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.     

Patient dose related to the complexity of interventional cardiology procedures

In interventional cardiology (IC) the PTCA (percutaneous transluminal coronary angioplasty) procedure is the most frequent procedure with the highest dose to the patient. The procedure is usually performed by cardiologists having, in general, insufficient knowledge of radiation physics, radiation technology and radiation protection. The need for radiation protection is of paramount importance in this field of interventional radiology. Correlation between the complexity of PTCA procedure and irradiation parameters (fluoroscopy time, number of images and dose-area product--DAP) has been demonstrated. The presence of severe tortuosity and occlusion of > or = 3 months play a major role. Fluoroscopy time is better correlated with technical factors than DAP, which also includes the influence of patient size, collimation, operation modes, and X ray beam orientation. The number of acquired images is less correlated with the complexity of the PTCA procedure. A complexity index was conceived and procedures were divided into three groups, defined as: simple, medium and complex, which were significantly different in terms of patient dose.     

Patient dosimetry in diagnostic and interventional radiology: a practical approach using trigger levels

Patient dosimetry is performed in radiology and interventional radiology to assess whether deterministic injuries may occur and to establish the risk of stochastic effects. A fundamental problem for patient dosimetry is that no single quantity can be used to accurately assess both the risk of stochastic effects and whether deterministic injuries will occur following a specific examination or procedure. In cardiology and interventional radiology, two different approaches to patient dosimetry are commonly used. Effective dose is a quantity which correlates reasonably well with the risk of stochastic effects. Effective dose may be deduced from the dose-area product (DAP) for the procedure if sufficient information is known. DAP does not correlate with maximum skin dose, which may be used to predict whether deterministic injuries may occur. DAP meter readings may be used as a trigger level for the investigation of maximum skin entrance dose. Trigger levels for different procedures are proposed.     

Measurement of radiation dose in dental radiology

Patient dose audit is an important tool for quality control and it is important to have a well-defined and easy to use method for dose measurements. In dental radiology, the most commonly used dose parameters for the setting of diagnostic reference levels (DRLs) are the entrance surface air kerma (ESAK) for intraoral examinations and dose width product (DWP) for panoramic examinations. DWP is the air kerma at the front side of the secondary collimator integrated over the collimator width and an exposure cycle. ESAK or DWP is usually measured in the absence of the patient but with the same settings of tube voltage (kV), tube current (mA) and exposure time as with the patient present. Neither of these methods is easy to use, and, in addition, DWP is not a risk related quantity. A better method of monitoring patient dose would be to use a dose area product (DAP) meter for all types of dental examinations. In this study, measurements with a DAP meter are reported for intraoral and panoramic examinations. The DWP is also measured with a pencil ionisation chamber and the product of DWP and the height H (DWP x H) of the secondary collimator (measured using film) was compared to DAP. The results show that it is feasible to measure DAP using a DAP meter for both intraoral and panoramic examinations. The DAP is therefore recommended for the setting of DRLs.     

Review of dosimetry instrumentation in digital and interventional radiology

Some dosimetry instruments and products are reviewed, the main emphasis being on patient dosimetry, recommendations for accuracy in different measurement applications and the results of some intercomparisons. It seems to be a common problem that the users of the general purpose air kerma (Ka) meters, dose-area product (DAP) meters or products such as thermoluminescence (TL) dosemeters are not always able to select the correct ionisation chamber, the calibration factor of a DAP meter or the TL dosemeter material and type, respectively, for different radiation conditions. The combined DAP and Ka meters developed recently, as well as the exposure data acquisition systems designed for monitoring one or more quantities or for determining the effective dose of a complicated examination, are described briefly. The most advanced software of these systems is able to display the dose distributions for the most exposed areas of the skin, on-line.     

Entrance radiation doses during paediatric cardiac catheterisations performed for diagnosis or the treatment of congenital heart disease

The purpose of this study was to estimate the radiation exposure of children, during cardiac catheterisations for the diagnosis or treatment of congenital heart disease. Radiation doses were estimated for 45 children aged from 1 d to 13 y old. Thermoluminescent dosemeters (TLDs) were used to estimate the posterior entrance dose (DP), the lateral entrance dose (DLAT), the thyroid dose and the gonads dose. A dose-area product (DAP) meter was also attached externally to the tube of the angiographic system and gave a direct value in mGy cm2 for each procedure. Posterior and lateral entrance dose values during cardiac catheterisations ranged from 1 to 197 mGy and from 1.1 to 250.3 mGy, respectively. Radiation exposure to the thyroid and the gonads ranged from 0.3 to 8.4 mGy to 0.1 and 0.7 mGy, respectively. Finally, the DAP meter values ranged between 360 and 33,200 mGy cm2. Radiation doses measured in this study are comparable with those reported to previous studies. Moreover, strong correlation was found between the DAP values and the entrance radiation dose measured with TLDs.     

Investigation of occupational radiation exposure during interventional cardiac catheterisations performed via radial artery

The purpose of this study was to determine the thyroid, sternum and hand radiation doses of radiologists who perform angiographies and angioplasties via the radial artery. Staff radiation dose was estimated for 21 cardiac interventional catheterisations. Thermoluminescence dosemeters (TLDs) were used to determine radiation dose for each procedure at the right and left wrist, at the sternum and the thyroid. A dose area product (DAP) meter was also attached to give a direct value in Gy cm2 for each procedure. Staff radiation doses varied between 34 and 235 microGy per procedure at the left wrist, 28 and 172 microGy at the right wrist, 16 and 106 microGy at the level of the thyroid and 16 and 154 microGy at the level of the sternum. The DAP values varied between 25 and 167 Gy cm2. Radiation doses in this study are comparable to those reported in previous studies. Moreover, good correlation was found between the DAP values and the occupational dose measured with TLDs.     

A chamber for determining the conventionally true value of Hp(10) and H*(10) needed by calibration laboratories

A secondary standard chamber for photon radiation developed for measuring directly the conventionally true value of the personal dose equivalent, Hp(10), in a slab phantom is now commercially available. In addition, this chamber can be used for determining the true value of the ambient dose equivalent, H*(10), in monodirectional radiation fields; for example, photon fields generated by X ray facilities. Once the chamber has been calibrated at the facility of the calibration laboratory, the true value of Hp(10) or H*(10) can be measured at other facilities without applying any conversion coefficients. For low energy photon fields the conversion coefficients are strongly dependent on the spectral distribution. For nominally the same radiation quality small spectral differences, caused, for example, by use of different X ray facilities, may lead to differences between the spectrum-averaged conversion coefficients from Ka to Hp(10) and H*(10), respectively, of up to several tens per cent. For this reason, tabulated conversion coefficients for low energy radiation fields cannot be used for calibration purposes, if the standard uncertainty is to be 2-5%. Direct measurement by the secondary standard chamber overcomes this problem.     

Filtered X ray beam dosimetry from 10(-3) to 10(2) Gy dose range by using phototransistors

Low-cost, commercially available phototransistor-type semiconductor devices have been tested for monitoring filtered X ray beam dose. A Pantak X-ray unit was used to generate aluminium filtered X ray beams from 60 to 120 kV potentials. The analysis of the radiation detection behaviour as a function of the X ray tube parameters (peak kilovoltage and electrical current) are presented. The changes of the phototransistor electronic parameters have been evaluated and the results indicate that phototransistors can be used as X ray detectors for dose estimation in two different ways: electrical current read-out from 1 to 100 mGy dose range, and the changing of the radiation detection sensitivity in the dose range from 0.1 to 100 Gy. In addition, the devices show high reliability with no sign of substantial performance degradation with use and, in certain dose ranges, the cumulative dose evaluations could be performed up to 10,000 times with no need for re-calibration.     

Comparison of TLD algorithms for monochromatic fluorescent radiation and continuous spectrum X rays

A personal dosimetry system is required to measure the personal dose equivalent accurately in a wide range of radiation fields. However, the dose evaluation algorithm at the Korea Atomic Energy Research Institute (KAERI) has been developed with the spectral X ray fields described in the American National Standards Institute (ANSI) Standard N13.11 and the actual fields to be monitored may be significantly different from these. To evaluate the dose more accurately when workers are exposed to non-ANSI N13.11 radiation fields, a dose evaluation algorithm using monochromatic radiation (monochromatic algorithm) was developed using the experimental data of the energy responses of CaSO4:Dy thermoluminescent materials irradiated by monochromatic fluorescent X ray fields recently established at KAERI; this was compared with another algorithm developed on the basis of the ANSI N13.11 continuous spectrum X ray fields (spectrum algorithm). The paper concludes with discussions about some results of the algorithm test, including mixed field irradiation and angular response, conducted in an International Atomic Energy Authority/Regional Cooperation of Asia (IAEA/RCA) intercomparison study.     

Radiation doses to patients from enteroclysis

The purpose of this study was to determine the patient doses during enteroclysis and compare them with the available bibliographical data. For 14 enteroclysis examinations, the dose-area product (DAP) meter readings, fluoroscopy time, number of radiographs and exposure data were recorded. From these data, the fluoroscopy and radiography contributions to DAP, the entrance surface dose (ESD) and the effective dose (E) for each examination were estimated. The mean DAP was 81 Gy cm(2) and the mean fluoroscopy time was 19.5 min. The fluoroscopy contribution to DAP was 77% and 8.7 films were acquired in each examination on average. The mean ESD and E were estimated to be 428 mGy and 21 mSv, respectively. The mean DAP and fluoroscopy time calculated in this study are quite high when compared with those reported in the literature, suggesting that the examination technique should be reviewed and the ways to reduce patient exposure without compromising the diagnostic quality should be acquired.     

Radiation dose measurements to the interventional cardiologist using an electronic personal dosemeter

The aim of this study was to investigate the use of an electronic personal dosemeter (EPD) worn by a senior cardiologist in an Interventional Cardiology (IC) Laboratory of a busy cardiac centre and how the results could help in the evaluation of radiation protection equipment used. Patient samples consist of 28 patients (10 coronary angiographies (CAs) and 18 percutaneous transluminal coronary angioplasties (PTCAs)). Patient dose was measured with a dose-area product (DAP) meter. Cardiologist radiation dose value written on the EPD as well as the protective equipment used was collected. Between patient and cardiologist dose, a significant correlation was found in CA and a moderate correlation in PTCA. Mean cardiologist effective dose E per procedure was found to be 0.2 microSv in CA and 0.3 microSv in PTCA. EPD proved to be an easy, direct and straightforward way to measure the radiation dose that the cardiologist receives in an IC laboratory.     

The influence of patient size on patient doses in cardiology

In cardiology and interventional radiology, areas that contribute large components to medical radiation exposure, a major source of variation in patient dose is the variation in complexity between cases for nominally identical procedures. In patient dose surveys, this variation tends to mask that due to patient size. The effect of applying a previously defined size correction to cardiology patient dose-area product (DAP) records was investigated. The correction method uses the experimentally determined relationship between patient diameter and DAP to derive a factor to convert DAP to that which would be expected had the patient been similar in size to ICRP Reference Man. The size correction was found to greatly reduce the residual correlation of DAP with patient weight. An implication of this finding is that data collection for the setting of diagnostic reference levels in cardiology can be performed for all patients rather than just 'standard-sized' patients.     

The dose-area product and assessment of the occupational dose in interventional radiology

This study used dose-area product (DAP) data to determine the relationship between the dose received by radiologists and the DAP. The working conditions were simulated by phantom measurements. The doses of scattered radiation were measured using various scattering angles, distances and tube voltages. The calculated doses of scattered radiation were compared with the measured doses of scattered radiation. To test the validity of using such data for assessing occupational doses, the scatter dose on the radiologist or cardiologist was calculated from the DAP using the measured scatter factors. The dose to the lenses of the eyes may exceed the annual limit, and may therefore restrict the number of interventional procedures. A relation between the DAP and the occupational dose is difficult to establish, especially because staff doses are associated with the use of protective devices, positions of projections with respect to the patient, and working methods. However, the DAP may provide a good reference value for the dosimetric monitoring of staff.     

40~125kV脉冲X射线参考辐射场的建立

为解决用于X射线诊断、安检等涉及到的脉冲X射线剂量监测仪表的时间响应修正问题,建立了模拟上述辐射条件的40~125kV脉冲X射线参考辐射场。该参考辐射场同时具备了常规辐射场特性和脉冲辐射场特性。基于栅控技术的高压发生器可以调控光管产生不同脉冲特性的X射线,使用脉冲时间测量模块对产生X射线的脉冲特性(上升和下降沿时间、曝光时间等)进行测量,得到的结果表明该参考辐射场可用于主动式剂量监测设备的时间响应修正和剂量溯源。     

Effective dose to patient during cardiac interventional procedures (Prague workplaces)

The aim of this study was to assess effective dose to a patient during cardiac procedures, such as coronary angiography (CA) and percutaneous transiluminal angioplasty (PTCA). Measurements were performed on 185 patients in four catheterisation laboratories in three hospitals in Prague using the dose area product (DAP) meter. Calculations of surface and effective dose were performed with Monte-Carlo-based program PCXMC. The mean DAP value per procedure determined in all workplaces ranged between 25.0 and 54.5 Gy cm2 for CA and 43.0-104.5 Gy cm2 for PTCA. In three cases, the surface dose exceeded the 2 Gy level for occurrence of transient erythema. The mean effective dose per procedure in all workplaces was determined to be in the range of 2.7-8.8 mSv for CA and 5.7-15.3 mSv for CA + PTCA combined. The results presented are comparable with those published by other authors.     

Field calibration studies for ionisation chambers in mixed high-energy radiation fields

The monitoring of ambient doses at work places around high-energy accelerators is a challenging task due the complexity of the mixed stray radiation fields encountered. At CERN, mainly Centronics IG5 high-pressure ionisation chambers are used to monitor radiation exposure in mixed fields. The monitors are calibrated in the operational quantity ambient dose equivalent H*(10) using standard, source-generated photon- and neutron fields. However, the relationship between ionisation chamber reading and ambient dose equivalent in a mixed high-energy radiation field can only be assessed if the spectral response to every component and the field composition is known. Therefore, comprehensive studies were performed at the CERN-EU high-energy reference field facility where the spectral fluence for each particle type has been assessed with Monte Carlo simulations. Moreover, studies have been performed in an accessible controlled radiation area in the vicinity of a beam loss point of CERN's proton synchrotron. The comparison of measurements and calculations has shown reasonable agreement for most exposure conditions. The results indicate that conventionally calibrated ionisation chambers can give satisfactory response in terms of ambient dose equivalent in stray radiation fields at high-energy accelerators in many cases. These studies are one step towards establishing a method of 'field calibration' of radiation protection instruments in which Monte Carlo simulations will be used to establish a correct correlation between the response of specific detectors to a given high-energy radiation field.     

The potential for reduction of radiation doses to patients undergoing some common X ray examinations in Tanzania

The potential for patient dose reduction in diagnostic radiology was investigated in five major Tanzanian hospitals. The aim of this study was to follow up previously reported suggestions for improved practices to achieve dose reductions. The suggestions were implemented and entrance surface dose measurement repeated by using well-calibrated LiF thermoluminescence dosemeters. The results show that dose reductions in chest PA X ray examinations ranged from 15% to 50%. For abdomen AP and pelvis AP X ray examinations, the dose reductions ranged from 24% to 73% and from 25% to 72%, respectively. The respective dose reductions for lumbar spine AP and LAT projections ranged from 4% to 58% and from 16% to 77%. Interestingly, the majority of radiographs obtained after the implementation of dose reduction measures were useful for intended diagnosis according to the opinion of radiologists. It is concluded that significant dose reductions can be achieved in the country without loss of diagnostic information. Such dose reductions also predict reductions of radiation risk to patients.     

The quality assurance and constancy checking of fluoroscopy and fluorography systems

X ray procedures which involve fluoroscopy often give significant radiation doses to patients. A valuable radiation protection procedure is the adoption of a quality assurance programme which will ensure the continual production of optimal quality images with the minimum necessary dose to the patient. Various publications exist which provide information on quality assurance (QA) and constancy checking of fluoroscopy and fluorography systems. These publications were reviewed and tests recommended for QA and constancy checking of fluoroscopy and fluorography systems are presented. It was found that not much information exists on QA and constancy checking for digital subtraction angiography and digital fluorography systems. More research is required in this field. Information on protocols used by various countries of the European Community for QA and constancy checking of fluoroscopy and fluorography systems was gathered. From this information it is apparent that there is a need for harmonisation within Europe.     

Calibration of dosemeters used in mammography with different X ray qualities: EUROMET project no. 526

The effect of different X ray radiation qualities on the calibration of mammographic dosemeters was investigated within the framework of a EUROMET (European Collaboration in Measurement Standards) project. The calibration coefficients for two ionization chambers and two semiconductor detectors were established in 13 dosimetry calibration laboratories for radiation qualities used in mammography. They were compared with coefficients for other radiation qualities, including those defined in ISO 4037-1, with first half value layers in the mammographic range. The results indicate that the choice of the radiation quality is not crucial for instruments with a small energy dependence of the response. However, the radiation quality has to be chosen carefully if instruments with a marked dependence of their response to the radiation energy are calibrated.