The use of dynamic phantoms in interventional radiology

The authors have constructed a 2D motor-controlled test object phantom holder to simulate clinical situations in which patient movement could be a cause of image degradation. The PAtient MOvement SImulation Test Object (PAMOSITO) has been constructed with modular parts to use different mobile test objects and static structures. The system allows the programming of different cycles of movement along two axes. PAMOSITO has been used in X ray equipment dedicated to interventional radiology. Those systems usually allow for different values for frame rate, pulse width or weighted frame averaging methods. The influence of selecting different values of the parameters, patient movement and its relation to patient dose and image quality has been studied. Image blurring due to motion has been evaluated with Leeds test objects TO.10 and 18FG. Spatial resolution limits and the threshold contrast detail detectability performance have been studied.     

Changing from image intensifier to flat detector technology for interventional cardiology procedures: a practical point of view

A small-scale internal audit has been used to evaluate the impact of the use of a dynamic flat panel detector in the clinical routine in the National Interventional Cardiology Centre in Luxembourg. The parameters tested during commissioning and constancy control of an X-ray system, the introduction of new clinical protocols, the patient and the personal staff dosimetry were considered. The technical parameters tested by the hospital physicist stay the same as for the image intensifier. No innovative protocols have been adopted due to the existence of the flat panel detector. A reduction in dose was noted after the installation of a flat detector, due mostly to the continuing education of the interventional cardiologists as well as the initial calibration of the radiological system. The understanding of the X-ray system and its possibilities is vital for the optimisation of clinical procedures in patient and staff exposure.     

The calibration of dosimetry instruments used in interventional radiology

No general agreement about the definition of the patient dose exists. As regards the radiation health risk, the doses to specific organs, Hi, are the ultimate measures for a patient dose. Values of the calibration measured, Hi, are provided only by calculational means. Out of the whole process of patient dose determination, the instruments to measure X ray spectra, FSD, field dimensions and Ka can be calibrated, X ray quality is derived from the total filtration and kV value. The actual dynamic and X ray quality ranges shall be considered when air kerma and DAP meters are calibrated. A DAP meter measurement averages the uniform radiation field specific for the X ray tube assembly used and for the beam shaping technique performed. Therefore, a DAP meter calibrated on site is preferable for patient dosimetry in interventional radiology.     

Quality control of equipment used in digital and interventional radiology

Digital and interventional radiology are increasingly important areas of radiology. Quality control (QC) of such equipment is of particular importance to avoid unnecessary high doses and to help to achieve good image quality. Within the DIMOND III project, equipment requirements and specifications for digital and interventional radiology have been formulated. A protocol for QC tests has been drafted based on various national and international recommendations. Tests are included for various parts of the imaging chain, i.e. X-ray tube and generator, X-ray tube control system, laser printer and display station, and image quality and patient dose. Preliminary tolerance levels have been set for the various tests, after initial measurements. To check the suitability of QC tests and stated tolerance levels, measurements were made at the University Hospital Gasthuisberg in Leuven for equipment used for paediatric radiology and a unit used for chest examinations. The results of the various tests are reported.     

Automatic management system for dose parameters in interventional radiology and cardiology

The purpose of this work was to develop an automatic management system to archive and analyse the major study parameters and patient doses for fluoroscopy guided procedures performed in cardiology and interventional radiology systems. The X-ray systems used for this trial have the capability to export at the end of the procedure and via e-mail the technical parameters of the study and the patient dose values. An application was developed to query and retrieve from a mail server, all study reports sent by the imaging modality and store them on a Microsoft SQL Server data base. The results from 3538 interventional study reports generated by 7 interventional systems were processed. In the case of some technical parameters and patient doses, alarms were added to receive malfunction alerts so as to immediately take appropriate corrective actions.     

System for personal dosimetry in interventional radiology

The progress made in radiological image processing and transmission is being widely applied in new branches of medicine. The increasing use of interventional radiology in research and clinical practice means that new groups of workers are being exposed to radiation and need to be covered by a system of radiation protection. Interventional radiology requires the operator and assisting personnel to remain close to the patient; typically these procedures require placement of the hands within the radiation field. A system of hand dose monitoring was introduced in Poland in 2000. This system uses ring badges with TL dosemeters. The measurements conducted so far characteristically show an asymmetric right-sided distribution of monthly doses. As expected, operators and their assistants are the most exposed groups of medical personnel. Average hand doses may be very dependent on the type of procedure, personal skills and quality of equipment. The hand doses of these personnel are significant from a radiological protection point of view.     

Double-dosimetry algorithm for workers in interventional radiology

Based on double-dosemeter readings, a conservative effective dose (E) estimation algorithm for lead apron workers in interventional radiology is proposed. Typical radiation conditions for various exposure geometries were simulated using the MCNPX 2.4.0 code. The simulation model consisted of an X-ray source and image intensifier, a patient phantom and a voxelised staff member phantom with lead apron. The effective staff dose and dosemeter readings for several positions of the worker were calculated. The effective dose to a physician, positioned in close proximity to the primary beam, can be estimated within a 10% underestimation margin by E = 1.64 H(p)(10)(thorax,under) + 0.075 H(p)(10)(neck,over). The dose to the eye lens can be estimated by a dosemeter reading at collar level (R(2) = 0.98).     

Approaches to establishing reference levels in interventional radiology

Reference levels in radiodiagnostics are a requirement stated by the Council Directive 97/43/EURATOM. Reference levels are also relevant for interventional procedures, in accordance with this Directive, which claims special attention to quality assurance programmes, including quality control and patient dose evaluations for special practices such as interventional radiology, to assess the convenience of corrective action depending on the measured doses. The present paper addresses a method of establishing reference levels in interventional radiology, in the framework of optimisation, discussing the ways of putting forward values with a degree of tolerance, to allow for procedure complexity, depending on patient pathology. The need for several estimators used together, namely fluoroscopy time, total number of images per procedure and dose-area product, is also emphasised, proposing a further skin dose estimate in case of risk of deterministic effects. Finally, a brief summary of principles is given for the correct management of reference levels in interventional radiology.     

Physician-received scatter radiation with angiography systems used for interventional radiology: comparison among many X-ray systems

Radiation protection for interventional radiology (IR) physicians is very important. Current IR X-ray systems tend to use flat-panel detectors (FPDs) rather than image intensifiers (IIs). The purpose of this study is to test the hypothesis that there is no difference in physician-received scatter radiation (PRSR) between FPD systems and II systems. This study examined 20 X-ray systems in 15 cardiac catheterisation laboratories (11 used a FPD and 9 used an II). The PRSR with digital cineangiography and fluoroscopy were compared among the 20 X-ray systems using a phantom and a solid-state-detector electronic pocket dosemeter. The maximum PRSR exceeded the minimum PRSR by ~12-fold for cineangiography and ~9-fold for fluoroscopy. For both fluoroscopy and digital cineangiography, the PRSR had a statistically significant positive correlation with the entrance surface dose (fluoroscopy, r = 0.87; cineangiography, r = 0.86). There was no statistically significant difference between the average PRSR of FPDs and IIs during either digital cineangiography or fluoroscopy. There is a wide range of PRSR among the radiography systems evaluated. The PRSR correlated well with the entrance surface dose of the phantom in 20 X-ray units used for IR. Hence, decreasing the dose to the patient will also decrease the dose to staff.     

Configuration of a genetic algorithm used to optimise fibre steering in composite laminates

In a previous study, a genetic algorithm (GA) was applied to define the optimum orientation of fibres in a unidirectional laminate in which the fibre orientations were allowed to vary continuously across the domain. The results were positive, but computation time was excessively long. The present study was undertaken to address this issue. The elements used by the GA (encoded representation, fitness criterion, operators affecting the population) were examined and optimised to reduce computation time. It was found that the use of a strain-based fitness criterion was better than use of a stress-based criterion, regardless of whether the load was above or below the elastic limit. A good balance of elitism and mixing was necessary in the GA parameters to obtain the fastest convergence. Automatic imaging of the GA output was achieved using the SAMCEF software package.     

Indicators for the finger doses in interventional radiology

Finger doses and other factors have been recorded in order to investigate parameters that could be used to assess the likely level of finger doses of interventional radiologists. A relatively good correlation between finger dose and dose-area product was found regardless of the type of procedure. The correlation between finger dose and screening time was less significant. Very significant correlation between finger doses and the personal dosemeter reading outside the lead apron was found. This strongly suggests that personal dosemeter worn outside the lead apron can serve as a screening device for finger or hand doses to the radiologists. For radiologists, surgeons and cardiologists likely to receive an annual personal dose reading of more than 20 mSv measured outside the lead apron, doses to the hands are likely to be higher than 50 mSv. In these cases, monitoring of finger doses is recommended to establish dose levels.     

Medical exposures directive: implications for interventional radiology

The new European Directive on Medical Exposures (97/43/EURATOM) specifically mentions 'high dose procedures' among the areas requiring special attention. This is universally interpreted as including the interventional procedures in radiology, cardiology and many of the special procedures involving fluoroscopy in these and related areas. This communication will focus on a definition of interventional procedures. It will examine the equipment, processes and patient and staff risks involved. From this examination it will be evident that new development is rapid in these areas and proceeding at a rate that is well ahead of both supporting research and regulatory framework. It will further note that the level of patient risk which is acceptable may be higher than in many other procedures. Finally it will note where the general provisions of the new Directive must be brought to bear on this new and developing field.     

Patient dose in interventional radiology: a European survey

Patient doses for a few common fluoroscopy-guided procedures in interventional radiology (IR) (excluding cardiology) were collected from a few radiological departments in 13 European countries. The major aim was to evaluate patient doses for the basis of the reference levels. In total, data for 20 procedures for about 1300 patients were collected. There were many-fold variations in the number of IR equipment and procedures per population, in the entrance dose rates, and in the patient dose data (total dose area product or DAP, fluoroscopy time and number of frames). There was no clear correlation between the total DAP and entrance dose rate, or between the total DAP and fluoroscopy time, indicating that a number of parameters affect the differences. Because of the limited number of patients, preliminary reference levels were proposed only for a few procedures. There is a need to improve the optimisation of IR procedures and their definitions and grouping, in order to account for their different complexities.     

Evaluating phantom image quality parameters to optimise patient radiation dose in dental digital radiology

Our objective was to obtain images of a predictable level of quality using an intraoral X-ray system with digital imaging, avoiding patient overexposure. A polymethylmethacrylate (PMMA) physical test phantom was imaged at different exposure times and at various PMMA thicknesses using a dental imaging coupled charge device. Two identical regions of interest (ROIs) were chosen in every image file, and quality was numerically evaluated by measuring high-contrast spatial resolutions, low-contrast thresholds and signal-to-noise ratios. In addition, three practitioners proposed personal quality scores by image inspection. Numerical contents in the ROIs, related to the image quality, were plotted against exposure time. From here, a simple expression linking the exposure time with the thickness to obtain images of comparable quality was deduced. As a result, the optimum exposure time for imaging with a predictable level of quality can be inferred. The potential effect could imply savings above 1000 man Sv, roughly 20 % of the collective dose due to dental imaging, over a population of 1540 millions.     

Development of a real-time hand dose monitor for personnel in interventional radiology

Medical procedures denoted as interventional radiology require operation near an X ray beam, which brings high dose exposures to the operators' hands. For the effectual control of their extremity doses, a prototype of a real-time wrist dosemeter has been developed, hand dose monitor (HDM), based on a single silicon detector. Experiments were performed to test its response to diagnostic X rays. The HDM was highly sensitive and showed a linear response down to doses of a few tens of microsieverts. Though dose rate, energy and angular dependence of the response were observed in some extreme conditions, the HDM was proved to be of practical use if it was appropriately calibrated. Since an HDM enables personnel to check their hand doses on a real-time basis, it would enable medical staff to control the exposure themselves.     

Equipment requirements and specification for digital and interventional radiology

During the past decade there has been a substantial growth in digital and interventional radiology. Equipment requirements and specification for digital (interventional) radiology are necessary to facilitate the purchase of proper installations for specific purposes. Inappropriate equipment might lead to increased dose to patients and staff, insufficient image quality and, for interventional radiology, to inefficient procedures and the potential for deterministic effects to occur. The equipment requirements and specifications are of various types. Requirements for dose displays and dose record keeping are dealt with in a separate contribution to this workshop. Detailed information is presented in this contribution on requirements and specifications in relation to ergonomic, dosimetric and image quality aspects.     

Training and accreditation in radiation protection for interventional radiology

Training in radiation protection is a basic aspect of the optimisation of medical exposures. Council Directive 97/43/EURATOM establishes the need for an adequate theoretical and practical training of the staff working in radiological practices, and competence in radiation, for which Member States shall ensure the establishment of appropriate curricula. Keeping in mind the different specialities and professional responsibilities, training curricula must be proposed and endorsed to achieve a common core of knowledge in radiation protection throughout Europe, for different groups of health workers. In interventional radiology, previous initiatives led to the definition of a syllabus of educational objectives and to its testing in a specific course. The present paper presents educational objectives for interventional radiology, developed in the framework of the DIMOND European concerted action.     

Using a multi-agent system to optimise resource utilisation in multi-site manufacturing facilities

Due to cost economies and better serving the global market, many enterprises expanded their manufacturing environment from a localised, single-site facility to more globalised, multi-site facilities. In order to take advantage of operating multi-site facilities, it is vital to make optimisation decisions of resource utilisation as if these facilities situated across different geographical locations are one integrated facility and take into account of the extended multi-site constraints and variables. This paper proposes a multi-agent system, using its characteristics of autonomy and intelligence, to integrate process planning and production scheduling across different facilities, so as to secure the most efficient and cost-effective plan and schedule to meet the demand. A currency-based agent iterative bidding mechanism is developed to facilitate the co-ordination of agents to achieve the goal. A genetic algorithm is employed to tune the currency values for agent bidding. In this paper, a case study is used for simulation in order to demonstrate the effectiveness and performance of the proposed agent system.     

A pilot experience launching a national dose protocol for vascular and interventional radiology

The design of a national dose protocol for interventional radiology has been one of the tasks during the European SENTINEL Coordination Action. The present paper describes the pilot experience carried out in cooperation with the Spanish Society on Vascular and Interventional Radiology (SERVEI). A prospective sample of procedures was initially agreed. A common quality control of the X-ray systems was carried out, including calibration of the air kerma area product (KAP) meters. Occupational doses of the radiologists involved in the survey were also included in the survey. A total of 10 Spanish hospitals with interventional X-ray units were involved. Six hundred and sixty-four patient dose data were collected from 397 diagnostic and 267 therapeutic procedures. Occupational doses were evaluated in a sample of 635 values. The obtained KAP median/mean values (Gy.cm(2)) for the gathered procedures were: biliary drainage (30.6/68.9), fistulography (4.5/9.8), lower limb arteriography (52.2/60.7), hepatic chemoembolisation (175.8/218.3), iliac stent (45.9/73.2) and renal arteriography (39.1/59.8). Occupational doses (mean monthly values, in mSv) were 1.9 (over apron); 0.3 (under apron) and 4.5 (on hands). With this National experience, a protocol was agreed among the SENTINEL partners to conduct future similar surveys in other European countries.     

Evaluation of methods to estimate the patient dose in interventional radiology

Dosimetric methods used for interventional and diagnostic radiology are reviewed and evaluated, including terms, quantities, equipment, calibration and measurements. Measurement of local skin dose and estimation of maximum local skin dose are emphasised. Aspects related to dosimetry in computed tomography and to methods of determining organ and tissue doses are not considered.