity to monitor the delivery precision, i.e. the ion range, is unquestionable, thus different approaches have been investigated, such as the detection of prompt photons or annihilation photons of positron emitter nuclei created during the therapeutic treatment. Based on the measurement of the induced β+ activity, our group has developed various in-beam PET prototypes: the one under test is composed by two planar detector heads, each one consisting of four modules with a total active area of 10 × 10 cm2. A single detector module is made of a LYSO crystal matrix coupled to a position sensitive photomultiplier and is read-out by dedicated frontend electronics. A preliminary data taking was performed at the Italian National Centre for Oncological Hadron Therapy (CNAO, Pavia), using proton beams in the energy range of 93–112 MeV impinging on a plastic phantom. The measured activity profiles are presented and compared with the simulated ones based on the Monte Carlo FLUKA package
Monitoring Proton Therapy Through In-Beam PET: An Experimental Phantom Study
In this paper, we investigate the use of a positron emission tomography (PET) system to monitor the proton therapy. The monitoring procedure is based on the comparison between the β+ activity generated in the irradiated volume during the treatment, with the β+ activity distribution obtained with Monte Carlo (MC) simulation. The dedicated PET system is a dual head detection system; each head is composed of nine scintillating LYSO crystal matrices read out independently with a custom modularized acquisition system. Our experimental data were acquired at the Cyclotron Centre Bronowice, Institute Nuclear Physics in Kraków, Poland, and were simulated with the FLUKA MC code. Homogeneous and heterogeneous plastic phantoms were irradiated with monoenergetic 130 MeV protons. The capabilities of our PET system to distinguish different irradiated materials were investigated, and the proton pencil-beams were used as probes. Our focus was to analyze the activity width and the total activity event number in several cases. Irradiations were performed using either single pencil-beams one at a time, or two pencil-beams during the same data taking. The comparison of 1-D activity profile for experimental data and MC simulation were always in good agreement showing that, the treatment quality assessment in proton therapy can be based on β+ activity measurements
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