High-energy Carbon Beams Research Articles

Theoretical tumor edge detection technique using multiple Bragg peak decomposition in carbon ion therapy

Purpose: The range precision in carbon ion therapy is extremely sensitive to tissue density variations. A high energy carbon beam, after crossing a high-gradient edge parallel to the beam direction, suffers from range mixing leading to the detection of multiple Bragg peaks (BPs) varying intensity and water equivalent thickness (WET). The purpose of this work was to introduce a model that determines the position of a high-gradient edge based on information acquired from carbon transmission imaging. Methods: A model was derived to determine the lateral distance between the irradiation beam propagation axis and the edge position. To validate it, carbon beams were simulated and propagated through two parametric phantoms: (1) a bone cube in a water tank and (2) a semi-cylindrical bone insert in a water tank. The method was tested in a lung tumor case where range mixing led to more than two BPs being detected, requiring an iterative BP decomposition to determine the fraction of carbon ions crossing the materials surrounding the edge of interest. Results: The theoretical model predicted the edge position relative to the beam position with an error ≤1 mm for all studied cases with a maximum dose delivered of 24 μGy. Conclusions: The method presented here is a proof of principle. It does not take into account clinical uncertainties. However, this approach provided promising results suggesting that future extension to assess the impact of clinical uncertainties should be performed.

Development of Carbon-Ion Radiotherapy Facilities at NIRS

Radiotherapy using high-energy carbon beams from the Heavy Ion Medical Accelerator in Chiba has been carried out at the National Institute of Radiological Sciences (NIRS) since June 1994, and more than 10 000 patients have been treated to date. With the prospective clinical results for the first ten years, we designed a compact accelerator facility for carbon-ion radiotherapy (CIRT), and performed related Research and Development (RD two of them have both horizontal and vertical fixed-irradiation-ports, and the other is a rotating-gantry port. For all ports, fast three-dimensional raster-scanning irradiation technology is employed. The rotating gantry equips ten combined-function superconducting magnets, and can deliver carbon ions having the energy of between E = 430 and 50 MeV/ u to an isocenter with irradiation angles of over ±180°. Construction as well as installation of the superconducting gantry was completed by the end of September 2015, and treatments using the gantry began since May 2015. Presently, we are further designing a next-generation compact facility as a future project; superconducting and laser technologies are to be used for accelerator design. In this paper, we report development of carbon-ion accelerator facilities as well as the future project.

Effect of High Energy Carbon Beam Irradiation on Carbon Nanotubes Modified Glassy Carbon and Its Application in Sensing of Deoxyguanosine

The effect of high energy carbon ion beam as the modification tool for the multiwalled carbon nanotubes (MWCNT) modified glassy carbon (GC) has been studied. The change in the morphology, length and diameter of the carbon nanotubes upon irradiation is analyzed using Raman spectroscopy, Atomic force microscopy and FE-SEM. The irradiated MWCNTs had a diameter in the range of 3-27 nm which is much lower in comparison to the diameter of the tubes present in the pristine state. All the bands in the Raman spectra, corresponding to the irradiated MWCNT, shifted towards higher wave numbers by 4-5 cm-1. The irradiated MWCNT/GCE has been further used as a sensor for the electrochemical investigation of deoxyguanosine and deoxyadenosine. A sharp oxidation peak with much enhanced peak current at ~930 mV, corresponding to the oxidation of deoxyguanosine, is observed at the irradiated sensor, whereas, no peak was observed at the bare GCE. A very small peak at ~ 975 mV is observed at MWCNT modified GCE. Thus, it can be concluded that irradiation leads to appreciable defects formation which promotes the electron transfer and leads to enhanced electrooxidation of deoxyguanosine on the irradiated sensor surface. It was found that the peak potential of both deoxyguanosine and deoxyadenosine depends on the pH of the supporting electrolyte and shifted to more positive potentials with increase in pH. The linear relation between pH and the peak potential (Ep) can be expressed by the following equations: Ep (Deoxyguanosine) = -52.96 pH + 1307.3 (R2 = 0.9928) Ep (Deoxyadenosine) = -49.94 pH + 1560.4 (R2 = 0.9990) From the linear current versus concentration relations, it can be seen that exposure of MWCNT to high energy carbon beam lead to ~ 7 times increase in sensitivity in the case of deoxyguanosine and ~ 2 times for deoxyadenosine. The limit of detection, calculated by 3σ/b where σ is the standard deviation of the blank solution and b is the slope of the calibration curve, is substantially changed on irradiation from 12 µM to 507 nM and 4.29 µM to 300 nM for deoxyguanosine and deoxyadenosine respectively. The simultaneous determination of the two analytes was performed using the fabricated sensor and its practical utility was tested by analyzing DNA, extracted from herring sperm and MCF7 cell line, for the presence of deoxyguanosine and deoxyadenosine. The common biomolecules present in blood and urine did not interfere in the determination and the high stability and reproducibility of the sensor confirmed its successful application in real sample analysis. Figure 1

Frontier of radiation therapy with high energy carbon beams

Frontier of radiation therapy with high energy carbon beams

Emulsion Cloud Chamber technique to measure the fragmentation of a high-energy carbon beam

Beams of Carbon nuclei are used or planned to be used invarious centers for cancer treatment around the world because of theirtherapeutic advantages over proton beams. The knowledge of thefragmentation of Carbon nuclei when they interact with the human bodyis important to evaluate the spatial profile of their energydeposition in the tissues, hence the damage to the tissues neighboringthe tumor. In this respect, the identification of the fragmentationproducts is a key element. We present in this paper the chargemeasurement of about 3000 fragments produced by the interaction of12C nuclei with an energy of 400 MeV/nucleon in a detectorsimulating the density of the human body. The nuclear emulsiontechnique is used, by means of the so-called Emulsion CloudChamber. In order to achieve the large dynamical range required forthe charge measurement, the recently developed techniques of theemulsion controlled fading are used. The nuclear emulsions areinspected using fast automated microscopes recently developed. Acharge assignment efficiency of more than 99% is achieved. Theseparation of Hydrogen, Helium, Lithium, Berillium, Boron and Carboncan be achieved at two standard deviations or considerably more,according to the track length available for the measurement.

CVD diamond dosimeters for heavy ion beams

Studies on dosimeters based on diamond grown by Chemical Vapour Deposition CVD for hadron therapy [G. Kraft, Nucl. Inst. and Meth. in Phys. Res. A 454 (2000) 1.] are presented. Online beam monitoring and non-integrating dosimetry by particle counting as well as passive thermoluminescence dosimetry is the aim of this work. Experiments have been performed with high-energy carbon beams (88–430 MeV/u) as well as low-energy (11.4 MeV/u) heavy charged-particles from 12C up to 238U. In order to benefit from its excellent signal-to-noise ratio single-crystal CVD samples have been used to count single-primary particles. The electronics is based on an ASIC and processed the current signals obtained from the detectors during the passage of every single particle in a bipolar readout configuration. The results have been compared with those obtained with broadband amplifiers. The counting efficiency has been measured to be 100% with an error of 7% for therapeutic carbon ions as well as for low energetic uranium ions. The thermoluminescence (TL) response of a batch of commercially available ‘mechanical grade’ polycrystalline CVD detectors has been studied. We found the TL signals of the dosimeters tested to be very reproducible and stable [M. Rębisz, A. Martemiyanov, E. Berdermann, M. Pomorski, B. Marczewska and B. Voss, Diamond Relat. Mater. 15 (2006) 822.]. In this paper the first measurements of the depth–dose distribution in specially prepared PMMA phantoms are presented.

RBE of carbon ions: Experimental data and the strategy of RBE calculation for treatment planning

The main reason for the application of heavy ions like carbon in radiotherapy is the enhanced relative biological effectiveness RBE. In contrast to neutrons where RBE is widely independent from penetration depth, high energy carbon beams have a low RBE at the entrance and a high RBE in the target-volume. Therefore, the side effects to normal tissue are small, while the tumor response can be maximized. In the paper, experimental RBE values for inactivation are compiled, that demonstrate the RBE dependence from the repair capacity. In a theoretical approach, the local effect model (LEM), this dependence is used to calculate clinical RBE. Examples for clinical RBEs are given that have been applied to patient treatments.

Electron density measurement with dual-energy x-ray CT using synchrotron radiation

Monochromatic x-ray computed tomography (CT) at two different energies provides information about electron density of human tissue without ambiguity due to the beam hardening effect. This information makes the treatment planning for proton and heavy-ion radiotherapy more precise. We have started a feasibility study on dual energy x-ray CT by using synchrotron radiation. A translation–rotation scanning CT system was developed for quantitative measurement in order to clarify what precision in the measurement was achieved. Liquid samples of solutions of K2HPO4 and solid samples of tissue equivalent materials were used to simulate human tissue. The experiments were carried out using monochromatic x-rays with energies of 40, 70 and 80 keV produced by monochromatizing synchrotron radiation. The solid samples were also measured in a complementary method using high-energy carbon beams to evaluate the electron densities. The measured electron densities were compared with the theoretical values or the values measured in the complementary method. It was found that these values were in agreement in 0.9% on average. Effective atomic numbers were obtained as well from dual-energy x-ray CT. The tomographic image based on each of the electron densities and the effective atomic number presents a different feature of the material, and its contrast drastically differs from that in a conventional CT image.

Low LET cross-section measurements using high energy carbon beam [DRAMs/SRAMs

This paper reports on results from high energy heavy ion testing of devices. The low LET zones of the cross-section curves are explored. High and low energy measurements are compared.