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
The magnitude of radiation dose imparted to patients who underwent Head Computed Tomography examination in a large tertiary hospital in South-Southern Nigeria has been estimated. CT-ExPO dosimetry software was used to...The magnitude of radiation dose imparted to patients who underwent Head Computed Tomography examination in a large tertiary hospital in South-Southern Nigeria has been estimated. CT-ExPO dosimetry software was used to determine the effective and organ doses to the head region of 40 adult patients. Scanning parameters were retrieved from the CT monitor for both contrast-enhanced and non-contrast head CT examinations. The tube potential ranged from 100 kVp to 120 kVp, while the mAs ranged from 127 mAs to 202 mAs. The mean values of the volume Computed Tomography Dose Index (CTDIvol) and Dose Length Product (DLP) for the contrast-enhanced Head CT examination were 166.4 ± 39.6 mGy and 3568.6 ± 756.1 mGy·cm, respectively, while for the non-contrast examination they were 86.6 ± 30.4 mGy and 2102.3 ± 870.3 mGy·cm, respectively. The effective doses were higher for the contrast-enhanced study than for the non-contrast study by a factor of 1.6. Results were compared with the European Union reference doses and other published data and were found to be higher. Doses to the organs which comprise of brain, red bone marrow, thyroid and eye lens were also estimated. The high variation in the doses in this study may be due to differences in imaging protocols such as large range of mAs and scan lengths and also the algorithm of the scanner.展开更多
目的评估及对比泪道CT造影检查中接受平扫与平扫联合三维重建患者所暴露的辐射剂量和获得的有效图像信息数量,探讨三维重建技术在泪道CT造影中的价值和必要性。方法回顾性分析96例因泪道阻塞需行泪道CT造影的患者,其中49例患者进行泪道C...目的评估及对比泪道CT造影检查中接受平扫与平扫联合三维重建患者所暴露的辐射剂量和获得的有效图像信息数量,探讨三维重建技术在泪道CT造影中的价值和必要性。方法回顾性分析96例因泪道阻塞需行泪道CT造影的患者,其中49例患者进行泪道CT平扫检查(平扫组),47例患者进行泪道CT平扫+三维重建检查(重建组)。对比观察两组患者在检查过程中暴露的射线剂量,获得的总CT图片的数量,统计有泪道相关参考价值的有效CT图片数量,并进行对比分析。结果重建组较平扫组暴露更多辐射剂量[(504.7±405.8)mGy×cm vs(363.8±159.9)mGy×cm,P=0.026],得到更多的总CT数(289±74 vs 230±57,P=0.000)和有效CT数(132±36 vs 112±29,P=0.003),但重建组CT有效率降低(45.67%±0.51%vs48.70%±0.71%,P=0.000)。结论平扫联合三维重建较平扫检查需暴露更多的辐射剂量,虽得到较多有效泪道CT图像,但有效率下降;两种检查方法均应该考虑减少与泪道显影无关的射线暴露。展开更多
目的:比较锥形束CT剂量指数(cone-beam CT dose index,CBDI)法、国际原子能机构(International Atomic Energy Agency,IAEA)5号报告建议的方法(以下简称“IAEA”)和美国医学物理学会(American Association of Physicists in Medicine,AA...目的:比较锥形束CT剂量指数(cone-beam CT dose index,CBDI)法、国际原子能机构(International Atomic Energy Agency,IAEA)5号报告建议的方法(以下简称“IAEA”)和美国医学物理学会(American Association of Physicists in Medicine,AAPM)111工作组建议的方法(TG111)3种锥形束CT辐射剂量测量方法的结果并分析差异,为锥形束CT质量控制中辐射剂量测量方法的选择提供依据。方法:按照CBDI、IAEA、TG1113种CBCT辐射剂量测量方法,使用圆柱形有机玻璃(poly methyl methacrylate,PMMA)模体、0.6cc指形电离室或100 mm笔形电离室,测量Varian CBCT系统各种扫描协议(标准剂量头、低剂量头、高质量头、低剂量胸、盆腔)下的辐射剂量,并计算加权辐射剂量和归一化辐射剂量,最终分析比较各扫描协议不同方法的辐射剂量差异。结果:加权辐射剂量在所有的扫描协议中均表现为TG111方法的值最高、CBDI方法次之、IAEA方法最低;归一化辐射剂量的结果在各协议中差异均较小,最大差异在低剂量头协议中(TG111和IAEA的差异为1.45 mGy),最小差异在低剂量胸协议中(CBDI和IAEA的差异为0.06 mGy)。结论:TG111方法是用于Varian CBCT系统辐射剂量测量的首选方法,不推荐IAEA的方法用于该类设备的测量。展开更多
CT-scan is the most irradiating tool in diagnostic radiology. For 5% - 10% of diagnostic X-ray procedures, it is responsible for 34% of irradiation according to UNSCEAR. Patients radiation protection must therefore be...CT-scan is the most irradiating tool in diagnostic radiology. For 5% - 10% of diagnostic X-ray procedures, it is responsible for 34% of irradiation according to UNSCEAR. Patients radiation protection must therefore be increased during CT-scan procedures. This requires the rigorous application of optimization principle which imposes to have “diagnostic reference levels”. Objective: The aim of this study was to determine the diagnostic reference levels (DRLs) of the four most frequent CT-scans examinations of adults in Cameroon. Material and Method: It was a cross-sectional pilot study carried out from April to September 2015 in five health facilities using CT-scan in Cameroon. The studied variables were: patients age and sex, type of CT-scan examination (cerebral, chest, abdomino-pelvic, lumbar spine), Used of IV contrast (IV﹣/ IV+), acquisition length, time of tube rotation, voltage (kV), mAs, pitch, thickness of slices, CTDIvol and DLP. For each type of examination, at least 30 patients were included per center, consecutively on the randomly predetermined days. The DRL for each type of examination was defined as the 75th percentile of its PDL and CTDIvol. Results: Of the 696 examinations, 41.2% were cerebral, 26.9% abdomino-pelvic, 17.7% lumbar spine and 14.2% chest. The mean age of patients was 52 ± 15 years [20 - 90 years], 58.9% were 50 years and older. The sex-ratio was 1.26 (55.9% males). The CT machines were 4, 8 and 16 multidetectors. The 75th percentile of DLP or DRLs [standard deviation] was: [1150 ± 278 mGy·cm], [770 ± 477 mGy·cm], [720 ± 170 mGy·cm] and [715 ± 187 mGy·cm] respectively for cerebral, lumbar spine, abdominopelvic and chest CT-scans. Taking in consideration the number of detectors, the 75th percentile of the Dose-Length product decreased with the increase number of detectors for cerebral examinations but was the highest with 16 MDCT for the abdominopelvic, lumbar spine and chest CT-scans. For the chest and lumbar spine examinations, there was a significant increase in patient-dose with the increase in the number of detectors. Conclusion: Our DRLs values lie between the norms of some European countries and those of some African countries. There is remarquable variation in dose for the commonest CT-scans examinations in Cameroon, requiring then an optimization process from these determined DRLs and establishment of national DRLs. Special attention to optimization should be paid when using 16 MDCT.展开更多
目的探究低剂量扫描对先天性耳聋诊断的临床应用价值,以为临床诊断提供科学依据。方法选取该院2011年5月—2014年8月收治的40(76耳)例先天性耳聋患者为研究对象,按照收治时间分为对照组与研究组各20(38耳)例,对照组采用原机标准条件(130...目的探究低剂量扫描对先天性耳聋诊断的临床应用价值,以为临床诊断提供科学依据。方法选取该院2011年5月—2014年8月收治的40(76耳)例先天性耳聋患者为研究对象,按照收治时间分为对照组与研究组各20(38耳)例,对照组采用原机标准条件(130 k V,100 m A)进行诊断扫描,研究组采取低剂量(130 k V,50 m A)进行诊断扫描,比对两组患者临床诊断效果。结果研究组采用低剂量扫描诊断,临床诊断准确率86.8%,与对照组92.1%相比较,差异无统计学意义(P>0.05);三维重建方面,二者清晰度之间差异无统计学意义(P>0.05);研究组患者头部CTDI(32±0.8)m Gy、(850±10)m Gy·cm,与对照组(58±1.0)m Gy、(1050±15)m Gy·cm相比较,差异有统计学意义(P<0.05)。结论低剂量扫描与标准计量扫描诊断结果差异有统计学意义,患者自身受到的辐射剂量明显偏低,有利于保护患者身体健康,具有较高的临床应用价值,值得在今后临床诊断工作中推广使用。展开更多
目的通过对CT胸部常规扫描与低剂量扫描模式下的剂量长度乘积(DLP)值进行比较,为CT胸部扫描时的条件选择提供数据参考。方法采用CT-DP检测探头和标准CT剂量体模,测量GE Revolution型256排CT胸部常规扫描模式与低剂量扫描模式下的DLP。...目的通过对CT胸部常规扫描与低剂量扫描模式下的剂量长度乘积(DLP)值进行比较,为CT胸部扫描时的条件选择提供数据参考。方法采用CT-DP检测探头和标准CT剂量体模,测量GE Revolution型256排CT胸部常规扫描模式与低剂量扫描模式下的DLP。结果对胸部低剂量模式,Chest_Lowdose LARGE SIZE模式,DLP测量值60.16 mGy·cm;Chest_Lowdose SMALL SIZE模式,DLP测量值33.65 mGy·cm。胸部常规扫描模式,DLP测量值276.68 mGy·cm。胸部常规扫描模式DLP值是Chest_Lowdose SMALL SIZE模式的8.22倍,是Chest_Lowdose LARGE SIZE模式的4.60倍。而同为胸部低剂量扫描,根据受检者体型不同,选择Chest_Lowdose LARGE SIZE模式DLP值是Chest_Lowdose SMALL SIZE模式的1.79倍。结论选择低剂量CT进行胸部扫描能显著降低受检者剂量,对体型瘦小的受检者选择合适的胸部低剂量扫描模式也会明显降低所受剂量。展开更多
Objective: In order to reduce the effective dose level of the patients to explore the best scanning conditions, various factors affecting the level of PET/CT examination were analyzed. Methods: The effective doses of ...Objective: In order to reduce the effective dose level of the patients to explore the best scanning conditions, various factors affecting the level of PET/CT examination were analyzed. Methods: The effective doses of CT and pet were calculated respectively during PET/CT examination, Scanning parameters of CT and PET were optimized to reduce the effective dose of patients to a minimum while maintaining the image quality. Results: The tube voltage and tube current of CT, the injection dose during PET examination can affect the effective dose of the patients significantly. Conclusion: According to different types of patients and diseases to develop personalized scanning program, the effective dose level of the patients can be significantly reduced.展开更多
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The magnitude of radiation dose imparted to patients who underwent Head Computed Tomography examination in a large tertiary hospital in South-Southern Nigeria has been estimated. CT-ExPO dosimetry software was used to determine the effective and organ doses to the head region of 40 adult patients. Scanning parameters were retrieved from the CT monitor for both contrast-enhanced and non-contrast head CT examinations. The tube potential ranged from 100 kVp to 120 kVp, while the mAs ranged from 127 mAs to 202 mAs. The mean values of the volume Computed Tomography Dose Index (CTDIvol) and Dose Length Product (DLP) for the contrast-enhanced Head CT examination were 166.4 ± 39.6 mGy and 3568.6 ± 756.1 mGy·cm, respectively, while for the non-contrast examination they were 86.6 ± 30.4 mGy and 2102.3 ± 870.3 mGy·cm, respectively. The effective doses were higher for the contrast-enhanced study than for the non-contrast study by a factor of 1.6. Results were compared with the European Union reference doses and other published data and were found to be higher. Doses to the organs which comprise of brain, red bone marrow, thyroid and eye lens were also estimated. The high variation in the doses in this study may be due to differences in imaging protocols such as large range of mAs and scan lengths and also the algorithm of the scanner.
文摘目的评估及对比泪道CT造影检查中接受平扫与平扫联合三维重建患者所暴露的辐射剂量和获得的有效图像信息数量,探讨三维重建技术在泪道CT造影中的价值和必要性。方法回顾性分析96例因泪道阻塞需行泪道CT造影的患者,其中49例患者进行泪道CT平扫检查(平扫组),47例患者进行泪道CT平扫+三维重建检查(重建组)。对比观察两组患者在检查过程中暴露的射线剂量,获得的总CT图片的数量,统计有泪道相关参考价值的有效CT图片数量,并进行对比分析。结果重建组较平扫组暴露更多辐射剂量[(504.7±405.8)mGy×cm vs(363.8±159.9)mGy×cm,P=0.026],得到更多的总CT数(289±74 vs 230±57,P=0.000)和有效CT数(132±36 vs 112±29,P=0.003),但重建组CT有效率降低(45.67%±0.51%vs48.70%±0.71%,P=0.000)。结论平扫联合三维重建较平扫检查需暴露更多的辐射剂量,虽得到较多有效泪道CT图像,但有效率下降;两种检查方法均应该考虑减少与泪道显影无关的射线暴露。
文摘目的:比较锥形束CT剂量指数(cone-beam CT dose index,CBDI)法、国际原子能机构(International Atomic Energy Agency,IAEA)5号报告建议的方法(以下简称“IAEA”)和美国医学物理学会(American Association of Physicists in Medicine,AAPM)111工作组建议的方法(TG111)3种锥形束CT辐射剂量测量方法的结果并分析差异,为锥形束CT质量控制中辐射剂量测量方法的选择提供依据。方法:按照CBDI、IAEA、TG1113种CBCT辐射剂量测量方法,使用圆柱形有机玻璃(poly methyl methacrylate,PMMA)模体、0.6cc指形电离室或100 mm笔形电离室,测量Varian CBCT系统各种扫描协议(标准剂量头、低剂量头、高质量头、低剂量胸、盆腔)下的辐射剂量,并计算加权辐射剂量和归一化辐射剂量,最终分析比较各扫描协议不同方法的辐射剂量差异。结果:加权辐射剂量在所有的扫描协议中均表现为TG111方法的值最高、CBDI方法次之、IAEA方法最低;归一化辐射剂量的结果在各协议中差异均较小,最大差异在低剂量头协议中(TG111和IAEA的差异为1.45 mGy),最小差异在低剂量胸协议中(CBDI和IAEA的差异为0.06 mGy)。结论:TG111方法是用于Varian CBCT系统辐射剂量测量的首选方法,不推荐IAEA的方法用于该类设备的测量。
文摘CT-scan is the most irradiating tool in diagnostic radiology. For 5% - 10% of diagnostic X-ray procedures, it is responsible for 34% of irradiation according to UNSCEAR. Patients radiation protection must therefore be increased during CT-scan procedures. This requires the rigorous application of optimization principle which imposes to have “diagnostic reference levels”. Objective: The aim of this study was to determine the diagnostic reference levels (DRLs) of the four most frequent CT-scans examinations of adults in Cameroon. Material and Method: It was a cross-sectional pilot study carried out from April to September 2015 in five health facilities using CT-scan in Cameroon. The studied variables were: patients age and sex, type of CT-scan examination (cerebral, chest, abdomino-pelvic, lumbar spine), Used of IV contrast (IV﹣/ IV+), acquisition length, time of tube rotation, voltage (kV), mAs, pitch, thickness of slices, CTDIvol and DLP. For each type of examination, at least 30 patients were included per center, consecutively on the randomly predetermined days. The DRL for each type of examination was defined as the 75th percentile of its PDL and CTDIvol. Results: Of the 696 examinations, 41.2% were cerebral, 26.9% abdomino-pelvic, 17.7% lumbar spine and 14.2% chest. The mean age of patients was 52 ± 15 years [20 - 90 years], 58.9% were 50 years and older. The sex-ratio was 1.26 (55.9% males). The CT machines were 4, 8 and 16 multidetectors. The 75th percentile of DLP or DRLs [standard deviation] was: [1150 ± 278 mGy·cm], [770 ± 477 mGy·cm], [720 ± 170 mGy·cm] and [715 ± 187 mGy·cm] respectively for cerebral, lumbar spine, abdominopelvic and chest CT-scans. Taking in consideration the number of detectors, the 75th percentile of the Dose-Length product decreased with the increase number of detectors for cerebral examinations but was the highest with 16 MDCT for the abdominopelvic, lumbar spine and chest CT-scans. For the chest and lumbar spine examinations, there was a significant increase in patient-dose with the increase in the number of detectors. Conclusion: Our DRLs values lie between the norms of some European countries and those of some African countries. There is remarquable variation in dose for the commonest CT-scans examinations in Cameroon, requiring then an optimization process from these determined DRLs and establishment of national DRLs. Special attention to optimization should be paid when using 16 MDCT.
文摘目的探究低剂量扫描对先天性耳聋诊断的临床应用价值,以为临床诊断提供科学依据。方法选取该院2011年5月—2014年8月收治的40(76耳)例先天性耳聋患者为研究对象,按照收治时间分为对照组与研究组各20(38耳)例,对照组采用原机标准条件(130 k V,100 m A)进行诊断扫描,研究组采取低剂量(130 k V,50 m A)进行诊断扫描,比对两组患者临床诊断效果。结果研究组采用低剂量扫描诊断,临床诊断准确率86.8%,与对照组92.1%相比较,差异无统计学意义(P>0.05);三维重建方面,二者清晰度之间差异无统计学意义(P>0.05);研究组患者头部CTDI(32±0.8)m Gy、(850±10)m Gy·cm,与对照组(58±1.0)m Gy、(1050±15)m Gy·cm相比较,差异有统计学意义(P<0.05)。结论低剂量扫描与标准计量扫描诊断结果差异有统计学意义,患者自身受到的辐射剂量明显偏低,有利于保护患者身体健康,具有较高的临床应用价值,值得在今后临床诊断工作中推广使用。
文摘目的通过对CT胸部常规扫描与低剂量扫描模式下的剂量长度乘积(DLP)值进行比较,为CT胸部扫描时的条件选择提供数据参考。方法采用CT-DP检测探头和标准CT剂量体模,测量GE Revolution型256排CT胸部常规扫描模式与低剂量扫描模式下的DLP。结果对胸部低剂量模式,Chest_Lowdose LARGE SIZE模式,DLP测量值60.16 mGy·cm;Chest_Lowdose SMALL SIZE模式,DLP测量值33.65 mGy·cm。胸部常规扫描模式,DLP测量值276.68 mGy·cm。胸部常规扫描模式DLP值是Chest_Lowdose SMALL SIZE模式的8.22倍,是Chest_Lowdose LARGE SIZE模式的4.60倍。而同为胸部低剂量扫描,根据受检者体型不同,选择Chest_Lowdose LARGE SIZE模式DLP值是Chest_Lowdose SMALL SIZE模式的1.79倍。结论选择低剂量CT进行胸部扫描能显著降低受检者剂量,对体型瘦小的受检者选择合适的胸部低剂量扫描模式也会明显降低所受剂量。
文摘Objective: In order to reduce the effective dose level of the patients to explore the best scanning conditions, various factors affecting the level of PET/CT examination were analyzed. Methods: The effective doses of CT and pet were calculated respectively during PET/CT examination, Scanning parameters of CT and PET were optimized to reduce the effective dose of patients to a minimum while maintaining the image quality. Results: The tube voltage and tube current of CT, the injection dose during PET examination can affect the effective dose of the patients significantly. Conclusion: According to different types of patients and diseases to develop personalized scanning program, the effective dose level of the patients can be significantly reduced.
