Patients undergoing recurrent CT exams: assessment of patients with non-malignant diseases,reasons for imaging and imaging appropriateness

To determine percent of patients without malignancy and ≤ 40 years of age with high cumulative radiation doses through recurrent CT exams and assess imaging appropriateness. From the cohort of patients who received cumulative effective dose (CED) of ≥ 100 mSv over a 5-year period, a sub-set was identified with non-malignant disease. The top 50 clinical indications leading to multiple CTs were determined. Clinical decision support (CDS) system scores were analyzed using a widely adopted standard of 1–3 (red) as “not usually appropriate,” 4–6 (yellow) “may or may not be appropriate,” and 7–9 (green) “usually appropriate.” Clinicians reviewed patient records to assess compliance with appropriate use criteria (AUC). 9.6% of patients in our series were with non-malignant conditions and 1.4% with age ≤ 40 years. CDS scores (rounded) were 2% red, 38% yellow, 27% green, and 33% unscored CTs. Clinical society guidelines for CT exams, wherever available, were followed in 87.5 to 100% of cases. AUCs were not available for several clinical indications as also referral guidelines for serial CT imaging. More than half of CT exams were unrelated to follow-up of a primary chronic disease. We are faced with a situation wherein patients in age ≤ 40 years require or are thought to require many CT exams over the course of a few years but the radiation risk creates concern. There is a fair number of conditions for which AUC are not available. Suggested solutions include development of CT scanners with lesser radiation dose and further development of appropriateness criteria.     

How to estimate effective dose for CT patients

• Rehani et al provide important insight into the status quo of CT dose and call an urgent attention to the high-dose group receiving over 100 mSv. • It is crucial to clearly understand the calculation algorithm of effective dose behind the CT dose reporting systems and potential uncertainties.     

Cumulative Radiation Dose in Patients With Hereditary Hemorrhagic Telangiectasia and Pulmonary Arteriovenous Malformations

Purpose

To determine the cumulative effective dose (CED) of radiation from medical imaging and intervention in patients with hereditary hemorrhagic telangiectasia (HHT) who have pulmonary arteriovenous malformations and to identify clinical factors associated with exposure to high levels of radiation.

Methods

All patients with at least 1 pulmonary arteriovenous malformation were identified from the dedicated patient database of a tertiary HHT referral centre. Computerized imaging and electronic patient records were systematically examined to identify all imaging studies performed from 1989-2010. The effective dose was determined for each study, and CED was calculated retrospectively.

Results

Among 246 patients (mean age, 53 years; 62.2% women) with a total of 2065 patient-years, 3309 procedures that involved ionizing radiation were performed. CED ranged from 0.2-307.6 mSv, with a mean of 51.7 mSv. CED exceeded 100 mSv in 26 patients (11%). Interventional procedures and computed tomography (CT) were the greatest contributors, which accounted for 51% and 46% of the total CED, respectively. Factors associated with high cumulative exposure were epistaxis (odds ratio 2.7 [95% confidence interval, 1.1-6.3]; P = .02), HHT-related gastrointestinal bleeding (odds ratio 2.0 [95% confidence interval, 1.0-3.8]; P = .04) and number of patient-years (P < .0001).

Conclusions

Patients with HHT are exposed to a significant cumulative radiation dose from diagnostic and therapeutic interventions. Identifiable subsets of patients are at increased risk. A proportion of patients receive doses at levels that are associated with harm. Imaging indications and doses should be optimized to reduce radiation exposure in this population.     

Estimated radiation exposure and cancer risk from CT and PET/CT scans in patients with lymphoma

Introduction

The purpose of this study was to estimate total effective dose and cancer risk related to treatment monitoring and surveillance computed tomography (CT) scans in a cohort of patients diagnosed with lymphoma.

Methods

76 patients with head, neck, chest, abdomen or pelvis CT and whole-body positron emission tomography (PET)/CT were identified from an institutional lymphoma database; this included 54 (71%) patients with non-Hodgkin and 22 (29%) patients with classical Hodgkin lymphoma. Average treatment and surveillance periods were 8 months (range, 3–14 mo) and 23 months (range, 1–40 mo), respectively. Radiation exposure was estimated from the dose-length product (DLP) for CT scans and milli-Curies and DLP for PET/CT scans. Cancer risk was estimated using the Biological Effects of Ionizing Radiation model.

Results

During their treatment period, 45 patients had 161 CT exams and 39 patients had 73 PET/CT exams. Mean effective dose was 39.3 mSv (range, 7.1–100 mSv). During the surveillance period, 60 patients had 378 CT exams and 25 patients had 39 PET/CT exams. Mean effective dose was 53.2 mSv (range, 2.6–154 mSv). Seventeen of 76 (22.4%) patients had total cumulative doses greater than 100 mSv. The mean increase in estimated cancer risk was 0.40%; the greatest estimated risk to any one patient was 1.19%.

Conclusion

Mean total effective dose and mean estimated cancer risk were low in patients with lymphoma undergoing serial imaging, suggesting that theoretical risks of radiation-induced cancer need not be a major consideration in radiologic follow-up.     

Cumulative radiation exposure from diagnostic imaging in intensive care unit patients

AIM:To quantify cumulative effective dose of intensive care unit(ICU)patients attributable to diagnostic imaging.METHODS:This was a prospective,interdisciplinary study conducted in the ICU of a large tertiary referral and level 1 trauma center.Demographic and clinical data including age,gender,date of ICU admission,primary reason for ICU admission,APACHE Ⅱ score,length of stay,number of days intubated,date of death or discharge,and re-admission data was collected on all patients admitted over a 1-year period.The overall radiation exposure was quantified by the cumulative effective radiation dose(CED)in millisieverts(mS v)and calculated using reference effective doses published by the United Kingdom National Radiation Protection Board.Pediatric patients were selected for subgroupanalysis.RESULTS:A total of 2737 studies were performedin 421 patients.The total CED was 1704 m Sv with a median CED of 1.5 mS v(IQR 0.04-6.6 mS v).Total CED in pediatric patients was 74.6 mS v with a median CED of 0.07 mS v(IQR 0.01-4.7 mS v).Chest radiography was the most commonly performed examination accounting for 83% of all studies but only 2.7% of total CED.Computed tomography(CT)accounted for 16% of all studies performed and contributed 97% of total CED.Trauma patients received a statistically significant higher dose [median CED 7.7 mS v(IQR 3.5-13.8 mS v)] than medical [median CED 1.4 m Sv(IQR 0.05-5.4 m Sv)] and surgical [median CED 1.6 mS v(IQR 0.04-7.5 mS v)] patients.Length of stay in ICU [OR = 1.12(95%CI:1.079-1.157)] was identified as an independent predictor of receiving a CED greater than 15 mS v.CONCLUSION:Trauma patients and patients with extended ICU admission times are at increased risk of higher CEDs.CED should be minimized where feasible,especially in young patients.     

Patient doses from computed tomography in Manitoba from 1977 to 1987

The number of patients undergoing computed tomographic (CT) examinations in the province of Manitoba is reported for the period 1977-1987. The annual patient throughput has increased from 4.2 per 10(3) population in 1978 to 18.2 per 10(3) population in 1987. Over the same period, the per capita population dose from CT has increased from 4.2 to 81.0 microSv. This substantial rise has occurred because of an increase in patient throughput, higher radiation doses associated with modern CT scanners and an increasing proportion of (higher dose) body CT studies. The mean patient dose on a second generation (EMI 5005) scanner was about 1.4 mSv, whereas the corresponding doses on third generation scanners operating in Manitoba were 3.9 mSv (GE 9800) and 5.6 mSv (Siemens DRH).     

Acute abdominal pain: value of non-contrast enhanced ultra-low-dose multi-detector row CT as a substitute for abdominal radiographs

The aim of this study was to evaluate a non-enhanced ultra-low-dose (ULD) abdominal–pelvic multi-detector row computerized tomography (MDCT) to assess patients with acute abdominal pain who would otherwise undergo three-view abdominal X-ray series. Institutional review board approval was obtained with waiver of informed consent. This study was Health Insurance Portability and Accountability Act-compliant. One hundred and sixty-three patients (mean age, 51 years; range, 19–82 years, M/F = 110:53) who underwent ULD MDCT were included in the study. Two subspecialty radiologists independently reviewed the images for abnormal findings and image quality parameters. The effective radiation dose was calculated for each patient and compared to standard-dose computed tomography (CT) scans of 50 matched controls. Findings were confirmed by reviewing the patients’ medical records, and statistical analysis was performed. ULD MDCT showed a high sensitivity (100%), specificity (98.5%), and positive predictive value (91.7%) for detection of free air, stones, and intestinal obstruction. For other sources of abdominal pain, the overall sensitivity, specificity, and positive predictive value were 86%, 96%, and 95%, respectively. Mean effective radiation dose from this study was 2.10 mSv (range of 0.67 to 6.64 mSv) with a 78% mean dose reduction compared to standard-dose CT. There was good inter-observer agreement (=0.4 to 0.81). ULD abdominal–pelvic MDCT provides rapid and reasonably accurate diagnostic information in patients with acute abdominal pain at a very low radiation dose. No financial grants were received for this study.     

CT arthrography of the glenohumeral joint: CT fluoroscopy versus conventional CT and fluoroscopy--comparison of image-guidance techniques

PURPOSE: To compare examination time with radiologist time and to measure radiation dose of computed tomographic (CT) fluoroscopy, conventional CT, and conventional fluoroscopy as guiding modalities for shoulder CT arthrography. MATERIALS AND METHODS: Glenohumeral injection of contrast material for CT arthrography was performed in 64 consecutive patients (mean age, 32 years; age range, 16-74 years) and was guided with CT fluoroscopy (n = 28), conventional CT (n = 14), or conventional fluoroscopy (n = 22). Room times (arthrography, room change, CT, and total examination times) and radiologist times (time the radiologist spent in the fluoroscopy or CT room) were measured. One-way analysis of variance and Bonferroni-Dunn posthoc tests were performed for comparison of mean times. Mean effective radiation dose was calculated for each method with examination data, phantom measurements, and standard software. RESULTS: Mean total examination time was 28.0 minutes for CT fluoroscopy, 28.6 minutes for conventional CT, and 29.4 minutes for conventional fluoroscopy; mean radiologist time was 9.9 minutes, 10.5 minutes, and 9.0 minutes, respectively. These differences were not statistically significant. Mean effective radiation dose was 0.0015 mSv for conventional fluoroscopy (mean, nine sections), 0.22 mSv for CT fluoroscopy (120 kV; 50 mA; mean, 15 sections), and 0.96 mSv for conventional CT (140 kV; 240 mA; mean, six sections). Effective radiation dose can be reduced to 0.18 mSv for conventional CT by changing imaging parameters to 120 kV and 100 mA. Mean effective radiation dose of the diagnostic CT arthrographic examination (140 kV; 240 mA; mean, 25 sections) was 2.4 mSv. CONCLUSION: CT fluoroscopy and conventional CT are valuable alternative modalities for glenohumeral CT arthrography, as examination and radiologist times are not significantly different. CT guidance requires a greater radiation dose than does conventional fluoroscopy, but with adequate parameters CT guidance constitutes approximately 8% of the radiation dose.     

核医学检查受检者所受辐射剂量分析

目的 对核医学检查受检者所受辐射剂量进行测量和分析,以有效剂量表征受检者受到的辐射强度。方法 对核医学检查受检者进行分类,并测量计算所受放射性药物的辐射剂量,受检者所受计算机断层扫描(CT)辐射剂量,通过CT扫描参数和受检者信息等计算得到,上述两者相加换算得到受检者检查所受的有效剂量,并分析受检者所受辐射剂量的影响因素。结果 受检者正电子发射断层计算机成像(PET-CT)检查受到正电子放射性药物¹⁸F-氟代脱氧葡萄糖(¹⁸F-FDG)、¹⁸F-氟代胸苷(¹⁸F-FLT)、¹¹C-胆碱(¹¹C-choline)、¹¹C-蛋氨酸(¹¹C-MET)和¹¹C-乙酸盐(¹¹C-Ac)辐射所致有效剂量分别为(5.06±0.73)、(4.74±1.29)、(1.71±0.05)、(3.18±0.69)和(1.08±0.19)mSv;CT常规扫描辐射有效剂量为(8.80±0.58)mSv,若增加诊断CT扫描,接受的有效剂量可增大至27 mSv;单光子发射计算机断层成像(ECT)检查受到单光子放射性药物⁹⁹Tc^m-亚甲基二磷酸盐(⁹⁹Tc^m-MDP)、⁹⁹Tc^m-大颗粒聚合白蛋白(⁹⁹Tc^m-MAA)、⁹⁹Tc^m-二乙基三胺五乙酸(⁹⁹Tc^m-DTPA)、⁹⁹Tc^m-甲氧基异丁基异腈(⁹⁹Tc^m-MIBI)和⁹⁹Tc^m-焦磷酸盐(⁹⁹Tc^m-PYP)辐照所致的有效剂量分别为(4.63±0.01)、(1.71±0.01)、(1.18±0.01)、(7.19±0.03)和(4.18±0.01)mSv。结论 核医学检查受检者受到放射性药物辐射的有效剂量在1.08~7.19 mSv之间,PET-CT检查中CT所致有效剂量是8.80 mSv。     

宁夏成年人常见CT检查项目的辐射剂量状况调查研究

目的 调查宁夏地区成年人常见CT检查项目的辐射剂量现状,为建立宁夏成年人患者CT检查的第一个诊断参考水平提供依据。方法 采用分层整群抽样的方法,对宁夏地区不同规模医疗机构的不同品牌及型号CT扫描设备的使用情况及辐射状况进行调查,采用间隔抽样,获取被调查单位每日不同检查项目的扫描参数及辐射剂量值。登记医院、CT设备、检查项目、检查类型及患者的基本信息,记录各检查项目的CT扫描参数、CT剂量指数（CTDI_vol）和剂量长度乘积（DLP）值,计算患者的有效剂量E值;对所得数据按检查项目分组统计分析,并与其他国家推荐的诊断参考水平（DRL）值和辐射剂量状况进行比较。结果 调查宁夏地区45家医疗机构（公立三甲10家、公立三乙5家、公立二甲23家、民营医院5家、体检中心2家）6个生产品牌的58台CT设备,成年人患者4 952名。常见检查项目的CTDI_vol、DLP值及患者E值的第75百分位数值（P₇₅）为：头颅65.67 mGy、860.74 mGy ·cm、1.64 mSv;颈部29.32 mGy、490.00 mGy ·cm、2.83 mSv,颈部增强36.92 mGy、954.42 mGy ·cm、4.87 mSv;胸部11.50 mGy、382.06 mGy ·cm、5.68 mSv,胸部增强45.8 mGy、1 713.22 mGy ·cm、25.01 mSv;上腹部20.1 mGy、506.59 mGy ·cm、7.75 mSv,上腹部增强50.07 mGy、1 434.19 mGy ·cm、21.94 mSv;腹盆部14.33 mGy、670.78 mGy ·cm、10.26 mSv,腹盆部增强48 mGy、2 294 mGy ·cm、35.10 mSv;盆腔16.1 mGy、471.58 mGy ·cm、6.08 mSv,盆腔增强31.04 mGy、1 138.78 mGy ·cm、14.69 mSv。结论 宁夏地区头颅、颈部、胸部及盆腔CT辐射剂量较其他国家偏低或相差不大,而腹部CT辐射剂量明显高于其他国家,迫切需要对宁夏腹部CT扫描方案进行优化。     

Feasibility study of computed tomography colonography using limited bowel preparation at normal and low-dose levels study

The purpose was to evaluate low-dose CT colonography without cathartic cleansing in terms of image quality, polyp visualization and patient acceptance. Sixty-one patients scheduled for colonoscopy started a low-fiber diet, lactulose and amidotrizoic-acid for fecal tagging 2 days prior to the CT scan (standard dose, 5.8–8.2 mSv). The original raw data of 51 patients were modified and reconstructed at simulated 2.3 and 0.7 mSv levels. Two observers evaluated the standard dose scan regarding image quality and polyps. A third evaluated the presence of polyps at all three mSv levels in a blinded prospective way. All observers were blinded to the reference standard: colonoscopy. At three times patients were given questionnaires relating to their experiences and preference. Image quality was sufficient in all patients, but significantly lower in the cecum, sigmoid and rectum. The two observers correctly identified respectively 10/15 (67%) and 9/15 (60%) polyps ≥10 mm, with 5 and 8 false-positive lesions (standard dose scan). Dose reduction down to 0.7 mSv was not associated with significant changes in diagnostic value (polyps ≥10 mm). Eighty percent of patients preferred CT colonography and 13% preferred colonoscopy (P<0.001). CT colonography without cleansing is preferred to colonoscopy and shows sufficient image quality and moderate sensitivity, without impaired diagnostic value at dose-levels as low as 0.7 mSv.     

Radiation doses to patients receiving computed tomography examinations in British Columbia.

OBJECTIVE: To estimate the diagnostic reference levels and effective radiation dose to patients from routine computed tomography (CT) examinations in the province of British Columbia, Canada. METHODS: The patient weight, height and computed tomography dose index or dose linear product (DLP) were recorded on study sheets for 1070 patients who were referred for clinically indicated routine CT examinations at 18 radiology departments in British Columbia. Sixteen of the scanners were multidetector row scanners. RESULTS: The average patient dose varied from hospital to hospital. The largest range was found for CT of the abdomen, for which the dose varied from 3.6 to 26.5 (average 10.1) mSv. For head CT, the range was 1.7 to 4.9 (average 2.8) mSv; for chest CT, it was 3.8 to 26 (average 9.3) mSv; for pelvis CT, it was 3.5 to 15.5 (average 9.0) mSv; and for abdomen-pelvis CT, it was 7.3 to 31.5 (average 16.3) mSv. Reference dose values were calculated for each exam. These DLP values are as follows: head, 1300 mGy cm; chest, 600 mGy cm; abdomen, 920 mGy cm; pelvis, 650 mGy cm; and abdomen-pelvis, 1100 mGy cm. CONCLUSION: Among hospitals, there was considerable variation in the DLP and patient radiation dose for a specific exam. Reference doses and patient doses were higher than those found in similar recent surveys carried out in the United Kingdom and the European Union. Patient doses were similar to those found in a recent survey in Germany.     

Challenges for managing the cumulative effective dose for patients

Notwithstanding that 100 mSv is not a threshold for radiation effects, cumulative effective dose (CED) for patients of ≥100 mSv derived from recurrent imaging procedures with ionising radiation has been recently the topic of several publications. The International Commission on Radiological Protection has alerted on the problems to use effective dose for risk estimation in individual patients but has accepted to use this quantity for comparison the relative radiation risks between different imaging modalities. A new International Commission on Radiological Protection document on the use of effective dose (including medicine), is in preparation. Recently published data on the number of patients with CED ≥100 mSv ranged from 0.6 to 3.4% in CT and around 4% in interventional radiology. The challenges to manage the existing situation are summarised. The main aspects identified are: 1) New technology with dose reduction techniques. 2) Refinements in the application of the justification and optimisation for these groups of patients. 3) Patient dose management systems with alerts on the cumulative high doses. 4) Education on the proper use of cumulative effective dose for referrers and practitioners including information for patients. 5) Future research programmes in radiation biology and epidemiology may profit the patient dose data from the groups with high cumulative dose values.

Cumulative effective doses for patients derived from recurrent imaging procedures with ionising radiation has been a topic of interest in the scientific literature since many years. However, its attention has been heightened in the last year with numerous publications, stating that at 100 mSv of effective dose, many organs may receive doses of 100 mGy or more.It was in 2009 when on one hand, IAEA announced its smart card project to track radiation exposure history of patients and on other hand a paper by Sodickson et al provided data on patients who underwent recurrent diagnostic CT examinations over the prior 22 years.^1,2 The approach was well received by the professional community³ but with the fear of its misuse.^4,5 In 2012, Durand et al⁴ considered it “dangerous” to use this approach for cancer risk estimations. Sometimes, it may cause patients or poorly informed physicians “to irrationally decide against medically indicated CT scans.” The authors remind the International Commission on Radiological Protection (ICRP) advice on this issue: “The use of effective dose is not appropriate for estimating the risk to an individual patient resulting from a diagnostic X-ray exam.”In 2014, Whalsh et al revisited the topic in a Commentary in the British Journal of Radiology focussing on the justification.⁶ One of the main aspects was if the radiation risks from previous examinations should affect the future procedures. The authors indicate that allowing cumulative dose estimates to influence whether a patient should get a scan would be equivalent to introducing dose limits for patients and, rather than improving patient safety, would unnecessarily restrict access to radiation-based diagnostic examinations.In the first ever multinational survey among referring physicians from 28 countries, the support for a system that provides radiation exposure history of the patient was demonstrated.⁷ A study from Finland covering 33 institutions in the Helsinki-Uusimaa Hospital District indicated that patient-specific justification and optimisation becomes possible using the tracking of radiologic procedures and radiation dose of individual patients.⁸Some recent papers have collected data to estimate number of patients with cumulative effective doses (CED) ≥100 mSv derived from recurrent CT examinations alone.^3,9,10 The papers estimated that around 0.9 million patients with CED ≥100 mSv are likely occurring every year globally.^3,9 The dose management systems used in some of the hospitals involved in these studies were able to calculate organ and effective doses allowing the analysis of the cumulative doses in the patients. In one of the papers,⁹ data were collected from 324 hospitals involving a total of 488 CT scanners in USA and 1 country in Central Europe (2.5 million patients with 4.8 million CT exams). The patients with CED ≥100 mSv vary from 0.64% to 3.4% in the different hospitals or institutions included in the study. Another paper contains the data of about 70,000 patients from 20 countries: 18 of them in Europe, 1 in Africa, and 1 in Asia with an average of 0.65% of 702,205 patients undergoing CT scans with CED ≥100 mSv.³The IAEA convened a meeting in 2019 with participants from 26 countries, representatives of various organisations, and experts in radiology, medical physics, radiation biology, and epidemiology.³ The meeting led to a Call for Action stating the need for urgent actions by all stakeholders to address the issue of high cumulative radiation doses to patients. The actions include development of appropriateness criteria/referral guidelines by professional societies for patients who require recurrent imaging studies, development of CT machines with lower radiation dose than today by manufacturers, and development of policies by risk management organisations to enhance patient radiation safety. Alert values for cumulative radiation exposures of patients should be set up and introduced in dose monitoring systems.³In another recent study with interventional radiology practices, Xinhua et al studied 25,253 patients who underwent 46,491 fluoroscopy-guided procedures (from January 2010 to January 2019). It was concluded that in 4% of them, the CED was ≥100 mSv and median age of the first procedures was 60 years. Around 80% patients underwent all of their procedures within 365 days.¹¹The automatic patient dose registries are able to set alarms informing clinicians in special situations. The referral criteria for patients with several (or many) previous imaging procedures involving moderated or high doses may be revisited¹⁰ and specific optimisation strategies could be considered in some cases. The European Working Group on “Dose Management” launched by the Eurosafe Imaging from the European Society of Radiology recommended setting alert trigger levels, to be able to send these alerts to professionals and to store and display cumulative patient dose values.¹²In a very recent paper Kachelrieß and Rehani identified several technology-related factors of the CT systems that can be used by manufacturers of CT equipment to achieve substantial reduction in radiation dose to the patients while maintaining or improving the image quality¹³ in line with need identified in recent papers.^3,9,10 The advances in the new systems used for interventional procedures may also allow remarkable decreases in patient doses.According to the ICRP recommendations, we should not use the radiation protection quantity “effective dose” to estimate radiation risks for individual patients.¹⁴ A new ICRP document on the use of effective dose (including medicine) is in preparation. Nevertheless, effective dose is useful to compare the doses and relative risks of different imaging modalities (e.g. CT, fluoroscopy-guided interventional procedures and nuclear medicine). This comparison is also useful for referrers when they balance the benefits and risks of the different examinations before suggesting one imaging modality.⁷ The quantity effective dose may also be useful to inform patients when they ask on the meaning of the different radiation units that may be included in the clinical reports: “mGy.cm” for CT, or Gy.cm² for interventional procedures, or MBq of a certain radiopharmaceutical in nuclear medicine procedures.The use of effective dose may have important limitations as the uncertainty in the calculation, the different implications on the patient risk depending on the age and gender, the radiation dose for the different organs and tissues may be distinct despite having the same value for effective dose. In many cases, effective doses can be estimated from a single conversion factor multiplying the practical radiation unit offered by the X-ray system or the activity of the radiopharmaceutical, and with this approach, the uncertainty may be much higher than using Monte Carlo calculations.The five main aspects to consider in the management of the cumulative effective doses could be summarised as follow:

1. Impact of technology: New technology with dose reduction techniques, especially for the high dose imaging modalities (CT, Interventional and PET-CT)^15,16 should be developed and promoted. Moreover, when available in health centres, they must be used for the high dose procedures. COCIR, the European Trade Association representing the medical imaging, radiotherapy, health ICT and electromedical industries, is doing an important effort to reduce the age of the imaging equipment in Europe to allow introducing the low dose techniques.¹⁷
2. Justification and optimisation: Professional societies could develop appropriateness criteria for patients who need series of imaging studies using ionising radiation. This group of patients may require some re-evaluation of the justification criteria, and improvements in the optimisation strategies for future procedures.
3. Patient dose management systems: Some alerts based on the cumulative dose should be included in the dose management systems. If effective doses are not available, other dosimetric quantities available from the X-ray systems may be used. However, these alerts should not be used to discourage any procedure if it is medically indicated. The clinical decision support systems may incorporate these alerts. The European Directive 2013/59/Euratom requires estimation of population doses from medical exposures and these data are required for the UNSCEAR surveys.
4. Proper use of cumulative dose: Education on the proper use of cumulative effective dose should be included in the training programmes for referrers and practitioners including the proper information for patients. In some cases, patients may accept a small additional radiation risk for a fast diagnosis or a second opinion, and this may be ethically acceptable as part of the autonomy and rights of the patient.¹⁸
5. Data for research: The future research programmes in radiation biology and epidemiology could use the data from the groups of patients with high dose values collected by the dose management systems allowing to estimate organ and effective doses.

     

Estimation of the radiation exposure of a chest pain protocol with ECG-gating in dual-source computed tomography

The aim of the study was to evaluate radiation exposure of a chest pain protocol with ECG-gated dual-source computed tomography (DSCT). An Alderson Rando phantom equipped with thermoluminescent dosimeters was used for dose measurements. Exposure was performed on a dual-source computed tomography system with a standard protocol for chest pain evaluation (120 kV, 320 mAs/rot) with different simulated heart rates (HRs). The dose of a standard chest CT examination (120 kV, 160 mAs) was also measured. Effective dose of the chest pain protocol was 19.3/21.9 mSv (male/female, HR 60), 17.9/20.4 mSv (male/female, HR 80) and 14.7/16.7 mSv (male/female, HR 100). Effective dose of a standard chest examination was 6.3 mSv (males) and 7.2 mSv (females). Radiation dose of the chest pain protocol increases significantly with a lower heart rate for both males (p = 0.040) and females (p = 0.044). The average radiation dose of a standard chest CT examination is about 36.5% that of a CT examination performed for chest pain. Using DSCT, the evaluated chest pain protocol revealed a higher radiation exposure compared with standard chest CT. Furthermore, HRs markedly influenced the dose exposure when using the ECG-gated chest pain protocol.     

Radiation dose evaluation in 64-slice CT examinations with adult and paediatric anthropomorphic phantoms

The objective of this study was to evaluate the organ dose and effective dose to patients undergoing routine adult and paediatric CT examinations with 64-slice CT scanners and to compare the doses with those from 4-, 8- and 16-multislice CT scanners. Patient doses were measured with small (<7 mm wide) silicon photodiode dosemeters (34 in total), which were implanted at various tissue and organ positions within adult and 6-year-old child anthropomorphic phantoms. Output signals from photodiode dosemeters were read on a personal computer, from which organ and effective doses were computed. For the adult phantom, organ doses (for organs within the scan range) and effective doses were 8–35 mGy and 7–18 mSv, respectively, for chest CT, and 12–33 mGy and 10–21 mSv, respectively, for abdominopelvic CT. For the paediatric phantom, organ and effective doses were 4–17 mGy and 3–7 mSv, respectively, for chest CT, and 5–14 mGy and 3–9 mSv, respectively, for abdominopelvic CT. Doses to organs at the boundaries of the scan length were higher for 64-slice CT scanners using large beam widths and/or a large pitch because of the larger extent of over-ranging. The CT dose index (CTDI_vol), dose–length product (DLP) and the effective dose values using 64-slice CT for the adult and paediatric phantoms were the same as those obtained using 4-, 8- and 16-slice CT. Conversion factors of DLP to the effective dose by International Commission on Radiological Protection 103 were 0.024 mSv⋅mGy⁻¹⋅cm⁻¹ and 0.019 mSv⋅mGy⁻¹⋅cm⁻¹ for adult chest and abdominopelvic CT scans, respectively.X-ray CT scanners have made remarkable advances over the past few years, contributing to the improvement of diagnostic image quality and the reduction of examination time. CT scanners with 64 slices, the clinical use of which started quite recently in many medical facilities, has enabled a large number of thin slices to be acquired in a single rotation. 64-slice CT technology accelerated the practical use of three-dimensional body imaging techniques such as coronary CT angiography and CT colonography with an increasing number of CT examinations. The increase in CT examination frequency not only for adults but also for children and the higher doses in CT examinations compared with other X-ray diagnostic procedures have raised concerns about patient doses and safety. An understanding of patient doses requires the evaluation of organ and effective doses for patients undergoing CT examinations, although these dose values in 64-slice CT scans have seldom been reported.One common method for estimating organ and effective doses is dose calculation from the CT dose index (CTDI) or dose–length product (DLP), which are both used as readily available indicators of radiation dose in CT examinations. Organ and effective doses can be estimated from the CTDI or DLP, and conversion factors derived from Monte Carlo simulation of photon interactions within a simplified mathematical model of the human body [1]. Another method is based on measurement using thermoluminescence dosemeters (TLDs) implanted in various organ positions within an anthropomorphic phantom [2–6]. Although TLD dosimetry is considered to be the standard method for measuring absorbed doses in a phantom, the dose measurement is laborious and time consuming. Hence, we devised an in-phantom dosimetry system using silicon photodiode dosemeters implanted in various organ positions, where absorbed dose at each position could be read electronically. In the present study, we evaluated organ and effective doses with 64-slice CT scan protocols used clinically for adult and paediatric patients undergoing chest and abdominopelvic CT examinations. We compared the doses with published dose values for 4-, 8- and 16-slice CT, and indicated the conversion factor of DLP to the effective dose in each examination of the chest and abdomen–pelvis for 64-slice CT scanners.     

Radiation effective doses to patients undergoing abdominal CT examinations

PURPOSE: To determine the radiation effective dose to adult and pediatric patients undergoing abdominal computed tomographic (CT) examinations. MATERIALS AND METHODS: Technique factors were obtained for three groups of randomly selected patients undergoing abdominal CT examinations: 31 children aged 10 years or younger; 32 young adults aged 11-18 years; and 36 adults older than 18 years. The radiographic techniques, together with the measured cross sections of patients, were used to estimate the total energy imparted to each patient. Each value of energy imparted was subsequently converted into the corresponding effective dose to the patient, taking into account the mass of the patient. RESULTS: All abdominal CT examinations were performed at 120 kVp with a section thickness of approximately 7 mm for all sizes of patients. The mean number of CT sections increased from 22.0 for children to 31.5 for adults, and the mean quantity of x radiation in milliampere-seconds increased from 220 mAs for children to 290 mAs for adults. The mean values (+/- SD) of energy imparted were 72.1 mJ +/- 24.4 for children, 183.5 mJ +/- 44.8 for young adults, and 234.7 mJ +/- 89.4 for adults. The corresponding mean values of patient effective dose were 6.1 mSv +/- 1.4 for children, 4.4 mSv +/- 1.0 for young adults, and 3.9 mSv +/- 1.1 for adults. CONCLUSION: Values of energy imparted to patients undergoing abdominal CT examinations were a factor of three higher in adults than in children, but the corresponding patient effective doses were 50% higher in children than in adults.     

Cancer induction caused by radiation due to computed tomography: a critical note

The considerable rise of computed tomography (CT) procedures over the past few decades has urged responsible authorities and researchers to evaluate the risk of carcinogenesis in the population in relation to the radiation dose delivered to the patient. A single patient undergoing CT may receive a radiation equivalent dose that varies between about 2 mSv (head ) to about 20 mSv (CT-based coronary angiography). Whereas the latter represents a substantial dose delivered to one patient it is, however, population-wise far below the area of the so-called low doses, i.e. 50 mSv in children and 100 mSv in adults. While at effective doses above 50 mSv the risk of cancer induction increases linearly with dose, this dose-response relation has not been demonstrated at doses below 50 mSv. Below 50 mSv no convincing epidemiological evidence for cancer risk exists. Calculations on this risk are based on scientifically questionable, if not invalid, extrapolations of data from higher doses. However, the failure to demonstrate that a risk of cancer exists does not mean that there is no risk. This paper summarizes the data mentioned in various articles from recent literature discussing cancer risks due to CT and puts the results of these studies in perspective of current scientific knowledge in the field of radiation protection. For this we follow the lead of the ICRP and UNSCEAR. Furthermore, we review the strategies and efforts of various national and international bodies and manufacturers of CT apparatus to lower the radiation dose to the patient.     

2016年广东省临床核医学基本状况调查

目的 调查广东省各地区临床核医学诊疗基本情况,评估临床核医学应用过程中的职业人员与公众的辐射照射风险,探讨防控辐射风险对策。方法 成立广东省临床核医学基本信息调查组,采用问卷普查及现场抽查形式,对全省核医学科工作人员、设备、核医学诊疗核素和人次、工作人员个人剂量水平以及医院放射防护管理措施等进行了调查。结果 2016年广东省开展核医学放射诊疗单位共71家,从业人员733人,核医学科工作人员人均年有效剂量为（0.55±0.66） mSv/年。全省核医学设备189台,其中SPECT/CT 59台（含SPECT 5台）,PET/CT 28台,甲状腺功能仪54台。使用核素总量1.15×10⁸ MBq,其中⁹⁹Tc^m为7.39×10⁷ MBq,¹⁸F为2.38×10⁷ MBq,¹³¹I为1.70×10⁷ MBq。全年核素诊疗325 903人次,平均频度为2.97人次/千人口。结论 近20年,广东省临床核医学得到飞速发展,21个市中18个市设立了核医学科;核素使用量比1998年增长了414%,核素诊疗年频度比1998年增长了111%。临床核医学的发展增加了职业人群、公众的潜在辐射照射及环境污染的风险,规范核医学科放射性药品的使用及排污管理是将来医用辐射管理的关注重点。     

Effective Dose of CT- and Fluoroscopy-Guided Perineural/Epidural Injections of the Lumbar Spine: A Comparative Study

The objective of this study was to compare the effective radiation dose of perineural and epidural injections of the lumbar spine under computed tomography (CT) or fluoroscopic guidance with respect to dose-reduced protocols. We assessed the radiation dose with an Alderson Rando phantom at the lumbar segment L4/5 using 29 thermoluminescence dosimeters. Based on our clinical experience, 4–10 CT scans and 1-min fluoroscopy are appropriate. Effective doses were calculated for CT for a routine lumbar spine protocol and for maximum dose reduction; as well as for fluoroscopy in a continuous and a pulsed mode (3–15 pulses/s). Effective doses under CT guidance were 1.51 mSv for 4 scans and 3.53 mSv for 10 scans using a standard protocol and 0.22 mSv and 0.43 mSv for the low-dose protocol. In continuous mode, the effective doses ranged from 0.43 to 1.25 mSv for 1–3 min of fluoroscopy. Using 1 min of pulsed fluoroscopy, the effective dose was less than 0.1 mSv for 3 pulses/s. A consequent low-dose CT protocol reduces the effective dose compared to a standard lumbar spine protocol by more than 85%. The latter dose might be expected when applying about 1 min of continuous fluoroscopy for guidance. A pulsed mode further reduces the effective dose of fluoroscopy by 80–90%.     

Multinational data on cumulative radiation exposure of patients from recurrent radiological procedures: call for action

European Radiology - To have a global picture of the recurrent use of CT imaging to a level where cumulative effective dose (CED) to individual patients may be exceeding 100 mSv at which organ...