ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

Low dose radiation and circulatory diseases: a brief narrative review

Exposure to high doses of ionizing radiation is associated with damage to the heart and coronary arteries. However, only recently have studies with high-quality individual dosimetry data allowed this risk to be estimated while adjusting for concomitant chemotherapy. An association between lower dose exposures and late-occurring circulatory disease has only recently been suspected in the Japanese atomic bomb survivors and in various occupationally exposed cohorts and is still controversial. Excess relative risks per unit dose in moderate- and low-dose epidemiological studies are variable, possibly resulting from confounding and effect-modification by well known (but unobserved) risk factors. Here, we summarize the evidence for a causal association between moderate- and low-level radiation exposure (whether at high or low dose rates) and circulatory disease.

Iterative Reconstruction Leads to Increased Subjective and Objective Image Quality in Cranial CT in Patients With Stroke

OBJECTIVE

The purpose of this study was to determine whether iterative reconstruction improves the quality of cranial CT (CCT) images of stroke patients.

MATERIALS AND METHODS

Fifty-one CCT studies of patients with infarction performed with either a low (260 mAs; n = 21) or standard (340 mAs; n = 30) dose were reconstructed with both filtered back projection (FBP) and sinogram-affirmed iterative reconstruction (SAFIRE) with five strength levels (S1-S5). The resulting six image sets (one FBP and one each for SAFIRE levels S1-S5) were rated separately by two blinded radiologists in terms of conspicuity of infarcted areas on a 5-point scale. Noise and infarct-to-normal brain as well as medullary-to-cortical contrast-to-noise ratios (CNRs) were measured. Ratings, noise, and CNRs were intraindividually compared within the same dose group (Fisher exact test) and interindividually between the different dose groups (Wilcoxon-Mann-Whitney U test).

RESULTS

The strength level S4 showed the best conspicuity of infarcted areas. Compared with FBP, SAFIRE S4 statistically significantly (p < 0.01) reduced noise and improved CNRs without statistically significant differences in all subjective and objective criteria (p > 0.01) when the dose was reduced. Patients examined with a 260-mAs low-dose were exposed to a statistically significantly lower dose (1.77 vs 2.33 mSv; p < 0.01).

CONCLUSION

Iterative reconstruction (SAFIRE at strength level S4) leads to increased subjective and objective image quality in CCT and allows dose reduction (-24%) without losses in the demarcation of ischemic lesions.

Radiation exposure to eye lens and operator hands during endovascular procedures in hybrid operating rooms

OBJECTIVE

The purpose of this study was to evaluate the radiation exposure of vascular surgeons' eye lens and fingers during complex endovascular procedures in modern hybrid operating rooms.

METHODS

Prospective, nonrandomized multicenter study design. One hundred seventy-one consecutive patients (138 male; median age, 72.5 years [interquartile range, 65-77 years]) underwent an endovascular procedure in a hybrid operating room between March 2012 and July 2013 in two vascular centers. The dose-area product (DAP), fluoroscopy time, operating time, and amount of contrast dye were registered prospectively. For radiation dose recordings, single-use dosimeters were attached at eye level and to the ring finger of the hand next to the radiation field of the operator for each endovascular procedure. Dose recordings were evaluated by an independent institution. Before the study, precursory investigations were obtained to simulate the radiation dose to eye lens and fingers with an Alderson phantome (RSD, Long Beach, Calif).

RESULTS

Interventions were classified into six treatment categories: endovascular repair of infrarenal abdominal aneurysm (n = 65), thoracic endovascular aortic repair (n = 32), branched endovascular aortic repair for thoracoabdominal aneurysms (n = 17), fenestrated endovascular aortic repair for complex abdominal aortic aneurysm, (n = 25), iliac branched device (n = 8), and peripheral interventions (n = 24). There was a significant correlation in DAP between both lens (P < .01; r = 0.55) and finger (P < .01; r = 0.56) doses. The estimated fluoroscopy time to reach a radiation threshold of 20 mSv/y was 1404.10 minutes (90% confidence limit, 1160, 1650 minutes). According to correlation of the lens dose with the DAP an estimated cumulative DAP of 932,000 mGy/m(2) (90% confidence limit, 822,000, 1,039,000) would be critical for a threshold of 20 mSv/y for the eyes.

CONCLUSIONS

Radiation protection is a serious issue for vascular surgeons because most complex endovascular procedures are delivering measurable radiation to the eyes. With the correlation of the DAP obtained in standard endovascular procedures a critical threshold of 20 mSv/y to the eyes can be predicted and thus an estimate of a potential harmful exposure to the eyes can be obtained.

Assessment of Local Dose Reference Values for Recanalization of Chronic Total Occlusions and Other Occlusions in a High-Volume Catheterization Center

The increasing number and complexity of these procedures have led to a higher number of patients at risk for tissue reactions like skin injuries. Monitoring of their dose indicators is essential in recognizing these patients. The aim of this work was to determine local diagnostic reference levels (DRLs) for recanalization of chronic total occlusion (CTO) and other occlusions procedures. All data from patients who underwent cardiac procedures were reviewed and classified according to their complexity. Dose indicators such as fluoroscopy time (FT), dose area product (DAP), and air kerma at patient entrance reference point (AKr) were recorded. Correlations with patient's body mass index, operators, procedure strategy, and complexity were studied. For CTO, the mean DAP, AKr, and FT were 252 ± 234 Gycm(2), 3,985 ± 3,579 mGy, and 47 ± 36 minutes, respectively. To better reflect the non-Gaussian distribution of data, the median and the 75th percentile values were also reported: median DAP, 172 Gycm(2); 75th percentile DAP, 350 Gycm(2); median AKr, 2,714 mGy; and 75th percentile AKr, 5,921 mGy. A tentative new set of values were suggested to take into account the complexity difference in recanalization of total occlusions according to their antegrade or retrograde approach. These approach-specific DRLs for total occlusions were mean DAP (120 ± 114 Gycm(2)), mean AKr (1,789 ± 1,933 mGy), and mean FT (22 ± 18 minutes) for antegrade approach and mean DAP (459 ± 304 Gycm(2)), mean AKr (6,881 ± 4,243 mGy), and mean FT (82 ± 40 minutes) for retrograde approach. The other significant values were median DAP (84 Gycm(2)), 75th percentile DAP (147 Gycm(2)), median AKr (1,160 mGy), and 75th percentile AKr (2,176 mGy) for antegrade approach and median DAP (422 Gycm(2)), 75th percentile DAP (552 Gycm(2)), median AKr (6,295 mGy), and 75th percentile AKr (8,064 mGy) for retrograde approach. In conclusion, a set of local DRL values from a large center were assessed. DRLs were provided for antegrade and retrograde approaches, reflecting the difference in difficulty from these 2 kinds of CTOs. The wide dose estimator values variations were explained through procedure complexity. The values obtained for the other more classic percutaneous coronary interventions were comparable with those found in the literature.

Radiotherapy for benign disease; assessing the risk of radiation-induced cancer following exposure to intermediate dose radiation

Most radiotherapy (RT) involves the use of high doses (>50 Gy) to treat malignant disease. However, low to intermediate doses (approximately 3-50 Gy) can provide effective control of a number of benign conditions, ranging from inflammatory/proliferative disorders (e.g. Dupuytren's disease, heterotopic ossification, keloid scarring, pigmented villonodular synovitis) to benign tumours (e.g. glomus tumours or juvenile nasopharyngeal angiofibromas). Current use in UK RT departments is very variable. This review identifies those benign diseases for which RT provides good control of symptoms with, for the most part, minimal side effects. However, exposure to radiation has the potential to cause a radiation-induced cancer (RIC) many years after treatment. The evidence for the magnitude of this risk comes from many disparate sources and is constrained by the small number of long-term studies in relevant clinical cohorts. This review considers the types of evidence available, i.e. theoretical models, phantom studies, epidemiological studies, long-term follow-up of cancer patients and those treated for benign disease, although many of the latter data pertain to treatments that are no longer used. Informative studies are summarized and considered in relation to the potential for development of a RIC in a range of key tissues (skin, brain etc.). Overall, the evidence suggests that the risks of cancer following RT for benign disease for currently advised protocols are small, especially in older patients. However, the balance of risk vs benefit needs to be considered in younger adults and especially if RT is being considered in adolescents or children.

Impact of radiation protection means on the dose to the lens of the eye while handling radionuclides in nuclear medicine

The human eye lens appears to be more radiosensitive than previously assumed. The reduction of the limit for the dose to the lens of the eye to 20 mSv per year has been passed in the current Euratom Directives (2013). Therefore, in this work the impact of laboratory glasses and X-ray protective goggles was investigated and reciprocal attenuation factors (i.e. transmission factors) for different nuclides (Tc-99m, I-131, Y-90, F-18 and Ga-68) were determined. The radionuclides in typical geometry (syringe, applicator) were positioned at a distance of 50 cm to the eyes of four Alderson-Head-Phantoms. Different dosemeters measuring H_p(3) respective H_p(0.07) were fixed to the eyes of the phantoms, either behind the glasses or without any protection means, respectively. The mean reciprocal attenuation factors were determined to be between unity for F-18 and I-131 using laboratory glasses (no attenuation effect) and < 0.01 for Y-90 using X-ray protective goggles. All other results were between these extremes. It has been shown, that prospective doses to the lens of the eye can be reduced significantly by using appropriate radiation protection means, especially for those dose-relevant beta radiation emitting nuclides such as Y-90.

[Estimation of Maximum Entrance Skin Dose during Cerebral Angiography]

Using radio-photoluminescence glass dosimeter, we measured the entrance skin dose (ESD) in 46 cases and analyzed the correlations between maximum ESD and angiographic parameters [total fluoroscopic time (TFT); number of digital subtraction angiography (DSA) frames, air kerma at the interventional reference point (AK), and dose-area product (DAP)] to estimate the maximum ESD in real time. Mean (± standard deviation) maximum ESD, dose of the right lens, and dose of the left lens were 431.2 ± 135.8 mGy, 33.6 ± 15.5 mGy, and 58.5 ± 35.0 mGy, respectively. Correlation coefficients (r) between maximum ESD and TFT, number of DSA frames, AK, and DAP were r=0.379 (P<0.01), r=0.702 (P<0.001), r=0.825 (P<0.001), and r=0.709 (P<0.001), respectively. AK was identified as the most useful parameter for real-time prediction of maximum ESD. This study should contribute to the development of new diagnostic reference levels in our country.

Application of Volumetric Modulated Arc Therapy and Simultaneous Integrated Boost Techniques to Prepare "Safe Margin" in the Rabbit VX2 Limb Tumor Model

Background

In this study, we aimed to establish the rabbit VX2 limb tumor model, and then prepare a “necrotic zone” as a safe margin by volumetric modulated arc therapy and simultaneous integrated boost (VMAT-SIB) technique applied in the areas where the tumor is located adjacent to the bone (GTV_boost area).

Material/Methods

Rabbits in the control group (n=10) were not treated, while those in the test group (n=10) were treated with the SIB schedule delivering a dose of 40Gy, 35Gy, 30Gy, and 25Gy to the GTV_boost, GTV (gross tumor volume), CTV (clinical target volume), and PTV (planning target volume) in 10 fractions. Magnetic resonance diffusion-weighted imaging (MRDWI), 3-dimensional power Doppler angiography (3D-PDA), and histological changes were observed after radiotherapy.

Results

After radiotherapy, the two groups showed a significant difference in the GTV_boost area. In the test group, the tumor necrosis showed a significantly low signal in DWI and high signal in apparent diffusion coefficient (ADC) maps. The 3D-PDA observation showed that tumor vascular structures decreased significantly. Histological analysis demonstrated that a necrotic zone could be generated in the GTV_boost area, and microscopic examination observed cell necrosis and fibroplasia.

Conclusions

This studies demonstrated the feasibility of using VMAT-SIB technique in the rabbit VX2 limb tumor model. The formation of a necrotic zone can be effectively defined as safe margin in the GTV_boost area. showing potential clinical applicability.

Radiation dose reduction during neurointerventional procedures by modification of default settings on biplane angiography equipment

BACKGROUND

Neurointerventional procedures represent a significant source of ionizing radiation. We sought to assess the effect during neurointerventional procedures of varying default rates of radiation dose in fluoroscopy (F) and image acquisition (IA) modes, and frame rates during cine acquisition (CINE) on total X-ray dose, acquisition exposures, fluoroscopy time, and complications.

METHODS

We retrospectively reviewed procedures performed with two radiation dose and CINE settings: a factory setting dose cohort (30 patients, F 45 nGy/pulse, IA 3.6 μGy/pulse, factory CINE frame rate) and a reduced dose cohort (30 patients, F 32 nGy/pulse, IA 1.2 μGy/pulse, with a decreased CINE frame rate). Total radiation dose, dose area product, number of acquisition exposures, fluoroscopy time, and complications were compared between the groups. Means comparisons (t tests) were employed to evaluate differences in the outcome variables between the two groups. p Value <0.05 was considered significant.

RESULTS

The reduced dose cohort had a significant reduction in mean radiation dose (factory, 3650 mGy; reduced, 1650 mGy; p=0.005) and dose area product (factory, 34 700 μGy×m(2); reduced, 15 000 μGy×m(2); p=0.02). There were no significant differences between cohorts in acquisition exposure (p=0.73), fluoroscopy time (p=0.45), or complications.

CONCLUSIONS

Significant reductions in radiation dose delivered by neurointerventional procedures can be achieved through simple modifications of default radiation dose in F and IA and frame rate during CINE without an increase in procedural complexity (fluoroscopy time) or rate of complications.

Evaluating Parameters Affecting Fluoroscopy Time During Percutaneous Nephrolithotomy: Focus on the Predictive Role of Guy's, S.T.O.N.E., and CROES Scoring Systems

OBJECTIVE

To identify parameters predicting prolonged fluoroscopy time (FT) during percutaneous nephrolithotomy (PCNL) and to evaluate the predictive ability of Guy's stone score, S.T.O.N.E. nephrolithometry, and CROES nomogram.

PATIENTS AND METHODS

We evaluated 153 consecutive patients who underwent a PCNL by a single experienced surgeon. Several preoperative, intraoperative, and postoperative parameters, including the three scoring systems, were assessed for their ability to predict FT.

RESULTS

FT was significantly associated with stone burden, stone location, number of stones, number of punctures, and number of tracts. It was also significantly associated with all scoring systems. Fluoroscopy use was significantly higher in patients who were effectively treated in these with longer hospitalization, probably reflecting case complexity. No association was found with postoperative complications.

CONCLUSIONS

FT during PCNL can be affected by several parameters. Identifying the ones that can affect FT can lead to fluoroscopy and radiation exposure decrease. Guy's stone score, S.T.O.N.E. nephrolithometry, and CROES nomogram can all predict complexed cases and the need for increased FT.

Hybrid Imaging for Patient-Specific Dosimetry in Radionuclide Therapy

Radionuclide therapy aims to treat malignant diseases by systemic administration of radiopharmaceuticals, often using carrier molecules such as peptides and antibodies. The radionuclides used emit electrons or alpha particles as a consequence of radioactive decay, thus leading to local energy deposition. Administration to individual patients can be tailored with regards to the risk of toxicity in normal organs by using absorbed dose planning. The scintillation camera, employed in planar imaging or single-photon emission computed tomography (SPECT), generates images of the spatially and temporally varying activity distribution. Recent commercially available combined SPECT and computed tomography (CT) systems have dramatically increased the possibility of performing accurate dose planning by using the CT information in several steps of the dose-planning calculation chain. This paper discusses the dosimetry chain used for individual absorbed-dose planning and highlights the areas where hybrid imaging makes significant contributions.

Radiation exposure to the eye lens of orthopaedic surgeons during various orthopaedic procedures

The aim of the present study was to assess the radiation dose to the eye lens of orthopaedic surgeons during various orthopaedic procedures and to make efforts to ensure that radiation protection is optimised. The study was performed for Fractura femoris and Fractura cruris procedures performed in orthopaedic operating theatres, as well as for fractures of wrist, ankle and hand/shoulder performed in the emergency trauma room. The highest mean value of the eye lens dose of 47.2 μSv and higher mean fluoroscopy time of 3 min, as well as the corresponding highest maximum values of 77.1 μSv and 5.0 min were observed for the Fractura femoris procedure performed with the Biplanar 500e fluoroscopy systems. At a normal workload, the estimated mean annual dose values do not exceed the annual occupational dose limit for the lens of eye, but at a heavy workload in the department, this dose limit could be achieved or exceeded. The use of protective lead glasses is recommended as they could reduce the radiation exposure of the lens of the eye. The phantom measurements demonstrated that the use of half-dose mode could additionally reduce dose to the operator's eye lens.

Staff eye doses in a large medical centre in Saudi Arabia: are they meeting the new ICRP recommendations?

A 5-y retrospective analysis of the cardiology staff eye doses was performed on 34 staff from different categories (cardiologists, nurses and technologists) at King Faisal Specialist Hospital and Research Centre (KFSHRC) in Riyadh, Saudi Arabia. KFSHRC is a tertiary medical centre with 800-bed capacity having more than 5000 cardiac catheterisation procedures performed annually. The aim of the study is to derive staff doses to the lens of the eyes using the personal dose equivalent Hp(0.07) values from the annual TLD dose report for the years 2008-2012 and determine the category of staff with high estimated eye doses. The study also aims to investigate the causes for high doses and recommend dose-reduction techniques. The dose to the lens of the eye was estimated by using the ratio Hp(0.07)slab/Hlens of 1.1 where Hp(0.07) values are the reported doses read from TLD badge worn at the collar level. The average annual eye dose of each category for the 5-y monitoring period was determined. Cardiologists tend to receive higher doses than the nurses by a factor of 2-4 and can exceed 5 mSv y(-1). No correlation exists between the eye doses of nurses and the cardiologists. There is a need to use a conversion coefficient in terms of eye lens dose per dose-area product for faster estimation of eye lens doses. However, there is a limitation on the use of the conversion coefficient because it will depend on the clinical procedure and the X-ray tube angulation. Further investigation on this limitation is needed.

Eye lens dose in interventional cardiology

The ICRP has recently recommended reducing the occupational exposure dose limit for the lens of the eye to 20 mSv y(-1), averaged over a period of 5 y, with no year exceeding 50 mSv, instead of the current 150 mSv y(-1). This reduction will have important implications for interventional cardiology and radiology (IC/IR) personnel. In this work, lens dose received by a staff working in IC is studied in order to determine whether eye lens dose monitoring or/and additional radiological protection measures are required. Eye lens dose exposure was monitored in 10 physicians and 6 nurses. The major IC procedures performed were coronary angiography and percutaneous transluminal coronary angioplasty. The personnel were provided with two thermoluminescent dosemeters (TLDs): one calibrated in terms of Hp(3) located close to the left ear of the operator and a whole-body dosemeter calibrated in terms of Hp(10) and Hp(0.07) positioned on the lead apron. The estimated annual eye lens dose for physicians ranged between 8 and 60 mSv, for a workload of 200 procedures y(-1). Lower doses were collected for nurses, with estimated annual Hp(3) between 2 and 4 mSv y(-1). It was observed that for nurses the Hp(0.07) measurement on the lead apron is a good estimate of eye lens dose. This is not the case for physicians, where the influence of both the position and use of protective devices such as the ceiling shield is very important and produces large differences among doses both at the eyes and on the thorax. For physicians, a good correlation between Hp(3) and dose area product is shown.

A set of patient and staff dose data for validation of Monte Carlo calculations in interventional cardiology

The purpose of this paper is to report a set of experimental values of patient and staff doses in a cardiac catheterisation laboratory using the range of radiographic and geometric parameters from routine clinical practice. The data obtained will be available for validation of Monte Carlo calculations and for training purposes. They will also help optimise radiation protection for patients and staff. Experimental measurements were made with an anthropomorphic phantom, and a monoplane flat detector-based X-ray system was used for interventional cardiology procedures. Standard operational protocols used in clinical practice were applied. Around 1000 patient dose and 5000 staff dose values were measured for different operational conditions (angulations, distances, collimation and wedge filter, magnification, phantom thicknesses, using Copper absorber, etc.). Uncertainties were also estimated. Increase factors of 3-10 for patients and staff doses were measured for the different C-arm angulations.

On the estimation of radiation-induced cancer risks from very low doses of radiation and how to communicate these risks

The article is intended to give a short overview of epidemiological data on cancer risks associated with very low absorbed doses of ionising radiation. The linear no-threshold (LNT) approach to estimate cancer risks involves the use of epidemiological data at higher doses (>100 mSv), but is supported by data from lower exposure of more sensitive population groups like fetuses and children and the presence of rare types of cancer. The International Commission on Radiological Protection (ICRP) concludes that the LNT model, combined with a dose and dose-rate effectiveness (reduction) factor (DDREF) of 2 for extrapolation from high doses, should be used. The numerical value of the DDREF is challenged by the findings from some recent epidemiological studies demonstrating risks per unit dose compatible with the risks observed in the higher dose studies. In general there is very limited knowledge about the cancer risk after low absorbed doses (10-100 mSv), as most of epidemiological studies have limitations in detecting small excess risks arising from low doses of radiation against fluctuations in the influence of background risk factors. Even if there may be significant deviations from linearity in the relevant dose range 0-100 mSv, one does not know the magnitude or even the direction of any such deviations. The risks could be lower than those predicted by a linear extrapolation, but they could also be higher. Until more results concerning the effects of low-dose exposure are available, a reasonable radiation protection approach is to consider the risk proportional to the dose.

Estimation of staff lens doses during interventional procedures. Comparing cardiology, neuroradiology and interventional radiology

The purpose of this article is to estimate lens doses using over apron active personal dosemeters in interventional catheterisation laboratories (cardiology IC, neuroradiology IN and radiology IR) and to investigate correlations between occupational lens doses and patient doses. Active electronic personal dosemeters placed over the lead apron were used on a sample of 204 IC procedures, 274 IN and 220 IR (all performed at the same university hospital). Patient dose values (kerma area product) were also recorded to evaluate correlations with occupational doses. Operators used the ceiling-suspended screen in most cases. The median and third quartile values of equivalent dose Hp(10) per procedure measured over the apron for IC, IN and IR resulted, respectively, in 21/67, 19/44 and 24/54 µSv. Patient dose values (median/third quartile) were 75/128, 83/176 and 61/159 Gy cm(2), respectively. The median ratios for dosemeters worn over the apron by operators (protected by the ceiling-suspended screen) and patient doses were 0.36; 0.21 and 0.46 µSv Gy(-1) cm(-2), respectively. With the conservative approach used (lens doses estimated from the over apron chest dosemeter) we came to the conclusion that more than 800 procedures y(-1) and per operator were necessary to reach the new lens dose limit for the three interventional specialties.

Basis for standards: ICRP activities

The purpose of this chapter is to describe work achieved recently by the International Commission on Radiological Protection (ICRP) and especially by Committee 3 (Protection in Medicine) and its use for standards. In March 1960, the Board of Governors of the International Atomic Energy Agency approved the Agency's 'Health and Safety Measures', stating that the Agency's 'Basic Safety Standards' (BSS) would be based, to the extent possible, on the recommendations of the ICRP. In a similar way, the Council of the European Union took into account the new recommendations of the ICRP when adopting the new Directive 2013/59/EURATOM that laid down BSS for protection against the dangers arising from exposure to ionising radiation. The new limit for the lens of the eyes for occupational exposures has been incorporated into these international standards and several articles dealing with medical exposures: justification, optimisation, recording patient doses, the use of diagnostic reference levels, training, accidental and unintended exposures, etc. have also been included in agreement with the ICRP recommendations.

Radiation exposure to patients and medical staff in hepatic chemoembolisation interventional procedures in Recife, Brazil

The purpose of this study was to evaluate patient and medical staff absorbed doses received from transarterial chemoembolisation of hepatocellular carcinoma, which is the most common primary liver tumour worldwide. The study was performed in three hospitals in Recife, capital of the state of Pernambuco, located in the Brazilian Northeastern region. Two are public hospitals (A and B), and one is private (C). For each procedure, the number of images, irradiation parameters (kV, mA and fluoroscopy time), the air kerma-area product (PKA) and the cumulative air kerma (Ka,r) at the reference point were registered. The maximum skin dose (MSD) of the patient was estimated using radiochromic film. For the medical staff dosimetry, thermoluminescence dosemeters (TLD-100) were attached next to the eyes, close to the thyroid (above the shielding), on the thorax under the apron, on the wrist and on the feet. The effective dose to the staff was estimated using the algorithm of von Boetticher. The results showed that the mean value of the total PKA was 267.49, 403.83 and 479.74 Gy cm(2) for Hospitals A, B and C, respectively. With regard to the physicians, the average effective dose per procedure was 17 µSv, and the minimum and maximum values recorded were 1 and 41 µSy, respectively. The results showed that the feet received the highest doses followed by the hands and lens of the eye, since the physicians did not use leaded glasses and the equipment had no lead curtain.

Eye dose assessment and management: overview

Some publications have shown that Hp(0.07) or even Hp(10) can be used as good operational quantities for X-rays in view of difficulties with Hp(3). With increasing awareness, there is tendency to use whatever dosimeter is available with correction factor to estimate eye lens dose. The best position for an eye lens dosimeter has been reported to be at the side of the head nearest to the radiation source, close to the eye. Recent studies have reported eye doses with cone beam CT (CBCT) both for patients and staff, and there are many papers reporting eye lens doses to staff in nuclear medicine. To minimise the dose to eyes, the user can take advantage of a feature of CBCT of projections acquired over an angular span of 180° plus cone angle of the X-ray tube and with tube under scan arcs.

Radiation Exposure in Transjugular Intrahepatic Portosystemic Shunt Creation

PURPOSE

Transjugular intrahepatic portosystemic shunt (TIPS) creation is considered as being one of the most complex procedures in abdominal interventional radiology. Our aim was twofold: quantification of TIPS-related patient radiation exposure in our center and identification of factors leading to reduced radiation exposure.

MATERIALS AND METHODS

Three hundred and forty seven consecutive patients underwent TIPS in our center between 2007 and 2014. Three main procedure categories were identified: Group I (n = 88)-fluoroscopic-guided portal vein targeting, procedure done in an image intensifier-based angiographic system (IIDS); Group II (n = 48)--ultrasound-guided portal vein puncture, procedure done in an IIDS; and Group III (n = 211)--ultrasound-guided portal vein puncture, procedure done in a flat panel detector-based system (FPDS). Radiation exposure (dose-area product [DAP], in Gy cm(2) and fluoroscopy time [FT] in minutes) was retrospectively analyzed.

RESULTS

DAP was significantly higher in Group I (mean ± SD 360 ± 298; median 287; 75th percentile 389 Gy cm(2)) as compared to Group II (217 ± 130; 178; 276 Gy cm(2); p = 0.002) and Group III (129 ± 117; 70; 150 Gy cm(2) p < 0.001). The difference in DAP between Groups II and III was also significant (p < 0.001). Group I had significantly longer FT (25.78 ± 13.52 min) as compared to Group II (20.45 ± 10.87 min; p = 0.02) and Group III (19.76 ± 13.34; p < 0.001). FT was not significantly different between Groups II and III (p = 0.73).

CONCLUSIONS

Real-time ultrasound-guided targeting of the portal venous system during TIPS creation results in a significantly lower radiation exposure and reduced FT. Further reduction in radiation exposure can be achieved through the use of modern angiographic units with FPDS.

Benefits of an automatic patient dose registry system for interventional radiology and cardiology at five hospitals of the Madrid area

The purpose of this article is to present the results of connecting the interventional radiology and cardiology laboratories of five university hospitals to a unique server using an automatic patient dose registry system (Dose On Line for Interventional Radiology, DOLIR) developed in-house, and to evaluate its feasibility more than a year after its introduction. The system receives and stores demographic and dosimetric parameters included in the MPPS DICOM objects sent by the modalities to a database. A web service provides a graphical interface to analyse the information received. During 2013, the system processed 10 788 procedures (6874 cardiac, 2906 vascular and 1008 neuro interventional). The percentages of patients requiring clinical follow-up due to potential tissue reactions before and after the use of DOLIR are presented. The system allowed users to verify in real-time, if diagnostic (or interventional) reference levels are fulfilled.

Reduction of occupational radiation dose in staff at the cardiac catheterisation laboratory by protective material placed on the patient

Reducing occupational radiation dose in cardiac catheterisation laboratories is one of the objectives of the radiation protection system because the procedures performed involve high levels of radiation compared with others in health care. Recommendations on protection methods used are referred to different structural types and personal protection tools. In this work, the effectiveness of a shielding drape above the patient in different geometric shapes for a standard procedure in interventional cardiology was evaluated. Values of personal dose equivalent Hp(10) obtained simultaneously with three active electronic semiconductor dosemeters located at the usual position of staff and at the C-arm have been used to show the usefulness of the shielding drape.

First results of an eye lens dosimetry survey in an interventional cardiology department

The eye lens annual dose limit for exposed personnel to ionizing radiation has recently been revised by the ICRP--International Commission on Radiological Protection and the proposed new limit has been accepted by European legislation through the Council Directive 2013/59/EURATOM 2013. Among medical exposed personnel, the staff performing interventional cardiology are usually affected by relevant doses. For this reason a survey, employing dosemeters characterized in terms of H(p)(3), was performed in order to get the order of magnitude of the doses received by the eye lens, at least as a first guess.The survey showed that the annual dose limit can easily be reached if a proper radiation protection approach is not implemented.

On the feasibility of utilizing active personal dosimeters worn on the chest to estimate occupational eye lens dose in x-ray angiography

The International Commission on Radiological Protection (ICRP) has recommended that the occupational dose limit to the eye lens be substantially reduced. To ensure compliance with these recommendations, monitoring of the occupational eye lens dose is essential in certain hospital work environments. For assessment of the eye lens dose it is recommended to use a supplementary dosimeter placed at a position adjacent to the eye(s). Wearing a dosimeter at eye level can, however, be impractical and distributing and managing additional dosimeters over long periods of time is cumbersome and costly for large clinical sites. An attractive alternative is to utilize active personal dosimeters (APDs), which are routinely used by clinical staff for real-time monitoring of the personal dose equivalent rate (H(p)(10)). In this work, a formalism for the determination of eye lens dose from the response of such APD's worn on the chest is proposed and evaluated. The evaluation is based on both phantom and clinical measurements performed in an x-ray angiography suite for interventional cardiology. The main results show that the eye lens dose to the primary operator and to the assisting clinical staff can be conservatively estimated from the APD response as D(eye)(conductor) = 2.0 APD chest and D(eye)(assisting) = 1.0 APD chest, respectively. However, care should be exercised for particularly short assisting staff and if radiation protection shields are misused. These concerns can be greatly mitigated if the clinical staff are provided with adequate radiation protection training.

Coniferyl aldehyde attenuates radiation enteropathy by inhibiting cell death and promoting endothelial cell function

Radiation enteropathy is a common complication in cancer patients. The aim of this study was to investigate whether radiation-induced intestinal injury could be alleviated by coniferyl aldehyde (CA), an HSF1-inducing agent that increases cellular HSP70 expression. We systemically administered CA to mice with radiation enteropathy following abdominal irradiation (IR) to demonstrate the protective effects of CA against radiation-induced gastrointestinal injury. CA clearly alleviated acute radiation-induced intestinal damage, as reflected by the histopathological data and it also attenuated sub-acute enteritis. CA prevented intestinal crypt cell death and protected the microvasculature in the lamina propria during the acute and sub-acute phases of damage. CA induced HSF1 and HSP70 expression in both intestinal epithelial cells and endothelial cells in vitro. Additionally, CA protected against not only the apoptotic cell death of both endothelial and epithelial cells but also the loss of endothelial cell function following IR, indicating that CA has beneficial effects on the intestine. Our results provide novel insight into the effects of CA and suggest its role as a therapeutic candidate for radiation-induced enteropathy due to its ability to promote rapid re-proliferation of the intestinal epithelium by the synergic effects of the inhibition of cell death and the promotion of endothelial cell function.

Summary of the European Directive 2013/59/Euratom: essentials for health professionals in radiology

The aspects of the new European Directive 2013/59/Euratom most relevant to diagnostic imaging and intervention are summarised. The Directive, laying down basic safety standards for protection against the dangers from exposure to ionising radiation, emphasises the need for justification of medical exposure (including asymptomatic individuals), introduces requirements concerning patient information and strengthens those for recording and reporting doses from radiological procedures, the use of diagnostic reference levels, the availability of dose-indicating devices and the improved role and support of the Medical Physics Experts in imaging. Relevant changes include new definitions, a new dose limit for the eye lens, non-medical imaging exposures, procedures in asymptomatic individuals, the use and regular review of diagnostic reference levels (including interventional procedures), dosimetric information in imaging systems and its transfer to the examination report, new requirements on responsibilities, the registry and analysis of accidental or unintended exposure and population dose evaluation (based on age and gender distribution). These changes will require Member States, the radiology community and the industry to adapt regulations, practices and equipment for a high standard of radiation safety. By 6 February 2018, the Directive has to be transposed into the national legislation of the Member States of the European Union.

Main messages

• The new European Basic Safety Standards Directive impacts radiology departments

• Changes in justification, patient information, responsibilities and dose reporting are most significant

• Diagnostic reference levels and the role of medical physics experts are clarified

• Dose limits to the eye lens are lower than in the previous directive

• Responsibilities in radiation safety have been defined

Radiation occupational health interventions offered to radiation workers in response to the complex catastrophic disaster at the Fukushima Daiichi Nuclear Power Plant

The Fukushima Daiichi Nuclear Power Plant (NPP) 1 was severely damaged from the chain reaction of the Great East Japan Earthquake and Tsunami on 11 March 2011, and the consequent meltdown and hydrogen gas explosions. This resulted in the worst nuclear accident since the Chernobyl accident of 1986. Just as in the case of Chernobyl, emergency workers were recruited to conduct a wide range of tasks, including disaster response, rescuing activities, NPP containment, and radiation decontamination. This paper describes the types and efficacy of the various occupational health interventions introduced to the Fukushima NPP radiation workers. Such interventions were implemented in order to prevent unnecessary radiation overexposure and associated adverse health effects and work injuries. Less than 1% of all emergency workers were exposed to external radiation of >100 mSv, and to date no deaths or health adversities from radiation have been reported for those workers. Several occupational health interventions were conducted, including setting of new regulatory exposure limits, improving workers' radiation dosimetry, administration of stable iodine, running an occupational health tracking system, and improving occupational medicine and preventative care. Those interventions were not only vital for preventing unnecessary radiation, but also for managing other general health issues such as mental health, heat illness and infectious diseases. Long-term administration of the aforementioned occupational health interventions is essential to ensure the ongoing support and care for these workers, who were put under one of the most severe occupational health risk conditions ever encountered.

Imaging the Parasinus Region with a Third-Generation Dual-Source CT and the Effect of Tin Filtration on Image Quality and Radiation Dose

BACKGROUND AND PURPOSE

CT is the imaging technique of choice in the evaluation of midface trauma or inflammatory disease. We performed a systematic evaluation of scan protocols to optimize image quality and radiation exposure on third-generation dual-source CT.

MATERIALS AND METHODS

CT protocols with different tube voltage (70-150 kV), current (25-300 reference mAs), prefiltration, pitch value, and rotation time were systematically evaluated. All images were reconstructed with iterative reconstruction (Advanced Modeled Iterative Reconstruction, level 2). To individually compare results with otherwise identical factors, we obtained all scans on a frozen human head. Conebeam CT was performed for image quality and dose comparison with multidetector row CT. Delineation of important anatomic structures and incidental pathologic conditions in the cadaver head was evaluated.

RESULTS

One hundred kilovolts with tin prefiltration demonstrated the best compromise between dose and image quality. The most dose-effective combination for trauma imaging was Sn100 kV/250 mAs (volume CT dose index, 2.02 mGy), and for preoperative sinus surgery planning, Sn100 kV/150 mAs (volume CT dose index, 1.22 mGy). "Sn" indicates an additional prefiltration of the x-ray beam with a tin filter to constrict the energy spectrum. Exclusion of sinonasal disease was possible with even a lower dose by using Sn100 kV/25 mAs (volume CT dose index, 0.2 mGy).

CONCLUSIONS

High image quality at very low dose levels can be achieved by using a Sn100-kV protocol with iterative reconstruction. The effective dose is comparable with that of conventional radiography, and the high image quality at even lower radiation exposure favors multidetector row CT over conebeam CT.

Reported radiation overexposure accidents worldwide, 1980-2013: a systematic review

BACKGROUND

Radiation overexposure accidents are rare but can have severe long-term health consequences. Although underreporting can be an issue, some extensive literature reviews of reported radiation overexposures have been performed and constitute a sound basis for conclusions on general trends. Building further on this work, we performed a systematic review that completes previous reviews and provides new information on characteristics and trends of reported radiation accidents.

METHODS

We searched publications and reports from MEDLINE, EMBASE, the International Atomic Energy Agency, the International Radiation Protection Association, the United Nations Scientific Committee on the Effects of Atomic Radiation, the United States Nuclear Regulatory Commission, and the Radiation Emergency Assistance Center/Training Site radiation accident registry over 1980-2013. We retrieved the reported overexposure cases, systematically extracted selected information, and performed a descriptive analysis.

RESULTS

297 out of 5189 publications and reports and 194 records from the REAC/TS registry met our eligibility criteria. From these, 634 reported radiation accidents were retrieved, involving 2390 overexposed people, of whom 190 died from their overexposure. The number of reported cases has decreased for all types of radiation use, but the medical one. 64% of retrieved overexposure cases occurred with the use of radiation therapy and fluoroscopy. Additionally, the types of reported accidents differed significantly across regions.

CONCLUSIONS

This review provides an updated and broader view of reported radiation overexposures. It suggests an overall decline in reported radiation overexposures over 1980-2013. The greatest share of reported overexposures occurred in the medical fields using radiation therapy and fluoroscopy; this larger number of reported overexposures accidents indicates the potential need for enhanced quality assurance programs. Our data also highlights variations in characteristics of reported accidents by region. The main limitation of this study is the likely underreporting of radiation overexposures. Ensuring a comprehensive monitoring and reporting of radiation overexposures is paramount to inform and tailor prevention interventions to local needs.

In vitro and in vivo application of radiolabeled gastrin-releasing peptide receptor ligands in breast cancer

Breast cancer (BC) consists of multiple subtypes defined by various molecular characteristics, for instance, estrogen receptor (ER) expression. Methods for visualizing BC include mammography, MR imaging, ultrasound, and nuclear medicine-based methods such as (99m)Tc-sestamibi and (18)F-FDG PET, unfortunately all lacking specificity. Peptide receptor scintigraphy and peptide receptor radionuclide therapy are successfully applied for imaging and therapy of somatostatin receptor-expressing neuroendocrine tumors using somatostatin receptor radioligands. On the basis of a similar rationale, radioligands targeting the gastrin-releasing peptide receptor (GRP-R) might offer a specific method for imaging and therapy of BC. The aim of this study was to explore the application of GRP-R radioligands for imaging and therapy of BC by introducing valid preclinical in vitro and in vivo models.

METHODS

GRP-R expression of 50 clinical BC specimens and the correlation with ER expression was studied by in vitro autoradiography with the GRP-R agonist (111)In-AMBA. GRP-R expression was also analyzed in 9 BC cell lines applying (111)In-AMBA internalization assays and quantitative reverse transcriptase polymerase chain reaction. In vitro cytotoxicity of (177)Lu-AMBA was determined on the GRP-R-expressing BC cell line T47D. SPECT/CT imaging and biodistribution were studied in mice with subcutaneous and orthotopic ER-positive T47D and MCF7 xenografts after injection of the GRP-R antagonist (111)In-JMV4168.

RESULTS

Most of the human BC specimens (96%) and BC cell lines (6/9) were found to express GRP-R. GRP-R tumor expression was positively (P = 0.026, χ(2)(4) = 12,911) correlated with ER expression in the human BC specimens. Treatment of T47D cells with 10(-7) M/50 MBq of (177)Lu-AMBA resulted in 80% reduction of cells in vitro. Furthermore, subcutaneous and orthotopic tumors from both BC cell lines were successfully visualized in vivo by SPECT/CT using (111)In-JMV4168; T47D tumors exhibited a higher uptake than MCF7 xenografts.

CONCLUSION

Targeting GRP-R-expressing BC tumors using GRP-R radioligands is promising for nuclear imaging and therapy, especially in ER-positive BC patients.

Fukushima radionuclides in the NW Pacific, and assessment of doses for Japanese and world population from ingestion of seafood

Variations of Fukushima-derived radionuclides ((90)Sr, (134)Cs and (137)Cs) in seawater and biota offshore Fukushima and in the NW Pacific Ocean were investigated and radiation doses to the Japanese and world population from ingestion of seafood contaminated by Fukushima radionuclides were estimated and compared with those from other sources of anthropogenic and natural radionuclides. The total effective dose commitment from ingestion of radionuclides in fish, shellfish and seaweed caught in coastal waters off Fukushima was estimated to be 0.6 ± 0.4 mSv/y. The individual effective dose commitment from consumption of radioactive-contaminated fish caught in the open Pacific Ocean was estimated to be 0.07 ± 0.05 mSv/y. These doses are comparable or much lower than doses delivered from the consumption of natural (210)Po in fish and in shellfish (0.7 mSv/y). The estimated individual doses have been below the levels when any health damage of the Japanese and world population could be expected.

Lens dose in routine head CT: comparison of different optimization methods with anthropomorphic phantoms

OBJECTIVE

The purpose of this study was to study different optimization methods for reducing eye lens dose in head CT.

MATERIALS AND METHODS

Two anthropomorphic phantoms were scanned with a routine head CT protocol for evaluation of the brain that included bismuth shielding, gantry tilting, organ-based tube current modulation, or combinations of these techniques. Highsensitivity metal oxide semiconductor field effect transistor dosimeters were used to measure local equivalent doses in the head region. The relative changes in image noise and contrast were determined by ROI analysis.

RESULTS

The mean absorbed lens doses varied from 4.9 to 19.7 mGy and from 10.8 to 16.9 mGy in the two phantoms. The most efficient method for reducing lens dose was gantry tilting, which left the lenses outside the primary radiation beam, resulting in an approximately 75% decrease in lens dose. Image noise decreased, especially in the anterior part of the brain. The use of organ-based tube current modulation resulted in an approximately 30% decrease in lens dose. However, image noise increased as much as 30% in the posterior and central parts of the brain. With bismuth shields, it was possible to reduce lens dose as much as 25%.

CONCLUSION

Our results indicate that gantry tilt, when possible, is an effective method for reducing exposure of the eye lenses in CT of the brain without compromising image quality. Measurements in two different phantoms showed how patient geometry affects the optimization. When lenses can only partially be cropped outside the primary beam, organ-based tube current modulation or bismuth shields can be useful in lens dose reduction.

Multiphase CT Angiography: A New Tool for the Imaging Triage of Patients with Acute Ischemic Stroke

PURPOSE

To describe the use of an imaging selection tool, multiphase computed tomographic (CT) angiography, in patients with acute ischemic stroke (AIS) and to demonstrate its interrater reliability and ability to help determine clinical outcome.

MATERIALS AND METHODS

The local ethics board approved this study. Data are from the pilot phase of PRoveIT, a prospective observational study analyzing utility of multimodal imaging in the triage of patients with AIS. Patients underwent baseline unenhanced CT, single-phase CT angiography of the head and neck, multiphase CT angiography, and perfusion CT. Multiphase CT angiography generates time-resolved images of pial arteries. Pial arterial filling was scored on a six-point ordinal scale, and interrater reliability was tested. Clinical outcomes included a 50% or greater decrease in National Institutes of Health Stroke Scale (NIHSS) over 24 hours and 90-day modified Rankin Scale (mRS) score of 0-2. The ability to predict clinical outcomes was compared between single-phase CT angiography, multiphase CT angiography, and perfusion CT by using receiver operating curve analysis, Akaike information criterion (AIC), and Bayesian information criterion (BIC).

RESULTS

A total of 147 patients were included. Interrater reliability for multiphase CT angiography is excellent (n = 30, κ = 0.81, P < .001). At receiver operating characteristic curve analysis, the ability to predict clinical outcome is modest (C statistic = 0.56, 95% confidence interval [CI]: 0.52, 0.63 for ≥50% decrease in NIHSS over 24 hours; C statistic = 0.6, 95% CI: 0.53, 0.68 for 90-day mRS score of 0-2) but better than that of models using single-phase CT angiography and perfusion CT (P < .05 overall). With AIC and BIC, models that use multiphase CT angiography are better than models that use single-phase CT angiography and perfusion CT for a decrease of 50% or more in NIHSS over 24 hours (AIC = 166, BIC = 171.7; values were lowest for multiphase CT angiography) and a 90-day mRS score of 0-2 (AIC = 132.1, BIC = 137.4; values were lowest for multiphase CT angiography).

CONCLUSION

Multiphase CT angiography is a reliable tool for imaging selection in patients with AIS.

Adipose-derived stem cells in radiotherapy injury: a new frontier

Radiotherapy is increasingly used to treat numerous human malignancies. In addition to the beneficial anti-cancer effects, there are a series of undesirable effects on normal host tissues surrounding the target tumor. While the early effects of radiotherapy (desquamation, erythema, and hair loss) typically resolve, the chronic effects persist as unpredictable and often troublesome sequelae of cancer treatment, long after oncological treatment has been completed. Plastic surgeons are often called upon to treat the problems subsequently arising in irradiated tissues, such as recurrent infection, impaired healing, fibrosis, contracture, and/or lymphedema. Recently, it was anecdotally noted - then validated in more robust animal and human studies - that fat grafting can ameliorate some of these chronic tissue effects. Despite the widespread usage of fat grafting, the mechanism of its action remains poorly understood. This review provides an overview of the current understanding of: (i) mechanisms of chronic radiation injury and its clinical manifestations; (ii) biological properties of fat grafts and their key constituent, adipose-derived stem cells (ADSCs); and (iii) the role of ADSCs in radiotherapy-induced soft-tissue injury.

Atrioventricular node ablation in Langendorff-perfused porcine hearts using carbon ion particle therapy: methods and an in vivo feasibility investigation for catheter-free ablation of cardiac arrhythmias

BACKGROUND

Particle therapy, with heavy ions such as carbon-12 ((12)C), delivered to arrhythmogenic locations of the heart could be a promising new means for catheter-free ablation. As a first investigation, we tested the feasibility of in vivo atrioventricular node ablation, in Langendorff-perfused porcine hearts, using a scanned 12C beam.

METHODS AND RESULTS

Intact hearts were explanted from 4 (30-40 kg) pigs and were perfused in a Langendorff organ bath. Computed tomographic scans (1 mm voxel and slice spacing) were acquired and (12)C ion beam treatment planning (optimal accelerator energies, beam positions, and particle numbers) for atrioventricular node ablation was conducted. Orthogonal x-rays with matching of 4 implanted clips were used for positioning. Ten Gray treatment plans were repeatedly administered, using pencil beam scanning. After delivery, positron emission tomography-computed tomographic scans for detection of β(+) ((11)C) activity were obtained. A (12)C beam with a full width at half maximum of 10 mm was delivered to the atrioventricular node. Delivery of 130 Gy caused disturbance of atrioventricular conduction with transition into complete heart block after 160 Gy. Positron emission computed tomography demonstrated dose delivery into the intended area. Application did not induce arrhythmias. Macroscopic inspection did not reveal damage to myocardium. Immunostaining revealed strong γH2AX signals in the target region, whereas no γH2AX signals were detected in the unirradiated control heart.

CONCLUSIONS

This is the first report of the application of a (12)C beam for ablation of cardiac tissue to treat arrhythmias. Catheter-free ablation using 12C beams is feasible and merits exploration in intact animal studies as an energy source for arrhythmia elimination.

Task-based measures of image quality and their relation to radiation dose and patient risk

The theory of task-based assessment of image quality is reviewed in the context of imaging with ionizing radiation, and objective figures of merit (FOMs) for image quality are summarized. The variation of the FOMs with the task, the observer and especially with the mean number of photons recorded in the image is discussed. Then various standard methods for specifying radiation dose are reviewed and related to the mean number of photons in the image and hence to image quality. Current knowledge of the relation between local radiation dose and the risk of various adverse effects is summarized, and some graphical depictions of the tradeoffs between image quality and risk are introduced. Then various dose-reduction strategies are discussed in terms of their effect on task-based measures of image quality.

Evaluation of occupational and patient radiation doses in orthopedic surgery

This study intends to measure the radiation dose to patients and staff during (i) Dynamic Hip Screw (DHS) and (ii) Dynamic Cannula Screw (DCS) and to evaluate entrance surface Air kerma (ESAK) dose and organ doses and effective doses. Calibrated Thermoluminescence dosimeters (TLD-GR200A) were used. The mean patients' doses were 0.46mGy and 0.07mGy for DHS and DCS procedures, respectively. The mean staff doses at the thyroid and chest were 4.69mGy and 1.21mGy per procedure. The mean organ and effective dose for patients and staff were higher in DHS compared to DCS. Orthopedic surgeons were exposed to unnecessary radiation doses due to the lack of protection measures. The radiation dose per hip procedure is within the safety limit and less than the previous studies.

Radiation in medicine: Origins, risks and aspirations

The use of radiation in medicine is now pervasive and routine. From their crude beginnings 100 years ago, diagnostic radiology, nuclear medicine and radiation therapy have all evolved into advanced techniques, and are regarded as essential tools across all branches and specialties of medicine. The inherent properties of ionizing radiation provide many benefits, but can also cause potential harm. Its use within medical practice thus involves an informed judgment regarding the risk/benefit ratio. This judgment requires not only medical knowledge, but also an understanding of radiation itself. This work provides a global perspective on radiation risks, exposure and mitigation strategies.

Effective radiation dose and eye lens dose in dental cone beam CT: effect of field of view and angle of rotation

OBJECTIVE

To quantify the effect of field of view (FOV) and angle of rotation on radiation dose in dental cone beam CT (CBCT) and to define a preliminary volume-dose model.

METHODS

Organ and effective doses were estimated using 148 thermoluminescent dosemeters placed in an anthropomorphic phantom. Dose measurements were undertaken on a 3D Accuitomo 170 dental CBCT unit (J. Morita, Kyoto, Japan) using six FOVs as well as full-rotation (360°) and half-rotation (180°) protocols.

RESULTS

For the 360° rotation protocols, effective dose ranged between 54 µSv (4 × 4 cm, upper canine) and 303 µSv (17 × 12 cm, maxillofacial). An empirical relationship between FOV dimension and effective dose was derived. The use of a 180° rotation resulted in an average dose reduction of 45% compared with a 360° rotation. Eye lens doses ranged between 95 and 6861 µGy.

CONCLUSION

Significant dose reduction can be achieved by reducing the FOV size, particularly the FOV height, of CBCT examinations to the actual region of interest. In some cases, a 180° rotation can be preferred, as it has the added value of reducing the scan time. Eye lens doses should be reduced by decreasing the height of the FOV rather than using inferior FOV positioning, as the latter would increase the effective dose considerably.

ADVANCES IN KNOWLEDGE

The effect of the FOV and rotation angle on the effective dose in dental CBCT was quantified. The dominant effect of FOV height was demonstrated. A preliminary model has been proposed, which could be used to predict effective dose as a function of FOV size and position.

Cone-beam computed tomography imaging: therapeutic staff dose during chemoembolisation procedure

Cone-beam computed tomography (CBCT) imaging is an important requirement to perform real-time therapeutic image-guided procedures on patients. The purpose of this study is to estimate the personal-doseequivalent and annual-personal-dose from CBCT imaging during transarterial chemoembolisation (TACE). Therapeutic staff doses (therapeutic and assistant physician) were collected during 200 patient (65 ± 15 years, range: 40–86) CBCT examinations over six months. Absorbed doses were assessed using thermo-luminescent dosimeters during patient hepatic TACE therapy. We estimated personal-dose-equivalent (PDE) and annual-personal-dose (APD) from absorbed dose based oninternational atomic energy agency protocol. APD for therapeutic procedure was calculated (therapeutic physician: 5.6 mSv; assistant physician: 5.08 mSv) based on institutional work load. Regarding PDE, the hands of the staff members received a greater dose compared to other anatomical locations (therapeutic physician: 56 mSv, 72 mSv; assistant physician: 12 mSv, 14 mSv). Annual radiation doses to the eyes and hands of the staff members were lower compared to the prescribed limits by the International Commission on Radiological Protection (ICRP). PDE and APD of both therapeutic staff members were within the recommended ICRP-103 annual limit. Dose to the assistant physician waslower than the dose to the therapeutic physician during imaging. Annual radiation doses to eye-lenses and hands of both staff members were lower than prescribed limits.

Derivation and application of dose reduction factors for protective eyewear worn in interventional radiology and cardiology

Doses to the eyes of interventional radiologists and cardiologists could exceed the annual limit of 20 mSv proposed by the International Commission on Radiological Protection. Lead glasses of various designs are available to provide protection, but standard eye dosemeters will not take account of the protection they provide. The aim of this study has been to derive dose reduction factors (DRFs) equal to the ratio of the dose with no eyewear, divided by that when lead glasses are worn. Thirty sets of protective eyewear have been tested in x-ray fields using anthropomorphic phantoms to simulate the patient and clinician in two centres. The experiments performed have determined DRFs from simulations of interventional procedures by measuring doses to the eyes of the phantom representing the clinician, using TLDs in Glasgow, Scotland and with an electronic dosemeter in Gothenburg, Sweden. During interventional procedures scattered x-rays arising from the patient will be incident on the head of the clinician from below and to the side. DRFs for x-rays incident on the front of lead glasses vary from 5.2 to 7.6, while values for orientations similar to those used in the majority of clinical practice are between 1.4 and 5.2. Specialised designs with lead glass side shields or of a wraparound style with angled lenses performed better than lead glasses based on the design of standard spectacles. Results suggest that application of a DRF of 2 would provide a conservative factor that could be applied to personal dosemeter measurements to account for the dose reduction provided by any type of lead glasses provided certain criteria relating to design and consistency of use are applied.