Radiation protection of patients in diagnostic and interventional radiology in Asian countries: Impact of an IAEA project

Recognizing the lack of information on image quality and patient doses in most countries in Asia, the International Atomic Energy Agency (IAEA) initiated a project to assess the status of imaging technology, practice in conventional radiography, mammography, computed tomography (CT) and interventional procedures, and to implement optimisation actions. A total of 20 countries participated. Obsolete practices of use of fluoroscopy for positioning, photofluorography, chest fluoroscopy and conventional tomography were reported by 4 out of 7 countries that provided this information. Low-kV technique for chest radiography is in use in participating countries for 20-85% of cases, and manual processing is in 5-85% of facilities in 5 countries. Instances of the use of adult CT protocol for children in three participating countries were observed in 10-40% of hospitals surveyed. After implementation of a Quality Control programme, the image quality in conventional radiography improved by zero to 13 percentage points in certain countries and dose reduction was from 10% to 85%. In mammography, poor quality, ranging from 10 to 29% of images in different countries was observed. The project increased attention to dose quantities and dose levels in computed tomography, although doses in most cases were not higher than reference levels. In this study 16-19% of patients in interventional cardiology received doses that have potential for either stochastic risk or tissue reaction. This multi-national study is the first of its kind in the Asia, and it provided insight into the situation and opportunities for improvement.     

多层CT辐射剂量与防护研究进展

多层CT(MDCT)可进行快速扫描和大范围容积扫描。与单层CT(SDCT)相比,MDCT特有的参数可能增加或减少受检者剂量。早期研究表明MDCT所致受检者剂量高于SDCT,但目前越来越多的研究表明两者剂量相似甚至MDCT的剂量较低。多层CT主要依靠CT的合理使用来降低辐射剂量。CT检查正当化判断是临床医生与放射医师共同的责任。扫描参数应根据扫描指征、受检者体形、年龄及扫描范围设置,并使用自动曝光控制等降低辐射剂量的技术。对临床医生和CT工作人员进行CT辐射防护培训有助于CT检查正当化及扫描方案与辐射剂量的最优化。     

Fractures of the thoracic spine in patients with minor trauma: Comparison of diagnostic accuracy and dose of biplane radiography and MDCT

Objectives

To investigate the accuracy of biplane radiography in the detection of fractures of the thoracic spine in patients with minor trauma using multidetector computed tomography (MDCT) as the reference and to compare the dose of both techniques.

Methods

107 consecutive trauma patients with suspected fractures of the thoracic spine on physical examination were included. All had undergone biplane radiography first, followed by a MDCT scan between October 2008 and October 2012. A fourfold table was used for the classification of the screening test results. Both the Chi-square test (χ²) and the mean dose-length product (DLP) were used to compare the diagnostic methods.

Results

MDCT revealed 77 fractures in 65/107 patients (60.7%). Biplane radiography was true positive in 32/107 patients (29.9%), false positive in 19/107 patients (17.8%), true negative in 23/107 (21.5%) and false negative in 33/107 patients (30.8%), showing a sensitivity of 49.2%, a specificity of 54.7%, a positive predictive value (PPV) of 62.7%, a negative predictive value (NPV) of 41.1%, and an accuracy of 51.4%. The presence of a fracture on biplane radiography was highly statistical significant, if this was simultaneously proven by MDCT (χ² = 7.6; p = 0.01). None of the fractures missed on biplane radiography was unstable. The mean DLP on biplane radiography was 14.5 mGy cm (range 1.9–97.8) and on MDCT 374.6 mGy cm (range 80.2–871).

Conclusions

The sensitivity and the specificity of biplane radiography in the diagnosis of fractures of the thoracic spine in patients with minor trauma are low. Considering the wide availability of MDCT that is usually necessary for taking significant therapeutic steps, the indication for biplane radiography should be very restrictive.     

核医学工作人员和受检者辐射防护现状

诊断核医学使用的放射性药物具有电离辐射效应,有可能损害核医学工作人员和受检者的健康或危及生命。笔者介绍了国内外诊断核医学近年来的发展趋势,并对核医学工作人员和受检者在不同检查项目中的辐射剂量进行重点分析,评估他们的辐射防护状况。笔者分析了近年来核医学辐射防护领域的研究,结果表明在采取有效防护措施的情况下,核医学工作人员的年有效剂量低于放射性工作人员的年剂量限值。受检者接受SPECT检查所致的辐射剂量主要来自99Tcm标记的单光子放射性药物,接受PET/CT检查所致的辐射剂量绝大部分来自CT扫描,所以选择合适的放射性药物活度和CT采集条件可以显著降低受检者的辐射剂量。     

医用X射线诊断受检者放射防护最优化研究

对于医学诊断中病人接受的剂量，个人剂量限值不适用，但放射防护最优化却可以发挥大的作用。本课题尝试将放射防护最优化的原方法运用于医学诊断的受检者防护，以期改善我国病人防护现状。调查以四川、山东和北京为重点调查区。为了最优化分析目的，本调查中将病人剂量划分为现实剂量，正当剂量和优化主一三种类型，以便分别估计管理因素和设备因素对病人剂量的影响。     

北京地区介入放射诊疗资源与防护状况调查与分析

目的 调查北京地区介入放射诊疗资源分布和放射防护状况,规范介入放射诊疗行为并促进放射防护监管措施的落实。方法 以北京地区开展介入放射诊疗工作的各级各类医疗机构为调查对象,设计专门的调查表并成立市区两级调查组,逐级调查各区域截至2020年底介入放射工作基本情况和介入放射工作人员职业健康监护情况,依据国家有关法规标准对指标参数进行分析评估。结果 截至2020年底,北京地区开展介入放射工作的医疗机构93家,800 mA(含)以上数字减影血管造影机(DSA)236台;开展介入放射学手术135 593例,年介入手术量在1 000例以上的40家,10~1 000例的41家;介入放射工作人员3 539人,持有《放射工作人员证》者为99.0%,职业健康检查、个人剂量监测和放射防护培训通过率分别为96.9%、99.5%和95.8%;配置的工作人员防护用品3 532件,其中98.9%的机构配备了分体式铅衣或一体式铅衣,但6.5%的机构未配置铅防护眼镜、54.9%的机构未配置铅防护手套。结论 北京地区介入放射诊疗防护状况和防护管理总体较好,但应结合介入放射诊疗资源分布的现况进一步完善监管机制,强化人员的在岗期间职业健康检查、放射防护培训和防护用品的配置与使用。     

Estimation of dose to the unborn child at diagnostic X-ray examinations based on data registered in RIS/PACS

The aim of this work was to determine mean absorbed doses to the unborn child in common conventional X-ray and computed tomography (CT) examinations and to find an approach for estimating foetal dose based on data registered in the Radiological Information System/Picture Archive and Communication System (RIS/PACS). The kerma-area product (KAP) and CT dose index (CTDI_vol) in common examinations were registered using a human-shaped female dosimetry phantom. Foetal doses, D_f, were measured using thermoluminescent dosimeters placed inside the phantom and compared with calculated values. Measured foetal doses were given in relation to the KAP and the CTDI_vol values, respectively. Conversion factor D_f/KAP varies between 0.01 and 3.8 mGy/Gycm², depending on primary beam position, foetus age and beam quality (tube voltage and filtration). Conversion factors D_f/CTDI_vol are in the range 0.02 – 1.2 mGy/mGy, in which the foetus is outside or within the primary beam. We conclude that dose conversion factors based on KAP or CTDI_vol values automatically generated by the RIS/PACS system can be used for rapid estimations of foetal dose for common examination techniques. Ethical Committee: No patients were involved in this study.     

Unenhanced helical computed tomography vs intravenous urography in patients with acute flank pain: accuracy and economic impact in a randomized prospective trial

Unenhanced helical computed tomography (UHCT) has evolved into a well-accepted alternative to intravenous urography (IVU) in patients with acute flank pain and suspected ureterolithiasis. The purpose of our randomized prospective study was to analyse the diagnostic accuracy of UHCT vs IVU in the normal clinical setting with special interest on economic impact, applied radiation dose and time savings in patient management. A total of 122 consecutive patients with acute flank pain suggestive of urolithiasis were randomized for UHCT (n=59) or IVU (n=63). Patient management (time, contrast media), costs and radiation dose were analysed. The films were independently interpreted by four radiologists, unaware of previous findings, clinical history and clinical outcome. Alternative diagnoses if present were assessed. Direct costs of UHCT and IVU are nearly identical (310/309 Euro). Indirect costs are much lower for UHCT because it saves examination time and when performed immediately initial abdominal plain film (KUB) and sonography are not necessary. Time delay between access to the emergency room and start of the imaging procedure was 32 h 7 min for UHCT and 36 h 55 min for IVU. The UHCT took an average in-room time of 23 min vs 1 h 21 min for IVU. Mild to moderate adverse reactions for contrast material were seen in 3 (5%) patients. The UHCT was safe, as no contrast material was needed. The mean applied radiation dose was 3.3 mSv for IVU and 6.5 mSv for UHCT. Alternative diagnoses were identified in 4 (7%) UHCT patients and 3 (5%) IVU patients. Sensitivity and specificity of UHCT and IVU was 94.1 and 94.2%, and 85.2 and 90.4%, respectively. In patients with suspected renal colic KUB and US may be the least expensive and most easily accessable modalities; however, if needed and available, UHCT can be considered a better alternative than IVU because it has a higher diagnostic accuracy and a better economic impact since it is more effective, faster, less expensive and less risky than IVU. In addition, it also has the capability of detecting various additional renal and extrarenal pathologies. An erratum to this article is available at .     

Cycle-Consistent Generative Adversarial Network: Effect on Radiation Dose Reduction and Image Quality Improvement in Ultralow-Dose CT for Evaluation of Pulmonary Tuberculosis

ObjectiveTo investigate the image quality of ultralow-dose CT (ULDCT) of the chest reconstructed using a cycle-consistent generative adversarial network (CycleGAN)-based deep learning method in the evaluation of pulmonary tuberculosis.Materials and MethodsBetween June 2019 and November 2019, 103 patients (mean age, 40.8 ± 13.6 years; 61 men and 42 women) with pulmonary tuberculosis were prospectively enrolled to undergo standard-dose CT (120 kVp with automated exposure control), followed immediately by ULDCT (80 kVp and 10 mAs). The images of the two successive scans were used to train the CycleGAN framework for image-to-image translation. The denoising efficacy of the CycleGAN algorithm was compared with that of hybrid and model-based iterative reconstruction. Repeated-measures analysis of variance and Wilcoxon signed-rank test were performed to compare the objective measurements and the subjective image quality scores, respectively.ResultsWith the optimized CycleGAN denoising model, using the ULDCT images as input, the peak signal-to-noise ratio and structural similarity index improved by 2.0 dB and 0.21, respectively. The CycleGAN-generated denoised ULDCT images typically provided satisfactory image quality for optimal visibility of anatomic structures and pathological findings, with a lower level of image noise (mean ± standard deviation [SD], 19.5 ± 3.0 Hounsfield unit [HU]) than that of the hybrid (66.3 ± 10.5 HU, p < 0.001) and a similar noise level to model-based iterative reconstruction (19.6 ± 2.6 HU, p > 0.908). The CycleGAN-generated images showed the highest contrast-to-noise ratios for the pulmonary lesions, followed by the model-based and hybrid iterative reconstruction. The mean effective radiation dose of ULDCT was 0.12 mSv with a mean 93.9% reduction compared to standard-dose CT.ConclusionThe optimized CycleGAN technique may allow the synthesis of diagnostically acceptable images from ULDCT of the chest for the evaluation of pulmonary tuberculosis.     

320排CT冠状动脉成像:100 kV对不同体质量者图像质量、噪声及剂量的影响

目的 探讨100 kV对不同体质量者320排CT冠状动脉成像(CTCA)图像质量、噪声及剂量的影响.方法 连续搜集采用100 kV进行320排CT冠状动脉成像检查者472例,男254例,女218例,平均年龄(60.5±12.2)岁.其中15例心律不齐,4例频发早搏.心率＜65次/min者,曝光70％ ～80％ R-R时间窗;心率＞65次/min者,曝光30％～80％ R-R时间窗.按体重指数(BMI)＜ 20 kg/m2、20 kg/m2≤BMI≤25 kg/m2、25 kg/m2＜ BMI≤30 kg/m2分为3组.图像质量采用双盲5分评分法(1分为不能诊断,5分为图像质量优),并计算有效辐射剂量(ED).以感兴趣区(ROI)大小为2 cm×2 cm进行升主动脉根部层面噪声标准差(SD)的测量.评价每组间图像质量、SD及ED的差异.结果 图像质量评分4分以上占90.25％ (426/472).3组图像质量评分、SD及ED分别为(4.71±0.65)分、(4.60±0.78)分、(4.62±0.80)分;(26.13±6.59) HU、(30.25 ±7.15)HU、(33.94±7.44)HU; (4.80 ±2.67)mSv、(4.70±3.04) mSv、(4.20 ±2.81)mSv.3组间比较SD差异有统计学意义(P=0.000),图像质量评分及ED差异无统计学意义(P＞0.05).结论 320排CT在25 kg/m2＜ BMI≤30 kg/m2时采用100 kV行CTCA,图像质量能够满足临床诊断需求.使用70％～80％ R-R时间窗曝光,可进一步有效减少ED.     

Bonn call for action and the unfinished task of radiation protection of children and adolescents in low and middle-income countries: A focus on Sub-Saharan Africa

ObjectivesThe Bonn call for action, with the theme: “Setting the scene for the next decade,” was declared over nine years ago to strengthen radiation protection in medicine. This study reviews key actions and activities related to radiation protection of children and adolescents consistent with the Bonn call for action in sub-Saharan Africa to highlight progress and identify existing gaps.Key findingsA lot has happened since the declaration of the Bonn call-for-action such as a follow-up conference in 2017 on achieving change in the practice of radiation protection. However, there exists a huge gap that needs to be filled in the radiation protection of children and adolescents in low and middle-income countries particularly sub-Saharan Africa, where limited resources in health compete with radiation protection demands. Some of the gaps that remain are the apparent lack of implementation of the use of referral guidelines and establishment of national and regional diagnostic reference levels for paediatric imaging among others.ConclusionSeveral strides have been achieved on a global scale for the Bonn call for action, ranging from the justification of medical exposures to the current drive for radiation safety culture in medical imaging. However, several unmet needs for radiation protection for children and adolescents remain such as implementation of referral guidelines for justification and paediatric diagnostic reference levels.Implications for practiceStep up actions and close collaboration is required to strengthen the practice of paediatric radiation protection in low and middle-income countries because children account for a greater proportion of the population and are vulnerable to the negative effects of radiation like possible cancer induction.     

Chest CT in patients with shortness of breath: Comparing high pitch CT and conventional CT on respiratory artefacts and dose

IntroductionTo investigate chest respiratory artefact reduction using High Pitch Dual Source Computed Tomography (HPCT) compared to conventional CT (CCT) in symptomatic patients with shortness of breath.MethodsForty patients were prospectively examined on a second-generation Dual Source scanner. They were randomly divided into two groups: twenty patients underwent an experimental HPCT protocol and twenty control cases CCT protocol. Respiratory artefacts were evaluated using an ordinal score (0, 1 and 2) assigned by two readers with five and thirty years of experience. A qualitative assessment was performed using two categorical groups, group 1 = acceptable and group 2 = unacceptable. Dose Length Product (DLP) was compared.ResultsThe two groups showed a statistical difference in artefacts reduction (p < 0.0001). HPCT demonstrated no artefacts in 82% of cases, while CCT showed no artefacts in 39% of cases. DLP showed no statistical differences (p = 0.6) with mean = 266.9 for HPCT and mean = 282.65 for CCT. HPCT provides high table speed in the z-direction allowing a high temporal resolution, which reduces respiratory artefacts during free-breathing acquisition. Despite the use of two x-ray tubes, the HPCT did not increase the dose to the patient but provided the highest images quality.ConclusionsIn the emergency setting, HPCTs have been critical for achieving good image quality in uncooperative patients.Implications for practiceAcute respiratory failure is a common emergency department presentation, and the choice of high-speed acquisition CT may increase image quality.     

Dose reduction in computed tomography: the effect of eye and testicle shielding on radiation dose measured in patients with beryllium oxide-based optically stimulated luminescence dosimetry

The aim of this study was to assess the effect of eye and testicle shielding on radiation dose to the lens and the testes of patients undergoing CT examinations. Fifty-one male patients underwent CT twice with identical protocols initially without, the second time with protective garments. Doses to the testes and the lenses were recorded with beryllium oxide-based dosimeters. The dose to the testes and lenses from CT exposure was reduced by 96.2% ± 1.7% and 28.2% ± 18.5%, when testicle and eye shielding was used, respectively. The effect of the eye shielding on the eye lens dose was found to depend on the x-ray tube position when the eye is primarily exposed during the scan. The maximum eye lens dose reduction achieved was found to be 43.2% ± 6.5% corresponding to the anterior position of the tube. A significant correlation between the patient’s body mass index and dose exposure could not be found. Eye and testicle shields, apart from being inexpensive and easy to use, were proven to be effective in reducing eye lens and testicle radiation dose burden from CT exposures.     

Radiation Dose Reduction of Chest CT with Iterative Reconstruction in Image Space - Part I: Studies on Image Quality Using Dual Source CT

Objective

To determine whether the image quality (IQ) is improved with iterative reconstruction in image space (IRIS), and whether IRIS can be used for radiation reduction in chest CT.

Materials and Methods

Standard dose chest CT (SDCT) in 50 patients and low dose chest CT (LDCT) in another 50 patients were performed, using a dual-source CT, with 120 kVp and same reference mAs (50 mAs for SDCT and 25 mAs for LDCT) employed to both tubes by modifying a dual-energy scan mode. Full-dose data were obtained by combining the data from both tubes and half-dose data were separated from a single tube. These were reconstructed by using a filtered back projection (FBP) and IRIS: full-dose FBP (F-FBP); full-dose IRIS (F-IRIS); half-dose FBP (H-FBP) and half-dose IRIS (H-IRIS). Objective noise was measured. The subjective IQ was evaluated by radiologists for the followings: noise, contrast and sharpness of mediastinum and lung.

Results

Objective noise was significantly lower in H-IRIS than in F-FBP (p < 0.01). In both SDCT and LDCT, the IQ scores were highest in F-IRIS, followed by F-FBP, H-IRIS and H-FBP, except those for sharpness of mediastinum, which tended to be higher in FBP. When comparing CT images between the same dose and different reconstruction (F-IRIS/F-FBP and H-IRIS/H-FBP) algorithms, scores tended to be higher in IRIS than in FBP, being more distinct in half-dose images. However, despite the use of IRIS, the scores were lower in H-IRIS than in F-FBP.

Conclusion

IRIS generally helps improve the IQ, being more distinct at the reduced radiation. However, reduced radiation by half results in IQ decrease even when using IRIS in chest CT.     

Assessment of the awareness of radiation protection and related concepts among nursing staff mainly working in diagnostic imaging units,cath-labs and operation theatres in Sri Lanka: A survey-based study

IntroductionThis study was carried out to evaluate the awareness of radiation protection, radiation types, medical imaging equipment and radiation effects among nurses for the first time in Sri Lanka. Since nurses are involved as direct caregivers in diagnostic and therapeutic radiography and radiation treatment procedures, they need to have a good understanding of the areas mentioned above.MethodsA self-administered questionnaire was used to collect data from 391 nurses working in hospitals, clinics, and other healthcare settings. Forwarded questions gathered the participants' demographic details and assessed their awareness of radiation protection, medical imaging equipment, radiation type and radiation effects. The average score per awareness area for each demographic characteristic was calculated based on the responses. Additionally, the percentage of participants who scored above 50 and 75 was calculated for each awareness area.ResultsThe majority were female participants (81.1%) and possessed a diploma in nursing (66.0%) with 10.8 years of average work experience. 92.3%, 74.7%, 69.8% and 22.3% of the participants scored more than 50 marks for the questions related to radiation protection, medical imaging equipment, radiation type and radiation effects, respectively. The level of nursing education and prior training in radiation protection significantly influenced all awareness areas, whereas participants with a graduate qualification in nursing and with prior radiation protection training scored the highest average marks.ConclusionBased on the scores obtained, the Sri Lankan nurses have satisfactory awareness of the essential concepts related to radiation types, medical imaging equipment and radiation protection. However, there is a significant lacking of awareness of radiation effects. This can be attributed to the fact that most participants did not have any formal training in radiation protection. The results implicate that proper training in radiation protection can significantly influence awareness of radiation protection and related concepts. Therefore, it is a timely requirement to initiate short awareness programs and continuing education programs on radiation protection for nurses working in specialised radiation units.Implications for practiceThe study suggests the necessity of initiating continuous education programs for nursing staff radiation protection to overcome the awareness gaps.     

深化医学教学改革,加强介入放射学后备力量培养——医学生调查引起的反思

近年来介入放射学在疾病诊疗中的应用得到了广泛普及和认可,然而介入放射学科却面临着患者流失、人员缺乏等诸多挑战。本文着重从医学院校介入放射学教学现状和学生对本学科的认识上剖析其原因,以探求缓解供求矛盾的方法。     

64层螺旋CT胸痛三联排查扫描的新扫描协议设计与可行性研究：全主动脉、冠状动脉与肺动脉一站式成像

目的:评价64层螺旋CT改良胸痛三联排查(TRO)扫描(覆盖整个主动脉)的图像质量、辐射剂量及其临床价值.方法:连续选取2013年1月-2015年8月行改良TRO扫描的17例患者作为实验组,另连续选取2014年3月-2015年8月行常规TRO扫描的37例患者作为对照组,所有研究对象心率≤70次/分.采用秩和检验与两独立样本t检验比较两组的图像质量、辐射剂量及对比剂剂量.结果:实验组与对照组冠状动脉评分分别为(4.56±0.66)和(4.62±0.56)分(Z=-0.558,P=0.557).实验组与对照组主动脉根部CT值分别为(385.88±42.36)和(364.46±40.62) HU(t=1.748,P=0.091),肺动脉根部CT值分别为(354.29±68.44)和(332.46±49.97) HU(t=1.324,P=0.191).实验组与对照组有效剂量分别为(33.99±9.07)和(24.39±8.70)mSv(t=3.715,P=0.000);实验组与对照组对比剂剂量分别为(145.76±9.71)和(112.62±15.11)mL(t=8.269,P=0.000).结论:改良TRO对于低心率患者是可行且有效的,可以提高64层螺旋CT的适用范围,具有一定临床价值.