Track, calculate and optimise eye lens doses of interventional cardiologists using mEyeDose and mEyeDose_X.

The European epidemiological study EURALOC aimed to establish a dose response relationship for low dose radiation induced eye lens opacities using interventional cardiologists as the study group. Within the EURALOC project, two dosimetry methodologies were developed serving as the basis for cumulative eye lens dose assessment. Besides being the cornerstone of the epidemiological part of the project, these dosimetry methodologies were also used to develop two calculation tools, 'mEyeDose' and 'mEyeDose_X' which enable to track, calculate, optimise and analyse eye lens doses in interventional cardiology. mEyeDose was developed as a Mobile Web App and serves as a readily accessible, highly didactic educational tool for interventional cardiologists whereas the user-friendly desktop application mEyeDose_X is designed for radiation protection professionals. Both tools are freely available and can be used for a wide range of purposes such as optimisation of working practices, calculation of cumulative eye lens doses or risk assessment prior to routine eye lens dose monitoring.

Radiation-Induced Lens Opacities among Interventional Cardiologists: Retrospective Assessment of Cumulative Eye Lens Doses.

This study describes the retrospective lens dose calculation methods developed and applied within the European epidemiological study on radiation-induced lens opacities among interventional cardiologists. While one approach focuses on self-reported data regarding working practice in combination with available procedure-specific eye lens dose values, the second approach focuses on the conversion of the individual whole-body dose to eye lens dose. In contrast with usual dose reconstruction methods within an epidemiological study, a protocol is applied resulting in an individual distribution of possible cumulative lens doses for each recruited cardiologist, rather than a single dose estimate. In this way, the uncertainty in the dose estimate (from measurement uncertainty and variability among cardiologists) is represented for each individual. Eye lens dose and whole-body dose measurements have been performed in clinical practice to validate both methods, and it was concluded that both produce acceptable results in the framework of a dose-risk evaluation study. Optimal results were obtained for the dose to the left eye using procedure-specific lens dose data in combination with information collected on working practice. This method has been applied to 421 interventional cardiologists resulting in a median cumulative eye lens dose of 15.1 cSv for the left eye and 11.4 cSv for the right eye. From the individual cumulative eye lens dose distributions obtained for each cardiologist, maxima up to 9-10 Sv were observed, although with low probability. Since whole-body dose values above the lead apron are available for only a small fraction of the cohort and in many cases not for the entire working career, the second method has only been used to benchmark the results from the first approach. This study succeeded in improving the retrospective calculation of cumulative eye lens doses in the framework of radiation-induced risk assessment of lens opacities, but it remains dependent on self-reported information, which is not always reliable for early years. However, the calculation tools developed can also be used to make an assessment of the eye lens dose in current practice.

ENERGY AND ANGULAR DEPENDENCE OF RADIOPHOTOLUMINESCENT GLASS DOSEMETERS FOR EYE LENS DOSIMETRY.

Recent studies demonstrated that lens opacities can occur at lower radiation doses than previously accepted. In view of these studies, the International Commission of Radiological Protection recommended in 2011 to reduce the eye lens dose limit from 150 mSv/y to 20 mSv/y. This implies in the need of monitoring doses received by the eye lenses. In this study, small rod radiophotoluminescent glass dosemeters (GD-300 series; AGC, Japan) were characterized in terms of their energy (ISO 4037 X-rays narrow spectrum series, S-Cs and S-Co) and angular dependence (0  up to 90 degrees, with 2 ISO energies: N-60 and S-Cs). All acquisitions were performed at SCK•CEN-Belgium, using the ORAMED proposed cylindrical phantom. For selected energies (N-60, N-80, N-100, N-120 and N-250), the response of dosemeters irradiated on the ISO water slab phantom, at the Ruder Boskovic Institute-Croatia, was compared to those irradiated on the cylindrical phantom. GD-300 series showed good energy dependence, relative to S-Cs, on the cylindrical phantom. From 0 up to 45 degrees, the dosemeters showed no significant angular dependence, regardless whether they were tested when placed vertically or horizontally on the cylindrical phantom. However, at higher angles, some angular dependence was observed, mainly when the dosemeters were irradiated with low-energy photons (N-60). Results showed that GD-300 series have good properties related to Hp(3), although some improvements may be necessary.

Skin dose rate conversion factors after contamination with radiopharmaceuticals: influence of contamination area, epidermal thickness and percutaneous absorption.

Skin contamination with radiopharmaceuticals can occur during biomedical research and daily nuclear medicine practice as a result of accidental spills, after contact with bodily fluids of patients or by inattentively touching contaminated materials. Skin dose assessment should be carried out by repeated quantification to map the course of the contamination together with the use of appropriate skin dose rate conversion factors. Contamination is generally characterised by local spots on the palmar surface of the hand and complete decontamination is difficult as a result of percutaneous absorption. This specific issue requires special consideration as to the skin dose rate conversion factors as a measure for the absorbed dose rate to the basal layer of the epidermis. In this work we used Monte Carlo simulations to study the influence of the contamination area, the epidermal thickness and the percutaneous absorption on the absorbed skin dose rate conversion factors for a set of 39 medical radionuclides. The results show that the absorbed dose to the basal layer of the epidermis can differ by up to two orders of magnitude from the operational quantity Hp(0.07) when using an appropriate epidermal thickness in combination with the effect of percutaneous absorption.

Mapping very low level occupational exposure in medical imaging: a useful tool in risk communication and decision making.

OBJECTIVES: The use of ionising radiation in medical imaging is accompanied with occupational exposure which should be limited by optimised room design and safety instructions. These measures can however not prevent that workers are exposed to instantaneous dose rates, e.g. the residual exposure through shielding or the exposure of discharged nuclear medicine patients. The latter elements are often questioned by workers and detailed assessment should give more information about the impact on the individual radiation dose. METHODS: Cumulated radiation exposure was measured in a university hospital during a period of 6 months by means of thermoluminescent dosimeters. Radiation exposure was measured at background locations and at locations where enhanced exposure levels are expected but where the impact on the individual exposure is unclear. RESULTS: The results show a normal distribution of the cumulated background radiation level. No enhanced cumulated radiation exposure which significantly differs from this background level could be found during the operation of intra-oral apparatus, during ultrasonography procedures among nuclear medicine patients and at operator consoles of most CT-rooms. CONCLUSIONS: This 6 months survey offers useful information about occupational low level exposure in medical imaging and the findings can be useful in both risk communication and decision making.

Quality control of micro-computed tomography systems.

The rapid proliferation of micro-computed tomography (micro-CT) scanners in preclinical small animal studies has created a need for a method on scanner performance evaluation and scan parameter optimisation. The purpose of this study was to investigate the performance of the scanner with a dedicated micro-CT phantom. The phantom was developed with different independent sections that allow for measurement of major scanner characteristics such as uniformity, linearity, contrast response, dosimetry and resolution. The results of a thorough investigation are discussed.

The introduction of automated dispensing and injection during PET procedures: a step in the optimisation of extremity doses and whole-body doses of nuclear medicine staff.

Significant staff exposure is generally expected during PET-and PET/CT applications. Whole-body doses as well as extremity doses are usually higher per procedure compared with SPECT applications. Dispensing individual patient doses and manual injection involves high extremity doses even when heavy weighted syringe shields are used. In some cases the external radiation causes an exposure to the fingertips of more than 500 mSv y(-1), which is the yearly limit. Whole-body doses per procedure are relatively lower compared with extremity doses and are generally spread over the entire procedure (Guillet, B., Quentin, P., Waultier, S., Bourrelly, M., Pisano, P. and Mundler, O. Technologist radiation exposure in routine clinical practice with 18F-FDG PET. J. Nucl. Med. Technol. 33, 175-179 (2005). Optimisation of the individual workload is often used to restrict staff doses, but many PET centres face the need for further optimisation to reduce the staff doses to an acceptable level. During this study the effect of the use of an automated dispensing and injection system for (18)FDG on whole-body doses and extremity doses was evaluated. Detailed dosimetric studies using thermoluminescent and direct ion storage dosimetry were carried out before and after the introduction of this system. The results show that the extremity doses can be reduced by more than 95 % up to a mean level of 10 muSv per handled GBq. At the same time, whole-body doses can be halved during injection of the tracer. This results in a dose reduction of 20 % during the entire procedure of injection, escorting and positioning. In this way, the study shows that with the use of automated dispensing and injection a considerable staff dose reduction can be obtained.

Testing the direct ion storage dosemeter for personal dosimetry in a nuclear research centre and a hospital.

The direct ion storage (DIS) dosemeter can have some clear advantages in personal dosimetry. Before introducing the DIS into practice in the dosimetry service, a series of tests was performed on the linearity, angular and energy dependence, temperature influences and hard resets. After that, for several months, the DIS dosemeters were worn in parallel with the legal dosemeters (thermoluminescent badge) in a nuclear research centre and in several departments of a university hospital. The conclusions are that the DIS has good characteristics to be used as legal personal dosemeter, and that the comparison with the TLD badge is good. Only in interventional radiology and cardiology fields the DIS gives significant lower values than the TLD badge.

Dealing with pregnancy in radiology: a thin line between science, social and regulatory aspects.

The participation of pregnant women in radiology can be an emotional experience. The word "radiation" understandably invokes fear and uncertainty. Irradiation of a foetus should be avoided whenever possible. However, radiological examinations of pregnant women are often justified and unintended exposures do occur. Also pregnant radiology staff may remain working in the department. Lack of knowledge about the effects of both ionising (X-rays) and non-ionising (MRI) radiation is responsible for anxiety of patients and workers. If foetal exposures occur, they must be quantitatively evaluated and the risk put into perspective. This paper is intended to inform radiology managers, radiologists, technologists and referring clinicians in their management with pregnant patients and co-workers. The paper describes conceptus doses for both patient and worker that are associated with radiology practice, reviews the risks and effects of in utero irradiation, and discusses current national policies, international guidelines and practical aspects.

Extremity ring dosimetry intercomparison in reference and workplace fields.

An intercomparison of ring dosemeters has been organised with the aim of assessing the technical capabilities of available extremity dosemeters and focusing on their performance at clinical workplaces with potentially high extremity doses. Twenty-four services from 16 countries participated in the intercomparison. The dosemeters were exposed to reference photon ((137)Cs) and beta ((147)Pm, (85)Kr and (90)Sr/(90)Y) fields together with fields representing realistic exposure situations in interventional radiology (direct and scattered radiation) and nuclear medicine ((99 m)Tc and (18)F). It has been found that most dosemeters provided satisfactory measurements of H(p)(0.07) for photon radiation, both in reference and realistic fields. However, only four dosemeters fulfilled the established requirements for all radiation qualities. The main difficulties were found for the measurement of low-energy beta radiation. Finally, the results also showed a general under-response of detectors to (18)F, which was attributed to the difficulties of the dosimetric systems to measure the positron contribution to the dose.

Personal dose monitoring in hospitals: global assessment, critical applications and future needs.

It is known that medical applications using ionising radiation are wide spread and still increasing. Physicians, technicians, nurses and others constitute the largest group of workers occupationally exposed to man-made sources of radiation. Many hospital workers are consequently subjected to routine monitoring of professional radiation exposures. in the university hospital, UZ Brussel, 600 out of 4000 staff members are daily monitored for external radiation exposures. The most obvious applications of ionising radiation are diagnostic radiology, diagnostic or therapeutic use of radionuclides in nuclear medicine and external radiation therapy or brachytherapy in radiotherapy departments. Other important applications also include various procedures in interventional radiology (IR), in vitro biomedical research and radiopharmaceutical production around cyclotrons. Besides the fact that many of the staff members, involved in these applications, are not measurably exposed, detailed studies were carried out at workplaces where routine dose monitoring encounters difficulties and for some applications where relatively high occupational exposures can be found. most of the studies are concentrated around nuclear medicine applications and IR. They contain assessments of both effective dose and doses at different parts of the body. The results contribute to better characterisation of the different workplaces in a way that critical applications can be identified. Moreover, conclusions point out future needs for practical routine dose monitoring and optimisation of radiation protection.

The use of extremity dosemeters in a hospital environment.

A general overview is given on the use of extremity dosemeters, their calibration, the units and phantoms to be used. One of the major applications of extremity dosemeters is to monitor the personnel in a hospital environment. In nuclear medicine, brachytherapy and interventional radiology (IR) skin doses to hands and legs can be substantial. Here, we report on two studies that are presently being undertaken in Belgium. The first one tries to map the dose distribution on the hands, in function of the manipulation in nuclear medicine. Some preliminary results are also given from a nationwide survey study for patient and personnel doses during IR and cardiology. The radiologists' hands, legs and forehead are monitored during a whole range of procedures in different hospitals.

Health screening with CT: prospective assessment of radiation dose and associated detriment.

The use of computed tomography (CT) for screening of targeted diseases is gaining much interest in the international medical community. An important aspect in the justification of screening with such a high dose examination is the radiation dose to the patient. The objective of this study was to perform a prospective assessment of the radiation dose and associated risk for deleterious effects from a CT screening programme. The excess lifetime risk of fatal cancer for various screening strategies was quantified by estimating the effective dose and by using age dependent mortality risk factors. The accrued data shows that the excess mortality risk due to screening with CT could be substantial. It ranges from 0.01% up to a few percent, strongly depending on the type and method of screening. Consequently, radiation dose and associate risk should be included as fundamental parameters for outlining and deciding a screening approach with CT. Recent technical developments, such as tube current modulation, are promising tools for dose reduction within the constraint of desired image quality.

Mineral content of vertebral trabecular bone: accuracy of dual energy quantitative computed tomography evaluated against neutron activation analysis and flame atomic absorption spectrometry.

The goal of this study was to evaluate the accuracy of preprocessing dual energy quantitative computed tomography (QCT) for assessment of trabecular bone mineral content (BMC) in lumbar vertebrae. The BMC of 49 lumbar vertebrae taken from 16 cadavers was measured using dual energy QCT with advanced software and hardware capabilities, including an automated definition of the trabecular region of interest (ROI). The midvertebral part of each vertebral body was embedded in a polyester resin and, subsequently, an experimental ROI was cut out using a scanjet image transmission procedure and a computer-assisted milling machine in order to mimic the ROI defined on QCT. After low temperature ashing, the experimental ROIs reduced to a bone powder were submitted to either nondestructive neutron activation analysis (n = 49) or to flame atomic absorption spectrometry (n = 45). BMC obtained with neutron activation analysis was closely related (r = 0.896) to that derived from atomic absorption spectrometry, taken as the gold standard, with, however, a slight overestimation. BMC values measured by QCT were highly correlated with those assessed using the two reference methods, all correlation coefficients being > 0.841. The standard errors of the estimate ranged 47.4-58.9 mg calcium hydroxyapatite in the regressions of BMC obtained with reference methods against BMC assessed by single energy QCT, 47.1-51.9 in the regressions involving dual energy QCT. We conclude that the trabecular BMC of lumbar vertebrae can be accurately measured by QCT and that the superiority in accuracy of dual energy is moderate, which is possible a characteristic of the preprocessing method.

Size of cortical bone and relationship to bone mineral density assessed by quantitative computed tomography image segmentation.

RATIONALE AND OBJECTIVES: The accuracy of the measurement of the size of cortical bone on computed tomography (CT) images of human vertebrae was evaluated using an automated contour detection and segmentation procedure. METHODS: Forty human lumbar vertebrae were scanned using 8-mm slices and an automated detection for definition of trabecular and cortical region of interest. The vertebrae were embedded in a polyester resin and 8-mm-thick midvertebral specimens were excised using a diamond circular saw. Contact radiographs of these specimens were performed and, after photograph magnification, the cortical area was measured using computerized planimetry. RESULTS: Cortical area measured on CT images was highly correlated with the area measured by planimetry on the specimens (r = .91; P < .001) with, however, a systematic over-estimation. A significant relationship was found between density and width of the cortex (r = .56; P < .001). CONCLUSIONS: Computed tomography is able to assess the size of cortical bone in human vertebrae, but a threshold detection algorithm, as used in the current study, is not adequate to obtain the precise anatomic dimensions.

Excision of a trabecular ROI from resin-embedded vertebrae: report on a computer-assisted method.

A major problem when evaluating the accuracy of quantitative computed tomography (QCT) against chemical analysis of bone mineral is to ensure that the same region of interest (ROI) is measured with two techniques. The method described here attempts to reach this objective. Forty-nine lumbar vertebrae were scanned. The mid-vertebral portion was sawed and embedded in a polyester resin. The ROI defined with an automated contour detection was transmitted, using a Hewlett-Packard scanjet, to a computer-assisted milling machine which excised a trabecular ROI sample. The volume of each trabecular sample was determined using an Archimedian method. ROI volumes assessed on QCT were highly correlated with those obtained with the Archimedian method (r = 0.98). The standard error of the estimate was 170 mm3 (4.5%). These results suggest that trabecular samples obtained with this method optimally agree with the ROIs selected on QCT examination.

Dual-energy X-ray absorptiometry of lumbar vertebrae: relative contribution of body and posterior elements and accuracy in relation with neutron activation analysis.

The bone mineral content of 34 lumbar vertebrae obtained from ten cadavers (three men, seven women; age 61-88 years) was measured using a pulsed source dual-energy X-ray absorptiometry (DEXA) apparatus. Scanning was performed in the frontal projection and was repeated on the vertebral bodies obtained after removal of the posterior elements of the vertebrae. Subsequently a nondestructive neutron activation analysis (NAA) was performed. The mineral content of the vertebral bodies was found to represent (mean, SEM) 53.0% (1.9%) of the content of the whole vertebrae. The mineral content of the vertebral bodies assessed with NAA (BMC NAA) and with DEXA (BMC DEXA) showed a high correlation: BMC NAAA = (1.016 x BMC DEXA) + 0.990 r = 0.949 (p less than 0.001). We conclude that the mineral content of lumbar vertebral bodies can be accurately measured in vitro in a water environment by DEXA, and that the mean contribution of the posterior elements of the vertebra to the calcium hydroxyapatite content of whole vertebrae measured in the frontal projection is as high as 47.0%.