Evaluation of patient and staff doses during various CT fluoroscopy guided interventions

As CT scanners are more routinely used as a guidance tool for various types of interventional radiological procedures, concern has grown for high patient and staff doses. CT fluoroscopy provides the physician immediate feedback and can be a valuable tool to dynamically assist various types of percutaneous interventions. However, the fixed position of the scanning plane in combination with high exposure factors may lead to high cumulative patient skin doses that can reach deterministic threshold limits. The staff is also exposed to a considerable amount of scatter radiation while standing next to the patient during the procedures. Although some studies have been published dealing with this subject, data of patient skin doses determined by direct in vivo dosimetry remains scarce. The purpose of this study is to quantify and to evaluate both patient and staff doses by direct thermoluminescent dosimetry during various clinical CT fluoroscopy guided procedures. Patient doses were quantified by determining the entrance skin dose with direct thermoluminescent dosimetry and by estimating the effective dose (E). Staff doses were quantified by determining the entrance skin dose at the level of the eyes, thyroid, and both the hands with direct thermoluminescent dosimetry. For a group of 82 consecutive patients, the following median values were determined (data per procedure): patient E (19.7 mSv), patient entrance skin dose (374 mSv), staff entrance skin dose at eye level (0.21 mSv), thyroid (0.24 mSv), at the left hand (0.18 mSv), and at the right hand (0.76 mSv). The maximum recorded patient entrance skin dose stayed well below the deterministic threshold level of 2 Gy. Poor correlation between both patient/staff doses and integrated procedure mAs emphasizes the need for in vivo measurements. CT fluoroscopy doses are markedly higher than classic CT-scan doses and are comparable to doses from other interventional radiological procedures. They consequently require adequate radiation protection management. An important potential for dose reduction exists by limiting the fluoroscopic screening time and by reducing the tube current (mA) to a level sufficient to provide adequate image quality.     

Skin entrance radiation dose in an interventional radiology procedure

Monitoring of skin entrance radiation exposure in lengthy interventional procedures has been recommended because of the potential for skin injury. Fluoroscopy duration and dose-area product (DAP) are readily available real-time measurements. It would be of interest to study the correlation of these parameters and skin entrance radiation. Twenty neurological interventional procedures performed through the aortic arch were monitored. Two pieces of GafChromic XR Type R film were placed between the patient and the examination table. An observer recorded the fluoroscopy duration and DAP for each phase of the procedure. Each film was scanned post-procedure in RBG mode, and then the image was analyzed for peak skin entrance radiation dose (in air kerma). All DAP values were corrected according to a calibration with an ion chamber. With the DAP values for the respective phases of a procedure, the effective dose in a Reference Man was calculated. For these twenty cases, the means and standard deviations were 17.2+/-6.4 min for x ray on-time, 256+/-65 Gy cm (-2) for DAP, 94+/-34 cGy for peak skin entrance dose in air kerma, and 19.2+/-5.0 mSv for effective dose, respectively. The peak skin entrance dose was correlated to fluoroscopy duration, DAP, and effective dose with the r(2)-values of 0.48, 0.46, and 0.09, respectively. The correlation with DAP or fluoroscopy duration was not sufficiently strong to infer skin entrance dose from either of these parameters. Therefore, skin entrance dose should be determined directly.     

Skin dose measurement for patients using imaging plates in interventional radiology procedures

A method using europium-doped BaFBr imaging plates (IPs) has been developed to estimate and map values of entrance skin doses during interventional radiology (IR). IPs offer many advantages for measuring the entrance skin dose because they have a wide dynamic range (up to 100 Gy), provide high spatial resolution as a detector of two-dimensional images, and can be used repeatedly. The entrance skin dose was measured by fitting a 40x40 cm IP sheet around a patient's back using a corset in clinical studies involving IR procedures at two hospitals. The corset can minimize a geometric discrepancy in dose estimates between the IP and the patient body. The entrance skin dose was measured by using photoluminescent glass dosimeters simultaneously, and both values were compared. The spatial relative dose profiles from both dose estimates showed generally good agreement; however, the doses obtained with glass dosimeter chips were often lower than those obtained with IPs. This discrepancy comes from a radiation shielding effect for x rays by IPs and a strong angular dependence of the glass dosimeter in low energy x-ray fields. Comprehensive results of this study demonstrated that IPs were able to measure entrance skin dose in even high dose regions with steep dose gradients and to determine the peak skin dose, without missing hot spots, over all ranges used during interventional radiology procedures. Use of the corset minimized variations associated with angular dependence.     

上海市“九五”期间X射线诊断医疗照射剂量水平调查

[目的 ]　了解上海市“九五”期间X射线诊断医疗照射所致公众的剂量水平。　 [方法 ]　用TLD剂量计调查上海市 19种X射线诊断平均每次检查受检者体表剂量 ,估算平均每次检查所致受检者各器官吸收剂量及全身有效剂量当量 ,再结合上海市医疗照射调查频率数据 ,进一步估算X射线诊断检查所致公众集体剂量负担。　 [结果 ]　上海市19种X射线诊断检查所致公众年集体剂量当量 1996年为 5 2 0 .92人·Sv ,1998年为 5 46.93人·Sv ;19种X射线诊断检查所致全市年人均有效剂量当量 1996年为 0 .0 40mSv ,1998年为 0 .0 42mSv。　 [结论 ]　上海市X射线诊断医疗照射的剂量水平有增高的趋势 ,应重视医疗照射正确合理应用的问题     

Dose audit and evaluation of work practices during barium procedures using digital radiography techniques

Effective dose and organ doses during barium procedures performed using digital radiography machines were estimated and the related work practices were evaluated. Measured values of dose area product (DAP) were used for the calculation of effective doses. One hundred and thirty eight patients undergoing barium procedures were included in the study. The use of additional 0.2 mm copper filter during barium procedures effectively reduced patient doses. The effective dose during barium swallow procedure varied from 0.03 mSv to 3.5 mSv; during barium meal it varied from 0.18 mSv to 2.62 mSv; and during barium enema it varied from 0.56 mSv to 4.24 mSv. Dose auditing was done on the basis of patient doses, imaging techniques and image quality. Selection of optimized exposure factors imparted lower dose to patients during barium procedures.     

Regular radon activity concentration and effective dose measurements inside the great pyramid with passive nuclear track detectors

Radon activity concentrations and equilibrium factors inside the great pyramid of "Cheops" were measured with passive nuclear track detectors. The variation of these concentrations in location was investigated. Seasonal variation of radon activity concentrations with winter maximum and summer minimum were observed inside the pyramid. The 1-y average radon activity concentration ranged from a minimum of 20 to a maximum of 170 Bq m(-3). Results show that the yearly average equilibrium factor between radon and its progeny was assessed as 0.16 and 0.36 inside the pyramid and near entrance, respectively. Moreover, the estimated annual effective dose was 0.05 mSv to tour guides and varied from 0.19 to 0.36 mSv for the pyramid guards; for visitors the average effective dose was 0.15 microSv per visit. These are lower than the 3-10 mSv y(-1) dose limit recommend by ICRP 65.     

A survey of radiation doses to adults from diagnostic radiology in Victoria.

This study examines doses to adult patients from diagnostic radiology. Measurements were made at 37 hospitals and private radiology centres in the state of Victoria. Skin entrance doses in air were measured for the exposure factors used by the radiographer for an average size patient for the following procedures: abdomen AP; pelvis AP; lumbar spine AP, lat, LSJ; and skull AP, lat. There was a large range of doses observed for each particular procedure. Factors contributing to the range of doses were identified. Guidance levels for adult radiography based on the third quartile values of the skin entrance dose have been adopted for use in Victoria.     

Normalized organ doses and effective doses to a reference Indian adult male in conventional medical diagnostic x-ray examinations

This work discusses the dose computations of 80 kV diagnostic x-rays made on a mathematical phantom representing an average Indian adult, since it is felt that results based on MIRD adult phantom calculations are not strictly appropriate for the population in India. Normalized organ equivalent doses and effective doses for an Indian adult male have been estimated. Normalization is done with respect to the entrance skin dose of the patient. Twenty common diagnostic x-ray examinations have been considered in this study and the doses are presented. This study would enable estimation of radiation induced detriment to the patient subpopulation in India. Since the external dimensions of the phantom are nearly the same as that of 15-y-old NRPB pediatric phantom, our results are also compared with those of latter and the agreement was found to be satisfactory.     

Estimation of the secondary cancer risk induced by diagnostic imaging radiation during proton therapy

We have estimated the secondary cancer risk (SCR) introduced by image-guided procedures during proton therapy. The physical dose from imaging radiation and the corresponding organ equivalent dose were calculated for the case of a lumbar spine patient. The maximum physical dose delivered to the patient during the imaging procedure was estimated to be ~0.35% of the prescribed dose of 46 Gy. However, this small imaging dose substantially raised the radiation-induced SCR by ~8%. In addition, the clinical benefit (improved accuracy during the procedure) and costs (extra SCR) associated with image-guided procedures were quantitatively modelled by systematically investigating the changes in SCR as a function of the prescribed dose, treatment target volume and imaging field size. The results showed that the SCR varied sensitively with the volume receiving the imaging and the therapeutic radiation, whereas the SCR depended to a lesser extent on the magnitude of the applied therapeutic radiation. These results showed that the additional SCR introduced by imaging radiation could be efficiently reduced by minimizing the imaging field size during image-guided procedures.     

Radiation doses to patients from extracorporeal shock wave lithotripsy

The aim of this study was to determine the radiation doses to patients during extracorporeal shock wave lithotripsy (ESWL) and compare them with the available bibliographical data. In this method localization of the renal stones is attained by the use of fluoroscopy, and thus ESWL is included among those medical practices associated with patient radiation exposure. The entrance surface dose was measured using 3-4 thermoluminescent dosimeters positioned on the patients' backs at the entrance surfaces of the two x-ray beams for 50 ESWL procedures. Fluoroscopy time and number of spot films were also recorded. The average entrance surface dose at the patient's side with the renal stone was estimated to be 76.5 mGy for the oblique x-ray beam and 44.5 mGy for the PA x-ray beam. The mean fluoroscopy time was 204 s while 4 spot films were acquired on average. The mean effective dose (E) was estimated as 1.63 mSv per patient. The mean entrance surface dose values recorded in this study are comparable to but smaller than the values reported in the literature for ESWL, while the mean fluoroscopy time is within the range of values reported by other authors. On the other hand, the estimated E value is relatively higher compared to the corresponding values given in the literature based on patient measurements. However, it is comparable to recent published data acquired using extended measurements in an anthropomorphic phantom.     

Direct measurement of a patient's entrance skin dose during pediatric cardiac catheterization

Children with complex congenital heart diseases often require repeated cardiac catheterization; however, children are more radiosensitive than adults. Therefore, radiation-induced carcinogenesis is an important consideration for children who undergo those procedures. We measured entrance skin doses (ESDs) using radio-photoluminescence dosimeter (RPLD) chips during cardiac catheterization for 15 pediatric patients (median age, 1.92 years; males, n = 9; females, n = 6) with cardiac diseases. Four RPLD chips were placed on the patient''s posterior and right side of the chest. Correlations between maximum ESD and dose–area products (DAP), total number of frames, total fluoroscopic time, number of cine runs, cumulative dose at the interventional reference point (IRP), body weight, chest thickness, and height were analyzed. The maximum ESD was 80 ± 59 (mean ± standard deviation) mGy. Maximum ESD closely correlated with both DAP (r = 0.78) and cumulative dose at the IRP (r = 0.82). Maximum ESD for coiling and ballooning tended to be higher than that for ablation, balloon atrial septostomy, and diagnostic procedures. In conclusion, we directly measured ESD using RPLD chips and found that maximum ESD could be estimated in real-time using angiographic parameters, such as DAP and cumulative dose at the IRP. Children requiring repeated catheterizations would be exposed to high radiation levels throughout their lives, although treatment influences radiation dose. Therefore, the radiation dose associated with individual cardiac catheterizations should be analyzed, and the effects of radiation throughout the lives of such patients should be followed.     

Calculation of midplane dose for total body irradiation from entrance and exit dose MOSFET measurements

This work is the development of a MOSFET based surface in vivo dosimetry system for total body irradiation patients treated with bilateral extended SSD beams using PMMA missing tissue compensators adjacent to the patient. An empirical formula to calculate midplane dose from MOSFET measured entrance and exit doses has been derived. The dependency of surface dose on the air-gap between the spoiler and the surface was investigated by suspending a spoiler above a water phantom, and taking percentage depth dose measurements (PDD). Exit and entrances doses were measured with MOSFETs in conjunction with midplane doses measured with an ion chamber. The entrance and exit doses were combined using an exponential attenuation formula to give an estimate of midplane dose and were compared to the midplane ion chamber measurement for a range of phantom thicknesses. Having a maximum PDD at the surface simplifies the prediction of midplane dose, which is achieved by ensuring that the air gap between the compensator and the surface is less than 10 cm. The comparison of estimated midplane dose and measured midplane dose showed no dependence on phantom thickness and an average correction factor of 0.88 was found. If the missing tissue compensators are kept within 10 cm of the patient then MOSFET measurements of entrance and exit dose can predict the midplane dose for the patient.     

Estimation of the genetically significant dose from diagnostic X-ray procedures in the Islamic Republic of Iran

The genetically significant dose from diagnostic X-ray sources has been estimated. Age and sex distribution was based on a survey of 13,100 patients. Dosimetry was performed on patients and on an equivalent-man Rando phantom. Child-expectancy factors were estimated from the census results of fertility and mortality rates. The GSD value for the diagnostic procedures to the Iranian population was estimated to be 9.2 mrem/yr in 1980.     

Boron neutron capture therapy (BNCT) for malignant melanoma with special reference to absorbed doses to the normal skin and tumor

Twenty-two patients with malignant melanoma were treated with boron neutron capture therapy (BNCT) using 10B-p-boronophenylalanine (BPA). The estimation of absorbed dose and optimization of treatment dose based on the pharmacokinetics of BPA in melanoma patients is described. The doses of gamma-rays were measured using small TLDs of Mg2SiO4 (Tb) and thermal neutron fluence was measured using gold foil and wire. The total absorbed dose to the tissue from BNCT was obtained by summing the primary and capture gamma-ray doses and the high LET radiation doses from 10B(n, alpha)7Li and 14N(n,p)14C reactions. The key point of the dose optimization is that the skin surrounding the tumour is always irradiated to 18 Gy-Eq, which is the maximum tolerable dose to the skin, regardless of the 10B-concentration in the tumor. The neutron fluence was optimized as follows. (1) The 10B concentration in the blood was measured 15-40 min after the start of neutron irradiation. (2) The 10B-concentration in the skin was estimated by multiplying the blood 10B value by a factor of 1.3. (3) The neutron fluence was calculated. Absorbed doses to the skin ranged from 15.7 to 37.1 Gy-Eq. Among the patients, 16 out of 22 patients exhibited tolerable skin damage. Although six patients showed skin damage that exceeded the tolerance level, three of them could be cured within a few months after BNCT and the remaining three developed severe skin damage requiring skin grafts. The absorbed doses to the tumor ranged from 15.7 to 68.5 Gy-Eq and the percentage of complete response was 73% (16/22). When BNCT is used in the treatment of malignant melanoma, based on the pharmacokinetics of BPA and radiobiological considerations, promising clinical results have been obtained, although many problems and issues remain to be solved.     

A comparison of entrance skin dose delivered by clinical angiographic c-arms using the real-time dosimeter: the MO<Emphasis Type="Italic">Skin</Emphasis>

Coronary angiography is a procedure used in the diagnosis and intervention of coronary heart disease. The procedure is often considered one of the highest dose diagnostic procedures in clinical use. Despite this, there is minimal use of dosimeters within angiographic catheterisation laboratories due to challenges resulting from their implementation. The aim of this study was to compare entrance dose delivery across locally commissioned c-arms to assess the need for real-time dosimetry solutions during angiographic procedures. The secondary aim of this study was to establish a calibration method for the MOSkin dosimeter that accurately produces entrance dose values from the clinically sampled beam qualities and energies. The MOSkin is a real-time dosimeter used to measure the skin dose delivered by external radiation beams. The suitability of the MOSkin for measurements in the angiographic catheterisation laboratory was assessed. Measurements were performed using a 30 × 30 × 30 cm³ PMMA phantom positioned at the rotational isocenter of the c-arm gantry. The MOSkin calibration factor was established through comparison of the MOSkin response to EBT2 film response. Irradiation of the dosimeters was performed using several clinical beam qualities ranging in energy from 70 to 105 kVp. A total of four different interventional c-arm machines were surveyed and compared using the MOSkin dosimeter. The phantom was irradiated from a normal angle of incidence using clinically relevant protocols, field sizes and source to image detector distance values. The MOSkin was observed to be radiotranslucent to the c-arm beam in all clinical environments. The MOSkin response was reproducible to within 2 % of the average value across repeated measurements for each beam setting. There were large variations in entrance dose delivery to the phantom between the different c-arm machines with the highest observed cine-acquisition entrance dose rate measuring 326 % higher than the lowest measured cine-acquisition entrance dose rate and with the highest measured fluoroscopic entrance dose rate measuring 346 % higher than the lowest measured fluoroscopic entrance dose rate. This comparison of entrance dose delivery across local clinical c-arms demonstrated the disparity in entrance dose delivery across catheterisation laboratories and outlined a need for real-time dose monitoring systems for patients during angiographic procedures. Through use of our calibration method, an average MOSkin calibration of 7.37 mV/cGy was established. The calibration method allowed entrance dose to be measured across a range of beam energies and beam qualities without the input of the c-arm beam characteristics. This calibration factor was proven to reproduce entrance dose values to within 5 % value of the reference dosimeter’s response, suggesting potential for further studies and utilisation of the dosimeter in this field.     

Radiation doses from common radiographic procedures: a ten year perspective

Using a semi-empirical model patient doses for a number of plain film radiographic procedures following the implementation of Computed Radiography (CR) technology in our Hospital have been evaluated. The results are presented in terms of the entrance surface dose (ESD) and the effective dose. A comparison of these results, with those reported previously for 1988, suggests that with the exception of chest radiography, patient doses have decreased although in many instances the decreases are not statistically significant. The finding for chest examinations stands apart from all others in that the introduction of CR technology has resulted in a substantial increase in patient dose for the PA view by at least 18%. The major reason for these apparently contradictory findings has its roots in the effectively variable speed of CR systems and the willingness of radiologists to accept more noise in some CR images.     

2009—2011年在介入诊疗中患者受照剂量的调查

目的通过对不同年份介入治疗过程中不同患者所受辐射剂量的分析,探讨影响辐射剂量的主要因素。方法应用热释光测量法,对不同疾病患者体表受照剂量进行测量、统计分析。结果介入操作中,患者受照剂量差别很大,受多种因素(设备性能、病种、手术复杂程度、术者的操作技术等)影响。平均体表剂量中肝癌患者后背正中最高,为(142.92±75.56)mGy,其次为肿瘤患者。个体受照剂量最高为1 097.00 mGy,为骶尾部脊索瘤患者。2011年患者受照剂量较2009年呈不同程度的上升。结论应采取各种有效措施使患者的受照剂量合理降低,特别是主动防护。     

Radiotherapy verification film for estimating cumulative entrance skin exposure for fluoroscopic examinations

Measurement of skin entrance exposures during fluoroscopic procedures is complicated by the use of automatic exposure control devices and the presence of contrast media. Due to variability in positioning spot films from patient to patient, standard dosimeters, such as thermoluminescent, cannot be properly placed on the skin prior to examination. Prepackaged film of the type used for portal verification in radiation therapy held next to the patient's skin in a specially modified patient examination gown was found to be useful for determining the entrance skin exposure from both fluoroscopy and spot films during air contrast barium enema exams. The usable sensitivity range of this film has been found satisfactory for exposure measurements at exposures and kVps typically used for gastrointestinal fluoroscopic procedures. Errors in exposure estimates due to changes in film speed and contrast with kVp are less than 5% for the range of kVps used. Errors from variations in beam quality due to the adjacency of scattering material are approximately 5%. Entrance exposures determined with film agreed with those determined from TLD measurements to within 21%, with an average difference of 9%.     

腹部介入治疗患者受照剂量调查

目的通过采用DSA机自带的Area Exposure Product Meter穿透电离室型剂量监测系统测量剂量面积乘积值（DAP）以及参考点的累积剂量（CD）值,用Monte Carlo转换系数分别估算出患者的有效剂量（ED）及入射体表剂量率（ESDR）,测量腹部放射介入诊疗中患者的基本剂量学参数,开展放射介入诊断参考水平调查。方法数据处理采用SPSS v13.0版本,参照ICRP第103号出版物和WS/T189-1999《医用X射线诊断设备影像质量控制检验规范》及附录中提供的方法进行。结果肝动脉化疗栓塞组、肝部血管治疗和宫颈癌治疗组DAP的75%分位数分别为76.9、75.3、51.9 Gy/cm2;其中单次操作ED〉10 mSv在各组中所占比例分别为29.4%、29.2%和13.2%;仅有2例ESDR值超过100 mGy/min。结论 DAP的75%分位数可作为医疗照射相应放射介入操作的诊断参考水平（diagnostic reference lev-el,DRL）,为了确定某一地区某一特定操作类型的DRL值还需要收集大量的调查数据和开展剂量学模型的验证工作。     

某医院头部介入诊疗患者的受照剂量调查与分析

目的通过采用DSA机自带的Area Exposure Product Meter穿透电离室型剂量监测系统测量剂量面积乘积值（DAP）以及参考点的累积剂量（CD）值,用Monte Carlo转换系数分别估算出患者的有效剂量（ED）及入射体表剂量率（ESDR）,测量头部放射介入诊疗活动中患者的基本剂量学参数,开展放射介入诊断参考水平调查。方法数据处理采用SPSS v13.0版本,参照ICRP第103号出版物和WS/T189-1999《医用X射线诊断设备影像质量控制检验规范》及附录中提供的方法进行。结果头部全脑血管治疗、全脑血管造影和脑血管栓塞治疗DAP的75%分位数分别为124.9、123.4、185.3 Gy.cm2;其中单次操作ED〉10 mSv在各组中所占比例分别为36.3%、49.3%、55.0%;ESDR的超标率分别为1.9%、1.4%、10.0%结论 DAP的75%分位数可作为医疗照射相应放射介入操作的诊断参考水平（diagnostic reference level,DRL）,为了确定某一地区某一特定操作类型的DRL值还需要收集大量的调查数据和开展剂量学模型的验证工作。