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.     

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.     

Evaluation of exposure dose to patients undergoing catheter ablation procedures—a phantom study

The aim of this study was to evaluate entrance skin dose (ESD), organ dose and effective dose to patients undergoing catheter ablation for cardiac arrhythmias, based on the dosimetry in an anthropomorphic phantom. ESD values associated with mean fluoroscopy time and digital cine frames were in a range of 0.12–0.30 Gy in right anterior oblique (RAO) and 0.05–0.40 Gy in left anterior oblique (LAO) projection, the values which were less than a threshold dose of 2 Gy for the onset of skin injury. Organs that received high doses in ablation procedures were lung, followed by bone surface, esophagus, liver and red bone marrow. Doses for lung were 24.8–122.7 mGy, and effective doses were 7.9–34.8 mSv for mean fluoroscopy time of 23.4–92.3 min and digital cine frames of 263–511. Conversion coefficients of dose-area product (DAP) to ESD were 8.7 mGy/(Gy·cm²) in RAO and 7.4 mGy/(Gy·cm²) in LAO projection. The coefficients of DAP to the effective dose were 0.37 mSv/(Gy·cm²) in RAO, and 0.41 mSv/(Gy·cm²) in LAO projection. These coefficients enabled us to estimate patient exposure in real time by using monitored values of DAP.     

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.     

心血管病介入操作时患者受照剂量研究

目的 对心血管介入手术中患者所受辐射剂量及与辐射剂量相关的指标进行采集和分析,为改善患者的辐射防护提供依据.方法 对在省属三级甲等医院进行的26例完整的心血管介入手术的患者进行临床数据采集,按手术类别分成冠状动脉血管造影术(CA)及行冠状动脉血管造影术(CA)后继续行经皮穿刺腔内冠状动脉成形术(PTCA)两组,采用TLD个人剂量计照射野矩阵测量法,检测患者荧光照射时间、入射皮肤剂量(ESD)、最高皮肤剂量(PSD)、剂量-面积乘积(DAP)等指标,用TLD测量在模拟心血管手术条件下体模器官剂量.结果 荧光透视时间为(17.7±15.6)min,范围为0.80～42.4 min;ESD范围为(159±138)mGy,4.40～459 mGy;PSD范围为(769±705)mGy,22.6～2.43×103mGy.CA+PTCA组的荧光照射时间、ESD、PSD均大于CA组,差异有统计学意义.最大皮肤受照剂量与透视时间有较好的相关性(r=0.84,P＜0.01).结论 心血管病放射性介入操作时,可通过透视时间来估算最大皮肤受照剂量.

Abstract：

Objective To collect and analyze the radiation dose to patients in cardiovascular interventional procedures and the radiation dose-related indicators,in order to provide a basis for improving radiation protection of patients.MethodsThe clinical data of 26 cases of complete cardiovascular interventional procedures was collected in the municipal Grade A Class Three hospitals,including coronary angiography (CA) and percutaneous transluminal coronary angioplasty (PTCA),and the patient-received radiation doses and other related factors was studied.TLD personal dosimeter radiation field matrix method was used to measure fluorescence time,the entrance skin dose (ESD),the peak skin dose (PSD),dosearea product (DAP) and other indicators.TLD was used to measure the organ dose of the phantom under the cardiovascular interventional procedure condition.ResultsThe fluoroscopy time was (17.7 ±15.6) min during the range of 0.80-42.4 min.The average entrance skin dose (ESD) was (159 ± 138)mGy during the range of 4.40-459 mGy.The peak skin dose (PSD) was (769 ± 705) mGy during the range of 22.6 - 2.43 × 103mGy.The fluorescence time,entrance skin dose (ESD) ,peak skin dose (PSD) of the group CA + PTCA are greater than the group CA and the difference has statistical significan.The peak skin dose and the fluoroscopy time have good linear correlation (r = 0.84,P ＜ 0.01 ).Conclusion The peak skin dose the patient received in cardiovascular interventional radiological operation can be estimated through the fluoroscopy time.     

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.     

Risk of deterministic effects during endovascular aortic stent graft implantation

Since the 1990s, stent graft implantation for aortic pathology has become an alternative to extensive surgical procedures in some patients. Indeed, many patients with such pathology are now treated endovascularly. Only limited data concerning the risk of a deterministic effect during aortic stent graft implantation are available Accordingly, 179 consecutive patients treated in our institute between October 2002 and July 2008 with endovascular aortic stent grafts were included in this study. Dosimetric data (kerma area product (KAP) and cumulative dose at the interventional reference point (CD(irp))) from radiograph reports were analysed for 172 patients. On a group of 19 patients, GAFCHROMIC XR type dosimetric films were also used to verify the automatic measurements. Readings from the integrated KAP meter were found to be too high and were therefore corrected - KAP to dose area product (DAP) and CD(irp) to entrance skin dose (ESD). Median DAP was 153 Gy cm2 (35-700 Gy cm2) and median ESD was 0.44 Gy (0.12-2.73 Gy). Recorded dosimetric quantities were found to be good predictors of the skin dose and highlighted 4 patients (2.3%) who received skin doses that might cause possible deterministic effects. Endovascular stent graft implantation is less invasive than a surgical procedure and is widely used; mid-term results are encouraging. In a small number of patients, deterministic effects can occur even in departments with well-trained staff. Operators should inform the patients of possible skin injury after receiving high doses of ionising radiation and proper support must be available should that occur.     

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".     

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.     

Uterine arterial embolization: factors influencing patient radiation exposure

PURPOSE: To investigate patient radiation exposures during uterine arterial embolization and the factors responsible for those exposures. MATERIALS AND METHODS: Clinical and procedural factors were evaluated for 42 consecutive procedures performed in 39 patients by one operator. Seven patients were excluded because of early termination (n = 1) or unusual conditions that necessitated extended procedures (n = 6). Fluoroscopic time, number of images acquired, height, and weight were available in the 35 remaining patients, and dose-area product (DAP) was available in 20. Equipment factors were evaluated by using a Lucite phantom in four angiography units from three manufacturers. RESULTS: The mean fluoroscopic time per case decreased from 30.6 to 14.2 minutes between the 1st and 5th quintiles. Mean DAP decreased from 211.4 to 30.6 Gy. cm(2) with dose reduction techniques; this primarily reflected a decreased number of acquired images. Phantom studies demonstrated many significant dose variations with magnification and equipment position. Low-dose and pulsed fluoroscopic modes reduced exposure rates in units so equipped, but roadmapping caused a silent switch to continuous fluoroscopy in two such units, which doubled the exposure rate. CONCLUSION: With operator experience and careful technique, uterine arterial embolization can be performed at radiation exposures comparable to those used in routine diagnostic studies. However, operators must be familiar with the technical parameters of their angiographic equipment.     

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.     

Increased radiation dose by automatic exposure control system during fluoroscopy and angiography of pelvis due to contrast material in the bladder: experimental study

PURPOSE: To evaluate the increase of radiation dose caused by contrast material excreted in the bladder during vascular interventional procedures of the pelvis. MATERIALS AND METHODS: A latex balloon filled with diluted contrast material, simulating the bladder, was placed in a water phantom. Entrance dose rates were measured under various conditions with and without the balloon. In animal experiments, skin doses during fluoroscopy and angiographic image acquisitions were measured at the pelvis of a swine before and after the contrast was excreted in the bladder. RESULTS: In phantom experiments, fluoroscopic dose rates increased 1.3- to 3.9-fold when the contrast-filled balloon was placed at the periphery of the phantom. The dose rates increased 3.0- to 4.0-fold when the balloon was placed at the center. In the animal experiment, dose rates increased 1.4- to 2.0-fold when the bladder was filled with contrast material. Skin doses during 10-second angiographic image acquisition also increased 1.1- to 2.3-fold when the bladder was filled with contrast. CONCLUSION: When the bladder is filled with excreted contrast material, skin doses delivered by fluoroscopy and angiography will increase. Removal of urine is recommended during vascular interventional procedures of the pelvis.     

肝动脉化疗栓塞治疗肝癌患者的X射线辐射评价

目的　研究经肝动脉化疗栓塞 (THACE)治疗肝癌过程中 ,患者受到的X射线辐射 ,为THACE放射防护提供依据。方法　回顾性分析 82例HCC患者的辐射剂量资料 ,DSA机 (Angiostar Plus)配置穿透电离室型剂量监测系统 (DiamentorK1andDiamentorED) ,在线读取面积剂量乘积DAP(cGy cm2 )和入射表面剂量ESD(mGy) ,采用Monte Carlo转换因子估算有效剂量ED(mSv)。并分析近期 10例THACE患者 ,在提高基值管电压、减低透视脉冲频率和摄影帧数下对辐射剂量的影响。结果　 82例HCC患者透视时间 (35 3± 2 1 1)min ,摄影 (2 34± 10 8)帧 ,DAP为 (2 174 8± 12 4 2 4 )cGy cm2 ,ESD为 (96 4± 6 32 )mGy ,ED为 (34 8± 19 9)mSv。透视对总DAP的贡献 (2 4 0± 12 7) %小于摄影 (75 9± 12 7) % ,透视对ESD值的贡献 (4 9 8± 14 9) % ,与摄影相似 (5 1 6± 14 2 ) %。近期的 10例THACE患者的每分钟透视剂量、每帧摄影剂量及总剂量都比HCC患者明显降低。结论　在THACE过程中患者受到一次性较大剂量X射线照射。适度提高基值管电压、减低透视脉冲频率和缩减摄影帧数 ,可以有效降低患者的辐射剂量     

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.     

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.     

心血管介入手术中透视时间作为辐射剂量警示指标的可行性研究

目的以心血管介入术后采集空气比释动能(reference air kerma,AK)值和剂量面积乘积(dose-area product,DAP)值数据为依据,分析术中透视时间报警设置作为心血管介入手术辐射剂量的监测和警示工具的可行性。方法回顾性分析2016年11月至2018年1月上海长海医院736例冠状动脉造影术(CAG)和经皮冠状动脉治疗术(PCI)病例,收集术中透视时间、AK和DAP数据资料。德国西门子成像设备分组(Ceiling系统和Biplane系统)和手术类型分组(CAG和PCI),对辐射剂量数据进行比较,以及对心血管介入手术AK和DAP值与透视时间数据采用Spearman检验解析相关性。结果Ceiling和Biplane成像系统中手术透视时间为(8.9±7.8)和(8.6±7.3)min,透视AK均值和DAP均值分别为(472±474)、(510±509)mGy、(4548±4085)和(4255±3781)μGy·m^2,术中总(透视+造影)AK和DAP均值为(703±595)、(733±614)mGy、(6253±4938)和(5681±4432)μGy·m^2。CAG与PCI术中透视时间均值分别为(2.4±0.9)和(15.7±4.9)min。PCI透视辐射剂量(AK和DAP)与术中总辐射剂量比值分别为74%和78%。心血管介入手术中透视时间与AK值(r=0.822)和DAP值(r=0.844)都呈高度相关性(P<0.001)。结论透视采集辐射剂量是心血管介入手术中辐射剂量的主要来源,辐射剂量随透视时间延长而增加,透视时间监测和报警设置在心血管介入临床应用中作为术中辐射防护工具有一定的参考和警示价值。     

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.     

National Survey of Radiation Doses of Pediatric Chest Radiography in Korea: Analysis of the Factors Affecting Radiation Doses

Objective

To investigate radiation doses in pediatric chest radiography in a national survey and to analyze the factors that affect radiation doses.

Materials and Methods

The study was based on the results of 149 chest radiography machines in 135 hospitals nationwide. For each machine, a chest radiograph was obtained by using a phantom representing a 5-year-old child (ATOM® dosimetry phantom, model 705-D, CIRS, Norfolk, VA, USA) with each hospital''s own protocol. Five glass dosimeters (M-GD352M, Asahi Techno Glass Corporation, Shizuoka, Japan) were horizontally installed at the center of the phantom to measure the dose. Other factors including machine''s radiography system, presence of dedicated pediatric radiography machine, presence of an attending pediatric radiologist, and the use of automatic exposure control (AEC) were also evaluated.

Results

The average protocol for pediatric chest radiography examination in Korea was 94.9 peak kilovoltage and 4.30 milliampere second. The mean entrance surface dose (ESD) during a single examination was 140.4 microgray (µGy). The third quartile, median, minimum and maximum value of ESD were 160.8 µGy, 93.4 µGy, 18.8 µGy, and 2334.6 µGy, respectively. There was no significant dose difference between digital and non-digital radiography systems. The use of AEC significantly reduced radiation doses of pediatric chest radiographs (p < 0.001).

Conclusion

Our nationwide survey shows that the third quartile, median, and mean ESD for pediatric chest radiograph is 160.8 µGy, 93.4 µGy, and 140.4 µGy, respectively. No significant dose difference is noticed between digital and non-digital radiography systems, and the use of AEC helps significantly reduce radiation doses.     

Management of patient skin dose in fluoroscopically guided interventional procedures

PURPOSE: To simulate dose to the skin of a large patient for various operational fluoroscopic conditions and to delineate how to adjust operational conditions to maintain skin dose at acceptable levels. MATERIALS AND METHODS: Patient entrance skin dose was estimated from measurement of entrance air kerma (dose to air) to a 280-mm water phantom for two angiographic fluoroscopes. Effects on dose for changes in machine floor kVp, source-to-skin distance, air gap, electronic magnification, fluoroscopic dose rate control settings, and fluorographic dose control settings were examined. RESULTS: Incremental changes in operational parameters are multiplicative and markedly affect total dose delivered to a patient's skin. For long procedures, differences in doses of 8 Gy or more are possible for some combinations of operational techniques. CONCLUSIONS: Effects on skin dose from changes in operational parameters are multiplicative, not additive. Doses in excess of known thresholds for injury can be exceeded under some operating conditions. Adjusting operational parameters appropriately will markedly reduce dose to a patient's skin. Above all other operational factors, variable pulsed fluoroscopy has the greatest potential for maintaining radiation exposure at low levels.