Radiation exposure during endovascular aneurysm repair.

BACKGROUND: Endovascular stent-grafting is an established option for the repair of abdominal aortic aneurysm (AAA) that can involve prolonged manipulation under radiological control. The aim was to determine the average radiation exposure sustained during endovascular aneurysm repair (EVAR) and the first year of postoperative surveillance. METHODS: Prospective radiation dose data were recorded and used to calculate dose area product (DAP) values for 96 patients undergoing EVAR. The DAP data were then used to determine the entrance skin dose (ESD), an indicator of potential skin damage, and the effective dose, an indicator of long-term cancer risk, for each patient. RESULTS: The median ESD during EVAR was 0.85 (interquartile range 0.51-3.74) Gy. The threshold for possible radiation-induced skin damage of 2 Gy was exceeded in 29 per cent of procedures. The effective dose of radiation in the first year following EVAR was 79 mSv. CONCLUSION: Radiation doses administered during EVAR were higher than previously thought, with a potential risk of radiation-induced skin damage and later malignancy.

Radiation exposure to the hands of orthopaedic surgeons during procedures under fluoroscopic X-ray control.

The hands of the surgeon are most likely to be directly exposed to ionizing radiation during fluoroscopic screening in the orthopaedic theatre. There is however little information available on the level of exposure to radiation during the normal working pattern of individual surgeons. The purpose of this study was to directly measure the radiation exposure to the hands during fluoroscopic screening in a series of consecutive cases over a month in order to establish whether these staff need to be designated classified persons, and if not, whether they need to be routinely monitored. Extremity monitoring was carried out using thermoluminescent dosimeters. The dosimeter was secured to the operating surgeon's dominant index finger. 44 procedures were carried out by nine different surgeons. The total radiation dose received per surgeon ranged from 48-2329 microSv. In 80% of procedures the dose of radiation to the surgeon's hand was less than 100 microSv. The extrapolated annual dose, even for the surgeon with the highest radiation exposure, was well below the annual dose limit for extremities of 500 mSv per year recommended by the International Commission on Radiological Protection, and embodied in the Ionizing Radiations Regulations 1985. Despite the relatively low doses of radiation received by surgeons in this study, occupational exposure to all personnel should be kept to the lowest practicable levels, and a review of procedures, including dose measurements, from time to time is advised.

Effect of multislice scanners on patient dose from routine CT examinations in East Anglia.

As part of the dose optimization process, the Ionising Radiation (Medical Exposure) Regulations 2000 include requirements relating to the assessment of patient dose, and the setting and subsequent review of diagnostic reference levels. In East Anglia, audits of effective dose in CT have been carried out in 1996, 1999 and 2002. In the 2002 audit, nine of the 14 scanners assessed had been replaced since the previous audit. Eight of the new scanners were multislice scanners, acquiring up to 16 slices in a single rotation. The objective of the 2002 audit was to investigate the effect of the introduction of these multislice scanners on patient doses from routine CT examinations. Exposure parameters were collected for 10 different types of routine CT examination. In excess of 550 sets of patient data were obtained. For each of these, effective doses were calculated using the results of Monte Carlo simulations published by the National Radiological Protection Board. Averaged across all 10 examinations, regional mean effective doses are 34% higher than in 1999. The multislice scanners in the region give, on average, 35% more effective dose than the single-slice scanners. The effect of collimation in multislice scanners makes these effective dose differences most notable for examinations that use narrow slice widths. Further optimization of exposures on multislice scanners has the potential to reduce the differences observed between single-slice and multislice doses. However, when taken in combination with the increased use of CT in many hospitals, the effective dose increases observed are likely to result in a significant increase in the already substantial collective radiation dose from CT.

CT standard protocols are of limited value in assessing actual patient dose.

In the last 10 years the use of computed tomography in radiodiagnosis has increased markedly and CT scanners are now present in most district general hospitals. Modern CT scanners are versatile in their operation and offer the operator a wide choice in exposure parameters which affect the doses received by the patients. As CT is a major contributor to medical radiation doses, the National Radiological Protection Board (NRPB) recommends that an estimate of typical patient dose should be made for commonly used local scanning protocols. A survey has been undertaken in the Anglia and Oxford region covering 12 CT scanners. Common procedures were chosen, concentrating on those most frequently carried out and giving higher effective doses. These included routine heads, routine chests, high resolution chests and abdomen/pelvis examinations. Questionnaires were sent out to each CT centre to collect data on standard protocols and to record the procedure used for five actual patients for each examination type thus enabling a comparison of the two methodologies. This study has shown that many examinations are tailored to the individual patient size and clinical indications, particularly in the chest/abdomen/pelvis. Thus, assessing doses based on collecting standard protocols may not give a true indication of the effective doses being received by particular patients.

16-detector multislice CT: dosimetry estimation by TLD measurement compared with Monte Carlo simulation.

Computer simulations are widely used to estimate effective doses from CT examinations. The raw data often used in their estimations were obtained some years ago and made certain assumptions regarding CT unit design. At that time multidetector CT units were unavailable. Changes in design will limit the accuracy of computer simulated dosimetry on these machines. We therefore estimated CT dose on a 16-detector unit directly using thermoluminescent dosemeters (TLDs) and an anthropomorphic phantom. We found that the dose measured directly was 18% higher than the computer simulated dosimetry, in keeping with the previously recognised underestimation by computer simulation techniques compared with TLD measurements.

Is it safe to work with iodine-131 if you are pregnant? A risk assessment for nuclear medicine staff involved with cleaning and decontamination.

In the UK, Regulation 8(5) of the Ionising Radiation Regulations 1999 (In: Work with ionising radiation. London: HSE Books, 2000) requires employers to ensure that the dose to the foetus of a pregnant worker is unlikely to exceed 1 mSv. Risk assessments are required which are capable of predicting the total foetal dose. Work involving 131I is a particular problem. Foetal dose coefficients from the maternal intake of 131I for all stages of pregnancy have been published (Phipps AW, Smith TJ, Fell TP, Harrison JD. Doses to the embryo/fetus and neonate from intake of radionuclides by the mother. NRPB contract research report 397/2001. Didcot, Oxon.: National Radiological Protection Board (NRPB), 2001. Available on website www.hse.gov.uk/research/crr_pdf/2001/crr01397.pdf), and range from 0.08 microSv x kBq(-1) at conception to 55 microSv x kBq(-1) at week 35. This paper examines one aspect of work in a nuclear medicine department in which the source of 131I is uncontrolled to determine whether the risk assessment indicates that restrictions should apply to a pregnant member of staff. Following in-patient treatment with 131I, rooms are checked and decontaminated before being decontrolled. Cleaning staff were monitored immediately after the cleaning process with hand-held detectors and by whole-body monitoring. Total body contamination ranged up to 3.2 kBq; after a change of clothing, the maximum remaining activity was 0.68 kBq. Acquired contamination correlated with the total activity administered to the patient. Hand-held monitoring rarely detected contamination. Whole-body monitoring indicated that the levels of contamination encountered could lead to a dose limit for the foetus being exceeded. These levels are very difficult to detect with hand-held monitoring. The conclusion to be drawn is that pregnant staff should be excluded from situations in which accidents could arise, or where the source of 131I is uncontrolled or unpredictable.

An investigation into patient and staff doses from X-ray angiography during coronary interventional procedures.

Radiation doses to patients from interventional coronary X-ray procedures are relatively high when compared with conventional radiographic procedures. These high patient doses can translate into high staff doses owing to scattered radiation. This study investigates patient doses by means of dose-area product (DAP) meters installed in six rooms in two hospitals. DAP measurements in each room ranged from 28.0-39.3 Gy cm2 for coronary angiography and from 61.3-92.8 Gy cm2 for percutaneous transluminal coronary angioplasty, with the mean effective doses calculated to range between 5.1-6.6 mSv and 11.2-17.0 mSv, respectively. These values are comparable with those found in recent literature. DAP measurements were found to correlate strongly (correlation coefficient of 79%) with patient weight. The non-uniform scatter radiation fields surrounding the irradiated area during coronary angiography were also investigated using a tissue equivalent phantom and an ionization chamber. Exposure rates of scattered radiation from digital acquisition were found to be around 16 times higher than those generated from fluoroscopy, and oblique-angled imaging led to greater amounts of scatter owing to the increase in related exposure factors. The distribution of scatter from oblique projections confirms that X-ray photons in the diagnostic energy range are preferentially scattered backwards, toward the X-ray tube. These concepts are a major consideration when training individuals working in the angiography suite in order to keep doses "as low as reasonably practicable".