QA/acceptance testing of DEXA X-ray systems used in bone mineral densitometry.

New developments in dual energy X-ray absorptiometry (DEXA) imaging technology [fan beam and cone beam (CB)] result in higher exposure levels, shorter scan times, increased patient throughput and increased shielding requirements. This study presents the results of a European survey detailing the number and location of DEXA systems in SENTINEL partner states and the QA (quality assurance) currently performed by physicists and operators in these centres. The results of a DEXA equipment survey based on an in-house developed QA protocol are presented. Measurements show that the total effective dose to the patient from a spine and dual femur DEXA examination on the latest generation DEXA systems is comparable with a few microSv at most. Scatter measurements showed that the use of a mobile lead screen for staff protection was necessary for fan and CB systems. Scattered dose from newer generation systems may also exceed the exposure limits for the general public so structural shielding may also be required. Considerable variation in the magnitude and annual repeatability of half value layer was noted between different models of DEXA scanners. A comparative study of BMD (bone mineral density) accuracy using the European Spine Phantom highlighted a deviation of up to 7% in BMD values between scanners of different manufacturers.

High patient doses in interventional cardiology due to physicians' negligence: how can they be prevented?

Interventional cardiology procedures are usually associated with high patient doses and even deterministic radiation effects may occur. Expensive digital flat panels are preferably used to lower doses, and Athens General Hospital has recently installed one. However, this study shows that it is the cardiologists' practice that lowers patients' doses. Doses delivered to patients during two time periods (pre and after radiation protection training) on a total of 1196 coronary angiographies and 506 percutaneous transluminal coronary angioplasties were measured and analysed per cardiologist. Local reference levels (LRLs) were assessed and compared with the preliminary RLs provided by the European Research Program DIMOND. Results showed that although after the training patients' dose area product, fluoroscopy time, cumulative dose and number of images acquired were lowered, the situation remained unchanged for the cardiologist who delivered the highest doses. The question to answer next is how this bad practice can be prevented since no dose constraints apply to diagnostic or therapeutic procedures using ionising radiation.

Commissioning and constancy protocols for digital angiographic units.

During the European Concerted Action SENTINEL 'Safety and Efficacy for New Techniques and Imaging using New Equipment to Support European Legislation', protocols for commissioning and constancy tests for dynamic digital flat detectors angiography units have been developed in order to harmonise practice among the European counties. The commissioning protocol includes measurements on X-ray tube and generator, patient and detector radiation dose and image quality. The constancy protocol is based on the dose and image quality measurements. The commissioning protocol was tested by SENTINEL partners who expressed an interest in checking their dynamic digital systems using this protocol. The results of basic tests are reported.

Comparison of patient doses in interventional radiology procedures performed in two large hospitals in Greece.

Purpose of the study was to determine patient doses in the most common interventional radiology (IR) procedures performed in two large Greek hospitals. A total of 164 patients who underwent 4 types of IR procedures were studied. Fluoroscopy time, total exposure time, number of frames, number of runs, radiation field size, and cumulative dose-area product (DAP) were recorded. The median DAP values for carotid arteriography and lower limb arteriography were 66 and 123 Gy cm2 for hospital 'A' and 21 and 49 Gy cm2 for hospital 'B'. For the cerebral arteriographies performed in hospital 'A', the median DAP was 116 Gy cm2, while for the hepatic embolizations performed in hospital 'B', it was 104 Gy cm2. The DAP values observed in hospital 'A' for carotid arteriography and lower limb arteriography were almost three times than those of hospital 'B'. From the data analysis, it is evident that dose optimization in hospital 'A' should be pursued through revision of the techniques used.

Comparison of a CCD and a flat-panel digital system in an Interventional Cardiology Laboratory.

We evaluated the performances of angiographic units equipped with a flat-panel (FP) detector and image intensifier (II) charge-coupled device (CCD) in the Interventional Cardiology (IC) Department. Entrance dose rate and dose per image, along with the dose at the II level were measured using 2 mm copper sheets to simulate a patient. Image quality (IQ) was evaluated using a phantom. Doses increased with fluoroscopy level changing from low to high. FP presented higher doses than CCD. Periodic measurements showed differences of up to 35%. Low mode IQ did not significantly differ from normal and high mode for both systems. Low fluoroscopy mode was decided to be used routinely. Both X-ray systems performed within international recommendations for conventional systems with the exception of higher cine radiation doses and II dose rates, stressing the fact that more studies are required to investigate whether dose levels should be adjusted.

Correlation of patient and staff doses in interventional cardiology.

The purpose of this study was to measure staff radiation doses in representative institutions of five European countries performing coronary angiographies (CA) and percutaneous transluminal coronary angioplasties (PTCA), as well as to investigate any correlation with patient doses. Patient doses were recorded in terms of dose-area product (DAP). Staff doses were measured by thermoluminescence dosemeters placed on the operator's left shoulder and left foot. Radiation protection measures were also recorded. Third quartile shoulder and foot doses were 90 and 66 microSv in CA, and 157 and 173 microSv in PTCA, respectively. Shoulder dose was poorly correlated with DAP in CA (R2 = 0.29) and only moderately correlated in PTCA (R2 = 0.69). DAP and foot dose correlation was poor both in CA (R2 = 0.16) and in PTCA (R2 = 0.02). Protective measures taken by staff varied between countries, which may explain the poor correlation of patient and staff radiation doses.

Does digital imaging decrease patient dose? A pilot study and review of the literature.

The potential for decreasing patient dose is one of the main arguments for the justification of the cost of digital imaging equipment. However, the literature review with respect to patient doses using digital imaging modalities, presents conflicting results. During this study, patients' entrance surface doses were measured for three simple radiographic examinations, in European centres equipped with a computed radiography digital system. Results showed that doses between centres varied from 30% for chest LAT to 250% for chest PA examination. With the digital image quality criteria still under discussion, and with the post-processing parameters and/or image documentations varying, any dose comparisons between conventional/digital systems, as well as dose comparisons between different centre using digital units, are difficult. Clinical trials are required in order to define reference levels associated with quality of digital image necessary to address specific clinical requirements.

Comparison of a conventional and a flat-panel digital system in interventional cardiology procedures.

The purpose of the study was to analyse the technical characteristics of a newly installed flat-panel fluoroscopy (FPF) system in an interventional cardiology (IC) department and compare it with an older conventional system. A patient survey was performed to investigate the radiation doses delivered by the X-ray systems. Finally, methods of technique optimization regarding the new digital system were investigated. Dose rates in all fluoroscopic and cine modes were measured and image quality assessed using a dedicated test tool. 200 patients were investigated, half using the conventional and half using the digital FPF system. Patient data collected were: sex, age, weight, height, dose-area product (DAP), fluoroscopy time (T) and total number of frames (F). Our results are: (1) Digital FPF system: high contrast resolution (HCR) is not affected by fluoroscopic mode, whereas low contrast resolution (LCR) is slightly decreased in the low mode. (2) The digital FPF system has 2.5 times better HCR than the conventional system, with 5 times lower dose in the fluoroscopy mode. (3) Median values of DAP, T and F, respectively, in coronary angiography (CA) are: 27.7 Gycm(2), 4.1 min and 876 for the digital and 39.3 Gycm(2), 5.3 min and 1600 for the conventional system. Median values for percutaneous transluminal coronary angioplasty (PTCA) are: 51.1 Gycm(2), 12.7 min and 1184 for the digital and 44.3 Gycm(2), 7.4 min and 1936 for the conventional system. Digital DAP in CA is reduced by 30%, suggesting that a dose reduction in the FPF system is possible. The results of the study concerning the FPF system lead to the conclusion that the lowest fluoroscopic mode and the lowest frame rate should be used in routine practice.

Preliminary reference levels in interventional cardiology.

This article describes the European DIMOND approach to defining reference levels (RLs) for radiation doses delivered to patients during two types of invasive cardiology procedures, namely coronary angiography (CA) and percutaneous transluminal coronary angioplasty (PTCA). Representative centres of six European countries recorded patients' doses in terms of dose-area product (DAP), fluoroscopy time and number of radiographic exposures, using X-ray equipment that has been subject to constancy testing. In addition, a DAP trigger level for cardiac procedures which should alert the operator to possible skin injury, was set to 300 Gyxcm2. The estimation of maximum skin dose was recommended in the event that a DAP trigger level was likely to be exceeded. The proposed RLs for CA and PTCA were for DAP 45 Gyxcm2 and 75 Gyxcm2, for fluoroscopy time 7.5 min and 17 min and for number of frames 1250 and 1300, respectively. The proposed RLs should be considered as a first approach to help in the optimisation of these procedures. More studies are required to establish certain "tolerances" from the proposed levels taking into account the complexity of the procedure and the patient's size.

Patient dose values in a dedicated Greek cardiac centre.

The purpose of this study was to collect information on the practice and patient doses in a major Greek cardiac centre, investigate differences between senior cardiologists of various levels of experience and compare results with the literature, in order to optimize angiographic and interventional cardiology procedures. Radiation doses from 292 patients have been studied, 195 of which had undergone coronary angiography and 97 percutaneous transluminal coronary angioplasty. All procedures were undertaken on a Siemens Angioscop X-ray equipment. The system performed under automatic exposure control using pulsed fluoroscopy of 12.5 pulses s(-1) and cine frame rate of 25 frames s(-1). Dose-area product values, fluoroscopy times, total number of cine frames as well as operator's name were collected for each patient. Only senior cardiologists have participated in the study. Median values for dose-area product were 39.1 Gy cm(2) for coronary angiography and 58.3 Gy cm(2) for percutaneous transluminal coronary angioplasty. Median fluoroscopy time was 5.0 min and 9.7 min and median number of frames was 1588 and 1823 for coronary angiography and percutaneous transluminal coronary angioplasty, respectively. Comparison showed that patient dose-area product values were lower than other studies and fluoroscopy time values were comparable. However, the total number of frames used was much higher than other published results. Differences between cardiologists with increased experience have been found. Analysis of the patient dose values obtained initiated a program of radiation protection optimization. The need for continuous training in radiation protection for interventionalists has been verified.

Personnel doses in haemodynamic units in Greece.

Personnel of haemodynamic and interventional radiology units receive continuously increasing radiation doses due to extended fluoroscopy. Moreover, there is not a parallel increase in the number of cardiology specialists involved. Doses received by 15 cardiologists and 5 nurses, in 5 Athenian hospitals were measured using thermoluminescence dosemeters (TLD) and film badges. The workload and examination protocol of each cardiologist, the technical characteristics of the X ray unit, as well as availability and use of protective equipment were recorded. Results show that doses measured by TLD and film badges differ due mainly to the irregular wear of the latter. Although X ray units performed comparably with each other, dose per procedure received by each cardiologist varied widely, due to differences in examination protocol and beam collimation used. In all cases, nurses' dose was approximately one fourth of cardiologists' dose. In half of the cases assessed, the protective equipment available was not in full use. Estimation of dose per procedure, taking into account personnel's workload assesses annual personnel doses. Evaluation of risk level and check of compliance with regulatory dose limits should be part of continuing radiation protection education.

Review of patient dosimetry in cardiology.

The objective of the study is to review doses to patients undergoing interventional cardiology procedures, doses that are known to be substantial due to prolonged fluoroscopy time and multiple radiographic exposures. High doses together with the fact that the use of radiation in cardiology is increasing, makes the assessment of patient dose and the establishment of reference dose levels necessary. Thus MED 97 can be better implemented in all EU member countries. The literature review has shown that data is limited and difficult to compare due to various dose indicators, different physical parameters of X ray equipment, various examination protocols and variations in patients' size and complexity of case. For these reasons, European countries participating in DIMOND II submitted data for percutaneous transluminal coronary angioplasty and coronary angiography. Reference dose levels were defined in terms of dose-area product, fluoroscopic time and number of frames.

Effective dose to a patient undergoing coronary angiography.

Detailed data relating to patient dose have been acquired for 18, randomly chosen, patients undergoing coronary angiographies. During the procedure, dose-area product (DAP), kV and beam collimation were recorded for each projection. Total DAP, fluoroscopy time and number of cine frames were also noted. Patient effective doses were calculated using two different methods. Mean and median DAP values were 58 and 56 Gy.cm2 respectively, with a range between 26 and 125 Gy.cm2, screening time ranged from 3 to 37 min and cine frames from 1013 to 2344, depending on patient size, examination protocol and complexity of procedure. Our results correspond well with those obtained by other authors. Differences in the estimation of effective doses, due to the calculation method used and the approximation made, are discussed.