Although luminescence of water during radiation irradiations with energy lower than the Cerenkov-light threshold were found recently, it was not still obvious whether the luminescence or ...scintillation is produced or imaging is possible in commonly used float or silica glass. Thus we tried to image the produced light from plates and a block made of float or silica glasses during irradiations of radiations. We clearly detected the images of the produced light of glass plates by using an electron multiplied (EM) CCD camera during irradiation of alpha particles for silica glass and float glass. The silica and float glass plates produced 13 photons/MeV and 258 photons/MeV for alpha particles, respectively. The light spectrum showed high intensity for longer wavelength in silica glass plate and it was relatively broad for float glass plate. By combining the float glass plate with a photomultiplier tube (PMT), energy spectrum could be measured for 5.5 MeV alpha particles with the energy resolution of 65% FWHM. We also measured the scintillation image during irradiation of proton to a float glass block. The image in float glass block during irradiation of proton showed light distribution similar to the dose in the glass. These results suggest float or silica glass plates or blocks are promising materials for radiation detection and imaging.
Low-energy X-ray imaging of prompt secondary electron bremsstrahlung X-rays (prompt X-rays) emitted during particle-ion irradiation is a promising method for range estimation. However, measurements ...have so far been conducted mainly for uniform phantoms of water or an acrylic block. Prompt X-ray imaging for phantoms with air cavities has not yet been extensively measured or evaluated with realistic conditions. Consequently, we conducted imaging of prompt X-rays using a pinhole YAP(Ce) camera during irradiation by protons as well as carbon ions to non-uniform acrylic phantoms with small cavities and then evaluated the images and estimated the ranges from the measured prompt X-ray images. The non-uniform acrylic phantom used for imaging had a cylindrical cavity with a 20-mm or 10-mm diameter in the phantom. During irradiation by protons or carbon ions, imaging of one of the phantoms was conducted using the pinhole YAP(Ce) camera with an air cavity as well as filling the cavity with an acrylic rod. For the phantom with a 20-mm-diameter cavity, the prompt X-ray images measured for both protons and carbon ions showed the shape of the cavity in the images, and the ranges could be estimated from the images. For the phantom with a 10-mm-diameter hole, although the shape of the hole could not be clearly observed, the ranges could also be estimated from the images. Furthermore, Monte Carlo simulated prompt X-ray images with different spatial resolution of the X-ray camera showed similar images to the measured images. We confirmed that prompt X-ray imaging of phantoms with air cavities using the pinhole YAP(Ce) cameras was possible and that prompt X-ray imaging is a promising approach for estimating the ranges for both protons and carbon ions, even for phantoms with air cavities.
Particle therapy is an advanced cancer therapy that uses a feature known as the Bragg peak, in which particle beams suddenly lose their energy near the end of their range. The Bragg peak enables ...particle beams to damage tumors effectively. To achieve precise therapy, the demand for accurate and quantitative imaging of the beam irradiation region or dosage during therapy has increased. The most common method of particle range verification is imaging of annihilation gamma rays by positron emission tomography. Not only 511-keV gamma rays but also prompt gamma rays are generated during therapy; therefore, the Compton camera is expected to be used as an on-line monitor for particle therapy, as it can image these gamma rays in real time. Proton therapy, one of the most common particle therapies, uses a proton beam of approximately 200 MeV, which has a range of ∼ 25 cm in water. As gamma rays are emitted along the path of the proton beam, quantitative evaluation of the reconstructed images of diffuse sources becomes crucial, but it is far from being fully developed for Compton camera imaging at present. In this study, we first quantitatively evaluated reconstructed Compton camera images of uniformly distributed diffuse sources, and then confirmed that our Compton camera obtained 3 %(1σ) and 5 %(1σ) uniformity for line and plane sources, respectively. Based on this quantitative study, we demonstrated on-line gamma imaging during proton irradiation. Through these studies, we show that the Compton camera is suitable for future use as an on-line monitor for particle therapy.
Ultracompact Compton camera for innovative gamma-ray imaging Kataoka, J.; Kishimoto, A.; Taya, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2018, Letnik:
912
Journal Article
Recenzirano
A multipixel photon counter (MPPC) features excellent photon-counting capability as a radiation detector. In particular, a two-plane Compton camera consisting of Ce:GAGG scintillators coupled with ...MPPC arrays has significant application potential owing to its compact size and low weight. For example, the camera can be easily mounted on a commercial drone to identify radiation hot spots from the sky. In Fukushima, we demonstrated that a 137Cs distribution within a 100 m diameter can be mapped correctly within a couple of tens of minutes. The advanced use of the Compton camera is also anticipated in the field of proton therapy. We evaluated an image of 511 keV annihilation gamma-rays emitted from a PMMA phantom irradiated by 200 MeV protons to mimic an in-beam monitor for proton therapy. Finally, we developed an ultracompact Compton camera (weight = 580 g), for 3-D multicolor molecular imaging. In order to demonstrate the performance capabilities of the device, 131I (365 keV) , 85SrCl2 (514 keV), and 65ZnCl2 (1116 keV) were injected into a living mouse and the data were taken from 12 angles with a total acquisition time of 2 h. We confirmed that all tracers had accumulated on the target organs of the thyroid, bone, and liver, and that the obtained 3-D image was quantitatively correct with an accuracy of ±20%.
•First demonstration of a Compton camera onboard a drone for aerial snapshots in Fukushima.•Application of a Compton camera for prompt gamma-ray imaging during proton therapy.•3-D multicolor imaging of a living mouse by using an ultracompact Compton camera whose weight is only 580 g.
For safe and effective proton therapy, the proton range in a patient’s body is characterized by the water equivalent length (WEL), and must be accurately determined. Current treatment planning is ...based on X-ray computed tomography images, which might cause uncertainty because of the different energy loss processes between protons and X-rays. We develop a simple, novel, and real-time proton CT system. The system uses a CCD camera and scintillator, which is thin enough for protons to penetrate. Since protons lose energy when they pass through a phantom, different emissions corresponding to the proton energy loss are acquired in the scintillator. Images of the scintillator were gathered by the CCD camera with 70 MeV and 200 MeV proton beams. Since blurring due to proton reactions such as multiple Coulomb scattering and nuclear reactions significantly degrades the obtained images in both beams, we developed two kinds of effective correction methods. One method is applied to broad beam systems, while the other is applied to narrow beam systems. We successfully obtain clear images with minor proton reaction effects by applying these correction methods. Moreover, we confirm that the WEL values estimated from the acquired CT images agree well with the theoretical values for materials such as polymethyl methacrylate (PMMA) and isopropyl alcohol, within 1-σ uncertainty. Through simulations, we found that nuclear reactions significantly contribute to the uncertainty of WEL values.
We recently found that luminescence was emitted from water during proton irradiation at lower energy than the Cerenkov-light threshold and imaging was possible by using a CCD camera. However, since ...the measured distributions were projection images of the luminescence, precise dose estimations from the images were not possible. If the 3 dimensional images can be formed from the projection images, more precise dose information could be obtained. For this purpose, we calculate the 3-dimensional distribution of the proton beams from the luminescence images and use them for beam width estimations. We assumed that the proton beams have circular shape and the transverse images were reconstructed from the projection images using the filtered backprojection (FBP) algorithm for positron emission tomography (PET). The reconstructed images were compared to estimate the proton-beam widths with those obtained from the projection images and simulation results. We obtained 3-dimensional distributions of the proton beams from the projection images and also the reconstructed sagittal, coronal, and transverse images as well as volume rendering images. The estimated beam widths from the reconstructed images, which were slightly smaller than those obtained from the projection images, were identical to those calculated with the simulation. The 3-dimensional distributions of the luminescence images of water of proton beams could be reconstructed from the projection images and showed improved accuracy in estimating the beam widths of the proton beams.
Industrial mass production of nuclear emulsion film has been realized by the introduction of new photographic technologies.
In addition, emulsion-refreshing capability (erasing unwanted tracks before ...its use) was implemented by controlling the fading characteristics of the gel. The gel properties were optimized in order to satisfy this requirement; rapid track erasing at the erasing condition and minimum fading during the running of experiments.
Emulsion films with this capability are crucial for large-scale applications like the long base-line neutrino experiment, OPERA, which intend to detect Tau neutrino appearance at 732
km from the beam source.
We investigated the applicability of the repairable-conditionally repairable (RCR) model and the multi-target (MT) model to dose conversion in high-dose-per-fraction radiotherapy in comparison with ...the linear-quadratic (LQ) model. Cell survival data of V79 and EMT6 single cells receiving single doses of 2-12 Gy or 2 or 3 fractions of 4 or 5 Gy each, and that of V79 spheroids receiving single doses of 5-26 Gy or 2-5 fractions of 5-12 Gy, were analyzed. Single and fractionated doses to actually reduce cell survival to the same level were determined by a colony assay. Single doses used in the experiments and surviving fractions at the doses were substituted into equations of the RCR, MT and LQ models in the calculation software Mathematica, and each parameter coefficient was computed. Thereafter, using the coefficients and the three models, equivalent single doses for the hypofractionated doses were calculated. They were then compared with actually-determined equivalent single doses for the hypofractionated doses. The equivalent single doses calculated using the RCR, MT and LQ models tended to be lower than the actually determined equivalent single doses. The LQ model seemed to fit relatively well at doses of 5 Gy or less. At 6 Gy or higher doses, the RCR and MT models seemed to be more reliable than the LQ model. In hypofractionated stereotactic radiotherapy, the LQ model should not be used, and conversion models incorporating the concept of the RCR or MT models, such as the generalized linear-quadratic models, appear to be more suitable.
The software tools developed for the validation and verification of the standard electromagnetic physics package of Geant4 are described. The validation is being performed versus experimental data ...and in regression to a previous version of Geant4. Examples of validation results are presented.
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