Comparison of four techniques to estimate radiation dose to skin during angiographic and interventional radiology procedures

PURPOSE: Four techniques used to estimate radiation risk were compared to determine whether commonly used dosimetry measurements permit reliable estimates of skin dose. Peak skin dose (PSD) is known to be the most reliable estimate of risk to skin. The purpose of this study is to determine peak skin dose with use of real-time software measurements and to correlate other measures of dose with PSD. MATERIALS AND METHODS: Two hundred twelve patients undergoing arch aortography and bilateral carotid arteriography (referred to as "carotid"), abdominal aortography and bilateral lower extremity runoff ("runoff"), or tunneled chest wall port placement ("port") were studied. Fluoroscopy time, dose-area product (DAP), and cumulative dose at the interventional reference point were recorded for all procedures; PSD was recorded for a subset of 105 procedures. The dose index, defined as the ratio between PSD and cumulative dose, was also determined. RESULTS: In general, correlation values for comparisons between fluoroscopy time and the other measures of dose (r =.29 to.78) were lower than values for comparisons among DAP, cumulative dose, and PSD (r =.52 to.94). For all procedures, pair-wise correlations between DAP, cumulative skin dose, and PSD were statistically significant (P <.01) The ratio between PSD and cumulative skin dose (dose index) was significantly different for ports versus other procedures (carotid, Z = 4.62, P <.001; runoff, Z = 4.52, P <.001), but carotid and runoff procedures did not differ significantly in this regard (Z = 0.746, P =.22). Within each individual procedure type, the range of values for the dose index varied 156.7-fold for carotid arteriography, 3.2-fold for chest ports, and 175-fold for aortography and runoff. CONCLUSION: Fluoroscopy time is a poor predictor of risk because it does not correlate well with PSD. Cumulative dose and DAP are not good analogues of PSD because of weak correlations for some procedures and because of wide variations in the dose index for all procedures.     

Minimizing radiation-induced skin injury in interventional radiology procedures

Skin injury is a deterministic effect of radiation. Once a threshold dose has been exceeded, the severity of the radiation effect at any point on the skin increases with increasing dose. Peak skin dose is defined as the highest dose delivered to any portion of the patient's skin. Reducing peak skin dose can reduce the likelihood and type of skin injury. Unfortunately, peak skin dose is difficult to measure in real time, and most currently available fluoroscopic systems do not provide the operator with sufficient information to minimize skin dose. Measures that reduce total radiation dose will reduce peak skin dose, as well as dose to the operator and assistants. These measures include minimizing fluoroscopy time, the number of images obtained, and dose by controlling technical factors. Specific techniques-dose spreading and collimation-reduce both peak skin dose and the size of skin area subjected to peak skin dose. For optimum effect, real-time knowledge of skin-dose distribution is invaluable. A trained operator using well-maintained state-of-the art equipment can minimize peak skin dose in all fluoroscopically guided procedures.     

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.     

介入诊疗程序中患者皮肤最大受照剂量的检测与评价

目的测定冠脉造影、肝动脉造影、射频消融、脑动脉造影等介入程序中对患者主射束皮肤剂量分布和最大皮肤受照剂量，了解患者皮肤能否发生确定性效应。方法在冠脉造影、肝动脉造影和射频消融3种手术曝光前每个患者背部放9个测量点，每个点2片LiF（Mg，Cu，P）剂量片；脑动脉造影曝光前患者正、侧位各放1个测量点。手术后进行TLD测量。结果肝动脉造影手术时，患者皮肤最大吸收剂量为1683．9mGy，平均吸收剂量607．3mGy；脑动脉造影正位时最大值可达959．3mGy，平均值418．8mGy；侧位最高达704mGy。平均191．52mGy；射频消融最高值为853．8mGy。平均219．7mGy；冠脉造影最大值为456．1mGy，平均227．6mGy。结论本实验结果是对皮肤最大剂量的一种估计值，尚不能精确提供患者皮肤受照的最大值。因为剂量片布放不够密集，可能没有包括很小的高剂量部位。     

Radiation doses in interventional radiology procedures: the RAD-IR study: part II: skin dose

PURPOSE: To determine peak skin dose (PSD), a measure of the likelihood of radiation-induced skin effects, for a variety of common interventional radiology and interventional neuroradiology procedures, and to identify procedures associated with a PSD greater than 2 Gy. MATERIALS AND METHODS: An observational study was conducted at seven academic medical centers in the United States. Sites prospectively contributed demographic and radiation dose data for subjects undergoing 21 specific procedures in a fluoroscopic suite equipped with built-in dosimetry capability. Comprehensive physics evaluations and periodic consistency checks were performed on each unit to verify the stability and consistency of the dosimeter. Seven of 12 fluoroscopic suites in the study were equipped with skin dose mapping software. RESULTS: Over a 3-year period, skin dose data were recorded for 800 instances of 21 interventional radiology procedures. Wide variation in PSD was observed for different instances of the same procedure. Some instances of each procedure we studied resulted in a PSD greater than 2 Gy, except for nephrostomy, pulmonary angiography, and inferior vena cava filter placement. Some instances of transjugular intrahepatic portosystemic shunt (TIPS) creation, renal/visceral angioplasty, and angiographic diagnosis and therapy of gastrointestinal hemorrhage produced PSDs greater than 3 Gy. Some instances of hepatic chemoembolization, other tumor embolization, and neuroembolization procedures in the head and spine produced PSDs greater than 5 Gy. In a subset of 709 instances of higher-dose procedures, there was good overall correlation between PSD and cumulative dose (r = 0.86; P <.000001) and between PSD and dose-area-product (r = 0.85, P <.000001), but there was wide variation in these relationships for individual instances. CONCLUSIONS: There are substantial variations in PSD among instances of the same procedure and among different procedure types. Most of the procedures observed may produce a PSD sufficient to cause deterministic effects in skin. It is suggested that dose data be recorded routinely for TIPS creation, angioplasty in the abdomen or pelvis, all embolization procedures, and especially for head and spine embolization procedures. Measurement or estimation of PSD is the best method for determining the likelihood of radiation-induced skin effects. Skin dose mapping is preferable to a single-point measurement of PSD.     

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.     

Evaluation of a MOSFET radiation sensor for the measurement of entrance surface dose in diagnostic radiology

A patient dosimetry system using MOSFET technology (Thomson and Neilson Electronics Ltd, Canada) is evaluated for entrance surface dose measurements in diagnostic radiology. The system sensitivity for the standard MOSFET detector coupled to a high sensitivity bias supply was measured to be 1 mV mGy-1. Response of a new high sensitivity dosemeter was measured to be 3 mV mGy-1. The minimum detectable entrance surface dose at which a single measurement can be made with less than 25% total uncertainty at the 95% confidence level was estimated to be 4 mGy for the standard dosemeter and 1.5 mGy for the new high sensitivity dosemeter. The dosemeters were found to be linear with absorbed dose in air, linear with dose rate and reproducible, although they showed some energy dependence across the diagnostic energy range. The system is also compared with thermoluminescent dosimetry (TLD) as a tool for the measurement of entrance surface dose in diagnostic radiology. MOSFET detectors are considered to have advantages over TLD dosemeters with the instant readout of entrance surface dose. These dosemeters do have the disadvantage that they are visible in radiographs, they have a finite shelf life and can only accumulate absorbed dose up to a limiting value after which the dosemeters can no longer be used.     

Examination of patient skin dose during abdominal interventional radiology using a GAF system

Radiation-induced skin injury caused by interventional radiology(IVR)is a deterministic effect. If exposure dose exceeds threshold dose, injuries may occur. It therefore is important to understand the maximum exposure dose in skin. The purpose of this study was to determine the maximum exposure dose and its dose distribution. Moreover, to analyze the factors from measuring the absorbed dose in the incoming radiation side, a film-type dosimeter was used. When the measured results were determined in terms of the clinical aspect, fluoroscopic time(total time)in procedure, it ranged from 3.3 to 64.0 minutes, and DSA images obtained ranged from 8 to 280 images. Absorbed dose ranged from 0.3 to 6.0 Gy, with an average dose of 3.2 Gy. It thus exceeded 2 or 3 Gy, which was the threshold dose of temporary erythematic or depilation in 10 of 14 cases. The maximum dose was 6.0 Gy for a procedure of percutaneous transhepatic obliteration. The maximum exposure dose can be determined objectively by using a film-type dosimeter. It was also possible to grasp the overall dose distribution visually.     

Patient skin dose in interventional radiology using radiochromic dosimetry film

Various types of X-ray examinations are currently being carried out for the purpose of diagnosis. However, since dose limits for contamination by medical examinations have not been set, management of dose measurements and contamination records is called for. With increasing use of the IVR technique, reports of radiation injury and the symptoms associated with it have become more common. To advance our understanding of this situation and to reduce contamination, it is necessary to carry out contamination management. The reflection film on which colors are formed by irradiating X-rays has recently come into use. Dose measurement is possible with the use of this film, and, because effective results can be obtained as a result of performing fundamental examinations, the film actually provides dose measurements for the IVR technique. Another benefit is that maximum patient skin dose and dose distribution can be determined in addition to dose measurement. Moreover, since various methods were examined in this study, the method of dose evaluation is also reported for those wishing to employ it in the clinical setting.     

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.     

Evaluation of patient entrance dose rate of interventional X-ray equipment

Because interventional radiology (IVR) procedures are being performed with increasing frequency, patient X-ray exposure dose for X-ray fluoroscopic and radiographic procedures should not be ignored. In order to avoid excessive X-ray exposure, exposure dose rate limits are specified in the Japanese Industrial Standards (JIS) and by civil law at 50 mGy/min for usual fluoroscopy and 125 mGy/min for high-dose fluoroscopy. In the present study, we examined the difference in patient incident dose rate before and after using an X-ray generator that satisfied the above requirements. For incident dose to the image intensifier (I.I.), we investigated the differences between continuous and pulsed fluoroscopy, the effects of additional filters (Ta: tantalum, Al: aluminum), and the form of the X-ray spectrum. For pulsed fluoroscopy using PMMA (polymethyl-methacrylate), the maximum patient incident dose rates of usual and high-dose fluoroscopy were 59 mGy/min and 151 mGy/min, respectively. With regard to I.I. incident dose, saturation was observed beginning at a PMMA of 20 cm, and the X-ray dose was insufficient. In terms of the difference in patient incident dose rate with Ta and Al filters, the dose rate with the Ta filter was approximately 50% lower than that with the Al filter except for the saturation area. Concerning the X-ray spectrum, it was considered that a Ta filter not only minimizes patient X-ray exposure (because Ta reduces soft X-rays more effectively than Al) but also minimizes scattered X-rays because it filters out hard X-rays, leading to improved image quality. However, the use of the filter is appropriate only when a sufficient I.I. incident dose can be ensured. Specifically, the use of the filter under saturation conditions can lead to deterioration in image quality. Therefore, IVR X-ray systems must be equipped with an appropriate filter for reducing X-ray exposure while maintaining a sufficient I.I. incident dose rate.     

Reduction in patient skin dose during interventional radiology with the use of an air gap substitute

Scattered radiation is inevitably generated in the patient couch during interventional radiology (IVR) procedures that use an under-couch tube system. Most of this scatter reaches the patient's skin surface and results in an increase in the skin dose without contributing to the diagnostic image. We considered that this unnecessary exposure could be reduced by the addition of an air gap between the couch and the patient. Because it is physically impossible to place an air gap on top of the couch and under the patient, we devised a new process in which an expanded polystyrene (EPS; rho = 0.0125 g cm(-3)) board is used as a substitute for the air gap. The results show that the EPS board played an effective role in reducing the skin dose to the patient. Using an EPS board 6 cm thick as an air gap substitute resulted in skin dose savings of approximately 9%. This method is easy to set up in clinical circumstances and is inexpensive. We recommend that this simple method of skin dose reduction be used for all IVR procedures.     

平板DSA介入检查治疗患者的剂量调查

目的 调查平板数字减影血管造影(DSA)介入检查治疗患者的照射剂量,分析影响患者照射剂量的因素.方法 收集2009年3至6月来本院做DSA检查治疗的患者461例,手术种类包括全脑血管造影(CEA)、颅内动脉瘤弹簧圈栓塞(CAE)、肝脏动脉造影+超选化疗(SHAC)、冠状动脉造影(COA)、冠状动脉支架植入(PISI)、心脏射频消融(RFCA)、永久起搏器安装(PCPI).通过采集所有病例的剂量面积值(DAP)、累计皮肤表面人射剂量(CAK)、透视时间,采用转换因子计算有效剂量值.结果 CEA、CAE、SHAC、COA、PIST、RFCA、PCPI的有效剂量当量分别为(0.33±0.20)、(0.49±0.35)、(6.92±4.19)、(0.76±0.91)、(2.35±1.47)、(0.50±0.74)和(0.67±0.70)Sv;461例患者中超过1 Sv的达到120人次,占26%,超过10 Sv的达到10人次,均为SHAC患者.CAK分另为(0.55±0.43)、(1.34±1.11)、(0.95±0.57)、(0.32±0.31)、(0.91±0.33)、(0.16±0.22)和(0.15±0.14)Gy,CAK值超过1 Gy共为59例,占12.8%,超过2 Gy为11例,占2.4%,有2例超过3 Gy,为4.5和6.1 Gy,分别为CEA和CAE患者.结论 各项介入手术患者所受照射剂量个体差异较大.介入检查治疗患者接受的照射剂量较高,需要进行严格的监督以保证患者照射剂量得到最佳控制.

Abstract：

Objective To investigate the radiation doses for the patients undergoing interventional radiology and to analyze the dose - influencing factors.MethodsThe clinical data of 461 patients undergoing interventional radiology,including cerebral angiography ( CEA ),cerebral aneurysm embolism ( CAE ),superselective hepatic arterial chemoembolization ( SHAG ),coronary angiography ( COA ),percutaneous intracoronary stent implantation ( PIS1 ),cardiac radiofrequency catheter ablation ( RFCA ),and permanent cardiac pacemaker implantation(PCPI) were collected to observe the cumulative air kerma (CAK),dose area product (DAP),and fluoroscopy time,and effective dose was estimated using the conversion factors.Results The effective doses for CEA,CAE,SHAG,COA,PISI,RFCA,and PCPI were (0.33 ±0.20),(0.49 ±0.35),(6.92 ±4.19),(0.76 ±0.91),(2.35 ± 1.47),(0.50 ±0.74),and (0.67 ±0.70) Sv,respectively.In 126 of the 416 patients (26%),the effective doses were greater than 1 Sv,and the effective doses of 10 person-times were greater than 10 Sv,all of which were observed in the patients undergoing SHAG.The CAK values for CEA,CAE,SHAG,COA,PISI,RFCA,and PCPIwere (0.55 ±0.43),(1.34 ± 1.11),(0.95 ±0.57),(0.32 ±0.31),(0.91 ±0.33),(0.16 ±0.22),and (0.15 ±0.14) Gy,respectively.The CAK values were greater than 1 Gy in 59 of the 461 patients ( 12.8% ),greater than 2 Gy in 11 cases (2.4%) ,and greater than 3 Gy in 1 CEA cases and 1 CEA case,respectively.Conclusions There is a wide variation range in radiation dose for different procedures.As most interventional radiology procedure can result in clinically significant radiation dose to the patient,stricter dose control should be carried out.     

Measurement of patient skin dose in interventional radiology using passive integrating dosimeter

To avoid radiation injury from interventional radiology (IVR), quality assurance (QA) of IVR equipment based on dosimetry is important. In this study, we investigated the usefulness of measuring patient skin dose with a passive integrating dosimeter and water phantom. The optically stimulated luminescence dosimeter (OSLD) was chosen from among various passive integrating dosimeters. The characteristics of the OSLD were compared with a reference ionization dosimeter. The effective energy obtained from the OSLD was compared with that found by the aluminum attenuation method for using the reference ionization dosimeter. Doses and effective energies measured by OSLD correlated well with those of the reference ionization dosimeter. (dose: y=0.971x, r=0.999, effective energy: y=0.990x, r=0.994). It was suggested that OSLD could simultaneously and correctly measure both patient skin dose and effective energy. Patient skin dose rate and effective energy for 15 IVR units of 10 hospitals were investigated using OSLD and a water phantom for automatic brightness control fluoroscopy. The measurement was performed at the surface of a water phantom that was located on the interventional reference point, and source image intensifier distance was fixed to 100 cm. When the 9-inch field size was selected, the average patient skin dose rate was 16.3+/-8.1 mGy/min (3.6-32.0 mGy/min), the average effective energy was 34.6+/-4.1 keV (30.5-42.5 keV). As a result, it was suggested that QA should be performed not only for patient dose but also for effective energy. QA of equipment is integral to maintaining consistently appropriate doses. Consequently, the dosimetry of each IVR unit should be regularly executed to estimate the outline of patient skin dose. It was useful to investigate patient skin dose/effective energy with the passive integrating dosimeter for IVR equipment.     

A new reference point for patient dose estimation in neurovascular interventional radiology

In interventional radiology, dose estimation using the interventional reference point (IRP) is a practical method for obtaining the real-time skin dose of a patient. However, the IRP is defined in terms of adult cardiovascular radiology and is not suitable for dosimetry of the head. In the present study, we defined a new reference point (neuro-IRP) for neuro-interventional procedures. The neuro-IRP was located on the central ray of the X-ray beam, 9 cm from the isocenter, toward the focal spot. To verify whether the neuro-IRP was accurate in dose estimation, we compared calculated doses at the neuro-IRP and actual measured doses at the surface of the head phantom for various directions of the X-ray projection. The resulting calculated doses were fairly consistent with actual measured doses, with the error in this estimation within approximately 15 %. These data suggest that dose estimation using the neuro-IRP for the head is valid.     

五种介入程序中职业人员手部受照剂量水平的评估

目的 评估5种临床介入程序中,职业人员手部受照剂量水平。方法 选择北京4家医院进行5种介入程序的治疗,职业人员术中左右手各佩戴1枚热释光指环剂量计（TLD,LiF：Mg,Ti）,进行手部剂量当量H_p（0.07）监测,同时分别记录患者的透视电压、透视电流、透视时间、摄影数,总累积剂量、剂量面积乘积等影响因素信息,对影响因素进行分析。结果 本研究共监测5种介入程序,119例手术。对5种介入程序中职业人员左手与右手受照剂量进行分析,差异有统计学意义（t=1.99,P<0.05）。不同介入程序的第一术者手部受照剂量左手、右手差异均有统计学意义（F=455.83、116.45,P<0.01）。影响因素分析中,随着透视管电压,透视电流,透视时间,摄影数的增加,操作者手部剂量也增加（r=0.570、0.712、0.564、0.711,P<0.05）。将上述单因素分析有统计学意义的变量引入多元线性回归方程中,采用逐步回归法拟合方程。经拟合方程为y=225.763+1.862x₁-98.125x₂（F=22.726,P<0.05）。其中变量x₁为透视时间,x₂为摄影数。表明影响操作者手部剂量的主要因素是透视时间和摄影数。结论 在开展上述5种介入程序治疗时,第一术者的手部剂量最高,其次第二术者、助手或护士;5类介入程序中,第一术者的手部受照剂量水平高低排列为心脏起搏器植入术（PM） > 射频消融（RFA） > 冠状动脉血管造影术（CA） > 支架植入术（PTCA+PCI） > 脑动脉瘤介入术（ITCA）;大量开展PM手术时,第一术者手部的年当量剂量有可能超过限值。