目的:探讨iDose4迭代重建在冠状动脉CT血管造影(coronary CT angiography,CCTA)中的应用价值。方法:选择冠心病患者124例,均行CT扫描iDose4迭代重建与滤波反投影(filtered back-projection,FBP)重建。iDose4迭代重建患者依体质量指数(bo...目的:探讨iDose4迭代重建在冠状动脉CT血管造影(coronary CT angiography,CCTA)中的应用价值。方法:选择冠心病患者124例,均行CT扫描iDose4迭代重建与滤波反投影(filtered back-projection,FBP)重建。iDose4迭代重建患者依体质量指数(body mass index,BMI)进行分组,BMI≥20 kg/m2为迭代组1(135 k V),共56人,BMI<20 kg/m2为迭代组2(110 k V),共68人;FBP组均采用110 k V管电压进行扫描。分别对信噪比(signal noise ratio,SNR)、对比噪声比(contrast to noise ratio,CNR)及图像质量进行比较分析。结果:迭代组1与FBP组的SNR、CNR、辐射剂量及图像质量评分差异均存在且差异具有统计学意义(P<0.05)。迭代组2与FBP组的CNR及辐射剂量差异均存在且差异具有统计学意义(P<0.05),SNR、图像质量评分差异不具有统计学意义(P>0.05)。结论:低压iDose4重建法在64排CCTA中辐射剂量小且图像质量好,值得在临床中推广应用。展开更多
目的:比较容积CT剂量指数(volume CT dose index,CTDI_(VOL))及基于水当量直径的体型特异性剂量估计值(size-specific dose estimate based on water equivalent diameter,SSDE_(WED))在衡量儿童头颅CT辐射剂量中的差异性,并分析CTDI_(V...目的:比较容积CT剂量指数(volume CT dose index,CTDI_(VOL))及基于水当量直径的体型特异性剂量估计值(size-specific dose estimate based on water equivalent diameter,SSDE_(WED))在衡量儿童头颅CT辐射剂量中的差异性,并分析CTDI_(VOL)、SSDE_(WED)与曝光量、水当量直径(water equivalent diameter,WED)的相关性,以为临床检查中儿童头颅CT辐射剂量衡量提供参考。方法:回顾性分析2021年1—12月于某院进行头颅CT检查的1297例患儿的临床资料,根据年龄将患儿分为≤1个月组、>1个月~4岁组、>4~10岁组、>10~15岁组。记录患儿的曝光量、年龄、CTDI_(VOL)、剂量长度乘积,并计算WED、转换因子及SSDE_(WED)。比较CTDI_(VOL)与SSDE_(WED)的差异;建立CTDI_(VOL)、SSDE_(WED)与曝光量、WED的回归模型,并采用Pearson分析CTDI_(VOL)、SSDE_(WED)与曝光量、WED之间的相关性;对比国内诊断参考水平(diagnostic reference level,DRL)、欧盟DRL及本医疗机构诊断参考水平(local diagnostic reference level,LDRL)的差异。采用SPSS 25.0统计学软件进行分析。结果:患儿头颅CT的CTDI_(VOL)为(9.22±1.63)mGy,SSDE_(WED)为(8.14±0.84)mGy,CTDI_(VOL)较SSDE_(WED)高13.27%,差异有统计学意义(t=47.66,P<0.001)。CTDI_(VOL)、SSDE_(WED)与曝光量、WED均呈正相关关系(P<0.001);CTDI_(VOL)、SSDE_(WED)与曝光量、WED回归模型拟合性较强(R^(2)为0.58~0.99)。与国内DRL及欧盟DRL比较,LDRL均处于较低水平。结论:在儿童头颅CT辐射剂量衡量中,相较于CTDI_(VOL),SSDE_(WED)对辐射剂量的衡量更准确。同时定期对医疗机构的DRL值进行统计更新并优化检查参数,是减少辐射剂量的重要方式。展开更多
The most crucial requirement in radiation therapy treatment planning is a fast and accurate treatment planning system that minimizes damage to healthy tissues surrounding cancer cells. The use of Monte Carlo toolkits ...The most crucial requirement in radiation therapy treatment planning is a fast and accurate treatment planning system that minimizes damage to healthy tissues surrounding cancer cells. The use of Monte Carlo toolkits has become indispensable for research aimed at precisely determining the dose in radiotherapy. Among the numerous algorithms developed in recent years, the GAMOS code, which utilizes the Geant4 toolkit for Monte Carlo simula-tions, incorporates various electromagnetic physics models and multiple scattering models for simulating particle interactions with matter. This makes it a valuable tool for dose calculations in medical applications and throughout the patient’s volume. The aim of this present work aims to vali-date the GAMOS code for the simulation of a 6 MV photon-beam output from the Elekta Synergy Agility linear accelerator. The simulation involves mod-eling the major components of the accelerator head and the interactions of the radiation beam with a homogeneous water phantom and particle information was collected following the modeling of the phase space. This space was po-sitioned under the X and Y jaws, utilizing three electromagnetic physics mod-els of the GAMOS code: Standard, Penelope, and Low-Energy, along with three multiple scattering models: Goudsmit-Saunderson, Urban, and Wentzel-VI. The obtained phase space file was used as a particle source to simulate dose distributions (depth-dose and dose profile) for field sizes of 5 × 5 cm<sup>2</sup> and 10 × 10 cm<sup>2</sup> at depths of 10 cm and 20 cm in a water phantom, with a source-surface distance (SSD) of 90 cm from the target. We compared the three electromagnetic physics models and the three multiple scattering mod-els of the GAMOS code to experimental results. Validation of our results was performed using the gamma index, with an acceptability criterion of 3% for the dose difference (DD) and 3 mm for the distance-to-agreement (DTA). We achieved agreements of 94% and 96%, respectively, between simulation and experimentation for the three electromagnetic physics models and three mul-tiple scattering models, for field sizes of 5 × 5 cm<sup>2</sup> and 10 × 10 cm<sup>2</sup> for depth-dose curves. For dose profile curves, a good agreement of 100% was found between simulation and experimentation for the three electromagnetic physics models, as well as for the three multiple scattering models for a field size of 5 × 5 cm<sup>2</sup> at 10 cm and 20 cm depths. For a field size of 10 × 10 cm<sup>2</sup>, the Penelope model dominated with 98% for 10 cm, along with the three multiple scattering models. The Penelope model and the Standard model, along with the three multiple scattering models, dominated with 100% for 20 cm. Our study, which compared these different GAMOS code models, can be crucial for enhancing the accuracy and quality of radiotherapy, contributing to more effective patient treatment. Our research compares various electro-magnetic physics models and multiple scattering models with experimental measurements, enabling us to choose the models that produce the most reli-able results, thereby directly impacting the quality of simulations. This en-hances confidence in using these models for treatment planning. Our re-search consistently contributes to the progress of Monte Carlo simulation techniques in radiation therapy, enriching the scientific literature.展开更多
Ionizing radiation is extensively used in medicine and its contribution to both diagnosis and therapy is undisputable.However,the use of ionizing radiation also involves a certain risk since it may cause damage to tis...Ionizing radiation is extensively used in medicine and its contribution to both diagnosis and therapy is undisputable.However,the use of ionizing radiation also involves a certain risk since it may cause damage to tissues and organs and trigger carcinogenesis.Computed tomography(CT) is currently one of the major contributors to the collective population radiation dose both because it is a relatively high dose examination and an increasing number of people are subjected to CT examinations many times during their lifetime.The evolution of CT scanner technology has greatly increased the clinical applications of CT and its availability throughout the world and made it a routine rather than a specialized examination.With the modern multislice CT scanners,fast volume scanning of the whole human body within less than 1 min is now feasible.Two dimensional images of superb quality can be reconstructed in every possible plane with respect to the patient axis(e.g.axial,sagital and coronal).Furthermore,three-dimensional images of all anatomic structures and organs can be produced with only minimal additional effort(e.g.skeleton,tracheobronchial tree,gastrointestinal system and cardiovascular system).All these applications,which are diagnostically valuable,also involve a significant radiation risk.Therefore,all medical professionals involved with CT,either as referring or examining medical doctors must be aware of the risks involved before they decide to prescribe or perform CT examinations.Ultimately,the final decision concerning justification for a prescribed CT examination lies upon the radiologist.In this paper,we summarize the basic information concerning the detrimental effects of ionizing radiation,as well as the CT dosimetry background.Furthermore,after a brief summary of the evolution of CT scanning,the current CT scanner technology and its special features with respect to patient doses are given in detail.Some numerical data is also given in order to comprehend the magnitude of the potential radiation risk involved in comparison with risk from exposure to natural background radiation levels.展开更多
AIM: To investigate effect of body dimensions obtained from localizer radiograph and transverse abdominal computed tomography(CT) images on Size Specific Dose Estimate. METHODS: This study was approved by Institutiona...AIM: To investigate effect of body dimensions obtained from localizer radiograph and transverse abdominal computed tomography(CT) images on Size Specific Dose Estimate. METHODS: This study was approved by Institutional Review Board and was compliant with Health Insurance Portability and Accountability Act. Fifty patients with abdominal CT examinations(58 ± 13 years, Male: Female 28:22) were included in this study. Anteriorposterior(AP) and lateral(Lat) diameters were measured at 5 cm intervals from the CT exam localizer radiograph(simple X-ray image acquired for planning the CT exam before starting the scan) and transverse CT images. Average of measured AP and Lat diameters, as well as maximum, minimum and mid location AP and Lat were measured on both image sets. In addition, off centering of patients from the gantry iso-center was calculated from the localizers. Conversion factors from American Association of Physicists in Medicine(AAPM) report 204 were obtained for AP, Lat, AP + Lat, and effective diameter(√ AP * Lat) to determine size specificdose estimate(SSDE) from the CT dose index volume(CTDIvol) recorded from the dose reports. Data were analyzed using SPSS v19. RESULTS: Total number of 5376 measurements was done. In some patients entire body circumference was not covered on either projection radiograph or transverse CT images; hence accurate measurement of AP and Lat diameters was not possible in 11%(278/2488) of locations. Forty one patients were off-centered with mean of 1.9 ± 1.8 cm(range: 0.4-7 cm). Conversion factors for attained diameters were not listed on AAPM look-up tables in 3%(80/2488) of measurements. SSDE values were significantly different compared to CTDIvol, ranging from 32% lower to 74% greater than CTDIvol. CONCLUSION: There is underestimation and overestimation of dose comparing SSDE values to CTDIvol. Localizer radiographs are associated with overestimation of patient size and therefore underestimation of SSDE.展开更多
文摘目的:探讨iDose4迭代重建在冠状动脉CT血管造影(coronary CT angiography,CCTA)中的应用价值。方法:选择冠心病患者124例,均行CT扫描iDose4迭代重建与滤波反投影(filtered back-projection,FBP)重建。iDose4迭代重建患者依体质量指数(body mass index,BMI)进行分组,BMI≥20 kg/m2为迭代组1(135 k V),共56人,BMI<20 kg/m2为迭代组2(110 k V),共68人;FBP组均采用110 k V管电压进行扫描。分别对信噪比(signal noise ratio,SNR)、对比噪声比(contrast to noise ratio,CNR)及图像质量进行比较分析。结果:迭代组1与FBP组的SNR、CNR、辐射剂量及图像质量评分差异均存在且差异具有统计学意义(P<0.05)。迭代组2与FBP组的CNR及辐射剂量差异均存在且差异具有统计学意义(P<0.05),SNR、图像质量评分差异不具有统计学意义(P>0.05)。结论:低压iDose4重建法在64排CCTA中辐射剂量小且图像质量好,值得在临床中推广应用。
文摘The most crucial requirement in radiation therapy treatment planning is a fast and accurate treatment planning system that minimizes damage to healthy tissues surrounding cancer cells. The use of Monte Carlo toolkits has become indispensable for research aimed at precisely determining the dose in radiotherapy. Among the numerous algorithms developed in recent years, the GAMOS code, which utilizes the Geant4 toolkit for Monte Carlo simula-tions, incorporates various electromagnetic physics models and multiple scattering models for simulating particle interactions with matter. This makes it a valuable tool for dose calculations in medical applications and throughout the patient’s volume. The aim of this present work aims to vali-date the GAMOS code for the simulation of a 6 MV photon-beam output from the Elekta Synergy Agility linear accelerator. The simulation involves mod-eling the major components of the accelerator head and the interactions of the radiation beam with a homogeneous water phantom and particle information was collected following the modeling of the phase space. This space was po-sitioned under the X and Y jaws, utilizing three electromagnetic physics mod-els of the GAMOS code: Standard, Penelope, and Low-Energy, along with three multiple scattering models: Goudsmit-Saunderson, Urban, and Wentzel-VI. The obtained phase space file was used as a particle source to simulate dose distributions (depth-dose and dose profile) for field sizes of 5 × 5 cm<sup>2</sup> and 10 × 10 cm<sup>2</sup> at depths of 10 cm and 20 cm in a water phantom, with a source-surface distance (SSD) of 90 cm from the target. We compared the three electromagnetic physics models and the three multiple scattering mod-els of the GAMOS code to experimental results. Validation of our results was performed using the gamma index, with an acceptability criterion of 3% for the dose difference (DD) and 3 mm for the distance-to-agreement (DTA). We achieved agreements of 94% and 96%, respectively, between simulation and experimentation for the three electromagnetic physics models and three mul-tiple scattering models, for field sizes of 5 × 5 cm<sup>2</sup> and 10 × 10 cm<sup>2</sup> for depth-dose curves. For dose profile curves, a good agreement of 100% was found between simulation and experimentation for the three electromagnetic physics models, as well as for the three multiple scattering models for a field size of 5 × 5 cm<sup>2</sup> at 10 cm and 20 cm depths. For a field size of 10 × 10 cm<sup>2</sup>, the Penelope model dominated with 98% for 10 cm, along with the three multiple scattering models. The Penelope model and the Standard model, along with the three multiple scattering models, dominated with 100% for 20 cm. Our study, which compared these different GAMOS code models, can be crucial for enhancing the accuracy and quality of radiotherapy, contributing to more effective patient treatment. Our research compares various electro-magnetic physics models and multiple scattering models with experimental measurements, enabling us to choose the models that produce the most reli-able results, thereby directly impacting the quality of simulations. This en-hances confidence in using these models for treatment planning. Our re-search consistently contributes to the progress of Monte Carlo simulation techniques in radiation therapy, enriching the scientific literature.
文摘Ionizing radiation is extensively used in medicine and its contribution to both diagnosis and therapy is undisputable.However,the use of ionizing radiation also involves a certain risk since it may cause damage to tissues and organs and trigger carcinogenesis.Computed tomography(CT) is currently one of the major contributors to the collective population radiation dose both because it is a relatively high dose examination and an increasing number of people are subjected to CT examinations many times during their lifetime.The evolution of CT scanner technology has greatly increased the clinical applications of CT and its availability throughout the world and made it a routine rather than a specialized examination.With the modern multislice CT scanners,fast volume scanning of the whole human body within less than 1 min is now feasible.Two dimensional images of superb quality can be reconstructed in every possible plane with respect to the patient axis(e.g.axial,sagital and coronal).Furthermore,three-dimensional images of all anatomic structures and organs can be produced with only minimal additional effort(e.g.skeleton,tracheobronchial tree,gastrointestinal system and cardiovascular system).All these applications,which are diagnostically valuable,also involve a significant radiation risk.Therefore,all medical professionals involved with CT,either as referring or examining medical doctors must be aware of the risks involved before they decide to prescribe or perform CT examinations.Ultimately,the final decision concerning justification for a prescribed CT examination lies upon the radiologist.In this paper,we summarize the basic information concerning the detrimental effects of ionizing radiation,as well as the CT dosimetry background.Furthermore,after a brief summary of the evolution of CT scanning,the current CT scanner technology and its special features with respect to patient doses are given in detail.Some numerical data is also given in order to comprehend the magnitude of the potential radiation risk involved in comparison with risk from exposure to natural background radiation levels.
文摘AIM: To investigate effect of body dimensions obtained from localizer radiograph and transverse abdominal computed tomography(CT) images on Size Specific Dose Estimate. METHODS: This study was approved by Institutional Review Board and was compliant with Health Insurance Portability and Accountability Act. Fifty patients with abdominal CT examinations(58 ± 13 years, Male: Female 28:22) were included in this study. Anteriorposterior(AP) and lateral(Lat) diameters were measured at 5 cm intervals from the CT exam localizer radiograph(simple X-ray image acquired for planning the CT exam before starting the scan) and transverse CT images. Average of measured AP and Lat diameters, as well as maximum, minimum and mid location AP and Lat were measured on both image sets. In addition, off centering of patients from the gantry iso-center was calculated from the localizers. Conversion factors from American Association of Physicists in Medicine(AAPM) report 204 were obtained for AP, Lat, AP + Lat, and effective diameter(√ AP * Lat) to determine size specificdose estimate(SSDE) from the CT dose index volume(CTDIvol) recorded from the dose reports. Data were analyzed using SPSS v19. RESULTS: Total number of 5376 measurements was done. In some patients entire body circumference was not covered on either projection radiograph or transverse CT images; hence accurate measurement of AP and Lat diameters was not possible in 11%(278/2488) of locations. Forty one patients were off-centered with mean of 1.9 ± 1.8 cm(range: 0.4-7 cm). Conversion factors for attained diameters were not listed on AAPM look-up tables in 3%(80/2488) of measurements. SSDE values were significantly different compared to CTDIvol, ranging from 32% lower to 74% greater than CTDIvol. CONCLUSION: There is underestimation and overestimation of dose comparing SSDE values to CTDIvol. Localizer radiographs are associated with overestimation of patient size and therefore underestimation of SSDE.
