Real-time monitoring of the Bragg peak location of carbon ions is urgently required for the quality control of hadron therapy. In this study, we design an annular detector to monitor the Bragg peak location of carbon ...Real-time monitoring of the Bragg peak location of carbon ions is urgently required for the quality control of hadron therapy. In this study, we design an annular detector to monitor the Bragg peak location of carbon ions with Geant4 simulation. This 360° surrounding structure has a high detection efficiency for the small-dose situation. The detector consists of a multilayered collimator system and an Na I scintillator for prompt gamma counting. The multilayered collimator includes a lead layer to prevent unwanted gammas and the paraffin and boron carbide layers to moderate and capture fast neutrons. An inclination of the detector further diminishes the background signal caused by neutrons. The detector, with optimized parameters, is applicable to carbon ions of different energies. In addition, the scintillator is replaced by an improved EJ301 organic liquid scintillator to discriminate gammas and neutrons. Inserting thin Fe slices into the liquid scintillator improves the energy deposition efficiency. The Bragg peak location of 200 Me V/u carbon ions can be monitored by prompt gamma detection with the improved liquid scintillator.展开更多
The distribution of hydrogen near the notch tip of the austenitic steel 21Cr9Ni9MnN under mode Ⅰ loading has been studid with ion microprobe mass analyzer.Two peaks of hydrogen accumulation,one at notch tip and other...The distribution of hydrogen near the notch tip of the austenitic steel 21Cr9Ni9MnN under mode Ⅰ loading has been studid with ion microprobe mass analyzer.Two peaks of hydrogen accumulation,one at notch tip and other far apart from it,were found.The distribution of hydrostatic stress and plastic strain in front of the notch tip under planar stress condition were calculated using ADINA non-linear finite element method.The calculated result in compari- son with data measured showed that the hydrogen concentration peak at the notch tip is caused by trapping effect of dislocation on dissolved hydrogen,while the other from the hydrostatic stress.The influence of stress intensity factor on the distribution of hydrogen con- centration and the process of hydrogen accumulation near notch tip was also discussed.展开更多
In order to increase the peak depth of nitrogen atoms during the nitrogen plasma immersion ion implantation of Ti-6Al-4V alloy, the rare earth metal yttrium was applied. In the experiment, yttrium and nitrogen ions we...In order to increase the peak depth of nitrogen atoms during the nitrogen plasma immersion ion implantation of Ti-6Al-4V alloy, the rare earth metal yttrium was applied. In the experiment, yttrium and nitrogen ions were implanted under the voltage of 20 and 30 kV, respectively. In the samples with yttrium pre-implantation for 30 min, the Anger electron spectroscopy (AES) analysis shows that the peak depth of the nitrogen atoms increases from 50 up to 100 nm. It can also be seen from the tribological tests that the wear resistance of these samples is increased remarkably.展开更多
Endoscopic xenon ion laser induced autofluorescence spectra in various gastric diseases were tested in 104 patients diagnosed by endoscopy and biopsy, including 28 gastric cancer, 9 gastric ulcer, 46 chronic atrophic ...Endoscopic xenon ion laser induced autofluorescence spectra in various gastric diseases were tested in 104 patients diagnosed by endoscopy and biopsy, including 28 gastric cancer, 9 gastric ulcer, 46 chronic atrophic gastritis, and 21 superficial gastritis. The autofluorescence spectrum excited with the 365 nm line of pulsed xenon ion laser was measured. The xenon ion laser beam having an output energy of 0.5 mJ with a duration of 0.6μs and a repetition rate of 10 Hz was used as the excitation source. A coaxial optical cable for laser light and autofluorescent light transmission was inserted via the biopsy channel of an endoscope into the cavity of stomach. The tip of opitcal cable was aimed at the gastric tissue and autofluorescence spectrum was plotted on X-Y recorder. As the monochromator scanned in the range 500-750 nm, a single-pulse fluorescence spectrum could be obtained by using an optical multichannel analyser, and then this fluorescence spectrum was stored in the computer. The whole procedure could be completed within 15 seconds. The results of the present study show that autofluorescence spectra of gastric cancer have characteristic peaks near 630 nm and 690 nm, while no such peaks appear in the spectra of the corresponding normal regions. A consistency of 75% was observed in gastric cancer as compared with the pathologic diagnosis. It is claimed that this is a harmless, safe, simple, and fast procedure in the diagnosis of gastric cancer.展开更多
In comparison with conventional radiotherapy techniques,12C beam therapy has its significant advantage in cancer treatment because the radiation dose are mostly concentrated near the Bragg peak region and damage to no...In comparison with conventional radiotherapy techniques,12C beam therapy has its significant advantage in cancer treatment because the radiation dose are mostly concentrated near the Bragg peak region and damage to normal tissues along the beam path is thus greatly reduced.In-beam PET provides a way to monitor dose distribution inside human body since several kinds of positron-emitting nuclei are produced through the interaction between 12C beam and body matters.In this work,we study the quantitative relationship between the spatial location of the Bragg peak and the spatial distribution of positrons produced by positron-emitting nuclei.Monte Carlo package GATE is used to simulate the interactions between the incident 12C beam of different energies(337.5,270.0 and 195.0 MeV/u) and various target matters(water,muscle and spine bone).Several data post-processing operations are performed on the simulated positron-emitting nuclei distribution data to mimic the impacts of positron generation and finite spatial resolution of a typical PET imaging system.Simulation results are compared to published experimental data for verification.In all the simulation cases,we find that 10C and 11C are two dominant positron-emitting nuclei,and there exists a significant correlation between the spatial distributions of deposited energy and positrons.Therefore,we conclude that it is possible to determine the location of Bragg peak with 1 mm accuracy using current PET imaging systems by detecting the falling edge of the positron distribution map in depth direction.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11375073 and U1232206)
文摘Real-time monitoring of the Bragg peak location of carbon ions is urgently required for the quality control of hadron therapy. In this study, we design an annular detector to monitor the Bragg peak location of carbon ions with Geant4 simulation. This 360° surrounding structure has a high detection efficiency for the small-dose situation. The detector consists of a multilayered collimator system and an Na I scintillator for prompt gamma counting. The multilayered collimator includes a lead layer to prevent unwanted gammas and the paraffin and boron carbide layers to moderate and capture fast neutrons. An inclination of the detector further diminishes the background signal caused by neutrons. The detector, with optimized parameters, is applicable to carbon ions of different energies. In addition, the scintillator is replaced by an improved EJ301 organic liquid scintillator to discriminate gammas and neutrons. Inserting thin Fe slices into the liquid scintillator improves the energy deposition efficiency. The Bragg peak location of 200 Me V/u carbon ions can be monitored by prompt gamma detection with the improved liquid scintillator.
文摘The distribution of hydrogen near the notch tip of the austenitic steel 21Cr9Ni9MnN under mode Ⅰ loading has been studid with ion microprobe mass analyzer.Two peaks of hydrogen accumulation,one at notch tip and other far apart from it,were found.The distribution of hydrostatic stress and plastic strain in front of the notch tip under planar stress condition were calculated using ADINA non-linear finite element method.The calculated result in compari- son with data measured showed that the hydrogen concentration peak at the notch tip is caused by trapping effect of dislocation on dissolved hydrogen,while the other from the hydrostatic stress.The influence of stress intensity factor on the distribution of hydrogen con- centration and the process of hydrogen accumulation near notch tip was also discussed.
文摘In order to increase the peak depth of nitrogen atoms during the nitrogen plasma immersion ion implantation of Ti-6Al-4V alloy, the rare earth metal yttrium was applied. In the experiment, yttrium and nitrogen ions were implanted under the voltage of 20 and 30 kV, respectively. In the samples with yttrium pre-implantation for 30 min, the Anger electron spectroscopy (AES) analysis shows that the peak depth of the nitrogen atoms increases from 50 up to 100 nm. It can also be seen from the tribological tests that the wear resistance of these samples is increased remarkably.
文摘Endoscopic xenon ion laser induced autofluorescence spectra in various gastric diseases were tested in 104 patients diagnosed by endoscopy and biopsy, including 28 gastric cancer, 9 gastric ulcer, 46 chronic atrophic gastritis, and 21 superficial gastritis. The autofluorescence spectrum excited with the 365 nm line of pulsed xenon ion laser was measured. The xenon ion laser beam having an output energy of 0.5 mJ with a duration of 0.6μs and a repetition rate of 10 Hz was used as the excitation source. A coaxial optical cable for laser light and autofluorescent light transmission was inserted via the biopsy channel of an endoscope into the cavity of stomach. The tip of opitcal cable was aimed at the gastric tissue and autofluorescence spectrum was plotted on X-Y recorder. As the monochromator scanned in the range 500-750 nm, a single-pulse fluorescence spectrum could be obtained by using an optical multichannel analyser, and then this fluorescence spectrum was stored in the computer. The whole procedure could be completed within 15 seconds. The results of the present study show that autofluorescence spectra of gastric cancer have characteristic peaks near 630 nm and 690 nm, while no such peaks appear in the spectra of the corresponding normal regions. A consistency of 75% was observed in gastric cancer as compared with the pathologic diagnosis. It is claimed that this is a harmless, safe, simple, and fast procedure in the diagnosis of gastric cancer.
基金supported in part by Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP200800031071)National Natural Science Foundation of China (No. 10975086)the National High Technology Research and Development Program ("863" Program) of China (No. 2006AA020802)
文摘In comparison with conventional radiotherapy techniques,12C beam therapy has its significant advantage in cancer treatment because the radiation dose are mostly concentrated near the Bragg peak region and damage to normal tissues along the beam path is thus greatly reduced.In-beam PET provides a way to monitor dose distribution inside human body since several kinds of positron-emitting nuclei are produced through the interaction between 12C beam and body matters.In this work,we study the quantitative relationship between the spatial location of the Bragg peak and the spatial distribution of positrons produced by positron-emitting nuclei.Monte Carlo package GATE is used to simulate the interactions between the incident 12C beam of different energies(337.5,270.0 and 195.0 MeV/u) and various target matters(water,muscle and spine bone).Several data post-processing operations are performed on the simulated positron-emitting nuclei distribution data to mimic the impacts of positron generation and finite spatial resolution of a typical PET imaging system.Simulation results are compared to published experimental data for verification.In all the simulation cases,we find that 10C and 11C are two dominant positron-emitting nuclei,and there exists a significant correlation between the spatial distributions of deposited energy and positrons.Therefore,we conclude that it is possible to determine the location of Bragg peak with 1 mm accuracy using current PET imaging systems by detecting the falling edge of the positron distribution map in depth direction.
