Evaluation of patient doses in interventional radiology]

PURPOSE: To verify the suitability of indicative quantities to evaluate the risk related to patient exposure, in abdominal and vascular interventional radiology, by the study of correlations between dosimetric quantities and other indicators. MATERIAL AND METHODS: We performed in vivo measurements of entrance skin dose (ESD) and dose area product (DAP) during 48 procedures to evaluate the correlation among dosimetric quantities, and an estimation of spatial distribution of exposure and effective dose (E). To measure DAP we used a transmission ionization chamber and to evaluate ESD and its spatial distribution we used radiographic film packed in a single envelope and placed near the patient's skin. E was estimated by a calculation software using data from film digitalisation. RESULTS: From the data derived for measurements in 27 interventional procedures on 48 patients we obtained a DAP to E conversion factor of 0.15 mSv / Gy cm2, with an excellent correlation (r=.99). We also found a good correlation between DAP and exposure parameters such as fluoroscopy time and number of images. The greatest effective dose was evaluated for a multiple procedure in the hepatic region, with a DAP value of 425 Gy cm2. The greatest ESD was about 550 mGy. For groups of patients undergoing similar interventional procedures the correlation between ESD and DAP had conversion factors from 6 to 12 mGy Gy-1 cm-2. CONCLUSION: The evaluation of ESD and E by slow films represents a valid method for patient dosimetry in interventional radiology. The good correlation between DAP and fluoroscopy time and number of images confirm the suitability of these indicators as basic dosimetric information. All the ESD values found are lower than threshold doses for deterministic effects.     

Diagnostic reference levels and effective dose in paediatric cardiac catheterization

European states within the EEC are required to establish and use diagnostic reference levels (DRLs) in X-ray examinations. However, up to now there have been no DRLs for cardiac catheterization in children, nor as a rule is the effective dose estimated. We have evaluated the dose-area products (DAPs) for three different types of angiocardiography systems over a time span of 8 years. For each system DAP increased in proportion to the body weight (BW) over two orders of magnitude. The proportionality constant decreased over the years. To reduce the broad distribution of DAP the doses for cine acquisition (DAPA) and fluoroscopy (DAPF) were indexed with respect to the total numbers of acquired images (AN) and the total times of fluoroscopy (FT). DAPA/AN is directly proportional to BW with a high correlation (r = 0.896, n = 1346). Likewise, DAPF/FT is proportional to BW from 0.1 kg to 100 kg (r = 0.84, n = 2138). Therefore, by normalizing DAP to BW the growth dependent variation of DAP can be eliminated. There are numerous short examinations with very small total DAPs, which were separated from the group of diagnostic examinations. The mean DAP/BW of this group is 0.41 Gycm2 kg(-1) (90th percentile: 0.81 Gycm2 kg(-1), n = 1106). For interventional procedures in congenital heart diseases DAP/BW is significantly higher (p<0.001) (mean: 0.56 Gycm2 kg(-1), 90th percentile: 1.16 Gycm2 kg(-1), n = 883). There are significant differences between different types of interventional procedures, the mean values being between 0.35 Gycm2 kg(-1) (occlusion of patent ductus botalli, n = 165) and 1.30 Gycm2 kg(-1) (occlusion of ventricular septal defect, n = 32). For patients who are catheterized several times over the years, the cumulative effective dose (E) may reach high values, being especially high for patients with hypoplastic left heart syndrome (typically 11 mSv). E is derived from DAP/BW by use of a constant DAP/BW to E conversion factor, independent of the age of the patient. DAP/BW is appropriate to describe paediatric DRLs and is recommended instead of using mean DAP values for age groups.     

An investigation into patient and staff doses from X-ray angiography during coronary interventional procedures

Radiation doses to patients from interventional coronary X-ray procedures are relatively high when compared with conventional radiographic procedures. These high patient doses can translate into high staff doses owing to scattered radiation. This study investigates patient doses by means of dose-area product (DAP) meters installed in six rooms in two hospitals. DAP measurements in each room ranged from 28.0-39.3 Gy cm2 for coronary angiography and from 61.3-92.8 Gy cm2 for percutaneous transluminal coronary angioplasty, with the mean effective doses calculated to range between 5.1-6.6 mSv and 11.2-17.0 mSv, respectively. These values are comparable with those found in recent literature. DAP measurements were found to correlate strongly (correlation coefficient of 79%) with patient weight. The non-uniform scatter radiation fields surrounding the irradiated area during coronary angiography were also investigated using a tissue equivalent phantom and an ionization chamber. Exposure rates of scattered radiation from digital acquisition were found to be around 16 times higher than those generated from fluoroscopy, and oblique-angled imaging led to greater amounts of scatter owing to the increase in related exposure factors. The distribution of scatter from oblique projections confirms that X-ray photons in the diagnostic energy range are preferentially scattered backwards, toward the X-ray tube. These concepts are a major consideration when training individuals working in the angiography suite in order to keep doses "as low as reasonably practicable".     

10种介入诊疗程序中患者的辐射剂量调查

目的 调查研究介入诊疗程序中患者的受照剂量,评估其放射诊疗风险.方法 利用配置有符合IEC 60601-2标准的穿透型电离室的飞利浦Allura Xper FD20 DSA系统,收集记录10种介入诊疗程序共198例患者的剂量参数,估算出可供评估皮肤损伤的最高皮肤剂量及有效剂量.结果 累计透视时间范围为2.1～80.9 min,摄影帧数范围为15～678帧,剂量面积乘积范围为11～825 Gy·cm2,累计剂量范围为24～3374 mGy.有16例患者最高皮肤剂量超过1 Gy,79例患者有效剂量大于20 mSv.结论 有部分病例的最高皮肤剂量超过了皮肤损伤阈值,所以对患者的放射防护应给予足够的重枧.

Abstract：

Objective To investigate radiation dose to the patients undergoing interventional radiology and make radiation risk assessment.Methods Data was collected on 198 instances of 10 interventional radiology procedures by using Philips Allura Xper FD20 DSA, which was equipped with the transparent ionization chamber system in compliance with IEC 60601-2.Patient peak skin dose and effective dose were estimated.Results Cumulative fluoroscopy time was 2.1 - 80.9 min, and number of images monitored for PSD were above 1 Gy and 79 cases monitored for E were above 20 mSv.Conclusions Substantial number of cases exceeded the dose threshold for erythema.Due attention should be paid to radiation protection of patients.     

A study on maximum skin dose in cerebral embolization procedures

BACKGROUND AND PURPOSE: It is essential to measure the skin dose of radiation received by patients during interventional neuroradiologic procedures performed under fluoroscopic guidance, such as embolization of cerebral aneurysms, which is regarded as a high-dose interventional radiology procedure. In this study, we report a method for evaluating maximum skin dose (MSD), an ideal marker of radiation-induced effects, based on an innovative use of radiochromic films. MATERIALS AND METHODS: Forty-eight procedures were studied in 42 patients undergoing embolization of cerebral aneurysms. Fluoroscopic and digital dose-area product (DAP), fluoroscopy time, and total number of acquired images were recorded for all procedures. The MSD was measured using Gafchromic XR type R films. RESULTS: The MSD was measured in one group of 21 procedures. The coefficient (kappa) of the interpolation line between the skin dose and the DAP (kappa = 0.0029 cm(-2)) was determined. An approximate value of MSD from the DAP for the remaining 27 procedures was estimated by means of an interpolation line. The mean MSD was found to be 1.16 Gy (range, 0.23-3.20 Gy). CONCLUSION: The use of radiochromic XR type R films was shown to be an effective method for measuring MSD. These films have the advantage of supplying information on both the maximum dose and the distribution of the dose: this satisfies the most stringent interpretation of Food and Drug Administration, American College of Radiology, and international recommendations for recording skin dose.     

Contemporary Interventional Radiology Dosimetry: Analysis of 4,784 Discrete Procedures at a Single Institution

PurposeTo report dosimetry of commonly performed interventional radiology procedures and compare dose analogues to known reference levels.Materials and MethodsDemographic and dosimetry data were collected for gastrostomy, nephrostomy, peripherally inserted central catheter placement, visceral arteriography, hepatic chemoembolization, tunneled catheter placement, inferior vena cava filter placement, vascular embolization, transjugular liver biopsy, adrenal vein sampling, transjugular intrahepatic portosystemic shunt (TIPS) creation, and biliary drainage between June 12, 2014, and April 26, 2018, using integrated dosimetry software. In all, 4,784 procedures were analyzed. The study included 2,691 (56.2%) male subjects and 2,093 (43.8%) female subjects with mean age 55 ± 21 years (range: 0-104 years) and with mean weight of 76.9 ± 29.4 kg (range: 0.9-268.1 kg). Fluoroscopy time, dose area product (DAP), and reference dose were evaluated.ResultsTIPS had the highest mean fluoroscopy time (49.1 ± 16.0 min) followed by vascular embolization (25.2 ± 11.4 min), hepatic chemoembolization (18.8 ± 12.5 min), and visceral arteriography (17.7 ± 3.2 min). TIPS had the highest mean DAP (429.2 ± 244.8 grays per square centimeter [Gy·· cm²]) followed by hepatic chemoembolization (354.6 ± 78.6 Gy·· cm²), visceral arteriography (309.5 ± 39.0 Gy·· cm²), and vascular embolization (298.5 ± 29 Gy·· cm²). TIPS was associated with the highest mean reference dose (2.002 ± 1.420 Gy) followed by hepatic chemoembolization (1.746 ± 0.435 Gy), vascular embolization (1.615 ± 0.381 Gy), and visceral arteriography (1.558 ± 1.720 Gy). Of the six procedures available for comparison with the reference levels, the mean fluoroscopy time, DAP, and reference dose for each procedure were below the proposed reference levels.ConclusionAdvances in image acquisition technology and radiation safety protocols have significantly reduced the radiation exposure for a variety of interventional radiology procedures.     

X-ray dose and associated risks from radiofrequency catheter ablation procedures

The objectives of this study were to quantify the ionizing radiation exposure to patient and operator during radiofrequency (RF) catheter ablation and to estimate the risks associated with this exposure. The study consisted of 50 RF ablation procedures, all performed in the same electrophysiology laboratory. Occupational dose to two cardiologists who performed the procedures was measured using film badges and extremity thermoluminescent dosemeters (TLDs). Absorbed dose to the patients' skin was measured using TLDs. Dose-area product (DAP) was also measured. The effective dose to the cardiologists was less than 0.15 mSv per month. The mean equivalent dose to the cardiologists' left hand and forehead was 0.24 mSv and 0.05 mSv, respectively, per RF ablation procedure, which was more than twice the mean dose for the other cardiology procedures carried out in the centre. Yearly occupational dose to the cardiologists was much lower than the relevant statutory dose limits. The mean skin dose, fluoroscopy time and DAP to patients were 0.81 Gy, 67 min and 123 Gycm(2), respectively, with a maximum of 3.2 Gy, 164 minutes and 430 Gycm(2), respectively. Mean effective dose to patients was 17 mSv, from which the excess risk of developing fatal cancer is 0.1%. Six of the patients (12%) received a skin dose above the threshold dose for radiation skin injury (2 Gy), but no skin injuries were reported. Patient skin dose and DAP were closely correlated and this allows DAP to be used to monitor patient skin dose in real-time. DAP levels were locally adopted as diagnostic reference levels (DRLs) that provide an indication during a procedure that a patient is at risk of suffering deterministic skin injury.     

Radiation Exposure in Nonvascular Fluoroscopy-Guided Interventional Procedures

Purpose

To investigate the radiation exposure in non-vascular fluoroscopy guided interventions and to search strategies for dose reduction.

Materials and Methods

Dose area product (DAP) of 638 consecutive non-vascular interventional procedures of one year were analyzed with respect to different types of interventions; gastrointestinal tract, biliary interventions, embolizations of tumors and hemorrhage. Data was analyzed with special focus on the fluoroscopy doses and frame doses. The third quartiles (Q3) of fluoroscopy dose values were defined in order to set a reference value for our in-hospital practice.

Results

Mean fluoroscopy times of gastrostomy, jejunostomy, right and left sided percutaneous biliary drainage, chemoembolization of the liver and embolization due to various hemorrhages were 5.9, 8.6, 13.5, 16.6, 17.4 and 25.2 min, respectively. The respective Q3 total DAP were 52.9, 73.3, 155.1, 308.4, 428.6 and 529.3 Gy*cm². Overall, around 66% of the total DAP originated from the radiographic frames with only 34% of the total DAP applied by fluoroscopy (P < 0.001). The investigators experience had no significant impact on the total DAP applied, most likely since there was no stratification to intervention-complexity.

Conclusion

To establish Diagnostic Reference Levels (DRLs), there is a need to establish a registry of radiation dose data for the most commonly performed procedures. Documentation of interventional procedures by fluoroscopy “grabbing” has the potential to considerably reduce radiation dose applied and should be used instead of radiographic frames whenever possible.     

Main clinical, therapeutic and technical factors related to patient's maximum skin dose in interventional cardiology procedures

Objective: The study aimed to characterise the factors related to the X-ray dose delivered to the patient's skin during interventional cardiology procedures. Methods: We studied 177 coronary angiographies (CAs) and/or percutaneous transluminal coronary angioplasties (PTCAs) carried out in a French clinic on the same radiography table. The clinical and therapeutic characteristics, and the technical parameters of the procedures, were collected. The dose area product (DAP) and the maximum skin dose (MSD) were measured by an ionisation chamber (Diamentor; Philips, Amsterdam, The Netherlands) and radiosensitive film (Gafchromic; International Specialty Products Advanced Materials Group, Wayne, NJ). Multivariate analyses were used to assess the effects of the factors of interest on dose. Results: The mean MSD and DAP were respectively 389 mGy and 65 Gy cm(-2) for CAs, and 916 mGy and 69 Gy cm(-2) for PTCAs. For 8% of the procedures, the MSD exceeded 2 Gy. Although a linear relationship between the MSD and the DAP was observed for CAs (r=0.93), a simple extrapolation of such a model to PTCAs would lead to an inadequate assessment of the risk, especially for the highest dose values. For PTCAs, the body mass index, the therapeutic complexity, the fluoroscopy time and the number of cine frames were independent explanatory factors of the MSD, whoever the practitioner was. Moreover, the effect of technical factors such as collimation, cinematography settings and X-ray tube orientations on the DAP was shown. Conclusion: Optimising the technical options for interventional procedures and training staff on radiation protection might notably reduce the dose and ultimately avoid patient skin lesions.     

Patient and occupational dose in neurointerventional procedures

Neurointerventional procedures can involve very high doses of radiation to the patient. Our purpose was to quantify the exposure of patients and workers during such procedures, and to use the data for optimisation. We monitored the coiling of 27 aneurysms, and embolisation of four arteriovenous malformations. We measured entrance doses at the skull of the patient using thermoluminescent dosemeters. An observer logged the dose-area product (DAP), fluoroscopy time and characteristics of the digital angiographic and fluoroscopic projections. We also measured entrance doses to the workers at the glabella, neck, arms, hands and legs. The highest patient entrance dose was 2.3 Gy, the average maximum entrance dose 0.9+/-0.5 Gy. The effective dose to the patient was estimated as 14.0+/-8.1 mSv. Other average values were: DAP 228+/-131 Gy cm(2), fluoroscopy time 34.8+/-12.6 min, number of angiographic series 19.3+/-9.4 and number of frames 267+/-143. The highest operator entrance dose was observed on the left leg (235+/-174 microGy). The effective dose to the operator, wearing a 0.35 mm lead equivalent apron, was 6.7+/-4.6 microSv. Thus, even the highest patient entrance dose was in the lower part of the range in which nonstochastic effects might arise. Nevertheless, we are trying to reduce patient exposure by optimising machine settings and clinical protocols, and by informing the operator when the total DAP reaches a defined threshold. The contribution of neurointerventional procedures to occupational dose was very small.     

Skin dose and dose-area product values in patients undergoing intracoronary brachytherapy

Entrance skin doses, dose-area product (DAP) values, fluoroscopy times and digital cine acquisition data were measured for 86 patients undergoing intracoronary brachytherapy procedures with beta sources, to estimate risk of skin injuries. Interventions were carried out in three dedicated X-ray interventional cardiology rooms equipped with X-ray systems operating in pulsed modes, with high filtration and edge filter options. Skin dose distribution was analysed in detail in 56 patients using slow films and thermoluminescent dosimetry. Digital recording of Digital Imaging and Communications in Medicine cine images also allowed analysis of the technical parameters used throughout the procedures. A protocol for clinical follow-up of these patients at the cardiology service is also presented, which prescribes special attention when a threshold dose is reached. Median values for DAP, fluoroscopy time and number of frames were 81.2 Gy cm(2), 17.5 min and 1569 frames, respectively, and maximum values were 323.3 Gy cm(2), 46.2 min and 3213 frames, respectively. In two cases, maximum skin doses in a procedure reached 3.5 Gy and 4.6 Gy. Comparing median values in this study, intracoronary brachytherapy involved approximately two-fold the DAP used in percutaneous transluminal coronary angioplasty procedures performed during the same period in the same catheterization laboratories, as a consequence of the need to monitor the radioactive source location used for the treatment of stenoses and the intravascular ultrasound. Special care must be paid in those cases of high dose in relation to potential patient skin injuries and late effects.     

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.     

Radiation doses in interventional radiology procedures: the RAD-IR study: part I: overall measures of dose

PURPOSE: To determine patient radiation doses for interventional radiology and neuroradiology procedures, to identify procedures associated with higher radiation doses, and to determine the effects of various parameters on patient doses. MATERIALS AND METHODS: A prospective observational study was performed at seven academic medical centers. Each site contributed demographic and radiation dose data for subjects undergoing specific procedures in fluoroscopic suites equipped with built-in cumulative dose (CD) and dose-area-product (DAP) measurement capability compliant with International Electrotechnical Commission standard 60601-2-43. The accuracy of the dosimetry was confirmed by comprehensive measurements and by frequent consistency checks performed over the course of the study. RESULTS: Data were collected on 2,142 instances of interventional radiology procedures, 48 comprehensive physics evaluations, and 581 periodic consistency checks from the 12 fluoroscopic units in the study. There were wide variations in dose and statistically significant differences in fluoroscopy time, number of images, DAP, and CD for different instances of the same procedure, depending on the nature of the lesion, its anatomic location, and the complexity of the procedure. For the 2,142 instances, observed CD and DAP correlate well overall (r = 0.83, P <.000001), but correlation in individual instances is poor. The same is true for the correlation between fluoroscopy time and CD (r = 0.79, P <.000001). The correlation between fluoroscopy time and DAP (r = 0.60, P <.000001) is not as good. In 6% of instances (128 of 2,142), which were principally embolization procedures, transjugular intrahepatic portosystemic shunt (TIPS) procedures, and renal/visceral artery stent placements, CD was greater than 5 Gy. CONCLUSIONS: Most procedures studied can result in clinically significant radiation dose to the patient, even when performed by trained operators with use of dose-reducing technology and modern fluoroscopic equipment. Embolization procedures, TIPS creation, and renal/visceral artery stent placement are associated with a substantial likelihood of clinically significant patient dose. At minimum, patient dose data should be recorded in the medical record for these three types of procedures. These data should include indicators of the risk of deterministic effects as well as the risk of stochastic effects.     

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.     

Radiation doses to the legs of radiologists performing interventional procedures: are they a cause for concern?

The purpose of this study was to ascertain the magnitude and distribution of doses to the legs of radiologists when performing interventional procedures. LiF:Mg,Ti TLD100 chips were used to measure simultaneously doses to the lower limbs and, for comparison, the hands during 100 interventional procedures. Results show leg dose was dependent upon type and complexity of procedure, equipment used and whether lead protection was available. Where no lead protection was used, the doses to the lower limbs were frequently similar to or higher than those received by the hands. The mean dose to the legs ranged from 0.19 mSv to 2.61 mSv per procedure, compared with 0.04 mSv to 1.25 mSv to the hands. During transjugular intrahepatic portosystemic shunt and embolisation procedures the leg dose could be as much as 2-3 times greater than that to the hands. When lead protection was used, the dose to the legs was reduced significantly to 0.02 mSv to 0.5 mSv per procedure. A clear linear relationship was shown between the dose-area product (DAP) reading and the dose to the feet of the radiologist. As a "rule of thumb", a DAP reading of 100 Gy cm(2) will give a dose of 1 mSv to the legs, if no lead protection was used, dropping to approximately 0.02 mSv if lead protection was present. This study demonstrates that the dose to the legs of radiologists can be higher than that to the hands when no lead protection is used. The inclusion of a lead screen to protect the legs is an effective method of dose reduction when performing interventional procedures.     

Method of patient dose evaluation in the angiographic and interventional radiology procedures

PURPOSE: The aim of this study was to evaluate the effective dose in interventional radiology and angiography procedures on the basis of the dose-area product (DAP), either measured or calculated using two different methods. MATERIALS AND METHODS: We studied 2072 examinations carried out on several X-ray systems both in angiography and in interventional radiology. Some of the systems were equipped with an on-board transmission chamber for DAP measurements; for these systems we took direct DAP measurements for each type of examination. For the systems without the dose measurement device, we used a portable transmission chamber, acquiring the data from a set of sampling frames. We then derived the dose values from the systems' dosimetry data and the information about each examination. To this end, the dosimetry of each x-ray system was done by measuring tube output in the different acquisition modes, backscatter factor and field-homogeneity factor. Survey data sheets were filled in after every examination indicating the exposure data (mean Kv, mAs, focus-skin distance and field size). These values combined with the dosimetric data were used to evaluate the DAP for each exam. Where possible, we compared the measured and calculated DAP values by assessing the percentage deviation between each pair of values. A similar comparison was made for the single examinations using a simplified calculation algorithm reported in the literature. For all the examinations for which we had adequate survey data sheets, we estimated the DAP and the entrance dose values and, with the aid of WinODS software, the effective dose. RESULTS: The direct measurements of DAP showed that, in interventional radiology and angiographic procedures, the variability in examination conditions leads to a wide range of possible patient doses even within the same examination type.The comparison between the measured and calculated DAP using our algorithm showed substantial agreement (mean difference 30%, maximum 80%). By contrast, using the algorithm proposed in the literature, we obtained deviations higher than 100%.An estimate of the effective dose for all the recorded examinations (2072) permitted evaluation of both magnitude and variability of patient doses in special radiology procedures such as angiography and interventional radiology. However, it should be noted that evaluations based on calculated DAP values may be as uncertain as those estimated for DAP, and that clearly the evaluations made for the examinations for which direct measurements are available are more accurate.In particularly 'invasive' examinations in terms of entrance dose, where the threshold limits for deterministic effects might possibly be exceeded, the equivalent doses to critical organs were also assessed. This analysis showed that in a small percentage of patients (5%) 2 Gy to the skin was exceeded in the areas exposed with possible transient erythema, while in fewer than 2% of patients, the 3 Gy limit for temporary epilation was exceeded. CONCLUSIONS: Many interventional radiology, especially haemodynamic, examinations have shown to give significant exposure to patients. The direct dose measurement method has shown to be the only method able to provide reliable information on such exposure.However, the authors believe that since the patient dose cannot be established in advance, even in terms of magnitude and since direct dose measurement cannot be performed on all patients, it is nonetheless interesting to be able to assess, at least semiqualitatively, the amount of the above doses.     

Absorbed dose and deterministic effects to patients from interventional neuroradiology

Following the presentation of radiation-induced skin effects by three patients who had undergone glue embolisation of intracranial arteriovenous malformation (AVM), measurements were made of absorbed dose to the skin of patients undergoing other interventional neuroradiological procedures that involve long fluoroscopy times. The maximum absorbed dose to the skin measured by thermoluminescent dosemeters during these procedures was 4 Gy. From these measurements and from records of fluoroscopy time and the number of digital runs acquired, estimates of the maximum absorbed skin dose were made for the AVM patients. The best estimate of maximum absorbed dose to the skin received by any of the AVM patients during a procedure was 5 Gy, which is consistent with the skin effects presented by the AVM patients, that is temporary epilation and main erythema. Maximum absorbed dose to the skull was estimated to be 45 Gy and to the outer table of the skull 55 Gy. Although it is unlikely that the AVM patients will suffer serious effects from these skin doses, there remains some uncertainty over the risk of long-term effects to the skull. Examination of the fluoroscopy unit showed that the image intensifier was not performing optimally in terms of entrance dose rate and resolution. Replacement of the unit with modern X-ray equipment designed for interventional radiology was prioritized. Operators should be aware of the potential risks to patients from complex interventional neuroradiology procedures and should optimize their procedures to minimize such risks. Patients undergoing prolonged and complex procedures should be counselled regarding the symptoms and risks of large doses of radiation.     

How to set up and apply reference levels in fluoroscopy at a national level

A nationwide survey was launched to investigate the use of fluoroscopy and establish national reference levels (RL) for dose-intensive procedures. The 2-year investigation covered five radiology and nine cardiology departments in public hospitals and private clinics, and focused on 12 examination types: 6 diagnostic and 6 interventional. A total of 1,000 examinations was registered. Information including the fluoroscopy time (T), the number of frames (N) and the dose-area product (DAP) was provided. The data set was used to establish the distributions of T, N and the DAP and the associated RL values. The examinations were pooled to improve the statistics. A wide variation in dose and image quality in fixed geometry was observed. As an example, the skin dose rate for abdominal examinations varied in the range of 10 to 45 mGy/min for comparable image quality. A wide variability was found for several types of examinations, mainly complex ones. DAP RLs of 210, 125, 80, 240, 440 and 110 Gy cm² were established for lower limb and iliac angiography, cerebral angiography, coronary angiography, biliary drainage and stenting, cerebral embolization and PTCA, respectively. The RL values established are compared to the data published in the literature.     

Estimation of the effective dose of patient in interventional radiology: study of coronary angiography

The applications of interventional radiology (IVR) increasingly are being used in clinical examinations, where they tend to extend examination time. In addition, the risk of occupational exposure necessarily is increasing with this technology. In this study, the dose distributions in a sliced acrylic-acid phantom involving the bore for each irradiation condition were measured using a thermoluminescence dosimeter (TLD). Four patterns of set-up for the fluoroscopy unit were chosen as references for the conditions generally used clinically. Exposure also was measured with dose area product (DAP), and we then calculated the entrance skin dose and effective dose for the patient. The results showed that the effective dose was 7.0 mSv to 8.0 mSv at LAO45 degrees and RAO30 degrees; 100 kV, 2.3 mSv to 3.3 mSv at LAO45 degrees and RAO30 degrees; 80 kV. The effective dose is greatly influenced by the setup of fluoroscopy in IVR. The change in DAP is especially influenced. We found that the relation between DAP and effective dose was corrected with the exponential function. The effective doses were not necessarily less than those of other radiation examinations, and increase. When PCI and TAE are repeated many times in IVR, we propose that the effective dose should be taken into consideration together with the skin dose for dose control management.     

不同麻醉方式在小儿动脉导管未闭介入治疗中辐射剂量分析

目的：探讨不同麻醉方式在降低小儿动脉导管未闭(PDA)介入治疗中辐射剂量的影响。方法回顾2011—2014年采用2种麻醉方式接受 PDA 介入治疗的小儿(3~6岁)各25例,分为 A、B 2组,A 组为全麻组(男7例,女18例,平均体质量15.32 kg±2.415 kg),B组为局麻组(男13例,女12例,平均体质量16.40 kg±2.056 kg)。2组患者均由相同术者完成手术,采用 DSA 儿童心血管电影自动曝光模式(ped CARD)、摄影帧数15~30 f/s、非离子型对比剂碘克沙醇320 mg I/mL,记录患儿皮肤表面累积入射剂量(AK)、剂量面积乘积(DAP)和透视时间,并作统计学分析。结果50例患儿均顺利完成手术,统计显示,2组患儿的年龄、体质量及性别差异无统计学意义(年龄：t=1.924,P=0.060;体质量：t=1.703,P=0.095;性别：χ2=3.00,P=0.083);全麻组及局麻组辐射剂量 AK、DAP 及透视时间分别为(0.061±0.025)Gy、(0.094±0.046)Gy;(5.08±2.19)Gy·cm2、(8.41±3.587)Gy·cm2;(3.15±1.16)min、(6.86±3.27)min,差异均有统计学意义(AK：t=3.152,P=0.003;DAP：t=3.957,P=0.000;透视时间：t=5.346,P =0.000),2组在采集序列数及图像数相同的基础上,全麻组辐射剂量明显小于局麻组40%[(1-5.08/8.41)%],手术时间相差约1.17倍[(3.15-6.86)/3.15]。结论辐射剂量大小与麻醉方式有关,采用全麻方式进行小儿 PDA 介入治疗较局麻方式辐射剂量明显降低40%。