Prompt Gamma Research Articles

Isotope identification capabilities using time resolved prompt gamma emission from epithermal neutrons

We present a concept of integrated measurements for isotope identification which takes advantage of the time structure of spallation neutron sources for time resolved γ spectroscopy. Time resolved Prompt Gamma Activation Analysis (T-PGAA) consists in the measurement of gamma energy spectrum induced by the radioactive capture as a function of incident neutron Time Of Flight (TOF), directly related with the energy of incident neutrons. The potential of the proposed concept was explored on INES (Italian Neutron Experimental Station) at the ISIS spallation neutron source (U.K.). Through this new technique we show an increase in the sensitivity to specific elements of archaeometric relevance, through incident neutron energy selection in prompt γ spectra for multicomponent samples. Results on a standard bronze sample are presented.

Prompt gamma neutron activation analysis of large heterogeneous samples composed of concrete and polyethylene

The neutron moderating effect of concrete and polyethylene mixtures on the determination of the sample composition was investigated by irradiating 200 L steels drums with 14 MeV neutrons at the MEDINA (Multi Element Determination based on Instrumental Neutron Activation) facility. The elemental composition was evaluated using a quantification model validated for a concrete matrix in a previous work. The results obtained were found to agree with the expected values within ±34 % which is reasonable with regards to the samples heterogeneity.

Precise Determination of Silicon in Ceramic Reference Materials by Prompt Gamma Activation Analysis at JRR-3

Prompt gamma activation analysis using a thermal neutron-guided beam at Japan Atomic Energy Agency JRR-3M was applied for the precise determination of Si in silicon nitride ceramic reference materials [Japan Ceramic Reference Material (JCRM) R 003]. In this study, the standard addition method coupled with internal standard was used for the nondestructive determination of Si in the sample. Cadmium was used as internal standard to obtain the linear calibration curves and to compensate for the neutron beam variability. The analytical result of determining Si in JCRM R 003 silicon nitride fine powder ceramic reference materials using prompt gamma activation analysis was in good agreement with that obtained by classical gravimetric analysis. The relative expanded measurement uncertainty (k = 2) associated with the determined value was 2.4%.

Moderation and shielding optimization for a 252Cf based prompt gamma neutron activation analyzer system

Prompt Gamma Neutron Activation Analysis (PGNAA) is a fast, online and the non-destructive elemental analysis method which is widely used in industries such as cement and coal. In the present study, optimization of the moderator and gamma radiation shield of a 252Cf neutron source in a PGNAA setup, utilizing Monte Carlo simulation is succeed. The objective is to enhance the thermal neutron spectrum and minimize potential gamma rays. The results show that high density polyethylene (HDPE) with a thickness of 5 cm as the moderator and lead with a thickness of 4 cm as the gamma radiation shield are the best options for the intended purpose. As a result of this optimization, increased efficiency of the PGNAA setup through (nth,γ) reaction and elevated prompt gamma flux which provides higher accuracy for the detector system.

177 - Prompt gamma imaging of passively shaped proton fields with a knife-edge slit camera

177 - Prompt gamma imaging of passively shaped proton fields with a knife-edge slit camera

Absorbed Dose Rates in Tissue from Prompt Gamma Emissions from Near-thermal Neutron Absorption

Prompt gamma emission data from the International Atomic Energy Agency's Prompt Gamma-ray Neutron Activation Analysis database are analyzed to determine the absorbed dose rates in tissue to be expected when natural elements are exposed in a near-thermal neutron environment.

Determination of the effective sample thickness via radiative capture

A procedure for determining the effective thickness of non-uniform irregular-shaped samples via radiative capture is described. In this technique, partial γ-ray production cross sections of a compound nucleus produced in a neutron-capture reaction are measured using Prompt Gamma Activation Analysis and compared to their corresponding standardized absolute values. For the low-energy transitions, the measured cross sections are lower than their standard values due to significant photoelectric absorption of the γ rays within the bulk-sample volume itself. Using standard theoretical techniques, the amount of γ-ray self absorption and neutron self shielding can then be calculated by iteratively varying the sample thickness until the observed cross sections converge with the known standards. The overall attenuation, thus, provides a measure of the effective sample thickness illuminated by the neutron beam. This procedure is illustrated through radiative neutron capture using powdered oxide samples comprising enriched 186W and 182W from which their tungsten-equivalent effective thicknesses are deduced to be 0.077(3)mm and 0.042(8)mm, respectively.

PGAA: Prompt gamma and in-beam neutron activation analysis facility

Prompt gamma-ray activation analysis (PGAA) is typically used for the determination of elemental composition and concentration of solid samples (ca. down to ppm range). Liquids and gaseous samples can also be measured. The instrument PGAA is operated by the Institute of Nuclear Physics, University of Cologne and the Technische Universität München.

Recoil-decay tagging spectroscopy of74162W88

Excited states in the highly neutron-deficient nucleus W-162 have been investigated via the Mo-92(Kr-78, 2 alpha) W-162 reaction. Prompt gamma rays were detected by the JUROGAM II high-purity germa ...

BEAM MODELING FOR PGNAA EXPERIMENTAL FACILITY AT KARTINI REACTOR

BEAM MODELING FOR PGNAA EXPERIMENTAL FACILITY AT KARTINI REACTOR. A feasibility study on possible use of Kartini reactor’s beam port for Prompt Gamma Neutron Activation Analysis (PGNAA) experimental facility is going on. This work is part of the revitalization program activities of Kartini research reactor, including utilization of the available irradiation facilities. This paper presents results of beam modeling at the tangential beam port to get neutron beam meeting the specified criteria. The study was conducted by means of simulations using MCNPX code. The result concludes that there are several possible variations of collimator models that can provide neutron beam meeting the specified criteria and that tangential beam port is considered to be feasible enough for the purpose of PGNAA experimental facility

Analytical computation of prompt gamma ray emission and detection for proton range verification

A prompt gamma (PG) slit camera prototype recently demonstrated that Bragg Peak position in a clinical proton scanned beam could be measured with 1–2 mm accuracy by comparing an expected PG detection profile to a measured one. The computation of the expected PG detection profile in the context of a clinical framework is challenging but must be solved before clinical implementation. Obviously, Monte Carlo methods (MC) can simulate the expected PG profile but at prohibitively long calculation times. We implemented a much faster method that is based on analytical processing of precomputed MC data that would allow practical evaluation of this range monitoring approach in clinical conditions.Reference PG emission profiles were generated with MC simulations (PENH) in targets consisting of either 12C, 14N, 16O, 31P or 40Ca, with 10% of 1H. In a given geometry, the local PG emission can then be derived by adding the contribution of each element, according to the local energy of the proton obtained by continuous slowing down approximation and the local composition. The actual incident spot size is taken into account using an optical model fitted to measurements and by super sampling the spot with several rays (up to 113). PG transport in the patient/camera geometries and the detector response are modelled by convolving the PG production profile with a transfer function. The latter is interpolated from a database of transfer functions fitted to MC data (PENELOPE) generated for a photon source in a cylindrical phantom with various radiuses and a camera placed at various positions.As a benchmark, the analytical model was compared to MC and experiments in homogeneous and heterogeneous phantoms. Comparisons with MC were also performed in a thoracic CT. For all cases, the analytical model reproduced the prediction of the position of the Bragg peak computed with MC within 1 mm for the camera in nominal configuration. When compared to measurements, the shape of the profiles was well reproduced and agreement for the estimation of the position of the Bragg peak was within 2.7 mm on average (1.4 mm standard deviation). On a non-optimized MATLAB code, computation time with the analytical model is between 0.3 to 10 s depending on the number of rays simulated per spot.The analytical model can be further used to determine which spots are the best candidates to evaluate the range in clinical conditions and eventually correct for over- and under-shoots depending on the acquired PG profiles.

Nitrogen-Doping in ZnO via Combustion Synthesis?

We report the synthesis and characterization of colored ZnO-based powders via solution combustion reaction of urea and zinc nitrate hexahydrate in varying molar ratios between 1:1 and 10:1. Among other techniques, we employ X-ray diffraction, nuclear magnetic resonance, and Raman spectroscopy to characterize the products. Within a narrow range of reactant ratios, we reproducibly find an unidentified, crystalline precursor phase related to isocyanuric acid next to ZnO. Finally, we complement our investigations by performing Prompt Gamma Activation Analysis (PGAA) on selected products in order to directly determine elemental bulk compositions and compare these with X-ray photoelectron spectroscopy (XPS) measurements. Our data show traces of nitrogen mainly on the surface of the particles, and thus we question the solution combustion method as a reliable synthesis toward N-doped ZnO. Furthermore, we exclude nitrogen as being responsible for the appearance of the four controversially discussed Raman bands sup...

SU‐E‐J‐142: Prompt Gamma Emission Measurements From a Passively Scattered Proton Beam On Targets Containing 16O, 12C and 14N

Purpose:To measure the prompt gamma emission from the important elements found in tissue (1 6O,1 2C and1 4N) in a clinical passive‐scatter treatment environment.Methods:The targets (composed of water, Perspex, graphite and liquid nitrogen) were irradiated with a 200 MeV passive‐scatter proton beam and the discrete prompt gamma energy spectra was detected by a high resolution 2′ × 2′ LaBr. detector. In order to reduce the high level of radiation produced by the beam line elements, the detector was surrounded by 10 cm of lead to attenuate the scattered gamma‐rays entering the detector with an extra 5 cm thick layer of lead added along the beam direction. A 10 cm thick collimator with a 5 cm × 10 cm rectangular opening was also used.Results:The prompt gamma peaks at 6.13 MeV and 4.44 MeV were clearly identified as a Result of the inelastic nuclear reaction between the protons and the 16O atoms found in the water target. The 6.13 MeV peak was 5% higher than the peak at 4.44 MeV for the water target. The 4.44 MeV peak was the only identified emission in the prompt gamma energy spectra from the graphite target (1 2C). The expected 2.313 MeV peak form the1 4N (liquid nitrogen target) was identified, but the other expected1 4N peaks could not be resolved.Conclusion:Prompt gamma measurements with a passive‐scatter proton beam are possible, but the presence of a high amount of background radiation from the patient final collimator presents a challenge at the treatment isocenter. The prominent prompt gamma peaks at 6.13 MeV and 4.44 MeV were identified from the water, Perspex and graphite targets. The prompt gammas from the liquid nitrogen target were difficult to see, but may not be significant in the in‐vivo verification process.

TH-CD-BRA-03: Experimental Validation of An Analytical Model for Prompt Gamma Imaging

Purpose: A prompt gamma (PG) slit camera prototype recently demonstrated a 1–2 mm accuracy to detect proton range shifts at clinical beam currents by comparing an expected PG detection profile to a measured one. An analytical model has been recently developed to compute the expected profile at practical speed (< 1 s). We present here its benchmark against measurements in heterogeneous phantoms. Methods: The analytical model is based on the computation of PG emission from Monte Carlo (MC) pre-generated PG emission profiles and the convolution of the emission profile with a transfer function that takes into account patient geometry and camera positioning. For the experimental benchmark, three phantom configurations were chosen, all built with slabs of tissue-equivalent plastics: 1) one homogeneous large slab (either adipose, bone or water); 2) slabs mimicking a typical succession of tissues in the brain (PMMA-adipose-bone-PMMA-water); 3) the same but for the lung with a geometry prone to range mixing effects (water-muscle followed by a mix of lung and muscle equivalent materials with the interface parallel to the beam). Several incident energies were selected, respectively: 1) 100, 150 and 200 MeV; 2) 115 and 145 MeV; 3) 110 MeV. The PG signal was measured by the PG camera placed at the position determined by the analytical model. Additional benchmark was performed using MC simulation with PENH. Results: For the analytical model versus measurements, agreement for range estimation was within 2.7 mm on average (1.4 mm standard deviation). Agreement between MC and experiments was similar. Finally, the analytical model reproduced MC predictions within 1 mm. Conclusion: Overall, excellent agreement was achieved with MC simulations and promising agreement with measurements was observed. The analytical model can potentially be used to select some probe spots that would be good candidates to verify the range prior to treatment delivery. Work supported by IBA

SU-C-204-03: In-Vivo Range Verification and Tissue Response to Proton Radiotherapy Using Prompt Gamma Volume Histograms

Purpose: To study if prompt gamma (PG) volume histograms created from PG images acquired during treatment delivery can be used to identify changes to beam range and tissue composition in response to proton radiotherapy. Methods: Monte Carlo simulations of a single field from a single treatment fraction (100 cGy) for prostate cancer were performed for the cases of: 1) an ideal patient setup, 1) a setup shift in the superior direction and 2) a reduction in oxygen concentration in the tumor. For each case, the 3 -Dimsional dose delivery and elemental PG emission in the patient for the treatment fraction were recorded and imported into a commercial treatment planning system. Changes in the dose volume histograms (DVH), as well as the PG volume histograms (PG-VH) for the PG emission from oxygen and for the total PG emission (from all elements) were analyzed. Results: For the 1 cm superior shift, the prostate DVH and total PG-VH both shifted toward lower doses with the shape of the curves remaining nearly unchanged, resulting in the DVH V95 dropping from 100 cGy to 90 cGy. For the total PG-VH, the V95 fell from 50 to 38. For the reduced oxygen case, both the DVHmore » and PG-VH had a much different shape than for the ideal case, with a significant downward slope in the curves as a function of dose. Conclusions: The shift in the prostate PG-VH for a superior shift in the patient setup correlated well with the DVH indicating it is possible to detect setup errors by analyzing the PG-VH from prompt gamma images obtained during daily proton treatment delivery. Additionally, it may be possible to detect changes in the elemental concentrations of irradiated tissues by analyzing the shape of the PG-VH.« less

SU‐E‐J‐149: Secondary Emission Detection for Improved Proton Relative Stopping Power Identification

Purpose:This research investigates application of secondary prompt gamma (PG) emission spectra, resulting from nuclear reactions induced by protons, to characterize tissue composition along the particle path. The objective of utilizing the intensity of discrete high‐energy peaks of PG is to improve the accuracy of relative stopping power (RSP) values available for proton therapy treatment planning on a patient specific basis and to reduce uncertainty in dose depth calculations.Methods:In this research, MCNP6 was used to simulate PG emission spectra generated from proton induced nuclear reactions in medium of varying composition of carbon, oxygen, calcium and nitrogen, the predominant elements found in human tissue. The relative peak intensities at discrete energies predicted by MCNP6 were compared to the corresponding atomic composition of the medium.Results:The results have shown a good general agreement with experimentally measured values reported by other investigators. Unexpected divergence from experimental spectra was noted in the peak intensities for some cases depending on the source of the cross‐section data when using compiled proton table libraries vs. physics models built into MCNP6. While the use of proton cross‐section libraries is generally recommended when available, these libraries lack data for several less abundant isotopes. This limits the range of their applicability and forces the simulations to rely on physics models for reactions with natural atomic compositions.Conclusion:Current end‐of‐range proton imaging provides an average RSP for the total estimated track length. The accurate identification of tissue composition along the incident particle path using PG detection and characterization allows for improved determination of the tissue RSP on the local level. While this would allow for more accurate depth calculations resulting in tighter treatment margins, precise understanding of proton beam behavior in tissue of various compositions is necessary requiring detailed simulations with a high degree of accuracy.

MO‐FG‐303‐05: A Feasibility Study of Using a Cherenkov Detector Material with the Prompt Gamma Range Verification Technique in Proton Therapy

Purpose:To simulate the feasibility of a Cherenkov glass material for the determination of the penetration depth of therapeutic proton beams in water.Methods:Proton pencil beams of various energies incident onto a water phantom with dimensions of 5 × 5 × 30 cm3 were used for simulation with the Geant4 toolkit. The model used standard electromagnetic packages, packages based on binary‐cascade nuclear model, several decay modules (G4Decay, G4DecayPhysics, and G4RadioactiveDecayPhysics), and optical photon components (G4OpticalPhysics). A Cherenkov glass material was modeled as the detector medium (7.2 g of In2O3 + 90 g cladding, density of 2.82 g/cm3, Zeff = 33.7, index of refraction n(600 nm) = 1.56, and energy threshold of production Eth = 156 keV ). The emitted secondary particles are analyzed characterizing their timing, energy, and angular distributions. A feasibility analysis was conducted for a simplistic detector system using this material to locate the position of the Bragg Peak.Results:The escaping neutrons have energies ranging from thermal to the incident proton energy and the escaping photons have energies &gt;10 MeV. Photon peaks between 4 and 6 MeV were attributed to originate from direct proton interactions with 12C (∼ 4.4 MeV) and 1⁶O (∼ 6 MeV), respectively. The escaping photons are emitted isotropically, while low (≤10 MeV) and high (&gt;10 MeV) neutrons are isotropic and forward‐directional, respectively. The emissions of photons are categorized into prompt (∼ns) and delayed (∼min) where the prompt photons include the 4.4 and 6 MeV. The Cherenkov material had on average &lt;2% of neutron interactions while LYSO and BGO scintillators had a minimum of ∼50%. Our simplistic detector system was capable of discerning Bragg Peak locations using a timing discrimination of ∼50 ns.Conclusion:We investigate the viability of using the Cherenkov material for MeV photon detection medium for the prompt gamma technique.

WE‐EF‐303‐07: Imaging of Prompt Gamma Rays Emitted During Delivery of Clinical Proton Beams with a Compton Camera: Feasibility Studies for Range Verification

Purpose:Evaluation of a prototype Compton camera (CC) for imaging prompt gamma rays (PG) emitted during clinical proton beam irradiation for in vivo beam range verification.Methods:We irradiated a water phantom with 114 MeV and 150 MeV proton pencil beams at clinical beam currents ranging from 1 nA up to 5 nA. The CC was placed 15 cm from the beam central axis and PGs from 0.2 MeV up to 6.5 MeV were measured during irradiation. From the measured data, 2‐dimensional (2D) PG images were reconstructed. One‐dimensional (1D) profiles from the PG images were compared to measured depth dose curves.Results:The CC was able to measure PG emission during delivery of both a single 150 MeV pencil beam and a 5 cm × 5 cm mono‐energetic layer of 114 MeV pencil beams. From the 2D images, a strong correlation was seen between the depth of the distal falloff of PG emission and the Bragg peak (BP). 1D profiles extracted from the PG images show that the distal 60% falloff of the PG emission lined up well with the distal 90% of the BP. Shifts as small as 3 mm in the beam range could be detected on both the 2D PG images and 1D profiles with an uncertainty of 1.5 mm. With the current CC prototype, a minimum dose delivery of 400 cGy was required to produce usable PG images.Conclusions:It was possible to measure and image PG emission with our prototype CC during proton beam delivery and to detect shifts in the BP range in the images. Therefore prompt gamma imaging with a CC for the purpose of in vivo range verification is feasible. However, for the studied system improvements in detector efficiency and reconstruction algorithms are necessary to make it clinically viable.

SU‐C‐204‐01: A Fast Analytical Approach for Prompt Gamma and PET Predictions in a TPS for Proton Range Verification

Purpose:We describe and demonstrate a fast analytical tool for prompt‐gamma emission prediction based on filter functions applied on the depth dose profile. We present the implementation in a treatment planning system (TPS) of the same algorithm for positron emitter distributions.Methods:The prediction of the desired observable is based on the convolution of filter functions with the depth dose profile. For both prompt‐gammas and positron emitters, the results of Monte Carlo simulations (MC) are compared with those of the analytical tool. For prompt‐gamma emission from inelastic proton‐induced reactions, homogeneous and inhomogeneous phantoms alongside with patient data are used as irradiation targets of mono‐energetic proton pencil beams. The accuracy of the tool is assessed in terms of the shape of the analytically calculated depth profiles and their absolute yields, compared to MC. For the positron emitters, the method is implemented in a research RayStation TPS and compared to MC predictions. Digital phantoms and patient data are used and positron emitter spatial density distributions are analyzed.Results:Calculated prompt‐gamma profiles agree with MC within 3 % in terms of absolute yield and reproduce the correct shape. Based on an arbitrary reference material and by means of 6 filter functions (one per chemical element), profiles in any other material composed of those elements can be predicted. The TPS implemented algorithm is accurate enough to enable, via the analytically calculated positron emitters profiles, detection of range differences between the TPS and MC with errors of the order of 1–2 mm.Conclusion:The proposed analytical method predicts prompt‐gamma and positron emitter profiles which generally agree with the distributions obtained by a full MC. The implementation of the tool in a TPS shows that reliable profiles can be obtained directly from the dose calculated by the TPS, without the need of full MC simulation.

MO‐F‐CAMPUS‐J‐05: Verification for Prompt Gamma Ray Imaging During Proton Boron Fusion Therapy

Purpose:The purpose of this study is to verify the acquisition of the three dimensional single photon emission computed tomography (SPECT) image using prompt gamma ray originated from proton boron fusion therapy (PBFT).Methods:The real‐time imaging system during the PBFT was simulated to acquire the tomographic image of the prompt gamma ray from treated tumor by the proton boron reaction, using Monte Carlo simulation (MCNPX). We acquired percentage depth dose (PDD) of the proton beam in the water phantom including the boron uptake region (BUR), the energy spectra of the prompt gamma ray and tomographic image which can show treated tumor regions. The prompt gamma ray image was reconstructed using maximum likelihood estimation maximization (MLEM) reconstruction algorithm with 64 projections. In addition, in order to evaluate the reconstructed image, the image profiles between BURs were extracted from the image.Results:In the PDD results, the Bragg‐peak was amplified definitely when the proton's maximum dose level was located at the BUR. This amplification is based on the generation of alpha particles. In addition, the prompt gamma ray peak of 719 keV was observed from the energy spectrum. Through the previous process, the tomographic image of prompt gamma ray from the BUR was reconstructed. The line profile was extracted from image including BURs, and it shows high signal‐to‐noise ratio.Conclusion:We confirmed that the real‐time prompt gamma ray image during the PBFT was successfully deducted, and results of quantitative image analysis show good agreement with the original pattern of the BUR. This study first verified the imaging capability of the PBFT‐SPECT system. In conclusion, the PBFT‐SPECT system can realize the treated tumor monitoring during the PBFT.