Research On The Frequency Of X-ray Diagnostic Radiation In Some Areas And The Radiation Cancer Risk Induced By CT

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.