Optimization of the "Perth CT" Protocol for Preoperative Planning and Postoperative Evaluation in Total Knee Arthroplasty

Background and Objectives: Total knee arthroplasty (TKA) has become the treatment of choice for advanced osteoarthritis. The aim of this paper was to show the possibilities of optimizing the Perth CT protocol, which is highly effective for preoperative planning and postoperative assessment of alignment. Materials and Methods: The cross-sectional study comprised 16 patients for preoperative planning or postoperative evaluation of TKA. All patients were examined with the standard and optimized Perth CT protocol using advance techniques, including automatic exposure control (AEC), iterative image reconstruction (IR), as well as a single-energy projection-based metal artifact reduction algorithm for eliminating prosthesis artifacts. The effective radiation dose (E) was determined based on the dose report. Imaging quality is determined according to subjective and objective (values of signal to noise ratio (SdNR) and figure of merit (FOM)) criteria. Results: The effective radiation dose with the optimized protocol was significantly lower compared to the standard protocol (p < 0.001), while in patients with the knee prosthesis, E increased significantly less with the optimized protocol compared to the standard protocol. No significant difference was observed in the subjective evaluation of image quality between protocols (p > 0.05). Analyzing the objective criteria for image quality optimized protocols resulted in lower SdNR values and higher FOM values. No significant difference of image quality was determined using the SdNR and FOM as per the specified protocols and parts of extremities, and for the presence of prothesis. Conclusions: Retrospecting the ALARA ('As Low As Reasonably Achievable') principles, it is possible to optimize the Perth CT protocol by reducing the kV and mAs values and by changing the collimation and increasing the pitch factor. Advanced IR techniques were used in both protocols, and AEC was used in the optimized protocol. The effective dose of radiation can be reduced five times, and the image quality will be satisfactory.

UNCERTAINTY ASSOCIATED WITH THE USE OF SOFTWARE SOLUTIONS UTILIZING DICOM RDSR FOR SKIN DOSE ASSESSMENT IN INTERVENTIONAL RADIOLOGY AND CARDIOLOGY

PURPOSE

The purpose of this work is to provide a comprehensive analysis of uncertainties associated with the use of software solutions utilizing DICOM RDSRs for skin dose assessment in the interventional fluoroscopic environment.

METHODS AND RESULTS

Three different scenarios have been defined for determining the overall uncertainty, each with a specific assumption on the maximum deviations of factors affecting the calculated dose. Relative expanded uncertainty has been calculated using two approaches: the law of propagation of uncertainty and the propagation of distributions based on the Monte Carlo method. According to the propagation of uncertainty, it is estimated that the lowest possible relative expanded uncertainty of ~13% (at the 95% level of confidence, i.e. with the coverage factor of k = 2 assuming normal distribution) could only be achieved if all sources of uncertainties are carefully controlled, whereas maximum relative expanded uncertainty could reach up to 61% if none of the influencing parameters are controlled properly. When the influencing parameters are reasonably well-controlled, realistic relative expanded uncertainty amounts to 28%. Values for the relative expanded uncertainty obtained from the Monte Carlo propagation of distributions concur with the results obtained from the propagation of uncertainty to within 3% in all three considered scenarios, validating the assumption of normality.

CONCLUSIONS

The overall skin dose relative uncertainty has been found to range from 13 to 61%, emphasizing the importance of adequate analysis and control of all relevant uncertainty sources.

Intercomparison and performance assessment of radionuclide calibrators used in nuclear medicine departments in Serbia

The purpose of this work is to assess accuracy and compare the performance of radionuclide calibrators (RNCs) used in nuclear medicine departments in Serbia. Testing of the RNCs included verification of measurement accuracy, as well as analysis of routinely used quality control protocols, by using the certified radioactivity standards (⁵⁷Co, ¹³⁷Cs). RNCs performances were assessed with ^99mTc through comparison of reference value for radionuclide activity and RNC measurements. Results of the intercomparison revealed that RNCs, 15 in total, are accurate within 10% in vial geometry and within 15% in syringe geometry. Most of them showed similar performance. The results revealed that container geometry is an important influencing parameter in the accuracy of activity measurement. Obtained results indicate a need for regular calibration and implementation of Quality Control program in order to achieve and maintain the accuracy of activity measurements in nuclear medicine.

Voxel model of a rabbit: assessment of absorbed doses in organs after CT examination performed by two different protocols

The objective of this work was to assess absorbed doses in organs and tissues of a rabbit, following computed tomography (CT) examinations, using a dedicated 3D voxel model. Absorbed doses in relevant organs were calculated using the MCNP5 Monte Carlo software. Calculations were perfomed for two standard CT protocols, using tube voltages of 110 kVp and 130 kVp. Absorbed doses were calculated in 11 organs and tissues, i.e., skin, bones, brain, muscles, heart, lungs, liver, spleen, kidney, testicles, and fat tissue. The doses ranged from 15.3 to 28.3 mGy, and from 40.2 to 74.3 mGy, in the two investigated protocols. The organs that received the highest dose were bones and kidneys. In contrast, brain and spleen were organs that received the smallest doses. Doses in organs which are stretched along the body did not change significantly with distance. On the other hand, doses in organs which are localized in the body showed maximums and minimums. Using the voxel model, it is possible to calculate the dose distribution in the rabbit's body after CT scans, and study the potential biological effects of CT doses in certain organs. The voxel model presented in this work can be used to calculated doses in all radiation experiments in which rabbits are used as experimental animals.

Recommendations for the use of active personal dosemeters (APDs) in interventional workplaces in hospitals

Occupational radiation doses from interventional procedures have the potential to be relatively high. The requirement to optimise these doses encourages the use of electronic or active personal dosimeters (APDs) which are now increasingly used in hospitals. They are typically used in tandem with a routine passive dosimetry monitoring programme, with APDs used for real-time readings, for training purposes and when new imaging technology is introduced. However, there are limitations when using APDs. A survey in hospitals to identify issues related to the use of APDs was recently completed, along with an extensive series of APD tests by the EURADOS Working Group 12 on Dosimetry for Medical Imaging. The aim of this review paper is to summarise the state of the art regarding the use of APDs. We also used the results of our survey and our tests to develop a set of recommendations for the use of APDs in the clinical interventional radiology/cardiology settings, and draw attention to some of the current challenges.

Use of out-of-field contact shielding on patients in medical imaging: A review of current guidelines, recommendations and legislative documents

The use of patient contact-shielding has become a topic of intensive scientific debate. While it has been common practice during the last decades, some studies have questioned the efficiency of using such shielding while others have highlighted the inconsistencies in its application. The objective of this work is to review current recommendations and legislative documents on the use of out-of-field shielding in X-ray imaging, including those from national authorities and from international and national organisations and professional bodies. The review, performed within the framework of the activities of EURADOS Working Group 12, covers available recommendations on use of contact shielding in adult, pregnant and paediatric patients in general radiography, fluoroscopy, computed tomography, mammography and dental radiology. It includes a comprehensive search of 83 documents from 32 countries and 6 international organisations over the last 39 years. In general, using shielding is recommended only under two conditions: if it does not compromise the diagnostic task and the performance of the procedure and/or if it reassures the patient and comforters that they are appropriately protected against potentially harmful effects of radiation. There are very few specific regulatory requirements to use shielding in a particular imaging modality, although they may consider use of shielding either as part of good radiological practice or as requirements for availability of protective or ancillary tools, without further specification of their use. There is a wide variety of positions among documents that recommend out-of-field shielding, those that do not recommend it and those that are not specific. Therefore, evidence-based consensus is still needed to ensure best and consistent practice.

Towards National Diagnostic Reference Levels for Mammography in Serbia

The objective of this work is to investigate the possibility to set a national diagnostic reference levels (nDRLs) for diagnostic and screening mammography in Serbia based on local practice and available resources. This study included all types of mammography systems that are currently used in Serbia, namely screen-film mammography (SFM), computed radiography (CR) and full-field digital mammography (FFDM). The nDRLs are provided in terms of mean glandular dose (MGD) for different breast thicknesses simulated by polymethyl methacrylate (PMMA) phantom. For each breast thickness, MGD was calculated for the X-ray tube output, using clinically used exposure parameters. DRLs were chosen as the 75th percentile of MGD distribution for 20-, 40-, 45-, 60- and 70-mm phantom thicknesses. For SFM units proposed nDRL values are 0.7, 2.1, 2.7, 4.6 and 6.8 mGy; for CR units proposed nDRL values are 0.7, 1.8, 2.4, 4.5 and 5.6 mGy; and corresponding values for FFDM units are 0.8, 1.7, 2, 2. and 3.2 mGy for 20-, 40-, 45-, 60- and 70-mm PMMA thickness, respectively.

EVALUATION OF RADIATION DOSE FOR PATIENTS UNDERGOING MAMMOGRAPHY IN QATAR

In the absence of information on radiation doses in mammography in the Gulf countries, this study was designed to assess patient dose in terms of entrance surface air kerma and average glandular dose (AGD) in three mammography units in Qatar that covers 21% of all mammography systems in the country. The study of 150 patients involving 600 projections indicated that the average value of AGD in patients was 2.2 mGy for cranio-caudal and 2.5 mGy for mediolateral-oblique views, respectively. Dose assessment was also performed for polymethyl methacrylate phantoms of thicknesses, ranging from 20 to 80 mm. Comparing the patient dose values with several other publications in literature for full-field digital mammography, our values are typically higher, which can be likely attributed to the larger compressed breast thickness.

SKIN DOSE MAPPING IN INTERVENTIONAL CARDIOLOGY: A PRACTICAL SOLUTION

Numerous cases of radiation-induced tissue reactions following interventional cardiology (IC) procedures have been reported, resulting in the need for an optimized and personalized dosimetry. At present, there are many fluoroscopy units without Digital Imaging and Communications in Medicine (DICOM) Radiation Dose Structured Report globally installed. Many of these have not been updated yet, and may never be, therefore, the main objectives of this paper are to develop an offline skin dose mapping application, which uses DICOM headers for the peak skin dose (PSD) assessment and to compare the PSD assessment results to XR-RV3 Gafchromic film for common IC procedures. The mean deviation between the measured and the calculated PSD was 8.7 ± 26.3%. Simulated skin dose map showed good matching with XR-RV3 Gafchromic film. The skin dose mapping application presented in this paper is an elegant solution and a suitable alternative to XR-RV3 Gafchromic film.

THE USE OF ACTIVE PERSONAL DOSEMETERS IN INTERVENTIONAL WORKPLACES IN HOSPITALS: COMPARISON BETWEEN ACTIVE AND PASSIVE DOSEMETERS WORN SIMULTANEOUSLY BY MEDICAL STAFF

Medical staff in interventional procedures are among the professionals with the highest occupational doses. Active personal dosemeters (APDs) can help in optimizing the exposure during interventional procedures. However, there can be problems when using APDs during interventional procedures, due to the specific energy and angular distribution of the radiation field and because of the pulsed nature of the radiation. Many parameters like the type of interventional procedure, personal habits and working techniques, protection tools used and X-ray field characteristics influence the occupational exposure and the scattered radiation around the patient. In this paper, we compare the results from three types of APDs with a passive personal dosimetry system while being used in real clinical environment by the interventional staff. The results show that there is a large spread in the ratios of the passive and active devices.

OCCUPATIONAL EYE LENS DOSE ESTIMATED USING WHOLE-BODY DOSEMETER IN INTERVENTIONAL CARDIOLOGY AND RADIOLOGY: A MONTE CARLO STUDY

Medical personnel performing interventional procedures in cardiology and radiology is considered to be a professional group exposed to high doses of ionizing radiation. Reduction of the eye lens dose limit made its assessment in the interventional procedures one of the most challenging topics. The objective of this work is to assess eye lens doses based on the whole-body doses using methods of computational dosimetry. Assessment included different C-arm orientations (PA, LAO and RAO), tube voltages (80 -110 kV) and efficiency of different combinations of protective equipment used in interventional procedures. Center position at the height of the thyroid gives best estimate of eye lens dose, with spreads of 11% (13%), 13% (17%) and 14% (13%) for the left (right) eye lens. The conversion factors of 1.03 (0.83), 1.28 (1.06) and 1.36 (1.06) to convert whole body to eye lens dose were derived for positions of first operator, nurse and radiographer, respectively. The eye lens dose reduction factors for different combinations of applied protective equipment are 178, 5 and 6, respectively.

IAEA survey of dental cone beam computed tomography practice and related patient exposure in nine Central and Eastern European countries

OBJECTIVES

Cone beam CT (CBCT) in dentistry and maxillofacial surgery is a widely used imaging method for the assessment of various maxillofacial and dental pathological conditions. The objective of this study was to summarize the results of a multinational retrospective-prospective study that focused on patient exposure in this modality.

METHODS

The study included 27 CBCT units and 325 adult and paediatric patients, in total. Data on patients, clinical indications, technical parameters of exposure, patient dose indicator, or, alternatively, dose to phantom were collected. The dose indicator used was air kerma-area product, P_KA.

RESULTS

In most scanners operators are offered with a variety of options regarding technical parameters, especially the field of view size. The median and the third quartile value of P_KA for adult patients in 14 different facilities were 820 mGy cm² and 1000 mGy cm² (interquartile range = 1058 mGy cm²), and 653 mGy cm² and 740 mGy cm² (interquartile range = 1179 mGy cm²) for children, as reported by four different institutions. Phantom dose data were reported from 15 institutions, and median P_KA ranged from 125 mGy cm² to 1951 mGy cm². Median P_KA values varied by more than a 10-fold between institutions, mainly due to differences in imaging protocol used, in particular field of view and tube current-exposure time product.

CONCLUSIONS

The results emphasize the need for a cautious approach to using dental CBCT. Imaging only when the clinical indications are clear, accompanied with the appropriate radiographic techniques and the optimum imaging protocol, will help reduce radiation dose to patients.

Past and present work practices of European interventional cardiologists in the context of radiation protection of the eye lens-results of the EURALOC study

This paper investigates over five decades of work practices in interventional cardiology, with an emphasis on radiation protection. The analysis is based on data from more than 400 cardiologists from various European countries recruited for a EURALOC study and collected in the period from 2014 to 2016. Information on the types of procedures performed and their annual mean number, fluoroscopy time, access site choice, x-ray units and radiation protection means used was collected using an occupational questionnaire. Based on the specific European data, changes in each parameter have been analysed over decades, while country-specific data analysis has allowed us to determine the differences in local practices. In particular, based on the collected data, the typical workload of a European cardiologist working in a haemodynamic room and an electrophysiology room was specified for various types of procedures. The results showed that when working in a haemodynamic room, a transparent ceiling-suspended lead shield or lead glasses are necessary in order to remain below the recommended eye lens dose limit of 20 mSv. Moreover, the analysis revealed that new, more complex cardiac procedures such as chronic total occlusion, valvuloplasty and pulmonary vein isolation for atrial fibrillation ablation might contribute substantially to annual doses, although they are relatively rarely performed. The results revealed that considerable progress has been made in the use of radiation protection tools. While their use in electrophysiology procedures is not generic, the situation in haemodynamic procedures is rather encouraging, as ceiling-suspended shields are used in 90% of cases, while the combination of ceiling shield and lead glasses is noted in more than 40% of the procedures. However, we find that still 7% of haemodynamic procedures are performed without any radiation protection tools.

Use of active personal dosimeters in hospitals: EURADOS survey

Considering that occupational exposure in medicine is a matter of growing concern, active personal dosimeters (APDs) are also increasingly being used in different fields of application of ionising radiation in medicine. An extensive survey to collect relevant information regarding the use of APDs in medical imaging applications of ionising radiation was organised by the EURADOS (European Radiation Dosimetry Group) Working Group 12. The objective was to collect data about the use of APDs and to identify the basic problems in the use of APDs in hospitals. APDs are most frequently used in interventional radiology and cardiology departments (54%), in nuclear medicine (29%), and in radiotherapy (12%). Most types of APDs use silicon diodes as the detector; however, in many cases their calibration is not given proper attention, as radiation beam qualities in which they are calibrated differ significantly from those in which they are actually used. The survey revealed problems related to the use of APDs, including their reliability in pulsed x-ray fields that are widely used in hospitals. Guidance from regulatory authorities and professional organisations on the testing and calibration of APDs used in hospital would likely improve the situation.

Performance Testing Of Selected Types of Electronic Personal Dosimeters in X- and Gamma Radiation Fields

Electronic personal dosimeters (EPDs) are increasingly being used alongside conventional thermoluminescent dosimeters to measure the dose of legal record in terms of personal dose equivalent. Therefore, it is of great importance to execute performance tests of these dosimeters in photon fields of various energies and at various angles of incidence. This testing is done in order to simulate the behavior of these dosimeters in realistic multidirectional polyenergetic ionizing radiation fields. Tests of accuracy, linearity, energy response, and angular response have been performed on 10 EPDs from multiple manufacturers. Various radiation qualities have been used in the energy range from 33 keV to 1.33 MeV and for angles of incidence 0° to 80°. This research proves that many of the EPDs tested performed according to the manufacturer's specifications and the requirements of the international standards regarding personal dosimetry.

Influence of radiation dose in computed tomography on antioxidant enzyme activity in rabbit erythrocytes

The objective of this study was to assess the radiation dose in computed tomography examinations of rabbits using different examination protocols and to correlate these values with the activity of antioxidant enzymes in their red blood cells following irradiation. The presented results revealed that a single, routine computed tomography scan exposure led to a different response of the activity of antioxidant enzymes in red blood cells regarding both dose and time. The results indicate that there is a dose threshold that is about 25 mGy. Doses below that level do not produce any significant changes in the level of antioxidant enzymes activity. On the other hand, the level just above that threshold had a significant impact on the antioxidant defence, but in a relatively short time period (2 hours after exposure), compared to the higher dose that requires a longer adaptive period.

EYE LENS EXPOSURE TO MEDICAL STAFF PERFORMING ELECTROPHYSIOLOGY PROCEDURES: DOSE ASSESSMENT AND CORRELATION TO PATIENT DOSE

The purpose of this study was to assess the patient exposure and staff eye dose levels during implantation procedures for all types of pacemaker therapy devices performed under fluoroscopic guidance and to investigate potential correlation between patients and staff dose levels. The mean eye dose during pacemaker/defibrillator implementation was 12 µSv for the first operator, 8.7 µSv for the second operator/nurse and 0.50 µSv for radiographer. Corresponding values for cardiac resynchronisation therapy procedures were 30, 26 and 2.0 µSv, respectively. Significant (p < 0.01) correlation between the eye dose and the kerma-area product was found for the first operator and radiographers, but not for other staff categories. The study revealed eye dose per procedure and eye dose normalised to patient dose indices for different staff categories and provided an input for radiation protection in electrophysiology procedures.

HAND DOSE EVALUATION OF OCCUPATIONALLY EXPOSED STAFF IN NUCLEAR MEDICINE

Manipulation of unsealed radiation sources in nuclear medicine (NM) departments involves non-uniform exposure to staff and high skin doses to the upper extremities from direct and scattered radiations. Conducted studies have shown that the annual dose limits could be exceeded and the continuous dose monitoring of NM worker's hands is needed. The aim of this article is to show results of hand dose monitoring in terms of operational quantity Hp(0.07) for occupationally exposed NM workers to beta and gamma radiations in the largest NM centre in Serbia. Dose assessment was done by means of thermoluminescent ring dosemeters DXT-RAD (LiF:Mg,Ti). Monthly and annual doses were evaluated for a 5-y period (2010-14). Monitored NM staff was categorised according to the type of work, as nurses, radiographers, laboratory technicians and radiochemists. Performed evaluation showed that annual hand doses were within the annual limit for all staff categories, but further optimisation of working practice is needed.

OCCUPATIONAL DOSE ASSESSMENT IN INTERVENTIONAL CARDIOLOGY IN SERBIA

The objective of this work is to assess the occupational dose in interventional cardiology in a large hospital in Belgrade, Serbia. A double-dosimetry method was applied for the estimation of whole-body dose, using thermoluminescent dosemeters, calibrated in terms of the personal dose equivalent Hp(10). Besides the double-dosimetry method, eye dose was also estimated by means of measuring ambient dose equivalent, H*(10), and doses per procedure were reported. Doses were assessed for 13 physicians, 6 nurses and 10 radiographers, for 2 consequent years. The maximum annual effective dose assessed was 4.3, 2.1 and 1.3 mSv for physicians, nurses and radiographers, respectively. The maximum doses recorded by the dosemeter worn at the collar level (over the apron) were 16.8, 11.9 and 4.5 mSv, respectively. This value was used for the eye lens dose assessment. Estimated doses are in accordance with or higher than annual dose limits for the occupational exposure.

Sensitivity and fading of pMOS dosemeters irradiated with X-ray radiation doses from 1 to 100 cGy

In this paper, the results of pMOS dosemeters sensitivity to X-ray radiation and 28-d fading at room temperature are presented. Two types of dosemeters were used, which differ in gate oxide layer thickness. The sensitivity of pMOS dosemeters with gate oxide layer thickness of 1 µm was followed in the dose intervals of 1 to 10 cGy and 10 to 100 cGy, whereas that of 400 nm was in the interval of 10 to 100 cGy. The sensitivity was characterised by the threshold voltage shift, which was determined as a function of absorbed radiation dose and time after irradiation. Linear dependence between threshold voltage shift and absorbed radiation dose was established, as well as that considerable fading occurs during the first few days after irradiation. The mechanisms responsible for threshold voltage shift during irradiation and latter annealing have been also discussed.

Comparison of pencil-type ionization chamber calibration results and methods between dosimetry laboratories

A comparison of calibration results and procedures in terms of air kerma length product, PKL, and air kerma, K, was conducted between eight dosimetry laboratories. A pencil-type ionization chamber (IC), generally used for computed tomography dose measurements, was calibrated according to three calibration methods, while its residual signal and other characteristics (sensitivity profile, active length) were assessed. The results showed that the "partial irradiation method" is the preferred method for the pencil-type IC calibration in terms of PKL and it could be applied by the calibration laboratories successfully. Most of the participating laboratories achieved high level of agreement (>99%) for both dosimetry quantities (PKL and K). Estimated relative standard uncertainties of comparison results vary among laboratories from 0.34% to 2.32% depending on the quantity, beam quality and calibration method applied. Detailed analysis of the assigned uncertainties have been presented and discussed.

Radiation exposure during X-ray examinations in a large paediatric hospital in Serbia

Objective of this work is to evaluate radiation exposure from X-ray examinations in a large paediatric hospital in Serbia, including radiographic, fluoroscopic and computed tomography (CT) examinations in four age groups: 0-1, 1-5, 5-10 and 10-15 y. Incident air kerma was assessed for the following radiographies: chest (AP, PA, LAT), spine (AP, LAT), pelvis (AP), urinary tract (AP, PA) and skull (AP, PA, LAT). Kerma-area product was measured for the fluoroscopy examinations: barium swallow, barium meal, barium enema and micturating cystography. Dose in CT was assessed in terms of volume CT dose index and dose-length product for examinations of the head, chest and abdomen. The collected data were compared with other similar studies, which indicated a need to expand such survey to other paediatric hospitals in Serbia.

Measurement of maximum skin dose in interventional radiology and cardiology and challenges in the set-up of European alert thresholds

To help operators acknowledge patient dose during interventional procedures, EURADOS WG-12 focused on measuring patient skin dose using XR-RV3 gafchromic films, thermoluminescent detector (TLD) pellets or 2D TL foils and on investigating possible correlation to the on-line dose indicators such as fluoroscopy time, Kerma-area product (KAP) and cumulative air Kerma at reference point (CK). The study aims at defining non-centre-specific European alert thresholds for skin dose in three interventional procedures: chemoembolization of the liver (CE), neuroembolization (NE) and percutaneous coronary interventions (PCI). Skin dose values of >3 Gy (ICRP threshold for skin injuries) were indeed measured in these procedures confirming the need for dose indicators that correlate with maximum skin dose (MSD). However, although MSD showed fairly good correlation with KAP and CK, several limitations were identified challenging the set-up of non-centre-specific European alert thresholds. This paper presents preliminary results of this wide European measurement campaign and focuses on the main challenges in the definition of European alert thresholds.

Eye dosimetry in interventional radiology and cardiology: current challenges and practical considerations

Interventional radiology and cardiology are areas with high potential for risk to eye lens. Accurate assessment of eye dose is one of the most important aspects of correlating doses with observed lens opacities among workers in interventional suites and ascertaining compliance with regulatory limits. The purpose of this paper is to review current approaches and opportunities in eye dosimetry and assess challenges in particular in accuracy and practicality. The possible approaches include practical dosimetry using passive dosemeters or active dosemeters with obvious advantage of active dosimetry. When neither of these is available, other approaches are based on either retrospective dose assessment using scatter radiation dose levels or correlations between patient dose indices and eye doses to the operators. In spite of all uncertainties and variations, estimation of eye dose from patient dose can be accepted as a compromise. Future challenges include development of practical methods for regular monitoring of individual eye doses and development of better techniques to estimate eye dose from measurements at some reference points.

Radiation exposure to nuclear medicine staff involved in PET/CT practice in Serbia

The purpose of this work is to evaluate the radiation exposure to nuclear medicine (NM) staff in the two positron emission tomography-computed tomography centres in Serbia and to investigate the possibilities for dose reduction. Dose levels in terms of Hp(10) for whole body and Hp(0.07) for hands of NM staff were assessed using thermoluminescence and electronic personal dosemeters. The assessed doses per procedure in terms of Hp(10) were 4.2-7 and 5-6 μSv, in two centres, respectively, whereas the extremity doses in terms of Hp(0.07) in one of the centres was 34-126 μSv procedure(-1). The whole-body doses per unit activity were 17-19 and 21-26 μSv GBq(-1) in two centres, respectively, and the normalised finger dose in one centre was 170-680 μSv GBq(-1). The maximal estimated annual whole-body doses in two centres were 3.4 and 2.0 mSv, while the corresponding extremity dose in the later one was 45 mSv. Improvements as introduction of automatic dispensing system and injection and optimisation of working practice resulted in dose reduction ranging from 12 up to 67 %.

Performance of radiation survey meters in X- and gamma-radiation fields

The aim of this work was to investigate the different types of radiation detectors commonly used for radiation protection purposes as survey meters. The study was performed on survey meters that use different detectors as ionisation chamber, Geiger Mueller (GM) counter and scintillation detector. For each survey meter, energy dependence and angular response in X- and gamma-radiation fields was tested. The following commercially available survey meters were investigated: ionisation chambers Victoreen 451P, Babyline 31 and VA-J-15A, Geiger counter MRK-M87, 6150 AD6 and FAG FH 40F2 and scintillation counter 6150 ADB. As a source of gamma radiation, (137)Cs and (60)Co were used whereas X-ray radiation fields were generated using an X-ray unit. The radiation characteristics of the survey meters were mostly in compliance with references estimated by standard IEC 1017-2. However, some of them showed larger deviation at lower energies. GM counters exhibit strong energy dependence for low-energy photons.

Radiation doses in adult computed tomography practice in Serbia: initial results

This work presents initial data on radiation doses in adult computed tomography (CT) in Serbia. Data were collected in terms of CT dose index (CTDIvol) and dose length product (DLP) values for head, chest and abdomen examination. The range of CTDIvol values was found to be 53-98, 11-34 and 8.5-227 mGy whereas for DLP was 803-1066, 350-845 and 1066-3078 mGy cm(-1) for head, chest and abdomen examination, respectively. Except for abdomen on one CT unit, all estimated values were in line with the reported data. This work also presents simple method on how to reduce radiation doses when scanning head. Using axial (step-and-shot) instead of helical mode and decreasing tube current-time product leads to significant dose reduction. CTDIvol was decreased by 20 % whereas DLP was reduced for a factor 2.

Radiation doses in cerebral perfusion computed tomography: patient and phantom study

The purpose of this study was to investigate radiation doses in cerebral perfusion computed tomography (CT) examination. As a part of routine patient monitoring, data were collected on patients in terms of the skin dose and CT dose index (CTDIvol) and dose-length product (DLP) values. For the estimation of the dose to the lens a phantom study was performed. Dose values for skin and lens were below the threshold for deterministic effects. The results were also compared with already published data. For better comparison, the effective dose was also estimated. The values collected on patients were in the ranges 230-680 mGy for CTDI and 2120-2740 mGy cm for DLP, while the skin dose and estimated effective dose were 340-800 mGy and 4.9-6.3 mSv, respectively. These values measured in the phantom study were similar, while the doses estimated to the lens were 53 and 51 mGy for the right and left lens, respectively.

Eye lens dosimetry in interventional cardiology: results of staff dose measurements and link to patient dose levels

Workers involved in interventional cardiology procedures receive high eye lens dose if protection is not used. Currently, there is no suitable method for routine use for the measurement of eye dose. Since most angiography machines are equipped with suitable patient dosemeters, deriving factors linking staff eye doses to the patient doses can be helpful. In this study the patient kerma-area product, cumulative dose at an interventional reference point and eye dose in terms of Hp(3) of the cardiologists, nurses and radiographers for interventional cardiology procedures have been measured. Correlations between the patient dose and the staff eye dose were obtained. The mean eye dose was 121 µSv for the first operator, 33 µSv for the second operator/nurse and 12 µSv for radiographer. Normalised eye lens doses per unit kerma-area product were 0.94 µSv Gy⁻¹ cm⁻² for the first operator, 0.33 µSv Gy⁻¹ cm⁻² for the second operator/nurse and 0.16 µSv Gy⁻¹ cm⁻² for radiographers. Statistical analysis indicated that there is a weak but significant (p < 0.01) correlation between the eye dose and the kerma-area product for all three staff categories. These values are based on a local practice and may provide useful reference for other studies for validation and for wider utilisation in assessing the eye dose using patient dose values.

Radiation-induced eye lens changes and risk for cataract in interventional cardiology

BACKGROUND

Recent studies have reported a significant increase in eye lens opacities among staff in the cardiac catheterization laboratory but indicated further studies are needed to confirm the findings.

OBJECTIVE

To evaluate the prevalence of opacities in eyes of cardiologists, radiographers and nurses working in interventional cardiology.

METHODS

The eyes of 52 staff in interventional cardiology facilities and 34 age- and sex-matched unexposed controls were screened in a cardiology conference held in Kuala Lumpur by dilated slit-lamp examination, and posterior lens changes were graded. Individual cumulative lens X-ray exposures were calculated from responses to a questionnaire in terms of workload and working practice.

RESULTS

The prevalence of posterior lens opacities among interventional cardiologists was 53%, while in nurses and radiographers it was 45%. Corresponding relative risks were 2.6 (95% CI: 1.2-5.4) and 2.2 (95% CI: 0.98-4.9), for interventional cardiologists and support staff, respectively.

CONCLUSIONS

This study confirms a statistically significant increase in radiation-associated posterior lens changes in the eyes of interventional cardiology staff.

ICRP Publication 117. Radiological protection in fluoroscopically guided procedures performed outside the imaging department

An increasing number of medical specialists are using fluoroscopy outside imaging departments, but there has been general neglect of radiological protection coverage of fluoroscopy machines used outside imaging departments. Lack of radiological protection training of those working with fluoroscopy outside imaging departments can increase the radiation risk to workers and patients. Procedures such as endovascular aneurysm repair, renal angioplasty, iliac angioplasty, ureteric stent placement, therapeutic endoscopic retrograde cholangio-pancreatography,and bile duct stenting and drainage have the potential to impart skin doses exceeding Gy. Although tissue reactions among patients and workers from fluoroscopy procedures have, to date, only been reported in interventional radiology and cardiology,the level of fluoroscopy use outside imaging departments creates potential for such injuries.A brief account of the health effects of ionising radiation and protection principles is presented in Section 2. Section 3 deals with general aspects of the protection of workers and patients that are common to all, whereas specific aspects are covered in Section 4 for vascular surgery, urology, orthopaedic surgery, obstetrics and gynaecology,gastroenterology and hepatobiliary system, and anaesthetics and pain management.Although sentinel lymph node biopsy involves the use of radio-isotopic methods rather than fluoroscopy, performance of this procedure in operating theatres is covered in this report as it is unlikely that this topic will be addressed in another ICRP publication in coming years. Information on radiation dose levels to patients and workers, and dose management is presented for each speciality.

Patient dose measurements in diagnostic radiology procedures in Montenegro

It was the aim of the study presented here to estimate for the first time patient dose levels in conventional diagnostic radiology in Montenegro. Measurements of patient dose in terms of entrance surface air kerma (ESAK) and kerma-area product (KAP) were performed on at least 10 patients for each examination type, in each of five randomly selected health institutions in Montenegro, so that a total of 872 patients for 16 different examination categories were included in the survey (817 patients for 1049 radiographies and 55 fluoroscopy patients). Exposure settings and individual data were recorded for each patient. Mean, median and third quartile values ESAK of patient doses are reported. The estimated mean ESAK values obtained are as follows: 4.7 mGy for pelvis anteroposterior (AP), 4.5 mGy for lumbar spine AP, 7.8 mGy for lumbar spine lateral (LAT), 3.1 mGy for thoracic spine AP and 4.3 mGy for thoracic spine LAT. When compared with the European diagnostic reference values, the mean ESAK for all studied examination types are found to be below the reference levels, except in chest radiography. Mean ESAK values for chest radiography are 0.9 mGy for posteroanterior (PA) projection and 2.0 mGy for LAT. The results exhibit a wide range of variation. For fluoroscopy examinations, the total KAP was measured. The mean KAP value per procedure for barium meal is found to be 22 Gy cm(2), 41 Gy cm(2) for barium enema and 19 Gy cm(2) for intravenous urography. Broad dose ranges for the same types of examinations indicate the necessity of applying practice optimisation in diagnostic radiology and establishment of national diagnostic reference levels.

Neutron dose equivalent measured at the maze door with various openings for the jaws and MLC

PURPOSE

This study was undertaken to explore the effects of the jaws and the MLC openings on the neutron dose equivalent (DE) at the maze door and neutron flux at the patient plane.

METHODS

The neutron dose equivalent was measured at the maze entrance door of a 15 MV therapy linear accelerator room. All measurements were performed using various field sizes up to 40 cm × 40 cm. Activation detectors constructed from natural Indium (In) were exposed at Cd envelope to neutrons in order to estimate relative changes of epithermal neutron fluences in the patient plane.

RESULTS

Our study showed that the dose equivalent at the maze door is at the highest when the jaw are closed and that maximal jaws opening reduces the DE by more than 20%. The neutron dose equivalent at the maze door measured for radiation fields defined by jaws do not differ significantly from the DE measured when MLC determines the same size radiation field. The epithermal capture reaction rate measured using different jaw openings differs by approximately 10%. When an MLC leaf is inserted into a fixed geometry for one opening of the jaws, an increase of the epithermal neutron capture reaction rate in Indium activation detectors was observed.

CONCLUSIONS

There is no significant difference in the neutron DE when MLC defines radiation field instead of jaws. This leads to the conclusion that the overall number of neutrons remains similar and it does not depend on how primary photon beam was stopped-by the jaws or the MLC. An increase of the fast neutron capture reaction rate when MLC leaves are inserted probably originates from the neutron scattering.

Status of radiation protection in interventional cardiology in four East European countries

Level of staff and patient radiation protection in interventional cardiology in four counties (Bosnia and Herzegovina, Croatia, Montenegro and Serbia) as a part of International Atomic Energy Agency project (RER/9/093) are presented. Patient doses were assessed in terms of air kerma area product (KAP), peak skin dose (PSD) or air kerma at interventional reference point (K(IRP)). Results were available from nine hospitals: 775 patients for KAP, 157 for PSD and 437 for K(IRP). Eight centres reported KAP >100 Gy cm(2) and five centres reported values >200 Gy cm(2). From patients monitored in terms of PSD, 14 (9 %) had PSD >2 Gy and 6 (3 %) patients from those monitored in terms of K(IRP) had value >5 Gy, indicating risk of skin injury. The results indicate need for optimisation and dose monitoring in complex fluoroscopically guided cardiology interventions.

Radiation and cataract

When this paper was about to go to press, the International Commission on Radiological Protection released a statement recommending a change in the threshold dose for the eye lens and dose limits for eye for occupationally exposed persons. It is clear that the earlier published threshold for radiation cataract is no longer valid. Epidemiological studies among Chernobyl clean-up workers, A bomb survivors, astronauts, residents of contaminated buildings, radiological technicians and recent surveys of staff in interventional rooms indicate that there is an increased incidence of lens opacities at doses below 1 Gy. Nevertheless, eye lens dosimetry is at a primitive stage and needs to be developed further. Despite uncertainties concerning dose threshold and dosimetry, it is possible to significantly reduce the risk of radiation cataract through the use of appropriate eye protection. By increasing awareness among those at risk and better adoption and increased usage of protective measures, radiation cataract can become preventable despite lowering of dose limits.

Comparison of different methods for shielding design in computed tomography

The purpose of this work is to compare different methods for shielding calculation in computed tomography (CT). The BIR-IPEM (British Institute of Radiology and Institute of Physics in Engineering in Medicine) and NCRP (National Council on Radiation Protection) method were used for shielding thickness calculation. Scattered dose levels and calculated barrier thickness were also compared with those obtained by scatter dose measurements in the vicinity of a dedicated CT unit. Minimal requirement for protective barriers based on BIR-IPEM method ranged between 1.1 and 1.4 mm of lead demonstrating underestimation of up to 20 % and overestimation of up to 30 % when compared with thicknesses based on measured dose levels. For NCRP method, calculated thicknesses were 33 % higher (27-42 %). BIR-IPEM methodology-based results were comparable with values based on scattered dose measurements, while results obtained using NCRP methodology demonstrated an overestimation of the minimal required barrier thickness.

Image quality and dose in mammography in 17 countries in Africa, Asia and Eastern Europe: results from IAEA projects

PURPOSE

The objective is to study mammography practice from an optimisation point of view by assessing the impact of simple and immediately implementable corrective actions on image quality.

MATERIALS AND METHODS

This prospective multinational study included 54 mammography units in 17 countries. More than 21,000 mammography images were evaluated using a three-level image quality scoring system. Following initial assessment, appropriate corrective actions were implemented and image quality was re-assessed in 24 units.

RESULTS

The fraction of images that were considered acceptable without any remark in the first phase (before the implementation of corrective actions) was 70% and 75% for cranio-caudal and medio-lateral oblique projections, respectively. The main causes for poor image quality before corrective actions were related to film processing, damaged or scratched image receptors, or film-screen combinations that are not spectrally matched, inappropriate radiographic techniques and lack of training. Average glandular dose to a standard breast was 1.5 mGy (mean and range 0.59-3.2 mGy). After optimisation the frequency of poor quality images decreased, but the relative contributions of the various causes remained similar. Image quality improvements following appropriate corrective actions were up to 50 percentage points in some facilities.

CONCLUSIONS

Poor image quality is a major source of unnecessary radiation dose to the breast. An increased awareness of good quality mammograms is of particular importance for countries that are moving towards introduction of population-based screening programmes. The study demonstrated how simple and low-cost measures can be a valuable tool in improving of image quality in mammography.