Ion Beam Applications Research Articles

27 - An online beam monitor detector for medical applications of ion beams

27 - An online beam monitor detector for medical applications of ion beams

X線光電子分光分析法と飛行時間型二次イオン質量分析法におけるアルゴンガスクラスターイオンビームの応用

X線光電子分光分析法と飛行時間型二次イオン質量分析法におけるアルゴンガスクラスターイオンビームの応用

Trans-National Access in the field of heritage science at the Laboratory of Ion Beam Applications, MTA Atomki

The Laboratory of Ion Beam Applications at MTA Atomki served as a Trans-National Access (TNA) host within the CHARISMA EU FP7 project. Although cultural heritage research is only one of the several applications in the laboratory, its importance is growing thanks to the success of CHARISMA. The variety of samples and analytical questions in this field provides constant motivation for development of the instrumentation and adaptation of new techniques. We have special expertise in investigations with high lateral resolution and the PIXE analysis of lighter elements but we can also host projects when the in-vacuum measurements are not feasible, at our external micro-beam set-up. We continue the TNA activity within the IPERION CH project.

Surrey Ion Beam Centre: the EPSRC “MRF” for Ion Beam Applications

Surrey Ion Beam Centre: the EPSRC “MRF” for Ion Beam Applications

Development of a new in-air micro-PIXE set-up with in-vacuum charge measurements in Atomki

A new external microbeam set-up has recently been installed as the extension of the existing microprobe system at the Laboratory of Ion Beam Applications of Atomki, Debrecen, Hungary. The external beam set-up, based on the system of Oxford Microbeams (OM), is equipped with two X-ray detectors for PIXE analysis, a digital microscope, two alignment lasers and a precision XYZ stage for easy and reproducible positioning of the sample. Exit windows with different thicknesses and of different materials can be used according to the actual demands, currently silicon-nitride (Si3N4) film with 200nm thickness is employed in our laboratory. The first application was demonstrated in the field of archaeometry, on Bronze Age hoards from Hungary.

SU‐E‐T‐03: 3 Year Clinical Experience with the IBA Proton Eyeline

Purpose:Over the past 3 years, more than 50 patients with ocular disease have been treated with a prototype commercial eyeline developed by Ion Beam Applications (IBA). It is particularly crucial for the dosimetry of the machine to be accurate, precise, and reproducible because of the small treatment volumes and several surrounding critical structures. A quality assurance (QA) program has been developed in order to regularly check and record the machine's dosimetry over time. In this study we have summarized and evaluated three years of patient and system QA data for the eyeline prototype.Methods:In order to accurately deliver the prescribed dose to the patient's treatment site, an output model was created based on several machine parameters. This output model, along with the requested system parameters, are regularly checked and recorded by a QA program. 10 standard proton fields have been created which have regular QA performed monthly with a water tank and parallel‐plate chamber, and recorded in a database. QA has additionally been performed for each patient‐specific treatment field. This is to verify and evaluate the patient output model as well as the system parameters for range&modulation combinations different than the standard QA fields.Results:140 beam measurements have been analyzed for range, modulation, and output. The range is typically within tolerance, although there are about 6 cases where the system did not perform as expected. The modulation appears to be very stable, always being within tolerance. Output for the standard QA fields are typically within 2.5% from the baseline value. The patient output measurements agree within 2.5% from the model.Conclusion:Overall the eyeline performs well within the tolerances set, and the patient output measurements agree within 2% of the model.

TU-EF-304-11: Therapeutic Benefits of Collimation in Spot Scanning Proton Therapy in the Treatment of Brain Cancer

Purpose: A dynamic collimation system (DCS) based on two orthogonal pairs of mobile trimmer blades has recently been proposed to reduce the lateral penumbra in spot scanning proton therapy (SSPT). The purpose of this work is to quantify the therapeutic benefit of using the DCS for SSPT of brain cancer by comparing un-collimated and collimated treatment plans. Methods: Un-collimated and collimated brain treatment plans were created for five patients, previously treated with SSPT, using an in-house treatment planning system capable of modeling collimated and un-collimated beamlets. Un-collimated plans reproduced the clinically delivered plans in terms of target coverage and organ-at-risk (OAR) sparing, whereas collimated plans were re-optimized to improve the organ-at-risk sparing while maintaining target coverage. Physical and biological comparison metrics such as dose distribution conformity, mean and maximum doses, normal tissue complication probability (NTCP) and risk of secondary brain cancer were used to evaluate the plans. Results: The DCS systematically improved the dose distribution conformity while preserving the target coverage. The average reduction of the mean dose to the 10-mm ring surrounding the target and the healthy brain were 7.1% (95% CI: 4.2%–9.9%; p<0.01) and 14.3% (95% CI: 7.8%–20.8%; p<0.01), respectively. This yielded an average reduction of 12.0% (95% CI: 8.2%–15.7%; p<0.01) for the brain necrosis NTCP using the Flickinger model, and 14.2% (95% CI: 7.7%–20.8%; p<0.01) for the risk of secondary brain cancer. The average maximum dose reductions for the brainstem, chiasm, optic nerves, cochleae and pituitary gland when comparing un-collimated and collimated plans were 14.3%, 10.4%, 11.2%, 13.0%, 12.9% and 3.4%, respectively. Evaluating individual plans using the Lyman-Kutcher-Burman NTCP model also yielded improvements. Conclusion: The lateral penumbra reduction performed by the DCS increases the normal tissue sparing capabilities of SSPT for brain tumor treatment while preserving the target coverage. This research was financially supported by Ion Beam Applications S.A. (IBA, Louvain-La-Neuve, Belgium).

SU‐E‐T‐187: Collimation Methods in Spot Scanning Proton Therapy: A Treatment Plan Comparison Between a Fixed Aperture and a Dynamic Collimation System

Purpose:Low‐energy treatments during spot scanning proton therapy (SSPT) suffer from poor conformity due to increased spot size. Collimation devices can reduce the lateral penumbra of a proton therapy dose distribution and improve the overall plan quality. The purpose of this work was to study the advantages of individual energy‐layer collimation, which is unique to a recently proposed Dynamic Collimation System (DCS), in comparison to a standard, fixed aperture that allows only a single shape for all energy layers.Methods:Three brain patients previously planned and treated with SSPT were re‐planned using an in‐house treatment planning system capable of modeling collimated and un‐collimated proton beamlets. The un‐collimated plans, which served as a baseline for comparison, reproduced the target coverage of the clinically delivered plans. The collimator opening for the aperture based plans included a 0.6 cm expansion of the largest cross section of the target in the Beam's Eye View, while the DCS based plans were created by optimizing the collimator position for beam spots near the periphery of the target in each energy layer.Results:The reduction of mean dose to normal tissue adjacent to the target, as defined by a 10 mm ring, averaged 9.13% and 3.48% for the DCS and aperture plans, respectively. The conformity index, as defined by the ratio of the volume of the 50% isodose line to the target volume, yielded an average improvement of 16.42% and 8.16% for the DCS and aperture plans, respectively.Conclusion:Collimation reduces the dose to normal tissue adjacent to the target and increases dose conformity to the target region for low‐energy SSPT. The ability of the DCS to provide collimation to each energy layer yields better conformity in comparison to fixed aperture plans.This work was partially funded by IBA (Ion Beam Applications S.A.).

Carbon-ion radiotherapy for locally advanced primary or postoperative recurrent epithelial carcinoma of the lacrimal gland

PurposeTo evaluate the applicability of carbon ion beams for the treatment of carcinoma of the lacrimal gland with regard to normal tissue morbidity and local tumor control. Methods and materialsBetween April 2002 and January 2011, 21 patients with locally advanced primary epithelial carcinoma of the lacrimal gland were enrolled in a Phase I/II clinical trial of carbon-ion radiotherapy (CIRT) at the National Institute of Radiological Sciences. Acute radiation toxicity was the primary endpoint of this dose-escalation study and the late toxicity, local control, and overall survival were additionally evaluated as secondary endpoints. Of the 21 subjects enrolled, all patients were followed for more than 6months and analyzed. ResultsThe radiation dose was increased from the initial dose of 48.0Gy equivalents (GyE)/12 fractions at 10% increments up to 52.8GyE. Of the 21 patients, five received a total dose of 48.0GyE, and 16 received a total dose of 52.8GyE. No patient developed grade 3 or higher skin toxicity. As late ocular/visual toxicity, three patients had grade 3 retinopathy and seven patients lost their vision. Among the 10 patients treated until May 2005, five patients had local recurrence, three of whom had marginal recurrence. Therefore, the margin for the CTV (clinical target volume) was set to a range according to the orbital exenteration since June 2005. After the application of the extended margin, no local recurrence has been observed. The three-year overall survival and local control rates were 82.2% and 79.0%, respectively. ConclusionCIRT can be applied for primary epithelial carcinoma of the lacrimal gland, with a borderline acceptable morbidity and sufficient antitumor effect when an extended margin is adopted.

Application of Li ion beam obtained by the cesium sputtering source for RBS analysis of optical layers

High energy Li ions of multiple charge states (Li + , Li 2+ and Li 3+ ) were produced in a tandem accelerator from a source of negative ions by a cesium sputtering (SNICS) ion source. The negative ion current of Li ions up to 32 nA was obtained in the preacceleration stage after the inflection magnet and retractable aperture. The current of the high energy ion beam obtained after acceleration and used for RBS spectra measurements was up to 3 nA. The Li target cone production procedure and design are presented in this work. Initial experiments using Li RBS were performed and their results indicate enhanced analytical application capabilities of RBS for an optical coating analysis, compared to the conventional proton RBS.

Focused particle beam nano-machining: the next evolution step towards simulation aided process prediction

During the last decade, focused ion beam processing has been developed from traditionally used Ga+ liquid ion sources towards higher resolution gas field ion sources (He+ and Ne+). Process simulations not only improve the fundamental understanding of the relevant ion–matter interactions, but also enable a certain predictive power to accelerate advances. The historic ‘gold’ standard in ion–solid simulations is the SRIM/TRIM Monte Carlo package released by Ziegler, Ziegler and Biersack 2010 Nucl. Instrum. Methods B 268 1818–23. While SRIM/TRIM is very useful for a myriad of applications, it is not applicable for the understanding of the nanoscale evolution associated with ion beam nano-machining as the substrate does not evolve with the sputtering process. As a solution for this problem, a new, adapted simulation code is briefly overviewed and finally addresses these contributions. By that, experimentally observed Ne+ beam sputter profiles can be explained from a fundamental point of view. Due to their very good agreement, these simulations contain the potential for computer aided optimization towards predictable sputter processes for different nanotechnology applications. With these benefits in mind, the discussed simulation approach represents an enormous step towards a computer based master tool for adaptable ion beam applications in the context of industrial applications.

Application of Ion Beam Induced Chemical Vapor Deposition for SiC Film Formation on Si Substrates using Methylsilane

We propose an experimental methodology for producing silicon carbide (SiC) films on Si substrates using an ion beam induced chemical vapor deposition (IBICVD) technique with methylsilane (SiH3CH3) as a gas source. Both methylsilane gas (1.2 sccm) and Ar ion beam (100 eV, 5μA) were simultaneously introduced onto Si(100) substrates. Temperatures of Si substrates were set at 600, 700, or 800°C. A SiC thin film was formed by the simultaneous introduction of methylsilane and Ar ions onto the Si substrate when the substrate temperature was 600°C. On the other hand, in the cases of 700 and 800°C, SiC films were formed by methylsilane gas alone and SiC film deposition rates by methylsilane gas with the Ar ion beam were approximately identical with those obtained without the Ar ion beam. We therefore conclude that the IBICVD technique with methylsilane is useful for SiC film formation on Si at relatively low substrate temperatures. [DOI: 10.1380/ejssnt.2015.174]

Sputter yield measurements of thin foils using scanning transmission ion microscopy

Scanning transmission ion microscopy (STIM) has been applied to measure sputter yields of thin Kovar foil. The results have been found in very good agreement with values determined by the weight loss method, demonstrating STIM as a feasible alternative measurement technique for sputter yield estimation of thin material samples. Measurements have been carried out under normal xenon ion incidence for ion energies in the range between 100 eV and 1000 eV. In addition, sputter yields of Kovar bulk samples are reported. The data might be interesting for ion beam applications such as solar electric propulsion, in which materials with low sputter yields are preferred to ensure a long operational lifetime of the system components.

Comparing C60+ and (H2O)n+ clusters for mouse brain tissue analysis

Time‐of‐flight SIMS is applied to the analysis of single cells and different types of biological tissue samples enabling the generation of images with high spatial resolution and chemical specificity. However, the low yield of secondary ions from this type of sample still remains a challenge. This low yield could potentially be increased by enhancing the protonation of ions with the presence of water. Here, we have explored the application of a prototype water cluster ion beam for the analysis of mouse brain tissue samples. A series of experiments acquired with 20 keV (H2O)3000+ and 20 keV (H2O)4500+ were compared with 20 keV C60+, showing ion yield enhancement when a (H2O)n+ cluster ion is employed in the analysis. The results have demonstrated the potential benefits provided by the use of (H2O)n+ clusters for the analysis of mouse brain tissue samples. © 2014 The Authors. Surface and Interface Analysis published by John Wiley &amp; Sons Ltd.

C235-V3 cyclotron for a proton therapy center to be installed in the hospital complex of radiation medicine (Dimitrovgrad)

Proton therapy is an effective method of treating oncologic diseases. In Russia, construction of several centers for proton and ion therapy is slated for the years to come. A proton therapy center in Dimitrovgrad will be the first. The Joint Institute for Nuclear Research (Russia) in collaboration with Ion Beam Application (IBA) (Belgium) has designed an C235-V3 medical proton cyclotron for this center. It outperforms previous versions of commercial IBA cyclotrons, which have already been installed in 11 oncologic hospital centers in different countries. Experimental and calculation data for the beam dynamics in the C235-V3 medical cyclotron are presented. Reasons for beam losses during acceleration are considered, the influence of the magnetic field radial component in the midplane of the accelerator and main resonances is studied, and a beam extraction system is designed. In 2011–2012 in Dubna, the cyclotron was mounted, its magnetic field was properly configured, acceleration conditions were optimized, and beam extraction tests were carried out after which it was supplied to Dimitrovgrad. In the C235-V3 cyclotron, an acceleration efficiency of 72% and an extraction efficiency of 62% have been achieved without diaphragming to form a vertical profile of the beam.

TH-C-BRD-05: Reducing Proton Beam Range Uncertainty with Patient-Specific CT HU to RSP Calibrations Based On Single-Detector Proton Radiography

Purpose: Beam range uncertainty in proton treatment comes primarily from converting the patient's X-ray CT (xCT) dataset to relative stopping power (RSP). Current practices use a single curve for this conversion, produced by a stoichiometric calibration based on tissue composition data for average, healthy, adult humans, but not for the individual in question. Proton radiographs produce water-equivalent path length (WEPL) maps, dependent on the RSP of tissues within the specific patient. This work investigates the use of such WEPL maps to optimize patient-specific calibration curves for reducing beam range uncertainty. Methods: The optimization procedure works on the principle of minimizing the difference between the known WEPL map, obtained from a proton radiograph, and a digitally-reconstructed WEPL map (DRWM) through an RSP dataset, by altering the calibration curve that is used to convert the xCT into an RSP dataset. DRWMs were produced with Plastimatch, an in-house developed software, and an optimization procedure was implemented in Matlab. Tests were made on a range of systems including simulated datasets with computed WEPL maps and phantoms (anthropomorphic and real biological tissue) with WEPL maps measured by single detector proton radiography. Results: For the simulated datasets, the optimizer showed excellent results. It was able to either completely eradicate or significantly reduce the root-mean-square-error (RMSE) in the WEPL for the homogeneous phantoms (to zero for individual materials or from 1.5% to 0.2% for the simultaneous optimization of multiple materials). For the heterogeneous phantom the RMSE was reduced from 1.9% to 0.3%. Conclusion: An optimization procedure has been designed to produce patient-specific calibration curves. Test results on a range of systems with different complexities and sizes have been promising for accurate beam range control in patients. This project was funded equally by the Engineering and Physical Sciences Research Council (UK) and Ion Beam Applications (Louvain-La-Neuve, Belgium).

SU‐E‐T‐267: Proton Pencil Beam Scanning for Mediastinal Lymphoma: 4‐Dimensional Feasibility Study

Purpose:To assess the feasibility of proton pencil beam scanning (PBS) for the treatment of mediastinal lymphoma.Methods:A group of 6 patients were planned using an anterior field with PBS. Spots with ∼5 mm σ were used for all patients, while large spots (∼10 mm σ) were employed for patients with motion perpendicular to the beam (≥5 mm). We considered volumetric repainting such that, in each fraction, the same field would be delivered twice. Four‐dimensional dose was calculated on initial and verification 4‐dimensional computed tomography (4D‐CT) scans (2—3) based on respiratory trace and beam delivery sequence. This was implemented by binning the spots into separate plans on each 4D‐CT phase respectively. Four starting phases were sampled for each painting and 4 energy switching times (0.5 s, 1 s, 3 s, and 5 s) were tested, resulting in 2560 dose distributions for the cohort. Plan robustness was measured for target and critical structures in terms of the percentage difference between delivered dose and planned dose.Results:For 5 of the 6 patients, the ITV (internal target volume) D&lt;sub&gt;98%&lt;/sub&gt; was degraded by &lt;3% (standard deviations ∼ 0.1%) when averaged over the whole course (up to 5% per fraction). Deviations of mean lung dose, heart maximum dose, and cord maximum dose were within 5% of prescribed dose. For one patient with motion perpendicular to the beam (up to 5 mm), the degradation of ITV D&lt;sub&gt;98%&lt;/sub&gt; was 9% over the whole course (12% per fraction), which was mitigated to 1% (3% per fraction) by employing large spots and repainting. No significant difference in coverage was observed for different energy switching times.Conclusion:This feasibility study demonstrates that, for mediastinal lymphoma, the PBS plan robustness can be maintained during delivery when target motion is measured and volumetric repainting and/or large spots are employed.This work was supported by Ion Beam Application.

SU-E-T-550: Range Effects in Proton Therapy Caused by Systematic Errors in the Stoichiometric Calibration

Purpose: The procedure for proton treatment planning involves the conversion of the patient's X-ray CT from Hounsfield units into relative stopping powers (RSP), using a stoichiometric calibration curve (Schneider 1996). In clinical practice a 3.5% margin is added to account for the range uncertainty introduced by this process and other errors. RSPs for real tissues are calculated using composition data and the Bethe-Bloch formula (ICRU 1993). The purpose of this work is to investigate the impact that systematic errors in the stoichiometric calibration have on the proton range. Methods: Seven tissue inserts of the Gammex 467 phantom were imaged using our CT scanner. Their known chemical compositions (Watanabe 1999) were then used to calculate the theoretical RSPs, using the same formula as would be used for human tissues in the stoichiometric procedure. The actual RSPs of these inserts were measured using a Bragg peak shift measurement in the proton beam at our institution. Results: The theoretical calculation of the RSP was lower than the measured RSP values, by a mean/max error of - 1.5/-3.6%. For all seven inserts the theoretical approach underestimated the RSP, with errors variable across the range of Hounsfield units. Systematic errors for lung (average of two inserts), adipose and cortical bone were - 3.0/-2.1/-0.5%, respectively. Conclusion: There is a systematic underestimation caused by the theoretical calculation of RSP; a crucial step in the stoichiometric calibration procedure. As such, we propose that proton calibration curves should be based on measured RSPs. Investigations will be made to see if the same systematic errors exist for biological tissues. The impact of these differences on the range of proton beams, for phantoms and patient scenarios, will be investigated. This project was funded equally by the Engineering and Physical Sciences Research Council (UK) and Ion Beam Applications (Louvain-La-Neuve, Belgium).

SU‐E‐T‐464: On the Equivalence of the Quality Correction Factor for Pencil Beam Scanning Proton Therapy

Purpose:In current practice, most proton therapy centers apply IAEA TRS‐398 reference dosimetry protocol. Quality correction factors (kQ) take into account in the dose determination process the differences in beam qualities used for calibration unit and for treatment unit. These quality correction factors are valid for specific reference conditions. TRS‐398 reference conditions should be achievable in both scattered proton beams (i.e. DS) and scanned proton beams (i.e. PBS). However, it is not a priori clear if TRS‐398 kQ data, which are based on Monte Carlo (MC) calculations in scattered beams, can be used for scanned beams. Using TOPAS‐Geant4 MC simulations, the study aims to determine whether broad beam quality correction factors calculated in TRS‐398 can be directly applied to PBS delivery modality.Methods:As reference conditions, we consider a 10×10×10 cm3 homogeneous dose distribution delivered by PBS system in a water phantom (32/10 cm range/modulation) and an air cavity placed at the center of the spread‐out‐Bragg‐peak. In order to isolate beam differences, a hypothetical broad beam is simulated. This hypothetical beam reproduces exactly the same range modulation, and uses the same energy layers than the PBS field. Ion chamber responses are computed for the PBS and hypothetical beams and then compared.Results:For an air cavity of 2×2×0.2 cm3, the ratio of ion chamber responses for the PBS and hypothetical beam qualities is 0.9991 ± 0.0016.Conclusion:Quality correction factors are insensitive to the delivery pattern of the beam (broad beam or PBS), as long as similar dose distributions are achieved. This investigation, for an air cavity, suggests that broad beam quality correction factors published in TRS‐398 can be applied for scanned beams.J. Sorriaux is financially supported by a public‐private partnership involving the company Ion Beam Applications (IBA).

High energy gas cluster ions for organic and biological analysis by time-of-flight secondary ion mass spectrometry

There is considerable excitement surrounding the application of gas cluster ion beams (GCIBs) for SIMS analysis in order to study organic materials and biological samples such as cells and tissues. These ion beams, that often comprise several thousand argon atoms in the primary ion, have been used mainly for the etching of organic materials to remove damage from the surface allowing molecular depth profiling experiments to be performed. The energy of the ion beam is normally 2–20keV. There have been relatively few studies reported on the use of GCIB as analysis beams, due to difficulties related to fast pulsing and focusing of the beam along with the sometimes low ionisation efficiency. In this study, we report on the use of a new higher energy (40keV) GCIB operated in a continuous mode. When compared to lower energies depth profiles on thin films of Irganox 1010 show an increase in sputter yield while fragmentation, damage accumulation and ionisation efficiency remains unchanged. Experiments on brain tissues show increased signal levels especially for higher mass secondary ions (m/z 500+) in comparison to C60+ at 40keV and Ar4000+ at 20keV impact energy. The use of higher energies facilitates better focusing of the primary ion beam as demonstrated here on a human hair sample where we achieve a spatial resolution of <3μm. Even with this small spot size, we can detect enough signal from and high mass species for clear localisation. All results indicate that higher energies are beneficial for most aspects of ToF-SIMS applications in biology.