Establishing diagnostic reference levels for interventional procedures in Kenya

PurposeTo quantify ionizing radiation exposure to patients during interventional procedures and establish national diagnostic reference levels (NDRLs) for clinical radiation exposure management.MethodsThe cumulative reference point air kerma, kerma area product, fluoroscopy time and other operational parameters were monitored for 50 children and 261 adult patient procedures in five catheterization medical laboratories in Kenya. To estimate the risk associated with the exposure, effective doses were derived from the kerma area product using conversion factors from Monte Carlo models.ResultsAbout 3% of the measured cumulative reference point air kerma for the interventional procedures approached the threshold dose limit with the potential to cause deterministic effects such as skin injuries. In interventional cardiology, the results obtained for both children and adults indicated 33% were below the diagnostic reference levels (DRLs). In adult interventional radiology, 29% for cumulative reference point air kerma, and 43% for kerma area product and fluoroscopy time respectively were below the diagnostic reference levels. NDRLs were proposed for routine use in the procedures considered and for the non-existent DRLs situations in paediatric interventional cardiology.ConclusionThe measured patient doses were above the DRLs available in the literature indicating a need for radiation optimization through, continuous monitoring and recording of patient dose. To promote radiation safety, facilities performing interventional procedures need to establish a radiation monitoring notification threshold for possible deterministic effects, in addition to the use of the newly established national diagnostic reference levels, as a quality assurance measure.     

Monitoring neurointerventional radiation doses using dose-tracking software: implications for the establishment of local diagnostic reference levels

Objectives

There is potential for high radiation exposure during neurointerventional procedures. Increasing regulatory requirements mandate dose monitoring of patients and staff, and justification of high levels of radiation exposure. This paper demonstrates the potential to use radiation dose-tracking software to establish local diagnostic reference levels.

Methods

Consecutive neurointerventional procedures, performed in a single institution within a one-year period, were retrospectively studied. Dose area product (DAP) data were collected using dose-tracking software and clinical data obtained from a prospectively generated patient treatment database.

Results

Two hundred and sixty-four procedures met the selection criteria. Median DAP was 100 Gy.cm² for aneurysm coiling procedures, 259 Gy.cm² for arteriovenous malformation (AVM) embolisation procedures, 87 Gy.cm² for stroke thrombolysis/thrombectomy, and 74 Gy.cm² for four-vessel angiography. One hundred and nine aneurysm coiling procedures were further studied. Six significant variables were assessed using stepwise regression analysis to determine effect on DAP. Aneurysm location (anterior vs posterior circulation) had the single biggest effect (p = 0.004).

Conclusions

This paper confirms variable radiation exposures during neurointerventional procedures. The 75th percentile (used to define diagnostic reference levels) of DAP measurements represents a reasonable guidance metric for monitoring purposes. Results indicate that aneurysm location has the greatest impact on dose during coiling procedures and that anterior and posterior circulation coiling procedures should have separate diagnostic reference levels.

Key Points

? Dose-tracking software is useful for monitoring patient radiation dose during neurointerventional procedures? This paper provides a template for methodology applicable to any interventional suite? Local diagnostic reference levels were defined by using the 75th percentile of DAP as per International Commission on Radiological Protection recommendations? Aneurysm location is the biggest determinant of radiation dose during coiling procedures.? Anterior and posterior circulation coiling procedures should have separate diagnostic reference levels.

     

The establishment of local diagnostic reference levels for paediatric interventional cardiology

BackgroundThere is a paucity of information worldwide on radiation exposure in paediatric interventional cardiology. At present Nationally established Diagnostic Reference Levels exist for adult interventional cardiology procedures in the UK but little data is available for paediatrics. In addition, interventional cardiology has been identified as one the highest contributors to medical exposure to ionising radiation and children are more radiosensitive than adults.ObjectiveThis study sought to determine current radiation dose levels in paediatric interventional cardiology (IC) with a view to establishing local diagnostic reference levels (LDRL).MethodsRadiation dose and examination details were recorded for 354 paediatric patients examined by IC in a specialised paediatric centre in Europe. Radiation doses were recorded using a Dose Area Product meter along with examination details. Procedures were categorised as either diagnostic (A) or therapeutic (B). Data was further sub-divided into five age ranges; (1) newborn <1 year (2) 1 <5 years (3) 5 <10 years (4) 10 <15 years (5) 15 years and over. Proposed LDRL were calculated from the mean dose area product readings.ResultsThe mean patient age was 2.6 years (range 0.0 days–16 years) and weight was 14.9 kg (range 2.4–112 kg). LDRL for the five age groupings were calculated as 190, 421, 582, 1289 and 1776 cGycm² respectively.ConclusionLocal dose reference levels have been proposed for paediatric IC and can be used as a benchmark for other hospitals to compare against their own radiation doses.     

Validation of the TOPAS Monte Carlo toolkit for HDR brachytherapy simulations

PurposeThe goal of this work is to validate the user-friendly Geant4-based Monte Carlo toolkit TOol for PArticle Simulation (TOPAS) for brachytherapy applications.Methods and MaterialsBrachytherapy simulations performed with TOPAS were systematically compared with published TG-186 reference data. The photon emission energy spectrum, the air-kerma strength, and the dose-rate constant of the model-based dose calculation algorithm (MBDCA)-WG generic Ir-192 source were extracted. For dose calculations, a track-length estimator was implemented. The four Joint AAPM/ESTRO/ABG MBDCA-WG test cases were evaluated through histograms of the local and global dose difference volumes. A prostate, a palliative lung, and a breast case were simulated. For each case, the dose ratio map, the histogram of the global dose difference volume, and cumulative dose-volume histograms were calculated.ResultsThe air-kerma strength was (9.772 ± 0.001) × 10^?8 U Bq^?1 (within 0.3% of the reference value). The dose-rate constant was 1.1107 ± 0.0005 cGy h^?1 U^?1 (within 0.01% of the reference value). For all cases, at least 96.9% of voxels had a local dose difference within [?1%, 1%] and at least 99.9% of voxels had a global dose difference within [?0.1%, 0.1%]. The implemented track-length estimator scorer was more efficient than the default analog dose scorer by a factor of 237. For all clinical cases, at least 97.5% of voxels had a global dose difference within [?1%, 1%]. Dose-volume histograms were consistent with the reference data.ConclusionsTOPAS was validated for high-dose-rate brachytherapy simulations following the TG-186 recommended approach for MBDCAs. Built on top of Geant4, TOPAS provides broad access to a state-of-the-art Monte Carlo code for brachytherapy simulations.     

The combined application of the contrast-to-noise index and 80 kVp for cardiac CTA scanning before atrial fibrillation ablation reduces radiation dose exposure

IntroductionTo compare the radiation dose, diagnostic accuracy, and the resultant ablation procedures using 80 and 120-kVp cardiac computed tomography angiography (CCTA) protocols with the same contrast-to-noise ratio in patients scheduled for atrial fibrillation (AF) ablation.MethodsThis retrospective study was performed following institutional review board approval. We divided 140 consecutive patients who had undergone CCTA using a 64-MDCT scanner into two equal groups. Standard deviation (SD) of the CT number was set at 25 Hounsfield units (HU) for the 120-kVp protocol. To facilitate a reduction in radiation dose it was set at 40 HU for the 80 kVp protocol. We compared the two protocols with respect to the radiation dose, the diagnostic accuracy for detecting left atrial appendage (LAA) thrombi, matching for surface registration, and the resultant ablation procedures.ResultsAt 120 kVp, the dose length product (DLP) was 2.2 times that at 80 kVp (1269.0 vs 559.0 mGy cm, p < 0.01). The diagnostic accuracy for thrombus detection was 100% using both protocols. There was no difference between the two protocols with respect to matching for surface registration. The protocols did not differ with respect to the subsequent time required for the ablation procedures and the ablation fluoroscopy time, and the radiation dose (p = 0.54, 0.33, and 0.32, respectively).ConclusionFor the same CNR, the DLP at 80 kVp (559.0 mGy cm) was 56% of that delivered at 120 kVp (1269.0 mGy cm). There was no reduction in diagnostic accuracy.Implications for practiceMaintaining CNR allows for a reduction in the radiation dose without reducing the image quality.     

A comparison of patient skin doses before and after replacement of a neurointerventional fluoroscopy unit

AIM: After several embolization patients presented with radiation-induced skin injury in our neuroradiology centre, replacement of the centre's interventional fluoroscopy unit was prioritized. The aims of the present study were to compare the maximum skin dose delivered to each patient by the old and new units, to devise a method of estimating skin dose from the displayed dose-area product and to set local reference doses. MATERIALS AND METHODS: On the old unit, skin dose was measured using thermoluminescent dosimeters on 12 patients undergoing Gugliemi detachable coil embolization. Similar skin dose measurements were undertaken and the dose-area product was recorded for a further 12 patients on the new unit. RESULTS: The maximum skin dose measured on each patient on the old and new units had a mean of 2.2 Gy and 0.47 Gy, respectively, and a maximum of 4.1 Gy and 1.0 Gy, respectively. Maximum dose delivered to patients' skin by the new equipment was less than a quarter of the dose from the old equipment (p < 0.0001). CONCLUSION: The large reductions in skin dose reduced the risk of patients suffering radiation injury and confirmed the validity of replacing ageing interventional fluoroscopy equipment with modern equipment that incorporates dose management systems. As patient skin dose was correlated with dose-area product, local reference dose levels were set in terms of dose-area product; this enabled the operator to monitor the likely maximum patient skin dose during embolization procedures. Other centres could use a similar method to set their own reference doses.     

Local skin and eye lens equivalent doses in interventional neuroradiology

Purpose

To assess patient skin and eye lens doses in interventional neuroradiology and to assess both stochastic and deterministic radiation risks.

Methods

Kerma–area product (P _KA) was recorded and skin doses measured using thermoluminescence dosimeters. Estimated dose at interventional reference point (IRP) was compared with measured absorbed doses.

Results

The average and maximum fluoroscopy times were 32 and 189 min for coiling and 40 and 144 min for embolisation. The average and maximum P _KA for coiling were 121 and 436 Gy cm², respectively, and 189 and 677 Gy cm² for embolisation. The average and maximum values of the measured maximum absorbed skin doses were 0.72 and 3.0 Sv, respectively, for coiling and 0.79 and 2.1 Sv for embolisation. Two out of the 52 patients received skin doses in excess of 2 Sv. The average and maximum doses to the eye lens (left eye) were 51 and 515 mSv (coiling) and 71 and 289 mSv (embolisation).

Conclusion

The ratio between the measured dose and the dose at the IRP was 0.44?±?0.18 mSv/mGy indicating that the dose displayed by the x-ray unit overestimates the maximum skin dose but is still a valuable indication of the dose. The risk of inducing skin erythema and lens cataract during our hospital procedures is therefore small.     

An evaluation of the effect that the implementation of the NICE rules may have on a diagnostic imaging department for the early management of head injuries

IntroductionGuidelines by the National Institute of Clinical Excellence (NICE) for the early management of minor head injuries initiate the use of computed tomography (CT) for patients who may be at risk of developing intracranial haematoma. This retrospective study was designed to evaluate the effect the implementation of the NICE guidelines would have on the diagnostic imaging department of a local district general hospital. The main objective was to establish if there would be an increase in the number of CT head referrals for patients with minor head injuries. Secondly to assess how the implementation of these guidelines would affect the workload to the diagnostic imaging department in terms of cost and time, and to discuss the issue of radiation dose to patients.MethodA sample of 100 patients who were referred from the Accident and Emergency department (A&E) for plain skull radiographs, over a 4-month period were selected. The clinical information on each of these patients' was then extracted and a data collection sheet was to assess each patient according to the NICE criteria.Results and conclusionThe study found an 18% (n = 100) increase in the referral rate for CT heads for patients presenting with minor head injuries. It was also found that the use of these guidelines would mean a decrease in cost to the diagnostic imaging department of £324. Furthermore a saving of 10 h of radiographers' time was established, although the effective radiation dose to patients would be increased by 29 mSv.The NICE guidelines have proved efficient in identifying patients with intracranial damage although this coincides with an 18% (n = 100) increase in referral rates for CT and increased radiation dose to patients. However, the use of these guidelines would reduce workload to the diagnostic imaging department in terms of cost and time.     

Evaluation of thyroid radiation dose during abdominal Computed Tomography procedures and dose reduction effectiveness of thyroid shielding

IntroductionDuring abdominal Computed Tomography (CT) studies, vicinity organs receive a dose from scatter radiation. The thyroid is considered an organ at greater risk due to high radiosensitivity.MethodsThe primary objective of this study was to determine the entrances surface dose (ESD) to the thyroid during abdominal CT studies and to evaluate the efficiency of dose reduction by lead shielding. The calibrated thermoluminescence dosimeter (TLD) chips were used to measure the ESD during 180 contrast-enhanced (CE) and non-contrast-enhanced (NC) abdominal CT studies in the presence and absence of lead shielding.ResultsThyroid shielding reduces the ESD by 72.3% (0.55 mGy), 86.5% (2.95 mGy) and 64.0% (2.24 mGy) during NC, 3–phase and 4–phase abdominal CT scans. Also, the patient height was identified as a parameter that inversely influenced the thyroid dose, proving that the taller patients receive less dose to the thyroid. Regardless, the scan parameters such as time and display field of view (DFOV) positively impact the thyroid dose.ConclusionLead shielding can prevent the external scatter reaching the thyroid region by 64%–87% during the non-vicinity scans such as abdomen CT. However, the actual dose saving lies between 0.2% and 0.4%, compared to the total effective dose of the whole CT procedure.Implications for practiceThe thyroid shield can effectively reduce external scatter radiation during abdominal CT procedures. However, the dose saving is insignificant compared to the total effective dose from the whole examination. Therefore, the use of thyroid shielding should be carefully evaluated during CT abdomen procedures.     

An option for optimising the radiographic technique for horizontal beam lateral (HBL) hip radiography when using digital X-ray equipment

AimTo investigate the optimum technique for the horizontal beam lateral (HBL) hip projection considering image quality and radiation dose.MethodsUsing digital radiography equipment an anthropomorphic phantom was positioned for a HBL projection of the hip. Radiographic exposures were undertaken across a range of acquisition parameters (tube potentials, source to image distances, object to detector distances, with and without an anti-scatter radiation grid/additional copper filtration). Each acquisition combination was imaged three times and the dose area product (DAP) and post-AEC mAs recorded. 168 images were acquired. A single observer evaluated five anatomical areas on all images using a two-alternative force choice technique. The reference image was selected based on the current locally accepted technique. 50 images out of the original 168 were independently assessed by a further four observers to ensure reliability of the results.ResultsImage quality, when comparing all the images to the reference, was improved on in two cases; however the radiation dose had increased. 18 images had equal image quality with some having an 80% reduction in the DAP. In terms of the diagnostic acceptability, 51 were considered acceptable with a lower radiation dose.ConclusionBy optimising acquisition factors for the HBL hip projection the radiation dose to the patient can be reduced. Based on the findings the factors proposed for HBL hip projections are 90 kVp, 135 cm SID, 45 cm ODD, grid and 0.1 mm copper filtration.     

Kerma-area product is not a useful indictor of potential tissue reactions in interventional radiology

Potential for tissue reactions post interventional radiological procedure is well recognised. Identifying tissue reactions is not always straight forward and implementation of international guidance varies.This single site study investigates the appropriateness of using a kerma-area product value of 500 Gy cm² (assumed field size 100 cm²) to highlight potential skin injury/tissue reactions post interventional radiology procedures.MethodKerma-area product doses for all interventional radiological procedures over a 2 year period in a major tertiary referral hospital were retrospectively audited. A P_KA of 500 Gy cm² was used as an indicator of necessitating patient follow up for potential tissue reactions (potential peak skin dose of 3 Gy). Procedure parameters were recorded for all procedures reaching this dose. These were used to devise clinically representative phantom studies to facilitate peak skin dose measurement for each procedure identified.Results5156 interventional radiology procedures were reviewed. 13 patients registered a kerma-area product dose of 500 Gy cm² or more. 6 patients underwent percutaneous cardiac interventions and 7 had embolization of gastro-intestinal haemorrhage.Subsequent phantom studies representative of percutaneous cardiac interventions and embolization of gastro-intestinal haemorrhage procedures resulted in peak skin doses of 2.6 Gy and 1.5 Gy respectively for a P_KA value of 500 Gy cm².ConclusionA Kerma-area product of 500 Gy cm² alone is not a useful indicator of potential tissue reactions for percutaneous cardiac interventions or gastrointestinal haemorrhage embolization's. Extensive analysis of procedure parameters (particularly c arm movement, focus to skin distance and mean field size) post procedure is suggested to further quantify potential for tissue reaction.     

Local diagnostic reference levels for skeletal surveys in suspected physical child abuse

IntroductionThe purpose was to determine if an age based, local diagnostic reference level for paediatric skeletal surveys could be established using retrospective data.MethodsAll children below two years of age referred for a primary skeletal survey as a result of suspected physical abuse during 2017 or 2018 (n = 45) were retrospectively included from a large Danish university hospital. The skeletal survey protocol included a total of 33 images. Dose Area Product (DAP) and acquisition parameters for all images were recorded from the Picture Archival and Communication System (PACS) and effective dose was estimated. The 75th percentile for DAP was considered as the diagnostic reference level (DRL).ResultsThe 75th percentile for DAP was 314 mGy1cm², 520 mGy1cm² and 779 mGy1cm² for children <1 month, 1–11 months and 12 < 24 months of age respectively. However, only the age group 1–11 months had a sufficient number of children (n = 27) to establish a local DRL. Thus, for the other groups the DAP result must be interpreted with caution. Effective dose was 0.19, 0.26 and 0.18 mSv for children <1, 1–11 months and 12 < 24 months of age respectively.ConclusionFor children between 1 and 11 months of age, a local diagnostic reference level of 520 mGy1cm² was determined. This may be used as an initial benchmark for primary skeletal surveys as a result of suspected physical abuse for comparison and future discussion.Implications for practiceWhile the data presented reflects the results of a single department, the suggested diagnostic reference level may be used as a benchmark for other departments when auditing skeletal survey radiation dose.     

Evaluation of the characteristics of various types of coils for the embolization of intracranial aneurysms with an optical pressure sensor system

Introduction  

In coil embolization for an intracranial aneurysm, it is important to appropriately choose the coil most suitable for coping with various unforeseen situations. Additionally, because dense coil packing of the aneurysm sac is the most important factor to avoid a recurrence, properly selecting the coil is essential. In this article, the authors measured the coil insertion pressure of various types of coils with a newly developed sensor system, and coil characteristics were investigated.     

Reducing Radiation Dose in Pediatric Diagnostic Fluoroscopy

PurposeTo assess radiation dose in common pediatric diagnostic fluoroscopy procedures and determine the efficacy of dose tracking and dose reduction training to reduce radiation use.MethodsFluoroscopy time and radiation dose area product (DAP) were recorded for upper GIs (UGI), voiding cystourethrograms (VCUGs), and barium enemas (BEs) during a six-month period. The results were presented to radiologists followed by a 1-hour training session on radiation dose reduction methods. Data were recorded for an additional six months. DAP was normalized to fluoroscopy time, and Wilcoxon testing was used to assess for differences between groups.ResultsData from 1,479 cases (945 pretraining and 530 post-training) from 9 radiologists were collected. No statistically significant difference was found in patient age, proportion of examination types, or fluoroscopy time between the pre- and post-training groups (P ≥ .1), with the exception of a small decrease in median fluoroscopy time for VCUGs (1.0 vs 0.9 minutes, P = .04). For all examination types, a statistically significant decrease was found in the median normalized DAP (P < .05) between pre- and post-training groups. The median (quartiles) for pretraining and post-training normalized DAPs (μGy·m² per minute) were 14.36 (5.00, 38.95) and 6.67 (2.67, 17.09) for UGIs; 13.00 (5.34, 32.71) and 7.16 (2.73, 19.85) for VCUGs; and 33.14 (9.80, 85.26) and 17.55 (7.96, 46.31) for BEs.ConclusionsRadiation dose tracking with feedback, paired with dose reduction training, can reduce radiation dose during diagnostic pediatric fluoroscopic procedures by nearly 50%.     

Optimizing Staff Dose in Fluoroscopy-Guided Interventions by Comparing Clinical Data with Phantom Experiments

PurposeTo evaluate conditions for minimizing staff dose in interventional radiology, and to provide an achievable level for radiation exposure reduction.Materials and MethodsComprehensive phantom experiments were performed in an angiography suite to evaluate the effects of several parameters on operator dose, such as patient body part, radiation shielding, x-ray tube angulation, and acquisition type. Phantom data were compared with operator dose data from clinical procedures (n = 281), which were prospectively acquired with the use of electronic real-time personal dosimeters (PDMs) combined with an automatic dose-tracking system (DoseWise Portal; Philips, Best, The Netherlands). A reference PDM was installed on the C-arm to measure scattered radiation. Operator exposure was calculated relative to this scatter dose.ResultsIn phantom experiments and clinical procedures, median operator dose relative to the dose-area product (DAP) was reduced by 81% and 79% in cerebral procedures and abdominal procedures, respectively. The use of radiation shielding decreased operator exposure up to 97% in phantom experiments; however, operator dose data show that this reduction was not fully achieved in clinical practice. Both phantom experiments and clinical procedures showed that the largest contribution to relative operator dose originated from left-anterior-oblique C-arm angulations (59%–75% of clinical operator exposure). Of the various x-ray acquisition types used, fluoroscopy was the main contributor to procedural DAP (49%) and operator dose in clinical procedures (82%).ConclusionsAchievable levels for radiation exposure reduction were determined and compared with real-life clinical practice. This generated evidence-based advice on the conditions required for optimal radiation safety.     

Radiation doses to patients in neurointerventional procedures.

PURPOSETo evaluate stochastic and deterministic risks associated with neurointerventional procedures for the patient.METHODSEight neurovascular interventional procedures were evaluated to determine the entrance skin dose and effective dose for the patient. Dosimetry was done with thermoluminescence dosimeters. The highest dose on the patient''s head was recorded as the maximum entrance skin dose. The equivalent dose was obtained by conversion of the dose-area product using published conversion tables.RESULTSThe maximum entrance skin dose varied from 129 to 1335 mGy. The mean effective dose was 1.67 mSv with a range of 0.44 to 3.44 mSv. No deterministic effect has been encountered. Stochastic risk linked to the highest effective dose value was approximately one death by fatal cancer for every 6000 procedures, according to the new International Commission on Radiological Protection coefficient.CONCLUSIONSBecause no deterministic effect has been detected, and stochastic risks were very low, radiation hazard to the patient is a minor consideration in deciding whether to undertake a neurointerventional procedure.     

Abciximab for thrombolysis during intracranial aneurysm coiling

Introduction  Thrombotic events are a common and severe complication of endovascular aneurysm treatment with significant impact on patients’ outcome. This study evaluates risk factors for thrombus formation and assesses the efficacy and safety of abciximab for clot dissolution. Materials and methods  All patients treated with abciximab during (41 patients) or shortly after (22 patients) intracranial aneurysm coil embolisation were retrieved from the institutional database (2000 to 2007, 1,250 patients). Sixty-three patients (mean age, 55.3 years, ±12.8) had received either intra-arterial or intravenous abciximab. Risk factors for clot formation were assessed and the angiographic and clinical outcome evaluated. Results  No aneurysm rupture occurred during or after abciximab application. The intra-procedural rate of total recanalisation was 68.3%. Thromboembolic complications were frequently found in aneurysms of the Acom complex and of the basilar artery, whilst internal carotid artery aneurysms were underrepresented. Two patients died of treatment-related intracranial haemorrhages into preexisting cerebral infarcts. Two patients developed a symptomatic groin haematoma. Conclusions  Abciximab is efficacious and safe for thrombolysis during and after endovascular intracranial aneurysm treatment in the absence of preexisting ischaemic stroke.     

Dose area product measurement in orthopaedic trauma: An attempt at establishing a local diagnostic reference level

BackgroundThe Ionizing Radiations Medical Exposure Regulations Act IR(ME)R2000, requires the establishment of diagnostic reference levels (DRL) for radiological examinations. Current National Radiation Protection Board guidelines do not have any dose data available on orthopaedic trauma. Where National guidelines are not available, the establishment of local DRLs, to collect dose data and to set intervention levels is important.Materials and methodsDose area product measurement in 1000 patients who underwent emergency trauma surgery was analyzed. This included 210 hip fractures, 315 wrist fractures, 117 ankle fixations, 94 supracondylar fractures, 47 intramedullary nailing, 24 joint relocations, and 139 other examinations of extremities. The median dose area product (DAP) along with the first and third quartile values for each procedure was calculated.ResultsIntramedullary nailing of femur was done at the highest exposure with the median DAP of 68.5 cGy cm², followed by hip pinning. Values for fracture neck of femur exceeded those of tibial nailing. Among close reduction tibia and fibula manipulation had the highest radiation values between first and third quartiles of the distribution to give a possible DRL range and this has been determined.DiscussionThe DRL is a measure of patient dose and serves as a quantitative guide to optimization of radiological protection. The IR(ME)R states that if the DRL for an examination is exceeded by a particular piece of equipment or operator, legislation requires that reasons be investigated and remedial action be taken. It is hoped the study will contribute to the establishment of a national DRL for orthopaedic examinations.     

一台引起放射性皮肤损伤的介入放射学设备检测结果调查与分析

目的 通过调查和分析一台引起放射性皮肤损伤的介入放射学设备的质量控制检测结果,为介入放射学程序运行过程中的放射防护最优化提供建议。方法 调取一台引起患者放射性皮肤损伤的介入放射学设备近3年的5次质量控制检测报告,比较检测结果的差异并分析存在的问题。结果 对于“透视受检者入射体表空气比释动能率典型值”项目,3家机构5次检测结果在6.08~24.89 mGy/min之间,符合相关标准的要求;不同曝光模式(普通剂量率透视模式、高剂量率透视模式、电影模式)和不同帧率对受检者入射体表空气比释动能率和透视防护区检测平面上周围剂量当量率检测结果影响较大;操作该设备的介入医生对设备的曝光模式了解不足,手术后未记录患者剂量。结论 通过对介入放射学设备的调试可显著降低患者剂量;建议在标准修订时增加参考点累积剂量或剂量面积乘积准确性指标的检测;加强对介入医生和技师的专业培训,使其充分了解设备不同曝光模式对患者和术者剂量的影响。     

A study on radiation doses and irradiated areas in cerebral embolisation

Patient radiation doses during interventional radiology procedures may reach the thresholds for radiation-induced skin and eye lens injuries. This study investigates the irradiated areas and doses received by patients undergoing cerebral embolisation, which is regarded as a high dose interventional radiology procedure. For each procedure the fluoroscopic and digital dose-area product (DAP), the fluoroscopic time, the total number of acquired images and entrance-skin dose (ESD) calculated by the angiographic unit were recorded. The ESD was measured by means of thermoluminescent dosimeters. In this study, the skin, eye and thyroid gland doses and the irradiated area for 30 patients were recorded. The average ESD was found to be 0.77 Gy for the posteroanterior plane and 0.78 Gy for the lateral plane. The average DAP was 48 Gy cm(2) for the posteroanterior plane and 58 Gy cm(2) for the lateral plane. The patient's average right eye dose was 60 mGy and the dose to the thyroid gland was 24 mGy. Seven patients received a dose above 1 Gy, one patient exceeded the threshold for transient erythema and one exceeded the threshold for temporary epilation. A good correlation between the DAP and the ESD for both planes has been found. The doctor's eye dose has also been measured for 17 procedures and the average dose per procedure was 0.13 mGy.