Analysis of radiation exposure data from common radiological procedures in Dutch hospitals

IntroductionIn the Netherlands, Diagnostic Reference Levels (DRLs) have not been based on a national survey as proposed by ICRP. Instead, local exposure data, expert judgment and the international scientific literature were used as sources. This study investigated whether the current DRLs are reasonable for Dutch radiological practice.MethodsA national project was set up, in which radiography students carried out dose measurements in hospitals supervised by medical physicists. The project ran from 2014 to 2017 and dose values were analysed for a trend over time. In the absence of such a trend, the joint yearly data sets were considered a single data set and were analysed together. In this way the national project mimicked a national survey.ResultsFor six out of eleven radiological procedures enough data was collected for further analysis. In the first step of the analysis no trend was found over time for any of these procedures. In the second step the joint analysis lead to suggestions for five new DRL values that are far below the current ones. The new DRLs are based on the 75 percentile values of the distributions of all dose data per procedure.ConclusionThe results show that the current DRLs are too high for five of the six procedures that have been analysed. For the other five procedures more data needs to be collected. Moreover, the mean weights of the patients are higher than expected. This introduces bias when these are not recorded and the mean weight is assumed to be 77 kg.Implications for practiceThe current checking of doses for compliance with the DRLs needs to be changed. Both the procedure (regarding weights) and the values of the DRLs should be updated.     

Occupational radiation exposure from fluoroscopically guided percutaneous transhepatic biliary procedures

PURPOSE: The aim of this study was to determine occupational dose levels for projections commonly used in fluoroscopically guided percutaneous transhepatic biliary (PTB) drainage and stent placement procedures. METHODS: Exposure data from 71 consecutive PTB examinations were analyzed to determine average examination parameters for biliary drainage and stent placement procedures. An anthropomorphic phantom was exposed at three projections common in PTB interventions according to the actual geometric parameters recorded in the patient study. Scattered air-kerma dose rates were measured for neck, waist, and gonad levels at various sites in the interventional radiology laboratory. To produce technique- and instrumentation-independent data, dose rate values were converted to dose-area product (DAP)-normalized air-kerma values. In addition, sets of thermoluminescent dosimetry crystals were placed in both hands of the interventional radiologist to monitor doses during all PTB procedures. RESULTS: Isodose maps of DAP-normalized air-kerma doses in the interventional laboratory for projections commonly used in PTB procedures are presented. To facilitate effective dose estimation, normalized dosimetric data at the interventional radiologist's position are presented for left and right access drainage procedures, metallic stent placement only, and drainage and metallic stent placement in one-session procedures with and without under-couch shielding. Doses to the hands of interventional radiologists are presented for left and right transhepatic biliary access and metallic stent placement. CONCLUSIONS: Body level-specific normalized air-kerma distributions from commonly used projections in PTB procedures may be useful to accurately quantify dose, maximum workloads, and possible radiogenic risks delivered to medical personnel working in the interventional radiology laboratory. Normalized dose data presented will enable occupational exposure estimation from other institutions.     

Compliance to Diagnostic Reference Levels for radiation exposure in common radiological procedures in Dutch hospitals: A nation-wide survey carried out by medical imaging students

IntroductionIn the Netherlands, hospitals have difficulty in implementing the formal procedure of comparing radiation dose values to Diagnostic Reference Levels (DRLs).MethodsTo support the hospitals, train radiography students, and carry out a nationwide dose survey, diagnostic radiography students performed 125 DRL comparisons for nine different procedures in 29 radiology departments. Students were instructed at three Dutch Universities of Applied Sciences with a radiography programme and supervised by medical physicists from the participating hospitals.ResultsAfter a pilot study in the western part of the country in eight hospitals, this study was enlarged to involve 21 hospitals from all over the Netherlands. The 86 obtained dose comparisons fall below the DRLs in 97% of all cases. This very high compliance may have been enhanced by the voluntary participation of hospitals that are confident about their performance.ConclusionThe results indicate that the current DRLs that were not based on a national survey, may need to be updated, sometimes to half their current value. For chest and pelvis examinations the DRLs could be lowered from 12 and 300 μGy·m² to the 75-percentile values found in this study of 5,9 and 188 μGy·m², respectively.     

The impact of radiological equipment on patient radiation exposure during endovascular aortic aneurysm repair

Objectives

To compare the patient radiation dose during endovascular aortic aneurysm repair (EVAR) using different types of radiological systems: a mobile fluoroscopic C-arm, mobile angiographic and fixed angiographic equipment.

Methods

Dose–area products (DAP) were obtained from a retrospective study of 147 consecutive patients, subjected to 153 EVAR procedures during a 3.5-year period. On the basis of these data, entrance surface dose (ESD) and effective dose (ED) were calculated. EVARs were performed using a fluoroscopic C-arm, mobile or fixed angiographic equipment in 79, 26 and 48 procedures, respectively.

Results

Fluoroscopy times were essentially equivalent for all the systems, ranging from 15 to 19?min. The clinical outcomes were not significantly different among the systems. Statistically significant differences among radiological equipment grouping were found for DAP (mobile C-arm: 32?±?20?Gy?cm²; mobile angiography: 362?±?164?Gy?cm²; fixed angiography: 464?±?274?Gy?cm²; P?<?10^?6), for ESD (mobile C-arm: 0.18?±?0.11?Gy; mobile angiography: 2.0?±?0.8?Gy; fixed angiography: 2.5?±?1.5?Gy; P?<?10^?6) and ED (mobile C-arm: 6.2?±?4.5?mSv; mobile angiography: 64?±?26?mSv; fixed angiography: 129?±?76?mSv; P?<?10^?6).

Conclusions

Radiation dose in EVAR is substantially less with a modern portable C-arm than with a fixed or mobile dedicated angiographic system.

Key Points

? Fluoroscopy during endovascular aortic aneurysm repair can impart a substantial radiation dose. ? Radiation doses during EVAR are higher when using mobile/fixed angiographic systems. ? Mobile C-arm fluoroscopy imparts a lower dose with an equivalent clinical outcome. ? Procedures need to be dose-optimised when using mobile/fixed angiographic systems.     

主动脉瘤血管内治疗中影像学设备对于病人辐射剂量的影响

目的采用移动透视C臂、移动血管造影机和固定血管造影机等不同的影像学设备,比较病人在进行主动脉瘤血管内治疗(EVAR)中的辐射剂量。材料与方法回顾研究3.5年时间内147例病人所进行的153次EVAR操作的剂量面积乘积(DAP)。根据这些数据,计算入射表面剂量(ESD)和有效剂量(ED)。使用透视C臂、移动和固定血管造影机的例数分别为79、26和48例。结果所有设备所采用的透视时间基本上相同,为15～19min。不同系统间的临床转归没有显著差异。不同影像设备间,DAP[移动C臂:(32±20)Gy.cm2;移动血管机:(362±164)Gy.cm2;固定血管机:(464±274)Gy.cm2;P<10-6]、ESD(移动C臂:(0.18±0.11)Gy;移动血管机:(2.0±0.8)Gy;固定血管机:(2.5±1.5)Gy;P<10-6)和ED[移动C臂:(6.2±4.5)mSv;移动血管机:(64±26)mSv;固定血管机:(129±76)mSv;P<10-6]差异具有统计学意义。结论采用现代便携式C臂进行EVAR时的辐射剂量远小于专用的固定或移动血管造影机。     

Effect of the learning process on procedure times and radiation exposure for CT fluoroscopy-guided percutaneous biopsy procedures

PURPOSE: To assess if the learning process associated with computed tomography fluoroscopy (CTF) technology influences procedure and fluoroscopy times for percutaneous biopsy procedures. MATERIALS AND METHODS: Prospective analysis of the initial 250 consecutive patients who underwent percutaneous biopsy with use of a CT scanner equipped with rapid image reconstruction and fluoroscopic capabilities in a 24-month period. All procedures were performed with both continuous and spot fluoroscopic technique, with typical radiation parameters of 50 mA, 120 kV, and a 10-mm-slice thickness. The procedures were all performed by a single experienced interventional radiologist to limit the variables of physician expertise, interventional materials used, and biopsy approach. The subject group was divided into five equal consecutive groups of 50 patients. In each subgroup, the authors recorded mean lesion size, success, and complication rates, as well as mean procedure and fluoroscopy times. RESULTS: The five subgroups were similar patient populations as documented by the absence of statistically significant differences when comparing mean lesion size, procedure success, and complication rates (P > .05; ANOVA test). A statistically significant decrease in mean fluoroscopy (groups 1-5: 50.26 vs 45.24 vs 33.86 vs 32.68 vs 25.8 sec/patient) and mean procedure times (groups 1-5: 30.08 vs 27.9 vs 26.34 vs 25.6 vs 21.6 min/patient) was recorded between the patient subgroups (P < .0001; ANOVA test). CONCLUSION: The learning process associated with CTF technology impacts procedure parameters by decreasing both mean procedure and fluoroscopy times, thereby increasing patient turnover and decreasing radiation exposure to the patient and the operator.     

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.     

Significantly reduced radiation exposure to operators during kyphoplasty and vertebroplasty procedures: methods and techniques

BACKGROUND AND PURPOSE: Vertebroplasty and kyphoplasty can be associated with significant radiation exposure to the operator. We compared the exposure levels to an operator performing vertebral fracture augmentation with vertebroplasty and kyphoplasty, to assess a cement injection and a monitoring technique designed to reduce this exposure. METHODS: A neuroradiologist performed 189 consecutive vertebral augmentation procedures in 135 patients with osteoporotic compression fractures by using a bilateral approach with biplane pulse fluoroscopy at 7.5 pulses/second. Cement delivery was performed with intermittent fluoroscopy with kyphoplasty and vertebroplasty by using syringes or continuous fluoroscopic monitoring with a cement delivery system (CDS). Data collection included time and operator exposure parameters. RESULTS: A total of 87 kyphoplasty procedures, 82 vertebroplasty procedures with a CDS (VP-CDS), and 20 vertebroplasty procedures with syringes (VP-S) were safely performed. Mean fluoroscopy time for device positioning was 4.3 minutes for each procedure type. Mean fluoroscopy time (minutes) for cement delivery was significantly different for the 3 procedure types; 2.1 for kyphoplasty, 3.7 for VP-CDS, and 1.5 for VP-S (P < .0001). Comparable mean radiation exposure rates (microsieverts/minute) were 0.8 for kyphoplasty, 1.1 for VP-CDS, and 0.3 for VP-S during device-positioning and 1.7 for kyphoplasty, 2.9 for VP-CDS, and 0.2 for VP-S during cement injection (P < .002). CONCLUSION: Use of the modified cement injection technique and intermittent fluoroscopy with kyphoplasty and vertebroplasty with syringes results in a significantly lower operator exposure rate compared with vertebroplasty with a CDS.     

Evolution of radiation exposure to operator in diagnostic and interventional radiology procedures and reduction of radiation exposure to operator with protective device

A study was performed to evaluate operator dose during diagnostic and interventional radiology procedures (IVR) and to establish methods of operator dose reduction with a radiation protective device. Operator dose was measured by glass dosimeters worn on the neck and on the abdomen outside the lead apron. In addition, the dose of the primary beam at the collimator surface was measured, which made it possible to define the correlation between the entrance air kerma, measured with Skin Dose Monitor, and operator dose exposed during the monitored procedure. IVR protectors were developed to decrease the amount of scatter radiation received by operators performing the procedures, and their effects were evaluated in abdominal and cardiac angiography procedures. The average effective dose and doses of the neck and abdomen outside the lead apron, estimated for individual procedures, were as follows: abdominal angiography procedures: effective dose, 0.07 mSv; neck area, 0.18 mSv; abdominal area, 0.51 mSv; cardiac angiography procedures: effective dose, 0.07 mSv; neck area, 0.13 mSv; abdominal area, 0.68 mSv. Operator doses were well correlated with exposure dose in abdominal angiography procedures (diagnostic procedure r=0.84, IVR r=0.77). It was found that 68.0% of the effective dose in abdominal angiography procedures and 43.0% of the effective dose in cardiac angiography procedures could be reduced by the use of IVR protectors. Operator and patient doses in interventional radiology were interdependent. The minimization of operator doses is particularly important during interventional radiology, and it is necessary to be aware of practical radiation protection procedures. Measures that reduce patient dose will also reduce occupational exposure. Moreover, operator dose could be substantially reduced by the use of IVR protectors in addition to wearing a protective lead apron during IVR. It was suggested that IVR protectors are effective radiation protective devices in interventional radiology procedures.     

PET imaging for differentiating recurrent brain tumor from radiation necrosis

The exact incidence of true radiation necrosis is largely unknown. It is probably much less frequent than indicated by MR or CT findings. Differentiating radiation necrosis from recurrent tumor is a diagnostic challenge, however, and has important implications for the patient's management. Even though the first results were published 20 years ago, the total number of case studies using FDG-PET in this indication remains limited. Several reports are also hampered by methodologic limitations. The technique has been largely criticized, notably in articles that themselves were not completely free of methodological flaws. Overall however, FDG-PET seems to be a valuable clinical tool. As a general rule, suspicious lesions on MR imaging that show increased FDG uptake (ie, uptake equal to or great than that in normal cortex) are likely to represent tumor recurrence. Sensitivity is an issue, especially but not exclusively with low-grade gliomas. Although false-positive results may occur, specificity is usually high in routine clinical practice. Coregistration with MR imaging surely improves the diagnostic performances of FDG-PET because it helps delineate the suspicious area. Another important aspect is the prognostic value of FDG uptake, which is now well established. It seems clear that only the combination of FDG with a radiolabeled amino acid analogue (MET or a more recent fluorinated compound) can provide a comprehensive characterization of suspected brain tumor recurrence.