Active Scanning System Research Articles

Improved active sub-terahertz imaging system for parcel inspection

Terahertz radiation has emerged as a prominent solution for imaging and detection beyond visible and infrared. Active terahertz imaging is a widely used technology in this context especially for security applications and screening. Such systems are built around an illuminating source, a detecting module and a beam shaping system to match the detectors geometry. The overall system performance is largely dependent on an optimized choice of these modules. In this work, an active sub-terahertz scanning system working at 100 GHz frequency is proposed to detect concealed objects in parcels and mail. The system is optimized based on an adapted design of the beam shaper and a preprocessing correction of the images to ensure uniformity of response and cleanness. The proposed system demonstrated through experimentation improved resolution with a uniform response along its detection area.

Unique Beam Scanning Device for Active Beam Delivery System in Proton Therapy

A new Beam Delivery System (BDS) has been proposed for a proton therapy project, partially funded, called AMIDERHA. That BDS is characterized by an active scanning system which irradiates target with a pencil beam. The feature of this project was the using of an accelerator Linac with variable final energies and the Robotized Patient Positioning System instead of the traditional gantry. The active BDS of AMIDERHA then does not include a gantry and a pencil beam scanning system with a relatively long Source to Axis Distance (SAD) could be used. In this condition, the using of a unique device capable of scanning the beam for both horizontal and vertical plane in the active BDS of the project is possible. In this contribution this new beam scanning device will be presented. Furthermore, a preliminary design of the device and the trajectory simulations for beam parameter optimization will also be discussed.

Calibrating projector flexibly for a real-time active 3D scanning system

A novel method for projector calibration is proposed that is supported by an uncalibrated camera. The use of an uncalibrated camera is motivated by the fact that camera calibration errors may negatively influence the projector calibration results. The principles of camera calibration are used to calibrate the projector by considering it as a camera that acts in a reverse manner. A regular shaped pattern with known dimensions such as a chessboard is projected by the projector, captured by the camera and then used for projector calibration. The re-projection error analysis indicates that the proposed method performs on par with the calibration results of a camera.

Abstract ID: 55 Beam characterization for the TULIP accelerator for protontherapy through full Monte Carlo simulations

TULIP, Turning LInac for Protontherapy, is a novel accelerator systems for protontherapy mounted on a rotating gantry designed by the TERA Foundation and CERN [1] , [2] . TULIP is natively designed with a 3D active scanning system that, besides the transverse scanning with fast magnets, features a fast beam energy variation from the linac to scan in the longitudinal direction in few ms. The main goal of this research is to characterize TULIP’s beams, through Full Monte Carlo (MC) simulations. The study combines the multi-particle tracking programs, RF Track [2] , Travel [3] , MADx-PTC [4] and the FLuka Monte-Carlo code [5] , [6] , enabling to follow each particle from the source through the linac, the beam transfer lines and the nozzle elements, until the isocenter such that transverse and longitudinal phase space characteristics are accounted for each particle. The particle fluence results in air at the isocenter and in upstream and downstream positions along the beam direction and the depth-dose curves are obtained and presented in a beamline model for a set of beam energy values and scanning magnet kick strengths. The results, suitable for characterizing in detail the beam spots for this particular accelerator system, can be used as input to generate a beam model in a commercial TPS and thus to allow the comparison with Fluka results in real patient case scenarios.

Abstract ID: 169 Monte Carlo calculated correction factors for a proton calorimeter in clinical proton beams

Calorimetry is the only fundamental method for measuring the absorbed dose according to its definition. A calorimeter measures the temperature rise resulting from irradiation in an absorber, assuming all the energy deposited in a material appears as a heat. Unlike other detectors, e.g. ionization chambers, a calorimeter inherently provides a method to measure the energy deposited by radiation directly. In particular, the National Physical Laboratory (NPL) has developed and is now commissioning a graphite calorimeter as a primary standard of absorbed dose for clinical proton beams. To determine the absorbed dose to graphite from calorimeter measurements, different correction factors have to be calculated, including the gap correction factor ( k gap ) and a volume averaging correction factor ( k vol ) [1] . The former is related to the effect due to the presence of vacuum gaps within the calorimeter, the latter converts the mean absorbed dose in the graphite core to the absorbed dose in a point located at the centre of the core. A separate conversion factor is then applied to convert the absorbed dose to graphite in the calorimeter to the absorbed dose at the reference depth in water. Monte Carlo simulations are currently the most precise tool to calculate these corrections in complex experimental configurations. A Monte Carlo application has been developed with the TOPAS platform, based on the Geant4 toolkit to calculate k gap and k vol for monoenergetic proton beams with energies ranging between 60 and 230 MeV [2] . Initial results indicate that k gap ranges from 0.06% above unity at 60 MeV to 0.36% above unity at 230 MeV with k vol being of a similar magnitude at these energies. Moreover, to obtain the corrections in a more realistic environment close to clinical conditions, a typical passive proton therapy beam line for ocular melanoma treatment has been simulated in detail and similar results are being obtained for active scanning systems. The results of the presented work will significantly contribute to the establishment of the NPL calorimeter as a primary standard in proton therapy.

New Beam Scanning Device for Active Beam Delivery System (BDS) in Proton Therapy

A new Beam Delivery System (BDS) has been studied in the framework of a new proton therapy project, called AMIDERHA. It is characterized by an active scanning system for target irradiation with a pencil beam. The project is based on the use of a Linac with variable final energy and the Robotized Patient Positioning System instead of the traditional gantry. As a consequence, in the active BDS of AMIDERHA a pencil beam scanning system with a relatively long Source to Axis Distance (SAD) can be used. In this contribution, the idea of using a unique new device capable of both horizontal and vertical beam scansion for the AMIDERHA active BDS will be presented and discussed. Furthermore, a preliminary design of that device will be shown, together with the results of simulations.

Characterization of a terahertz wave scanned imaging system for threat detection at standoff distances

A terahertz active scanned imaging system is developed in order to acquire images of various targets at stand-off distances. The images are analyzed with respect to the experimentally obtained beam profile at the target plane using a commercially available mm-wave/terahertz camera. The active scanning system utilizes a heterodyne, continuous wave transceiver unit operating at 340 GHz and 2-D opto-mechanical scanning of the target plane is performed using two large area mirror coupled galvanometers. 340 GHz working frequency allows standoff imaging with adequate resolution with the help of a suitable optical design. Results given here correspond to the imaging of various objects placed at least 120 cm away from the transceiver, with a 5 × cm2 field of view. Image resolution is about 0.6 cm in the horizontal, 0.3 cm in the vertical direction which was assessed by analyzing the measured beam profiles on the target plane with a commercial mm-wave/terahertz camera.

SU‐F‐T‐213: Commissioning Results of the Prototype Active Scanning Irradiation System of Korea Heavy Ion Medical Accelerator

Purpose:A prototype actives scanning beam delivery system was designed, manufactured and installed as a part of the Korea Heavy Ion Medical Accelerator Project. The prototype system includes the most components for steering, modulating, detecting incident beam to patient. The system was installed in MC‐50 cyclotron beam line and tested to extract the normal operation conditions.Methods:The commissioning process was completed by using 45 MeV of proton beam. To measure the beam position accuracy along the scanning magnet power supply current, 25 different spots were scanning and measured. The scanning results on GaF film were compared with the irradiation plan. Also, the beam size variation and the intensity reduction using range shifter were measured and analyzed. The results will be used for creating a conversion factors for asymmetric behavior of scanning magnets and a dose compensation factor for longitudinal direction.Results:The results show asymmetry operations on both scanning × and y magnet. In case of scanning magnet × operation, the current to position conversion factors were measured 1.69 mm/A for positive direction and 1.74 mm/A for negative direction. The scanning magnet y operation shows 1.38mm/A and 1.48 mm/A for both directions. The size of incoming beam which was 18 mm as sigma becomes larger up to 55 mm as sigma while using 10 mm of the range shifter plate. As the beam size becomes large, the maximum intensity of the was decreased. In case of using 10 mm of range shifter, the maximum intensity was only 52% compared with no range shifter insertion.Conclusion:For the appropriate operation of the prototype active scanning system, the commissioning process were performed to measure the beam characteristics variation. The obtained results would be applied on the irradiation planning software for more precise dose delivery using the active scanning system.

Design and analysis of ballistic ground scanning system based on dynamics simulation

While active ground scanning systems like unmanned aerial vehicle are being widely used for detection of object in a wide area, there are needs for scanning systems that can instantly detect and respond to potential hazards in a defined area. This study develops a ballistic ground scanning system based on computer simulations of a dynamics model. We built a dynamics model in ADAMS software, and the validity of the dynamics model was tested through projectile experiments. Using the developed dynamics model, we determined design parameters of the scanning system and investigated the effects of the parameters on the system performance.

Geant4 simulation for a study of a possible use of carbon ion pencil beams for the treatment of ocular melanomas with the active scanning system at CNAO

The aim of this work was to study a possible use of carbon ion pencil beams (delivered with active scanning modality) for the treatment of ocular melanomas at the Centro Nazionale di Adroterapia Oncologica (CNAO). The promising aspect of carbon ions radiotherapy for the treatment of this disease lies in its superior relative radio-biological effectiveness (RBE). The Monte Carlo (MC) Geant4 10.00 toolkit was used to simulate the complete CNAO extraction beamline, with the active and passive components along it. A human eye modeled detector, including a realistic target tumor volume, was used as target. Cross check with previous studies at CNAO using protons allowed comparisons on possible benefits on using such a technique with respect to proton beams. Experimental data on proton and carbon ion beams transverse distributions were used to validate the simulation.

Preliminary results, obtained by using a proton beam, for an active scanning system to installed on the KHIMA

The active scanning technique is a pencil beam delivery method in particle therapy. The active scanning beam delivery system consists of a beam scanner, beam monitor, energy modulator, and related programs, such as the irradiation control and planning programs. A proposed prototype active scanning system was designed and installed on MC-50 at the Korea Institute of Radiological and Medical Science (KIRAMS) with a 45-MeV proton beam. The laminated magnetic yoke of the scanning magnet supported fast ramping. The beam intensity and the beam profile monitors were designed for measuring the beam’s properties. Both the range shifter and the ridge filter modulate the incoming beam energy. The LabVIEW®-based beam-irradiation-control program operates the system in a sequential operation manner for use with the MC-50 cyclotron. In addition, an in-housecoded irradiation-planning program generates an optimal irradiation path. A scanning experiment was successfully completed to print the logo of the Korea Heavy Ion Medical Accelerator (KHIMA) on GaF film. Moreover, the beam’s position accuracy was measured as 0.62 mm in the x-direction and as 0.83 mm in the y-direction.

Semi-automatic Low Cost 3D Laser Scanning Systems for Reverse Engineering

This paper is focused on the development, implementation and testing of a semi-automated low cost motorized active 3D slit laser scanning system. The scanner is based on the software platform of the DAVID LaserScanner Vision Systems GmbH's. The authors implemented motorized movements on a CNC milling machine, controlling the systems by the Mach3 CNC software. The authors have combined and personalized different software, mainly low cost or open-source: a specific program was written and compiled for processing; establishing communication between the scanning software (David-Laserscan) and control software/hardware of the milling machine (Mach3) throw two double virtual communication ports. Video abstract [Display omitted]

SU-E-T-594: Preliminary Active Scanning Results of KHIMA

Purpose: To verify the design criteria on heavy ion beam irradiation, developing a proto type active scanning system was purposed. The active scanning system consists of scanning magnet, power supplies, beam monitors, energy modulation system, and irradiation control system. Methods: Each components of the active scanning system was designed for carbon beam first. For the fast ramping a laminated yoke was purposed. To measure incoming dose and profile, a plate and strip type of ion chambers were designed. Also, ridge filter and range shifter was manufactured. And, the scanning system was modified to adopt 45 MeV of proton beam because of the absence of carbon ion beam in Korea. The system was installed in a beam line at MC-50, KIRAMS. Also, the irradiation control system and planning software was provided. Results: The scanning experiment was performed by drawing KHIMA logo on GaF film. The logo was scanned by 237 scanning points through time normalized intensity modulation. Also, a grid points scanning was performed to measure the scanning resolution and intensity resolution. Conclusion: A prototype active scanning system was successfully designed and manufactured. Also, an initial experiment to print out a drawing on GaF film through the scanning system was completed. More experiments would be required to specify the system performance.

Ridge filter design for a particle therapy line

The beam irradiation system for particle therapy can use a passive or an active beam irradiation method. In the case of an active beam irradiation, using a ridge filter would be appropriate to generate a spread-out Bragg peak (SOBP) through a large scanning area. For this study, a ridge filter was designed as an energy modulation device for a prototype active scanning system at MC-50 in Korea Institute of Radiological And Medical Science (KIRAMS). The ridge filter was designed to create a 10 mm of SOBP for a 45-MeV proton beam. To reduce the distal penumbra and the initial dose, [DM] determined the weighting factor for Bragg Peak by applying an in-house iteration code and the Minuit Fit package of Root. A single ridge bar shape and its corresponding thickness were obtained through 21 weighting factors. Also, a ridge filter was fabricated to cover a large scanning area (300 × 300 mm2) by Polymethyl Methacrylate (PMMA). The fabricated ridge filter was tested at the prototype active beamline of MC-50. The SOBP and the incident beam distribution were obtained by using HD-810 GaF chromatic film placed at a right triangle to the PMMA block. The depth dose profile for the SOBP can be obtained precisely by using the flat field correction and measuring the 2-dimensional distribution of the incoming beam. After the flat field correction is used, the experimental results show that the SOBP region matches with design requirement well, with 0.62% uniformity.

Secondary neutron doses in a compact proton therapy system

Proton therapy offers several advantages compared with classical radiotherapy owing to a better dose conformity to the tumour volume. However, proton interactions with beam transport elements and the human tissues lead to the production of secondary neutrons, resulting in an extra whole-body dose with some carcinogenic potential. In this study, the secondary neutron doses generated with an active beam scanning system and with two compact proton therapy systems recently appeared on the market are compared.

GATE as a GEANT4-based Monte Carlo platform for the evaluation of proton pencil beam scanning treatment plans

Active scanning delivery systems take full advantage of ion beams to best conform to the tumor and to spare surrounding healthy tissues; however, it is also a challenging technique for quality assurance. In this perspective, we upgraded the GATE/GEANT4 Monte Carlo platform in order to recalculate the treatment planning system (TPS) dose distributions for active scanning systems. A method that allows evaluating the TPS dose distributions with the GATE Monte Carlo platform has been developed and applied to the XiO TPS (Elekta), for the IBA proton pencil beam scanning (PBS) system. First, we evaluated the specificities of each dose engine. A dose-conversion scheme that allows one to convert dose to medium into dose to water was implemented within GATE. Specific test cases in homogeneous and heterogeneous configurations allowed for the estimation of the differences between the beam models implemented in XiO and GATE. Finally, dose distributions of a prostate treatment plan were compared. In homogeneous media, a satisfactory agreement was generally obtained between XiO and GATE. The maximum stopping power difference of 3% occurred in a human tissue of 0.9 g cm−3 density and led to a significant range shift. Comparisons in heterogeneous configurations pointed out the limits of the TPS dose calculation accuracy and the superiority of Monte Carlo simulations. The necessity of computing dose to water in our Monte Carlo code for comparisons with TPSs is also presented. Finally, the new capabilities of the platform are applied to a prostate treatment plan and dose differences between both dose engines are analyzed in detail. This work presents a generic method to compare TPS dose distributions with the GATE Monte Carlo platform. It is noteworthy that GATE is also a convenient tool for imaging applications, therefore opening new research possibilities for the PBS modality.

SU-E-T-282: Preliminary Simulation Study for 3 Dimensional Dose Delivery in Carbon Beam Active Scanning System of KHIMA.

KHIMA (Korea Heavy Ion Medical Accelerator) project has a plan to develop and construct a research beam line for carbon beam active scanning system. The carbon beam line consists with scanning magnet, beam-monitoring system, energy modulation system. In this study, the significant components, scanning magnets and ridge filter, were designed for the carbon beam active scanning beam line. The designed scanning magnet and ridge filter were used for 3 dimensional active beam dose delivery simulation by Geant4 Monte Carlo code. The target volume of the active scanning was 10 × 10 × 5 cm2 on the water phantom with 400 MeV/u of carbon beam. The transvers plane on the target was scanned by 3mm of step size. And, the optimized weighting factors of transverse scanning were obtained by MINUIT fitting package of ROOT. An aluminum ridge filter was designed to generate 5 cm of physical SOBP through step shape, which was optimized through in-house iteration method and the MINUIT package.The simulation was performed with Geant4 through applying the transverse scanning with the obtained weighting factor and the designed ridge filter. The uniformity on the transverse plan will be expected below 4% when it considered scattered beam. Also, the uniformity for longitudinal plane will be expected lower then 5%. This preliminary computational study was shown a possibility of using ridge filter for acceptable 3 dimensional uniformity on active beam delivery system in carbon beam therapy line. The optimization process to reach an acceptable uniformity on clinical use should be followed. In addition, it would be used for the design of treatment planning system software for KIHMA project.

The status of CNAO

The CNAO (Italian acronym that stands for National Centre for Oncological Hadrontherapy) has been realised in Pavia, Italy. It is a clinical facility created and financed by the Italian Ministry of Health and conceived to supply hadrontherapy treatments to patients recruited all over the Country. A qualified network of clinical and research institutes, the CNAO Collaboration, has been created to build and to run the centre. This organizational model turned out to be very efficient and fruitful to reach the goal of introducing the most advanced techniques and procedures of hadrontherapy. Three treatment rooms with four beam ports (three horizontal and one vertical) are operational and one experimental room has been built. Beams of protons with kinetic energies up to 250MeV and beams of carbon ions with maximum kinetic energy of 400MeV/u are transported and delivered by active scanning systems. The machine operation started in 2009 with the commissioning of the high-technology components that form the acceleration chain from the sources to the patient. The dosimetry and radiobiology tests have been completed with proton beams and CNAO obtained the authorisation to start treating patients. Statistics from the Italian Association of Radiotherapists and Oncologists (AIRO) have estimated that more than 3% of the overall Italian radiotherapy annual patients, i.e. more than 3000 new patients per year, would preferably be treated with hadrontherapy, but this number is steadily increasing. Pre-selection criteria are defined on the basis of established clinical protocols and the hospitals and the clinics in the network will address to the CNAO those patients that satisfy the criteria. This paper outlines the project development, the technical aspects of the realisation and commissioning and the clinical issues relevant for the patients treatments at CNAO.

SU‐FF‐T‐312: Dosimetry for Radiobiological Evaluation of the Active Beam Scanning System at Loma Linda University Medical Center

Purpose: Active beam scanning is a new and important innovation in proton therapy, potentially allowing for a more conformal proton treatment through dynamic manipulation of proton pencil beams. Active beam scanning thus requires accurate online dosimetry to track the proton pencil beam both in space and time, whilst at the same time monitoring dose delivered to a given point within the patient. Radiobiological validation of this new technology is equally important. Currently, with passive proton beam delivery a uniform RBE of 1.1 is assumed, and this has lead to satisfactory clinical results both in terms of tumor control and side effects. However, it is unclear whether this RBE value is also appropriate for active beam scanning treatments. Methods and Materials: To investigate this, researchers at Loma Linda University Medical Center are utilizing a multilayered system to evaluate radiobiological parameters at multiple positions within a water tank along the depth dose profile. The results obtained are being compared with identical experiments completed with Co‐60 photons and passively delivered protons. As a prerequisite for accurate and meaningful comparisons, precise dosimetry ensuring compatibility of dose rate, depth dose profile, dose uniformity and absolute dose have to be performed for all three radiation modalities. This presentation describes in detail the dosimetry methodology associated with the project, including film and ion chamber evaluation of the three radiation modalities. Results: Initial results indicate that the active beam scanning system provides proton radiation fields comparable to that utilizing passive beam delivery with a flatness and symmetry within 3% (TG45) at all positions along the Bragg peak. Further, dose rates experienced with this system are also comparable to that for passive beam delivery. Conclusions: This preclinical work will provide a unique opportunity to discuss both dosimetry‐ and radiobiology‐associated issues of automatic beam scanning in proton therapy.

Image-based motion compensation for structured light scanning of dynamic surfaces

Many structured light scanning systems based on temporal pattern codification produce dense and robust results on static scenes but behave very poorly when applied to dynamic scenes in which objects are allowed to move or to deform during the acquisition process. The main reason for this lies in the wrong combination of encoded correspondence information because the same point in the projector pattern sequence can map to different points within the camera images due to depth changes over time. We present a novel approach suitable for measuring and compensating such kind of pattern motion. The described technique can be combined with existing active range scanning systems designed for static surface reconstruction making them applicable for the dynamic case. We demonstrate the benefits of our method by integrating it into a gray code-based structured light scanner, which runs at 30 3D scans per second.