Successfully utilized non-axisymmetric endwalls to enhance turbine efficiencies(aerodynamic and turbine inlet temperatures)by controlling the characteristics of the secondary flow in a blade passage.This is accomplish...Successfully utilized non-axisymmetric endwalls to enhance turbine efficiencies(aerodynamic and turbine inlet temperatures)by controlling the characteristics of the secondary flow in a blade passage.This is accomplished by steady-state numerical hydrodynamics and deep knowledge of the field of flow.Because of the interaction between mainstream and purge flow contributing supplementary losses in the stage,non-axisymmetric endwalls are highly susceptible to the inception of purge flow exit compared to the flat and any advantage rapidly vanishes.The conclusions reveal that the supreme endwall pattern could yield a lowering of the gross pressure loss at the design stage and is related to the size of the top-loss location being productively lowered.This has led to diminished global thermal exchange lowered in the passage of the vane alone.The reverse flow adjacent to the suction side corner of the endwall is migrated farther from the vane surface,as the deviated pressure spread on the endwall accelerates the flow and progresses the reverse flow core still downstream.The depleted association between the tornado-like vortex and the corner vortex adjacent to the suction side corner of the endwall is the dominant mechanism of control in the contoured end wall.In this publication,we show that the non-axisymmetric endwall contouring by selective numerical shape change method at most prominent locations is advantageous in lowering the thermal load in turbines to augment the net heat flux reduction as well as the aerodynamic performance using multi-objective optimization.展开更多
This study designs a microstrip patch antenna with an inverted T-type notch in the partial ground to detect tumorcells inside the human breast.The size of the current antenna is small enough(18mm×21mm×1.6mm)...This study designs a microstrip patch antenna with an inverted T-type notch in the partial ground to detect tumorcells inside the human breast.The size of the current antenna is small enough(18mm×21mm×1.6mm)todistribute around the breast phantom.The operating frequency has been observed from6–14GHzwith a minimumreturn loss of−61.18 dB and themaximumgain of current proposed antenna is 5.8 dBiwhich is flexiblewith respectto the size of antenna.After the distribution of eight antennas around the breast phantom,the return loss curveswere observed in the presence and absence of tumor cells inside the breast phantom,and these observations showa sharp difference between the presence and absence of tumor cells.The simulated results show that this proposedantenna is suitable for early detection of cancerous cells inside the breast.展开更多
BACKGROUND Supernumerary phantom limb(SPL)sensation is the experience of additional limbs,either single or a pair of limbs.Unique to traumatic spinal cord injuries,we report effect of transcranial direct current stimu...BACKGROUND Supernumerary phantom limb(SPL)sensation is the experience of additional limbs,either single or a pair of limbs.Unique to traumatic spinal cord injuries,we report effect of transcranial direct current stimulation(tDCS)on SPL pain in a patient with cervical cord injury.CASE SUMMARY The subject was a 57-year-old man who was diagnosed with complete spinal cord injury(C6/C5,motor level;C5/C5,sensory level;AIS-A)approximately three months ago.After a period of 2 wk,we administered anodal tDCS over the motor cortex for 15 minutes at an intensity of 1.5 mA.Following that treatment,the patient experienced a decrease of SPL pain intensity and frequency,which lasted for 1 week after the end of treatment.CONCLUSION Targeting the motor cortex through neuromodulation appears to be a promising option for the management of SPL pain.展开更多
Traumatic amputations remain one of the most frequent and disturbing wounds of armed conflict.In this scenario,most amputees develop residual and phantom limb pain,impacting their quality of life.There are several ele...Traumatic amputations remain one of the most frequent and disturbing wounds of armed conflict.In this scenario,most amputees develop residual and phantom limb pain,impacting their quality of life.There are several elective surgical procedures available for both conditions,such as neuroma excision followed by nerve reconstruction,nerve relocation,e.g.,surgically implanting a transected nerve into a muscle,nerve transfers in cases of associated paralysis,and most recently,regenerative peripheral nerve interface surgery.Whenever possible in the post-conflict phase,a coordinated effort between traveling humanitarian surgeons specializing in reconstructive microsurgery and local healthcare providers is essential for successfully treating phantom and chronic residual limb pain in post-conflict amputees.While providing a detailed logistical framework for global humanitarian missions is beyond the scope of this article,we provide a brief perspective on a topic of utmost importance for reconstructive surgeons worldwide:the high-quality care and treatment of refugees and those whose lives have been impacted by conflict,disaster,or displacement.展开更多
Modulated electro-hyperthermia (mEHT) targets tissue’s natural electric and thermal heterogeneities to heat the cancer cells selectively. The applied 13.56 MHz radiofrequency (RF) is a carrier of the low-frequency mo...Modulated electro-hyperthermia (mEHT) targets tissue’s natural electric and thermal heterogeneities to heat the cancer cells selectively. The applied 13.56 MHz radiofrequency (RF) is a carrier of the low-frequency modulation. The high-frequency part was chosen to select the malignant lesion using the specialties of the tumor: the higher conductivity and dielectric constant of the tumor than its host. The electric field selects the tumor, and the low-frequency amplitude modulation polarizes and excites the transmembrane proteins of the malignant cells. The dominant absorption of the energy by the microscopic clusters of the membrane rafts acts like nanoparticle heating. Exciting the membrane produces various apoptotic signals. The processes were modeled using silico and phantom experiments, which proved the concept. The preclinical verification was made in vitro and in vivo, and in the end, clinical proofs validated the method. Our objective is to follow all the development steps from the laboratory to the clinics in a trilogy of articles. This present is the first part, which deals with in silico, phantom, and in vitro research.展开更多
BACKGROUND The authors describe a technique for building an alternative jawbone phantom using dental gypsum and rice for research and dental radiology instruction.AIM To investigate the potential of an alternative pha...BACKGROUND The authors describe a technique for building an alternative jawbone phantom using dental gypsum and rice for research and dental radiology instruction.AIM To investigate the potential of an alternative phantom to simulate the trabecular bone aspect of the human maxilla in periapical radiographs.METHODS Half-maxillary phantoms built from gypsum-ground rice were exposed to X-rays,and the resulting images(experimental group)were compared to standardized radiographic images produced from dry human maxillary bone(control group)(n=7).The images were blindly assessed according to strict criteria by three examiners for the usual trabecular aspects of the surrounding bone,and significant differences between groups and in assessment reliability were compared using Fisher’s exact and kappa tests(α=0.05).RESULTS The differences in the trabecular aspects between groups were not statistically significant.In addition,interobserver agreement among observers was 0.43 and 0.51 for the control and experimental groups,respectively,whereas intraobserver agreement was 0.71 and 0.73,respectively.CONCLUSION The tested phantom seemed to demonstrate potential for trabecular bone image Munhoz EA et al.Model of hard tissue simulation for dental radiography WJM https://www.wjgnet.com 2 March 20,2024 Volume 14 Issue 1 simulation on maxillary periapical radiographs.展开更多
Monte Carlo simulations are frequently utilized in radiation dose assessments.However,many researchers find the prevailing computing platforms to be intricate.This highlights a pressing need for a specialized framewor...Monte Carlo simulations are frequently utilized in radiation dose assessments.However,many researchers find the prevailing computing platforms to be intricate.This highlights a pressing need for a specialized framework for phantom dose evalua-tion.To address this gap,we developed a user-friendly radiation dose assessment platform using the Monte Carlo toolkit,Geant4.The Tsinghua University Phantom Dose(THUDosePD)augments the flexibility of Monte Carlo simulations in dosi-metric research.Originating from THUDose,a code with generic,functional,and application layers,THUDosePD focuses predominantly on anatomical phantom dose assessment.Additionally,it enables medical exposure simulation,intricate geometry creation,and supports both three-dimensional radiation dose analysis and phantom format transformations.The system operates on a multi-threaded parallel CPU architecture,with some modules enhanced for GPU parallel computing.Benchmark tests on the ICRP reference male illustrated the capabilities of THUDosePD in phantom dose assessment,covering the effective dose,three-dimensional dose distribution,and three-dimensional organ dose.We also conducted a voxelization conversion on the polygon mesh phantom,demonstrating the method’s efficiency and consistency.Extended applications based on THUDosePD further underline its broad adaptability.This intuitive,three-dimensional platform stands out as a valuable tool for phantom radiation dosimetry research.展开更多
Carbon ions,commonly referred to as particle therapy,have become increasingly popular in the last decade.Accurately predicting the range of ions in tissues is important for the precise delivery of doses in heavy-ion r...Carbon ions,commonly referred to as particle therapy,have become increasingly popular in the last decade.Accurately predicting the range of ions in tissues is important for the precise delivery of doses in heavy-ion radiotherapy.Range uncertainty is currently the largest contributor to dose uncertainty in normal tissues,leading to the use of safety margins in treatment planning.One potential method is the direct relative stopping measurement(RSP)with ions.Heavy-ion CT(Hi′CT),a compact segmented full digital tomography detector using monolithic active pixel sensors,was designed and evaluated using a 430 MeV/u high-energy carbon ion pencil beam in Geant4.The precise position of the individual carbon ion track can be recorded and reconstructed using a 30μm×30μm small pixel pitch size.Two types of customized image reconstruction algorithms were developed,and their performances were evaluated using three different modules of CAT-PHAN 600-series phantoms.The RSP measurement accuracy of the tracking algorithm for different types of materials in the CTP404 module was less than 1%.In terms of spatial resolution,the tracking algorithm could achieve a 20%modulation transfer function normalization value of CTP528 imaging results at 5 lp/cm,which is significantly better than that of the fast imaging algorithm(3 lp/cm).The density resolution obtained using the tracking algorithm of the customized CTP515 was approximately 10.5%.In conclusion,a compact digital Hi'CT system was designed,and its nominal performance was evaluated in a simulation.The RSP resolution and image quality provide potential feasibility for scanning most parts of an adult body or pediatric patient,particularly for head and neck tumor treatment.展开更多
Background:As mammography X-ray imaging technologies advance and provide elevated contrast in soft tissues,a need has developed for reliable imaging phantoms for use in system design and component calibration.In advan...Background:As mammography X-ray imaging technologies advance and provide elevated contrast in soft tissues,a need has developed for reliable imaging phantoms for use in system design and component calibration.In advanced imaging modalities such as refraction-based methods,it is critical that developed phantoms capture the biological details seen in clinical precancerous and cancerous cases while minimizing artifacts that may be caused due to phantom production.This work presents the fabrication of a breast tissue imaging phantom from cadaveric breast tissue suitable for use in both transmission and refraction-enhanced imaging systems.Methods:Human cancer cell tumors were grown orthotopically in nude athymic mice and implanted into the fixed tissue while maintaining the native tumor/adipose tissue interface.Results:The resulting human–murine tissue hybrid phantom was mounted on a clear acrylic housing for absorption and refraction X-ray imaging.Digital breast tomosynthesis was also performed.Conclusion:Both attenuation-based imaging and refraction-based imaging of the phantom are presented to confirm the suitability of this phantom's use in both imaging modalities.展开更多
With the development of China’s crewed space mission,the space radiation risk for astronauts is increasingly prominent.This paper describes a simulation of the radiation doses experienced by a Chinese female voxel ph...With the development of China’s crewed space mission,the space radiation risk for astronauts is increasingly prominent.This paper describes a simulation of the radiation doses experienced by a Chinese female voxel phantom on board the Chinese Space Station(CSS)performed using the Monte Carlo N-Particle(MCNP)software.The absorbed dose,equivalent dose,and effective dose experienced by the voxel phantom and its critical organs are discussed for different levels of shielding of the Tianhe core module.The risk of space-radiation exposure is then assessed by comparing these doses with the current risk limits in China(the skin dose limit for short-term low-earth-orbit missions)and the NASA figures(National Council on Radiation Protection and Measurements Report No.98)for female astronauts.The results obtained can be used to guide and optimize the radiation protection provided for manned space missions.展开更多
Introduction: The ring vortex phantom is a novel, cost-effective prototype which generates complex and well-characterised reference flows in the form of the ring vortex. Although its reproducibility has been demonstra...Introduction: The ring vortex phantom is a novel, cost-effective prototype which generates complex and well-characterised reference flows in the form of the ring vortex. Although its reproducibility has been demonstrated, with ring speeds routinely behaving within 10% tolerances at speeds of approximately 10 - 70 cm/s, a form of real-time QA of the device at the time of imaging is needed to confirm correct function on demand in any environment. Methods: The technology described here achieves real-time QA, comprising a linear encoder, laser-photodiode array, and Doppler probe, measuring piston motion, ring speed and intra-ring velocity respectively. This instrumentation does not interfere with imaging system QA, but allows QA to be performed on both the ring vortex and the device in real-time. Results: The encoder reports the reliability of the piston velocity profile, whilst ring speed is measured by laser behaviour. Incorporation of a calibrated Doppler probe offers a consistency check that confirms behaviour of the central axial flow. For purposes of gold-standard measurement, all elements can be related to previous Laser PIV acquisitions with the same device settings. Conclusion: Consequently, ring vortex production within tolerances is confirmed by this instrumentation, delivering accurate QA in real-time. This implementation offers a phantom QA procedure that exceeds anything seen in the literature, providing the technology to enhance quantitative assessment of flow imaging modalities.展开更多
A system for in vitro investigation of ultrasound contrast agent＇s enhancement effect is presented and evaluated. It includes the digital B-mode ultrasound scanner Belson3000A, the tissue-mimicking ultrasound phantom...A system for in vitro investigation of ultrasound contrast agent＇s enhancement effect is presented and evaluated. It includes the digital B-mode ultrasound scanner Belson3000A, the tissue-mimicking ultrasound phantoms and the software which is used for image quantitative analysis. The linear range, optimal settings and repeatability of the system are assessed and explored by scanning the ultrasound phantoms with different reflective intensities. The measurements are performed under an acoustic power from 4.8 to 12.3 mW, the scanner centre frequency is 3.5 MH and the gain setting is 50 dB. Both a self-made surfactant encapsulated microbubble and a commercial ultrasound contrast agent are scanned. The results show that the pixel intensity of ultrasonic images increases with the increase in the sound power, and for the stronger reflective phantoms of more particles, the increasing trend is much more evident. The system is optimal for evaluating the microbubble contrast agents＇ enhancement effects. It presents a simple, effective and real-time means for characterizing the enhancement ability of microbubbles.展开更多
文摘Successfully utilized non-axisymmetric endwalls to enhance turbine efficiencies(aerodynamic and turbine inlet temperatures)by controlling the characteristics of the secondary flow in a blade passage.This is accomplished by steady-state numerical hydrodynamics and deep knowledge of the field of flow.Because of the interaction between mainstream and purge flow contributing supplementary losses in the stage,non-axisymmetric endwalls are highly susceptible to the inception of purge flow exit compared to the flat and any advantage rapidly vanishes.The conclusions reveal that the supreme endwall pattern could yield a lowering of the gross pressure loss at the design stage and is related to the size of the top-loss location being productively lowered.This has led to diminished global thermal exchange lowered in the passage of the vane alone.The reverse flow adjacent to the suction side corner of the endwall is migrated farther from the vane surface,as the deviated pressure spread on the endwall accelerates the flow and progresses the reverse flow core still downstream.The depleted association between the tornado-like vortex and the corner vortex adjacent to the suction side corner of the endwall is the dominant mechanism of control in the contoured end wall.In this publication,we show that the non-axisymmetric endwall contouring by selective numerical shape change method at most prominent locations is advantageous in lowering the thermal load in turbines to augment the net heat flux reduction as well as the aerodynamic performance using multi-objective optimization.
基金the International Science and Technology Cooperation Project of the Shenzhen Science and Technology Commission(GJHZ20200731095804014).
文摘This study designs a microstrip patch antenna with an inverted T-type notch in the partial ground to detect tumorcells inside the human breast.The size of the current antenna is small enough(18mm×21mm×1.6mm)todistribute around the breast phantom.The operating frequency has been observed from6–14GHzwith a minimumreturn loss of−61.18 dB and themaximumgain of current proposed antenna is 5.8 dBiwhich is flexiblewith respectto the size of antenna.After the distribution of eight antennas around the breast phantom,the return loss curveswere observed in the presence and absence of tumor cells inside the breast phantom,and these observations showa sharp difference between the presence and absence of tumor cells.The simulated results show that this proposedantenna is suitable for early detection of cancerous cells inside the breast.
文摘BACKGROUND Supernumerary phantom limb(SPL)sensation is the experience of additional limbs,either single or a pair of limbs.Unique to traumatic spinal cord injuries,we report effect of transcranial direct current stimulation(tDCS)on SPL pain in a patient with cervical cord injury.CASE SUMMARY The subject was a 57-year-old man who was diagnosed with complete spinal cord injury(C6/C5,motor level;C5/C5,sensory level;AIS-A)approximately three months ago.After a period of 2 wk,we administered anodal tDCS over the motor cortex for 15 minutes at an intensity of 1.5 mA.Following that treatment,the patient experienced a decrease of SPL pain intensity and frequency,which lasted for 1 week after the end of treatment.CONCLUSION Targeting the motor cortex through neuromodulation appears to be a promising option for the management of SPL pain.
文摘Traumatic amputations remain one of the most frequent and disturbing wounds of armed conflict.In this scenario,most amputees develop residual and phantom limb pain,impacting their quality of life.There are several elective surgical procedures available for both conditions,such as neuroma excision followed by nerve reconstruction,nerve relocation,e.g.,surgically implanting a transected nerve into a muscle,nerve transfers in cases of associated paralysis,and most recently,regenerative peripheral nerve interface surgery.Whenever possible in the post-conflict phase,a coordinated effort between traveling humanitarian surgeons specializing in reconstructive microsurgery and local healthcare providers is essential for successfully treating phantom and chronic residual limb pain in post-conflict amputees.While providing a detailed logistical framework for global humanitarian missions is beyond the scope of this article,we provide a brief perspective on a topic of utmost importance for reconstructive surgeons worldwide:the high-quality care and treatment of refugees and those whose lives have been impacted by conflict,disaster,or displacement.
文摘Modulated electro-hyperthermia (mEHT) targets tissue’s natural electric and thermal heterogeneities to heat the cancer cells selectively. The applied 13.56 MHz radiofrequency (RF) is a carrier of the low-frequency modulation. The high-frequency part was chosen to select the malignant lesion using the specialties of the tumor: the higher conductivity and dielectric constant of the tumor than its host. The electric field selects the tumor, and the low-frequency amplitude modulation polarizes and excites the transmembrane proteins of the malignant cells. The dominant absorption of the energy by the microscopic clusters of the membrane rafts acts like nanoparticle heating. Exciting the membrane produces various apoptotic signals. The processes were modeled using silico and phantom experiments, which proved the concept. The preclinical verification was made in vitro and in vivo, and in the end, clinical proofs validated the method. Our objective is to follow all the development steps from the laboratory to the clinics in a trilogy of articles. This present is the first part, which deals with in silico, phantom, and in vitro research.
文摘BACKGROUND The authors describe a technique for building an alternative jawbone phantom using dental gypsum and rice for research and dental radiology instruction.AIM To investigate the potential of an alternative phantom to simulate the trabecular bone aspect of the human maxilla in periapical radiographs.METHODS Half-maxillary phantoms built from gypsum-ground rice were exposed to X-rays,and the resulting images(experimental group)were compared to standardized radiographic images produced from dry human maxillary bone(control group)(n=7).The images were blindly assessed according to strict criteria by three examiners for the usual trabecular aspects of the surrounding bone,and significant differences between groups and in assessment reliability were compared using Fisher’s exact and kappa tests(α=0.05).RESULTS The differences in the trabecular aspects between groups were not statistically significant.In addition,interobserver agreement among observers was 0.43 and 0.51 for the control and experimental groups,respectively,whereas intraobserver agreement was 0.71 and 0.73,respectively.CONCLUSION The tested phantom seemed to demonstrate potential for trabecular bone image Munhoz EA et al.Model of hard tissue simulation for dental radiography WJM https://www.wjgnet.com 2 March 20,2024 Volume 14 Issue 1 simulation on maxillary periapical radiographs.
基金This work was supported by the National Natural Science Foundation of China(General Program)(Nos.12175114,U2167209)the Foundation of Key Laboratory of Metrology and Calibration Technology(No.JLKG2022001C001)+2 种基金the Platform Development foundation of China Institute for Radiation Protection(No.YP21030101)the National Key R&D Program of China(No.2021YFF0603600)the Tsinghua University Initiative Scientific Research Program(No.20211080081).
文摘Monte Carlo simulations are frequently utilized in radiation dose assessments.However,many researchers find the prevailing computing platforms to be intricate.This highlights a pressing need for a specialized framework for phantom dose evalua-tion.To address this gap,we developed a user-friendly radiation dose assessment platform using the Monte Carlo toolkit,Geant4.The Tsinghua University Phantom Dose(THUDosePD)augments the flexibility of Monte Carlo simulations in dosi-metric research.Originating from THUDose,a code with generic,functional,and application layers,THUDosePD focuses predominantly on anatomical phantom dose assessment.Additionally,it enables medical exposure simulation,intricate geometry creation,and supports both three-dimensional radiation dose analysis and phantom format transformations.The system operates on a multi-threaded parallel CPU architecture,with some modules enhanced for GPU parallel computing.Benchmark tests on the ICRP reference male illustrated the capabilities of THUDosePD in phantom dose assessment,covering the effective dose,three-dimensional dose distribution,and three-dimensional organ dose.We also conducted a voxelization conversion on the polygon mesh phantom,demonstrating the method’s efficiency and consistency.Extended applications based on THUDosePD further underline its broad adaptability.This intuitive,three-dimensional platform stands out as a valuable tool for phantom radiation dosimetry research.
基金the National Natural Science Foundation of China(Nos.11975292,12205374,U2032209,and 12222512)Beijing Hope Run Special Fund of Cancer Foundation of China(No.LC2021B23)+1 种基金the CAS“Light of West China”Program,the CAS Pioneer Hundred Talent Program,the Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030008)the National Key Research and Development Program of China(No.2021YFA1601300 and 2020YFE0202002).
文摘Carbon ions,commonly referred to as particle therapy,have become increasingly popular in the last decade.Accurately predicting the range of ions in tissues is important for the precise delivery of doses in heavy-ion radiotherapy.Range uncertainty is currently the largest contributor to dose uncertainty in normal tissues,leading to the use of safety margins in treatment planning.One potential method is the direct relative stopping measurement(RSP)with ions.Heavy-ion CT(Hi′CT),a compact segmented full digital tomography detector using monolithic active pixel sensors,was designed and evaluated using a 430 MeV/u high-energy carbon ion pencil beam in Geant4.The precise position of the individual carbon ion track can be recorded and reconstructed using a 30μm×30μm small pixel pitch size.Two types of customized image reconstruction algorithms were developed,and their performances were evaluated using three different modules of CAT-PHAN 600-series phantoms.The RSP measurement accuracy of the tracking algorithm for different types of materials in the CTP404 module was less than 1%.In terms of spatial resolution,the tracking algorithm could achieve a 20%modulation transfer function normalization value of CTP528 imaging results at 5 lp/cm,which is significantly better than that of the fast imaging algorithm(3 lp/cm).The density resolution obtained using the tracking algorithm of the customized CTP515 was approximately 10.5%.In conclusion,a compact digital Hi'CT system was designed,and its nominal performance was evaluated in a simulation.The RSP resolution and image quality provide potential feasibility for scanning most parts of an adult body or pediatric patient,particularly for head and neck tumor treatment.
基金National Institutes of Health,Grant/Award Number:EB023969 and HL154687。
文摘Background:As mammography X-ray imaging technologies advance and provide elevated contrast in soft tissues,a need has developed for reliable imaging phantoms for use in system design and component calibration.In advanced imaging modalities such as refraction-based methods,it is critical that developed phantoms capture the biological details seen in clinical precancerous and cancerous cases while minimizing artifacts that may be caused due to phantom production.This work presents the fabrication of a breast tissue imaging phantom from cadaveric breast tissue suitable for use in both transmission and refraction-enhanced imaging systems.Methods:Human cancer cell tumors were grown orthotopically in nude athymic mice and implanted into the fixed tissue while maintaining the native tumor/adipose tissue interface.Results:The resulting human–murine tissue hybrid phantom was mounted on a clear acrylic housing for absorption and refraction X-ray imaging.Digital breast tomosynthesis was also performed.Conclusion:Both attenuation-based imaging and refraction-based imaging of the phantom are presented to confirm the suitability of this phantom's use in both imaging modalities.
基金Project supported by the Open Project Funds for the Key Laboratory of Space Photoelectric Detection and Perception(Nanjing University of Aeronautics and Astronautics),the Ministry of Industry and Information Technology of China(Grant No.NJ2022025-7)the Fundamental Research Funds for the Central Universities(Grant No.NJ2022025).
文摘With the development of China’s crewed space mission,the space radiation risk for astronauts is increasingly prominent.This paper describes a simulation of the radiation doses experienced by a Chinese female voxel phantom on board the Chinese Space Station(CSS)performed using the Monte Carlo N-Particle(MCNP)software.The absorbed dose,equivalent dose,and effective dose experienced by the voxel phantom and its critical organs are discussed for different levels of shielding of the Tianhe core module.The risk of space-radiation exposure is then assessed by comparing these doses with the current risk limits in China(the skin dose limit for short-term low-earth-orbit missions)and the NASA figures(National Council on Radiation Protection and Measurements Report No.98)for female astronauts.The results obtained can be used to guide and optimize the radiation protection provided for manned space missions.
文摘Introduction: The ring vortex phantom is a novel, cost-effective prototype which generates complex and well-characterised reference flows in the form of the ring vortex. Although its reproducibility has been demonstrated, with ring speeds routinely behaving within 10% tolerances at speeds of approximately 10 - 70 cm/s, a form of real-time QA of the device at the time of imaging is needed to confirm correct function on demand in any environment. Methods: The technology described here achieves real-time QA, comprising a linear encoder, laser-photodiode array, and Doppler probe, measuring piston motion, ring speed and intra-ring velocity respectively. This instrumentation does not interfere with imaging system QA, but allows QA to be performed on both the ring vortex and the device in real-time. Results: The encoder reports the reliability of the piston velocity profile, whilst ring speed is measured by laser behaviour. Incorporation of a calibrated Doppler probe offers a consistency check that confirms behaviour of the central axial flow. For purposes of gold-standard measurement, all elements can be related to previous Laser PIV acquisitions with the same device settings. Conclusion: Consequently, ring vortex production within tolerances is confirmed by this instrumentation, delivering accurate QA in real-time. This implementation offers a phantom QA procedure that exceeds anything seen in the literature, providing the technology to enhance quantitative assessment of flow imaging modalities.
基金The National Basic Research Program of China (973Program) (No.2006CB933206)the National Natural Science Foundation of China(No.50872021,60725101)
文摘A system for in vitro investigation of ultrasound contrast agent＇s enhancement effect is presented and evaluated. It includes the digital B-mode ultrasound scanner Belson3000A, the tissue-mimicking ultrasound phantoms and the software which is used for image quantitative analysis. The linear range, optimal settings and repeatability of the system are assessed and explored by scanning the ultrasound phantoms with different reflective intensities. The measurements are performed under an acoustic power from 4.8 to 12.3 mW, the scanner centre frequency is 3.5 MH and the gain setting is 50 dB. Both a self-made surfactant encapsulated microbubble and a commercial ultrasound contrast agent are scanned. The results show that the pixel intensity of ultrasonic images increases with the increase in the sound power, and for the stronger reflective phantoms of more particles, the increasing trend is much more evident. The system is optimal for evaluating the microbubble contrast agents＇ enhancement effects. It presents a simple, effective and real-time means for characterizing the enhancement ability of microbubbles.
