【作者】 苏垠平；

【导师】 孙全富；

【作者基本信息】 中国疾病预防控制中心 ， 劳动卫生与环境卫生学， 2014， 博士

【摘要】 研究背景随着医用辐射的蓬勃发展和不断普及,在造福人类的同时,也增加了个体和群体的辐射剂量。联合国原子辐射效应科学委员会(UNSCEAR)2008年报告中指出,美国医疗照射所致人均剂量等于或者已经超过天然本底辐射水平,其他国家今后也将出现这种情况,医疗照射正在成为公众最大的电离辐射照射源。我国在1984年与1996年先后组织开展了两次全国性大规模的医疗照射水平调查,为制定防护法规与标准积累了宝贵的数据资料,并且推动了我国医疗照射防护水平的不断提高,但随着放射诊疗设备应用的不断发展和扩大,至今我国仍未有更新的数据。随着X射线诊断照射尤其是CT扫描所占比重的增加,许多国家的调查结果显示一半以上的放射诊断影像的辐射剂量来自CT检查,因此CT扫描可能诱发癌症的风险也引起国际上越来越多的关注与研究,而目前未见针对我国CT扫描可能诱发癌症风险研究的相关报道。目的1、基于医院信息系统搜集了解不同县级地区X射线诊断照射,尤其是CT扫描的频度及其分布情况,为我国今后医疗照射频度调查提供新思路。2、通过估算CT扫描所致患者的器官剂量,利用BEIRⅦ风险预测模型并结合中国的数据估算CT扫描可能诱发癌症的风险,为今后CT扫描在临床应用中的辐射防护提供依据。研究方法1、选择W、M两个县所有医疗卫生机构(包括县医院(W1与M1)、中医院及乡镇卫生院)与E市两个县区医院(E1与E2),调查其X射线诊断照射的分布情况,及一家儿童医院(M2)调查其CT扫描的分布情况。利用上述医院的信息系统(包括RIS系统、PACS系统及纸质登记本),搜集2012年期间接受X射线诊断照射所有患者的就诊ID、性别、年龄、检查类型、受检部位、检查时间,其中针对CT扫描的受检者相关信息进一步搜集其就诊原因及检查结果(阳性／阴性)。2、根据CT扫描的分布,选择W1、E1及E2医院接受头部、胸部CT扫描的患者作为调查对象,通过填写纸质调查表或提取PACS系统内DICOM header头文件内的固定字段获取CT扫描参数,并根据所获取的扫描参数利用CT-Expo软件估算头部及胸部CT扫描所致不同年龄患者不同部位器官剂量。3、利用BEIRⅦ癌症风险预测模型并结合中国2008年癌症发病率及人口寿命表估算W1,E1和E2三级医院不同年龄、性别的患者接受单次CT扫描所致不同部位癌症的风险。研究结果1、本研究涉及7家医院及2个县级地区的乡镇卫生院,共调查2012年期间接受X射线诊断照射653622人次,其中CT扫描为197003人次。2012年W、M两个县CT检查的频次分别为79.65人次/千人口和46.05人次/千人口。不同X射线诊断照射类型中,除X射线诊断摄影以外,CT扫描所占比重较高,分别为26.6%和40.9%,而普通X射线透视检查则十分少见。2、对W1、M1、E1三家县医院X射线诊断照射频次分布调查,发现CT扫描在X射线诊断照射的比重分别为：28.3%、41.4%和52.0%。不同CT扫描部位,头部所占比例最高,县级人民医院头部CT比重范围为39.0～66.8%,区医院为33.7%,其中对儿童头部CT扫描的比例高达95%,据调查E2医院51.7%的儿童是由于外伤引起的。对CT扫描阳性率的调查结果显示,头部CT扫描阳性率相对低于其他部位,且年龄越小的患者其阳性率越低。头、胸部接受重复CT扫描的比重较高,并且随患者年龄的增加,CT重复检查的比例也相应增加。3、头部CT扫描所致大脑、唾液腺、骨表面和红骨髓的剂量相对较高,而胸部CT扫描所致甲状腺,肺以及胃、肝脏、骨表面和红骨髓器官剂量相对较高。由于不同医院对于相同年龄患者所使用的CT扫描参数不同,因此所致其剂量也不相同,其中头部扫描新生儿可相差5倍(如大脑31.5mSv:5.5mSv),而胸部扫描所致新生儿的器官剂量相差可达11倍(如肺36.6mSv:3.1mSv)。4、头部CT扫描所致白血病终生风险男性略高于女性,其范围分别为1.8～11.2/10万人口和1.3-9.4/10万人口,而女性甲状腺癌远高于男性(其风险分别为9.6/10万人口和1.8/10万人口)；胸部CT扫描所致女性乳腺癌风险最高,为423.5/10万人口,其次为女性甲状腺癌及肺癌分别为244.7/10万人口和240.9/10万人口,其中肺癌风险约为男性的两倍。此外,胸部扫描所致儿童(女)甲状腺癌的风险最高可达我国基线水平的66%。研究结论1、利用医院信息系统(RIS/PACS系统)搜集X射线诊断照射资料的方法经济、可行,为我国今后医疗照射频度调查提供了新思路。2、不同医院CT扫描所致患者器官剂量差异大,这提示放射科医生及物理师应当根据患者体重和扫描部位适当调整扫描参数,以减少其受照剂量,特别是对儿童受检者。3、胸部CT扫描所致患者甲状腺的终生癌症风险较高,因此胸部扫描时,应加强对甲状腺及其它辐射敏感器官的防护。更多还原

【Abstract】 BackgroundAs the rapid development and popularity of medical radiation, while it brought huge benefit for the human; it also increased the radiation dose from individual and the collective population. United Nation Scientific Committee on the Effect of Atomic Radiation reported that, medical exposure represented the major source of man-made radiation of the population, even per caput doses from medical exposures was greater than those from the natural background radiation in U.S.; other countries will follow, medical exposures is becoming the biggest radiation source for the public. Our nation conducted two-national wide survey of the frequency of medical exposure in1984and1996, respectively; it provided the valuable data for the development of regulations and standards and also promoted the improvement of the radiation protection from medical exposure in China. With the utilization of radiodiagnosis and radiotherapy devices is continuously developing and expanding, till now no updated data is reported in our nation. The propotion of X-ray diagnositc radiation from medical exposures was increasing, expecially for CT scanning. The surveyed results form many countries showed that half of radiation dose casued by diagnostic radiation imaging was from CT scanning. Therefore the potential radiaiotn cancer risk from CT scanning caused more and more concern around the world, the relative researches about cancer risk induced by CT has not been reported in China.Objective1. To understand the frequency and distribution of X-ray diagnositc radiation based on the hospital information system, especially for CT scanning, it can provide the new method for the survey of the medical exposure frequency in the future.2. To project the potential cancer risk from CT scanning through the calculated organ dose from CT and the BEIRⅦ model combined with Chinese population, it can provide the basis for the radiaiotn protection of the utilization of CT scanning in the clinical in the future.Methods1. In this study, seven hospitals and township health centers in two county regions were involved, and there were653622people who underwent X-ray diagnostic radiation in2012, among these,197003people were from CT. Through the hospital information system (such as radiology information system, PACS or paper registration) in the above hospitals, to collect the information of patients who underwent X-ray diagnositc radiation in2012, such as patient ID, sex, age, examination type, the exposed body part, examined date. For the patients who exposed CT scanning, the reason and result of examination should also be collected.2. According to the distribution of CT scanning, choosing the patients who underwent head or chest CT scanning in W1, E1and E2hospitals as the research object, investigating the parameters of CT scanning through survey tables or abstracting the fixed field in DICOM header from PACS, and then calculating the organ dose for patients with different age and sex by the CT-Expo software.3. Based on the cancer risk projection from BEIRⅦ report and combined the Chinese cancer incidence and lifetime table in2008, the cancer risk from a single CT scan for the patients with different age and sex in W1, E1and E2hospitals is calculated.Results1. The survey investigated the distribution of X-ray diagnositc radiation in all of medical institutions from W and M counties (including the County hospitals (W1and M1), the traditional Chinese medicine hospitals and township hosptials) and in two county-region hospitals (E1and E2), and the distribution of CT scanning in a Children’s hospital (M2). The frequency of CT scanning in W and M counties was79.65and46.05per thousand population in2012, respectively. In addition to the X-ray diagnostic radiography, CT scanning accounted for high proportion of the X-ray diagnositc radiation,26.6%and40.9%, respectively, while for the conventional X-ray was very small.2. Through the survey of distribution from X-ray diagnositc radiation in W1, M1and E1, it was found that the propotion of CT scannings was28.3%,41.4%and52.0%, repectively. According to the exposed body parts, head CT was higher than others, the range of propotion for head CT in county hospitals was39.0%-66.8%, while for district hospital was33.7%, especially for children that up to95%. There were51.7%of children who underwent CT scanning in E2hospital caused by trauma. The result of positive rate from CT scanning showed that head CT was lower than others and it increased with older patients. The higher propotions of recurrent CT scanning were head and chest, meanwhile, the propotion was also increasing for the older patients.3. The relatively higher radiation organ dose for head CT were brain, salivary gland, bone surface and bone marrow; while for chest CT, thyroid, lung, stomach, liver, bone surface and bone marrow have higher radiation dose than other tissues/organs. Due to the different radiation dose caused by the parameters used by CT scanning among different hospitals, there are5-fold diversity of organ dose for the newborn baby who exposed head CT (eg. brain31.5mSv vs5.5mSv); while for chest, there are11-fold difference (eg. lung36.6mSv vs3.1mSv).4. The lifetime risk of leukemia for male caused by head CT is higher than that for female, the range of them respectively are1.8-11.2per100thousand population and1.3-9.4per100thousand population; thyroid cancer risk for female was much higher than that for male (the risk is9.6and1.8per100thousand population, respectively). Breast cancer risk for female induced by chest CT is highest,423.5per100thousand population, the next was lung cancer and thyroid cancer which are244.7and240.9per100thousand population, respectively. Among these, lung cancer risk for female is two times higher than that for male. Additionally, the highest potential cancer risk for children from chest CT in this study was approximately66%of the baseline cancer risk in China.Conclusion 1. The method that collecting the data of X-ray diagnostic radiation based on the hospital information system (RIS/PACS) is more economical and feasible; it can provide the new idea for the survey of frequency from national medical exposure in the future.2. Due to the huge difference of organ dose induced by CT scanings among different hospitals, it indicated that radiologist and medical physicist should be adjust the parmeters depending on size of patients and the exposed body part, to reduce the radiation dose, especially for children.3. The surveyed result showed that the highest lifetime cancer risk of thyroid for chest CT was relatively higher, so more attention should be paid on the radiation protection of thyroid and other radiation-sensitive organs for patients who underwent chest CT scanning.更多还原