Dose-area Product Values Research Articles

Entrance Surface Dose during Three-dimensional Imaging with a Flat-panel Detector Angiography System

To measure the entrance surface dose (ESD) during three-dimensional (3D) imaging of a phantom and evaluate a method to estimate ESD with use of dose-area product (DAP) values. The present study used an angiographic unit with a digital flat-panel system for 3D imaging. DAP values and ESDs were evaluated on square phantoms with thicknesses of 12.0, 15.0, 18.0, 21.0, and 25.0 cm with use of 5-second acquisitions. ESDs were measured on the lateral and posterior surfaces of the square phantom. DAP values and ESDs were also evaluated on a human-shaped phantom with various table heights, with ESDs measured on the phantom surfaces on the posterior centerline, right middle axillary line, and their midpoint. The posterior ESDs were 7.3 mGy, 12.1 mGy, 18.8 mGy, 26.9 mGy, and 38.5 mGy for the square phantoms with thicknesses of 12 cm, 15 cm, 18 cm, 21 cm, and 25 cm, respectively. The DAP and the posterior ESDs were correlated (r = 0.998, P < .0001). The regression equation was D = DAP x 0.0014, where D was the posterior ESD (mGy). For the human-shaped phantom, the posterolateral ESD tended to be slightly larger than the posteromedial ESD, with the differences less than 10%. The estimated doses based on this relationship were almost equal to the actual posterolateral doses for each table height. The ESD of a single 3D imaging study was considerably lower than the thresholds for radiation skin injuries. The DAP values are useful to estimate the maximum patient ESD during 3D imaging.

Conversion coefficients for the estimation of effective doses in intraoral and panoramic dental radiology from dose-area product values

Conversion coefficients for the estimation of effective doses in intraoral and panoramic dental radiology from dose-area product (DAP) values were determined by measuring organ-absorbed doses and the corresponding DAP values. Measurements were performed for all standard intraoral radiological projections and standard panoramic examination at different exposure parameters. Organ-absorbed doses were measured using thermoluminescent detectors and an adult anthropomorphic phantom specially designed for dosimetric study in dental radiology. Different techniques for the calculation of effective doses were evaluated. Conversion coefficients derived from this study range from 0.008 to 0.132 microSv mGy(-1) cm(-2) for intraoral radiography and 0.055 to 0.238 microSv mGy(-1) cm(-2) for panoramic radiography.

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 cm(2)) in RAO and 7.4 mGy/(Gy cm(2)) in LAO projection. The coefficients of DAP to the effective dose were 0.37 mSv/(Gy cm(2)) in RAO, and 0.41 mSv/(Gy cm(2)) in LAO projection. These coefficients enabled us to estimate patient exposure in real time by using monitored values of DAP.

Zur Strahlenexposition von Kindern in der pädiatrischen Radiologie

Development of an algorithm for computer-assisted dose reconstruction using exposure data from a very large electronic database of a university children's hospital. Radiation dose values and new conversion factors for pediatric radiology were calculated and selected results for skull X-rays of 5-year-old patients will be presented. Since 1976 all relevant data from daily routine X-ray examinations performed in Dr. von Hauner's Kinderspital (children's hospital of the university of Munich, DvHK) have been stored electronically in a database. This database now encompasses basic personal patient data, type of radiological procedure, individual radiographic/fluoroscopic settings, dose measurements (dose area product), individual referral criteria and radiological diagnosis. After 30 years of data gathering, the database now includes 305 434 radiological examinations (radiographs and fluoroscopies) of all age groups, from newborns to adolescents. With a computer program, called PADOS, a specific algorithm was created to calculate radiation doses using the individual dose area product values and other known exposure parameters extracted from the databases. The dose reconstruction procedure is based on the conversion factor concept. By means of the PCXMC program developed by the Finnish Center for Radiation and Nuclear Safety (STUK, Helsinki), Monte Carlo simulations were performed to calculate new conversion factors for pediatric radiology based on the radiographic technique used in the DvHK. The entrance dose values of skull X-rays showed a very good correlation with the changes of examination technique in the last 30 years. In our sample, the measured dose values for skull X-rays were far below the reference dose levels set by the Bundesamt für Strahlenschutz (BfS) in 2003. Conversion factors for 28 different radiographic procedures, 6 age groups, 40 reference organs, 3 beam projections, 12 voltage settings and 3 total filtration levels were calculated. The influence of collimation on the organ doses of radiosensitive organs, e. g. thyroid, bone marrow, in all age groups, especially in the very young, was able to be demonstrated. The PADOS algorithm seems to be suitable for the handling of very large and heterogeneous radiological databases and allows the reconstruction of various dose entities.

Radiation exposure during endovascular aneurysm repair

Endovascular stent-grafting is an established option for the repair of abdominal aortic aneurysm (AAA) that can involve prolonged manipulation under radiological control. The aim was to determine the average radiation exposure sustained during endovascular aneurysm repair (EVAR) and the first year of postoperative surveillance. Prospective radiation dose data were recorded and used to calculate dose area product (DAP) values for 96 patients undergoing EVAR. The DAP data were then used to determine the entrance skin dose (ESD), an indicator of potential skin damage, and the effective dose, an indicator of long-term cancer risk, for each patient. The median ESD during EVAR was 0.85 (interquartile range 0.51-3.74) Gy. The threshold for possible radiation-induced skin damage of 2 Gy was exceeded in 29 per cent of procedures. The effective dose of radiation in the first year following EVAR was 79 mSv. Radiation doses administered during EVAR were higher than previously thought, with a potential risk of radiation-induced skin damage and later malignancy.

Patient doses and dosimetric evaluations in interventional cardiology

Interventional cardiological examinations may be associated with excessive radiation exposures which may cause skin injuries and higher probabilities of stochastic effects. Dose–area product (DAP) and skin doses of 325 patients were measured using alternative dosimetric techniques for different cardiological examinations. Data were collected from five different systems with the involvement of 11 cardiologists. All these dosimetric information has been collected separately for each of 10 projections together with the exposure parameters of X-ray systems. Mean DAP values measured with a transparent ion chamber were 49.1 Gy cm 2, 66.8 Gy cm 2, 106.9 Gy cm 2 and 124.7 Gy cm 2, respectively, for coronary angiography (CA), percutaneous transluminal coronary angioplasty (PTCA) or stent (PT-SI), coronary angiography and/or PTCA and/or stent (CA-PT-SI), and ablation examinations. Radiochromic films, thermoluminescent dosimeters (TLD) and point measurement of air kerma (AK) were carried out for skin dose assessments. Skin doses of 23 patients measured with radiochromic films were found to be between 2 Gy and 6 Gy. Although the complexity of the procedures was the major reason for these excessive doses, considerable contributions of high X-ray output of some fluoroscopy units were also noticed. In addition to the direct measurement of DAP, alternative DAP values were also determined from the skin dose measurement techniques; exposed areas were summed on digitized radiochromic films in one technique, The product of AK reading with X-ray field size measured at the patient entrance using slow X-ray films was taken as another DAP. Good correlations were found among the DAP results and also between the entrance skin doses calculated from AK measurements and direct DAP readings ( R 2 = 0.91). A trigger DAP value of 130 Gy cm 2 for the 2 Gy of skin doses was derived from this relationship. Collection of dosimetric data for each projection was also investigated regarding a possible standardization of clinical techniques; in the case of coronary angiography examinations LAO 45 and RAO 30 were found as the dominant projections which may also simplify the dosimetric technique.

Methods to reduce patients' maximum skin dose during percutaneous coronary intervention for chronic total occlusion

The purpose of this research is to assess the patient's entrance skin dose (ESD) during percutaneous coronary intervention (PCI) for chronic total occlusion (CTO), and discuss methods to reduce the maximum ESDs. Only a few reports are available on the methods to reduce patients' maximum ESD during the procedures. This study included consecutive 30 patients who underwent PCI procedures for CTO in the three institutions. Pearson correlation test was employed to determine the relationship between total fluoroscopic time (TFT) and the maximum ESD, dose area product (DAP) value, and the maximum ESD in each institution. There were significant correlations between the TFT and maximum ESD (Institution 1: P = 0.000410, Institution 2: P = 0.000525), and between the DAP and the maximum ESD (Institution 2: P < 0.0001). In Institution 1, TFT of 60 min was set as the upper limit, and the maximum ESDs were controlled within 7 Gy. In Institution 2, the angiographic unit was a biplane system, and two skin sites were exposed, corresponding to the angulation of each X-ray tube. In Institution 3, the interventionalist changed the beam angulations frequently by several degrees during the procedures, and the maximum ESD was controlled within 3 Gy even during procedures with a TFT of more than 1 hr. The TFT and DAP, the latter of which is preferable, are useful to estimate the maximum ESD. Limiting the TFT or DAP, or changing the beam angulations is important to control ESD during prolonged procedures.

A study of the correlation between dose area product and effective dose in vascular radiology

The purpose of the multi-centre study was to assess dose area product (DAP) and effective dose of patients undergoing angiography of the lower limbs in Belgium and to investigate the correlation between DAP and effective dose. DAP values were measured in 12 centres and compared with the national diagnostic reference levels (DRLs). The effective dose (E) was estimated by multiplying the DAP with case-specific conversion coefficients (CCs) that were calculated with Monte Carlo software MCNP5. As a model for the patient, a mathematical hermaphrodite phantom was used. Calculations showed that tube configurations and extra Cu filtration have a large influence on these CCs. Due to the use of Cu filtration, effective dose can be twice as high for comparable DAP values. Also the use of an over-couch tube configuration is a disadvantage when compared with the under-couch tube configuration. For centres working under-couch without the use of extra Cu-filtration, the DAP values correlate very well with effective dose (Spearman's rank correlation rho ; = 0.97). For these conditions, general CCs between DAP and E were calculated. They were 0.083 mSv Gy(-1) cm(-2) (ICRP 60) and 0.065 mSv Gy(-1) cm(-2) (ICRP 103).

Variation in radiation doses in paediatric cardiac catheterisation procedures

Paediatric cardiac catheterisation involves diagnostic and therapeutic procedures that range from simple to complex and can subject paediatric patients to varying radiation doses. The study aims to determine the variation in entrance doses in patients in terms of dose-area product (DAP) values and to investigate the methods for optimising radiation protection. A total of 190 paediatric patients belonging to age groups 0, 1, 5 and 10 y who underwent diagnostic and six selected therapeutic procedures at King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia were included in the study. Therapeutic procedures include coarctation (COA), patent ductus arteriosus (PDA), radiofrequency ablation, pulmonary, embolisation and septostomy. Fluoroscopy and cine radiography were used in all procedures. Patient demography (weight, age, gender and height), radiographic technique factors, fluoroscopy and cine time, frame rate, and DAP values were taken from patients records. Effective doses for each procedure were estimated from the DAP values. The mean DAP per procedure were analysed for correlation with patient equivalent cylindrical diameter, weight, fluoroscopy time and number of frames. Factors influencing the variation in doses were investigated. Initial results show that PDA occlusion has the highest mean DAP value of 23.21 Gy-cm2, while the diagnostic and septostomy procedures have the lowest value of 7.77 and 6.95 Gy-cm2, respectively.

Diagnostic reference levels in angiography and interventional radiology: a Belgian multi-centre study

The purpose of this study was to determine diagnostic reference levels (DRLs) for common angiographic and interventional procedures in Belgium. Dose Area Product (DAP) measurements were performed on 21 systems, (13 angiography and 4 vascular surgery centres). Type of procedure, total DAP, patient weight and height were collected on a daily basis during 1 y. The 75th percentile of the distribution of DAP values was defined as DRL. Preliminary DRLs were calculated for the three most frequent procedures for the whole population, for a weight class of patients (65-80 kg) and normalised to the standard size patient. Among them, the DRL for angiography of the lower limbs (30% of the procedures) from the whole population was 74.6 and 63.2 Gycm2 for the size corrected. The mean DAP values of each room was then compared to these DRLs.

Proposed preliminary diagnostic reference levels for three common interventional cardiology procedures in Ireland

This study has gathered data across Ireland to determine the range of radiation doses received during interventional cardiology (IC) investigations. Radiation doses for three common types of IC examinations where investigated: coronary angiography (CA), percutaneous coronary intervention (PCI) and pacemaker insertions (PPI). A total of 22 cardiac imaging suites participated in the study. Radiation dose was monitored for 1804 adult patients using dose area product (DAP) meters. Individual patient DAP values ranged from 136-23,101 cGy cm2, 475-41,038 cGy cm2 and 45-17,192 cGy cm2 for CA, PCI and PPI respectively, with third quartile values of 4654 cGy cm2, 10,650 cGy cm2 and 1686 cGy cm2. The importance of optimising radiation dose, while not compromising diagnostic efficacy is clear. Although setting reference levels for these complex procedures has some difficulties, it is important that some guideline values are available as a benchmark to guide the operators during these potentially high dose procedures. The third quartile values as described by this paper may offer such guidance.

Calculating effective dose on a cone beam computed tomography device: 3D Accuitomo and 3D Accuitomo FPD

This study evaluates two methods for calculating effective dose, CT dose index (CTDI) and dose-area product (DAP) for a cone beam CT (CBCT) device: 3D Accuitomo at field size 30x40 mm and 3D Accuitomo FPD at field sizes 40x40 mm and 60x60 mm. Furthermore, the effective dose of three commonly used examinations in dental radiology was determined. CTDI(100) measurements were performed in a CT head dose phantom with a pencil ionization chamber connected to an electrometer. The rotation centre was placed in the centre of the phantom and also, to simulate a patient examination, in the upper left cuspid region. The DAP value was determined with a plane-parallel transmission ionization chamber connected to an electrometer. A conversion factor of 0.08 mSv per Gy cm(2) was used to determine the effective dose from DAP values. Based on data from 90 patient examinations, DAP and effective dose were determined. CTDI(100) measurements showed an asymmetric dose distribution in the phantom when simulating a patient examination. Hence a correct value of CTDI(w) could not be calculated. The DAP value increased with higher tube current and tube voltage values. The DAP value was also proportional to the field size. The effective dose was found to be 11-77 microSv for the specific examinations. DAP measurement was found to be the best method for determining effective dose for the Accuitomo. Determination of specific conversion factors in dental radiology must, however, be further developed.

Interventional cardiology irradiation: clinical and dosimetric aspects of treated population

Context: Minimally invasive interventional cardiology procedures (ICP) have been widely used over the last 10 years, but can involve potentially high radiation doses to the patients. Although deterministic effects of ionising radiation are likely to occur in that field, stochastic effects, in particular radiation-induced cancers, have never been investigated in a population of adult patients. As a first step toward such investigation, a study was conducted with the view of characterizing clinical features and analysing variation factors of dosimetric data, based on a population undergoing ICP. Material and methods: A total of 1,591 patients who underwent 1 to 5 ICP, either coronarography and/or angioplasty, during the year 2005, at the Saint-Gatien Clinic in Tours (France), were included. Individual clinical characteristics were registered, dose-area product (DAP) values were recorded and patients’ organ doses to lung, œsophagus, bone marrow and breast were assessed by a mathematical modelling. A logistic regression to test associations between high doses and clinical and technical factors was used. Results: Mean age of patients was 68 years. More than 60% of them had hypertension, 60% hypercholesterolemia and 25% diabetes. One patient out of three was smoker or ex-smoker, with higher percentage of patients aged less than 60 years. As for dosimetry, patient mean cumulative DAP value was 78.9 Gy.cm² and the mean effective dose was 15.8 mSv. The corresponding estimated mean organ doses were: 62.3 mGy for lung, 54.9 mGy for œsophagus, 17.0 mGy for bone marrow and 5.6 mGy for breast. Based on univariate analysis, high DAP values (> 200 Gy.cm²) were significantly associated with gender, high body mass index, diabetes, hypertension, previous heart bypass, previous myocardial infarction, number of ICP, type of ICP (coronarography and/or angioplasty) and operator. In multivariate analysis, some of these factors remained significant: body mass index (OR=1.16, 95%CI=[1.10-1.21]), previous heart bypass (OR=3.13 [2.14-6.32]) and increased number of ICP (OR=3.82 [1.82-4.20]). Odds ratios were even higher when comparing coronary angioplasties to coronarographies (OR=20.72 [7.77-55.27]). Operator effect was also observed with an increased risk for one operator among the three others (OR=1.91 [1.15-3.18]). Conclusion: Radiation doses received by patients undergoing ICP can widely vary according to clinical characteristics but also technical characteristics of procedures. In order to plan epidemiological studies on the harmful stochastic effect of ionising radiation induced by ICP, such factors, which may be associated with higher DAP values, should be taken into account when designing epidemiological studies on highly irradiated patients.

Patient dosimetry in interventional cardiology at the University Hospital of Osijek

The interventional cardiology was recently implemented at the University Hospital of Osijek. Patients' absorbed doses during coronary angiography (CA) and the percutaneous transluminal coronary angioplasty (PTCA) procedures were measured and compared with published data and international standards. All patients undergoing CA or PTCA procedures during a 1-month period were included in the study. Patients' doses are expressed in terms of dose area product (DAP) per procedure. The patients' DAPs ranged from 2.6 to 210 Gy cm2 (average of 59 Gy cm2) during CAs, and from 61 to 220 Gy cm2 (average of 120 Gy cm2) during PTCAs. Patients' doses during CAs and PTCAs at the University Hospital of Osijek are in good agreement with the published ones. In complex cases, the radiochromic dosimetry films were used to show possible dose distributions across patient's skin. The film dosimetry showed a limitation of using only DAP values for the estimation of skin injuries risk.

Dose and image quality optimization in neonatal radiography

In a special care baby unit, neonates, mainly premature, encounter serious to life-threatening diseases, the timely diagnosis and treatment of which may require a large number of radiographs. Increased neonatal radiosensitivity and longer life expectancy increase the risk of radiation-induced cancer, which emphasizes the importance of minimizing dose while maintaining clinically satisfactory image quality. An optimization study on radiation dose and image quality in neonatal radiography is presented. Neonates were categorized into four groups depending on birthweight. For a total of 378 chest and chest-abdomen radiographs, exposure parameters were recorded. Entrance surface dose (ESD) was estimated and dose-area product (DAP) was measured. Image quality evaluation was performed by two observers and was based on the visibility of certain anatomical features and catheters placed during treatment using a five-grade scale. ESD values increased with neonatal weight and demonstrated wide variation (16.4-76.9 microGy, mean 38.2 microGy). A wide variation was also observed in DAP values (1.2-15.0 mGycm2, mean 7.2 mGycm2). Image quality evaluation revealed the feasibility of achieving a diagnostically satisfactory image (score >70%) using both low and high tube voltage techniques, with the latter resulting in reduced ESDs. The majority of estimated ESDs are in accordance with the reference level of 50 microGy recommended by the National Radiological Protection Board for neonatal radiography. The results suggest that the use of high tube voltage techniques could result in further reductions in neonatal dose, without image quality degradation, underlying the requirement for establishing standard examination protocols for neonatal radiography with respect to neonatal weight.

Organ and effective doses of patients arising from coronary angiography and percutaneous transluminal coronary angioplasty at two hospitals in Mashhad-Iran

A detailed study of radiation doses received by 83 patients who underwent coronary angiography (CA) and 26 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) by the femoral route in two hospitals in Mashhad-Iran is presented. All procedures were undertaken with Siemens angioscope X-ray equipment. Thermoluminescent dosimeters (TLD-100), suitably calibrated, were used to measure the dose received at five locations on the patient's skin (on the thyroid, gonads and lens of eyes). A dose area product (DAP) meter was also used. DAP values and fluoroscopy times were recorded for each patient. The mean values for DAP were 32.47+/-4.03 and 44.49+/-5.64 Gy cm2 for CA and PTCA, respectively. The patient dosimetry results revealed the thyroid receives the highest dose in CA and PTCA examinations. Also, in this study, DAP to effective dose conversion factors were estimated by means of a Rando phantom and the effective dose received by the patients was estimated for CA and PTCA examinations. The estimated mean values of effective dose were 6.75+/-0.85 and 9.61+/-1.24 mSv, respectively.

A large-scale multicentre study in Belgium of dose area product values and effective doses in interventional cardiology using contemporary X-ray equipment

In this paper, a large-scale multicentre patient dose study performed in eight Belgian interventional cardiology departments is presented. Effective dose (E) was calculated based on a detailed dose-area product (DAP)-registration during each procedure and by using conversion coefficients generated by the Monte Carlo-based computer program PCXMC. Conversion coefficients were found to be 0.177 mSv Gycm(-2) for systems that do not use any additional copper filtration in cineradiography and 0.207 mSv Gycm(-2) for systems that use additional copper filtration in cineradiography. Mean E values of 9.6 and 15.3 mSv for diagnostic and therapeutic procedures, respectively, were obtained. DAP distributions were investigated in order to derive dose reference levels: 71 and 106 Gycm2 for diagnostic and therapeutic procedures, respectively, are proposed. Significant differences were observed in DAP distributions taking into account whether additional copper filtration was used in the cineradiography mode. Apart from the skin, the organs most at risk are lungs and heart. The probability of fatal cancer for the studied population amounted to 1.1x10(-4) and 2.1x10(-4) for diagnostic and therapeutic procedures, respectively, for the age distribution of the patients considered in this multicentre study.

Obesity Is a Major Determinant of Radiation Dose in Patients Undergoing Pulmonary Vein Isolation for Atrial Fibrillation

This study sought to evaluate the impact of obesity on patient radiation dose during atrial fibrillation (AF) ablation procedures under fluoroscopic guidance. Obesity is a risk factor for AF and its recurrence after ablation. It increases patient radiation dose during fluoroscopic imaging, but this effect has not been quantified for AF ablation procedures. Effective radiation dose and lifetime attributable cancer risk were calculated from dose-area product (DAP) measurements in 85 patients undergoing AF ablation guided by biplane low-frequency pulsed fluoroscopy (3 frames/s). Three dose calculation methods were used (Monte Carlo simulation, dose conversion coefficients, and depth-profile dose curves). Median DAP for all patients was 119.6 Gy x cm2 (range 13.9 to 446.3 Gy x cm2) for procedures with a median duration of 4 h and 83 +/- 26 min of fluoroscopy. Body mass index was a more important determinant of DAP than total fluoroscopy time (r = 0.74 vs. 0.37, p < 0.001), with mean DAP values per hour of fluoroscopy of 58 +/- 40 Gy x cm2, 110 +/- 43 Gy x cm2, and 184 +/- 79 Gy x cm2 in normal, overweight, and obese patients, respectively. The corresponding effective radiation doses for AF ablation procedures were 15.2 +/- 7.8 mSv, 26.7 +/- 11.6 mSv, and 39.0 +/- 15.2 mSv, respectively (Monte Carlo). Use of conversion coefficients resulted in higher effective dose estimates than other methods, particularly in obese patients. Mean attributable lifetime risk of all-cancer mortality was 0.060%, 0.100%, and 0.149%, depending on weight class. Obese patients receive more than twice the effective radiation dose of normal-weight patients during AF ablation procedures. Obesity needs to be considered in the risk-benefit ratio of AF ablation and should prompt further measures to reduce radiation exposure.

Dose-area product measurements and determination of conversion coefficients for the estimation of effective dose in dental lateral cephalometric radiology

A study has been carried out to propose diagnostic reference levels (DRLs) for lateral cephalometric radiology in Germany based on the dose-area product (DAP). DRLs were proposed separately for child and adult exposure settings which are 26.4 and 32.6 mGy cm2, respectively. Organ absorbed doses from lateral cephalometric radiology were also measured using thermoluminescence detectors (TLDs) and an adult anthropomorphic phantom specially design for dosimetric study in dental radiology. Effective doses were then calculated using three different techniques where the salivary gland and brain tissue were given different weighting factors. Conversion coefficients for estimating effective dose from DAP value derived in this study range from 0.042 to 0.149 microSv/mGy cm2.

Thyroid Dose During Neurointerventional Procedures: Does Lead Shielding Reduce the Dose?

To assess radiation dose to the thyroid in patients undergoing neurointerventional procedures and to evaluate dose reduction to the thyroid by lead shielding. A randomized patient study was undertaken to evaluate the dose reduction by thyroid lead shields and assess their practicality in a clinical setting. Sixty-five patients attending for endovascular treatment of arteriovenous malformations (AVMs) and aneurysms were randomized into one of 2 groups a) No Thyroid Shield and b) Thyroid Lead Shield. Two thermoluminescent dosimeters (TLDs) were placed over the thyroid gland (1 on each side) at constant positions on each patient in both groups. A thyroid lead shield (Pb eq. 0.5 mm) was placed around the neck of patients in the thyroid lead shield group after the neurointerventional radiologist had obtained satisfactory working access above the neck. The total dose-area-product (DAP) value, number and type of digital subtraction angiography (DSA) runs and fluoroscopy time were recorded for all patients. Of the 72 patients who initially attended for neurointerventional procedures, 7 were excluded due to failure to consent or because of procedures involving access to the external carotid circulation. Of the remaining 65 who were randomized, a further 9 were excluded due to; procedureabandonment, unfeasible shield placement or shield interference with the procedure. Patient demographics included mean age of 47.9 yrs (15-74), F:M=1.4:1. Mean fluoroscopy time was 25.9 min. Mean DAP value was 13,134.8 cGy x cm(2) and mean number of DSA runs was 13.4. The mean relative thyroid doses were significantly different (p< 0.001) between the unshielded (7.23 mSv/cGy2 x 105) and shielded groups (3.77 mSv/cGy2 x 105). A mean thyroid dose reduction of 48% was seen in the shielded group versus the unshielded group. Considerable doses to the thyroid are incurred during neurointerventional procedures, highlighting the need for increased awareness of patient radiation protection. Thyroid lead shielding yields significant radiation protection, is inexpensive and when not obscuring the field of view, should be used routinely.