An Estimation of the Monetary Value of the Person-Sievert Useful for Occupational Radiological Protection within the Healthcare System of Sweden.

ABSTRACT: The As Low As Reasonably Achievable (ALARA) principle includes taking into account economic and societal factors. To consider these factors, decision-aiding techniques such as cost-benefit analysis were introduced by the International Commission on Radiological Protection (ICRP) 50 y ago. Over the years, developments in health economics have led to new ways of deriving the concept of a value of a statistical life (VSL), which now is influencing the monetary value assigned to a unit of collective dose for radiological protection purposes (the α value) used in cost-benefit analyses. The aim of the present study was to estimate an α value useful for occupational radiological protection within the healthcare system of Sweden. A survey based on the stated preference approach was developed and sent to staff who are exposed to ionizing radiation at their work in Region Västra Götaland (Sweden). The survey essentially contained two scenarios: the respondents' willingness to pay for measures against radon exposure at home and their willingness to accept compensation for x-ray exposure at work. Answers from 718 respondents were collected. In the sensitivity analysis of the survey, the overall median VSL based on the two scenarios was calculated to be $50 million (IQR $10 to 363 million). The corresponding α value was established to $1,600 person-mSv -1 ($2,100 person-mSv -1 if excess burden of taxes is excluded). The recommended α value is in the high end compared to other studies but within the interval of values being used by nuclear utilities today. The α value should be seen in the light of ICRP's recommendation about stakeholder involvement as an important part of the optimization process.

Evaluation of novel radiation protection devices during radiologically guided interventions.

BACKGROUND: In radiologically guided interventions, medical practitioners are subjected to radiation exposure, which may lead to radiation-induced diseases. In this study, novel radiation shields for the head and neck were evaluated for their potential to reduce radiation exposure. METHOD: An anthropomorphic phantom was exposed on its left side to scattered radiation from beneath to simulate the exposure of an operator in a x-ray operating room. Thermoluminescent dosimeters (TLDs) were positioned at different depths in five slices in the phantom, measuring personal dose equivalent. Two different set up situations were evaluated: a head protector designed to reduce radiation in the upper section of the head; and a novel thyroid protector prototype extended in the front and on both sides, designed to reduce radiation in the lower and middle sections of the head. A standard thyroid collar prototype and a ceiling mounted lead glass shield were used as comparisons. Furthermore, the head protector was evaluated in a clinical study in which TLDs were positioned to measure scattered radiation exposure to the heads of operators during endovascular interventions. RESULTS: The extended thyroid protector reduced the scattered radiation in the throat, chin, and ear slices. Some shielding effect was seen in the brain and skull slices. The head protector showed a shielding effect in the skull slice up to two cm depth where it covered the phantom head. As expected, the ceiling mounted lead glass shield reduced the scattered radiation in all measuring points. CONCLUSIONS: A ceiling mounted lead glass shield is an effective radiation protection for the head, but in clinical practice, optimal positioning of a ceiling mounted lead shield may not always be possible, particularly during complex cases when radiation protection may be most relevant. Added protection using these novel guards may compliment the shielding effect of the ceiling mounted lead shield. The head protector stand-alone did not provide sufficient protection of the head. The extended thyroid protector stand-alone provided sufficient protection in the lower and middle sections of the head and neck.

Lead aprons and thyroid collars: to be, or not to be?

Wearing lead aprons and thyroid collars for long periods of time has a subjective component: to balance the effective dose reduction with the effort of carrying a heavy load. Occupational radiation exposure has decreased dramatically in the last century within the health care system. During the same period the use of lead aprons and thyroid collars has also gone up. Therefore, a question that may be raised is: how safe is safe enough? In order to promote stakeholder involvement, the aim of the present study was to investigate staff's experience of discomforts associated with wearing lead aprons and thyroid collars for long periods of time, and also to investigate staff's willingness to tolerate personal dose equivalent (expressed as radiation dose) and the corresponding increase in future cancer risk to avoid wearing these protective tools. A questionnaire was developed and given to staff working in operating or angiography rooms at Skaraborg Hospital in Sweden. The results from the 245 respondents showed that 51% experienced bothersome warmth, 36% experienced fatigue and 26% experienced ache or pain that they believed was associated with wearing lead aprons. One third of the respondents would tolerate a personal dose equivalent of 1 mSv per year to avoid wearing lead aprons, but only a fifth would tolerate the corresponding increase in future cancer risk (from 43% to 43.2%). In conclusion, discomforts associated with wearing lead aprons and thyroid collars for long periods of time are common for the staff using them. At the same time, only a minority of the staff would tolerate a small increase in future cancer risk to avoid wearing them. The present study gives an example of stakeholder involvement and points at the difficulties in making reasonable decisions about the use of these protective tools.

A case study of cost-benefit analysis in occupational radiological protection within the healthcare system of Sweden.

The aim of the present study was to demonstrate cases of cost-benefit analysis within healthcare, of how economic factors can be considered in occupational radiological protection, in agreement with the as low as reasonably achievable principle and present Swedish legislations. In the first part of the present study, a comparison of examples within health economics used by authorities and institutes in Sweden was made. The comparison focused on value of a statistical life, quality-adjusted life year, and monetary cost assigned to a unit of collective dose for radiation protection purposes (α-value). By this comparison, an α-value was determined as an interval between $45 and $450 per man-mSv, for the Swedish society in 2021. The α-value interval can be interpreted as following: Less than $45 per man-mSv is a good investment. From $45 to $450 per man-mSv, other factors than costs and collective dose are important to consider. More than $450 per man-mSv is too expensive. In the second part of the present study, seven cases of cost-benefit analyses in occupational radiological protection were provided. The present study focused specifically on cases where the relevant factors were costs and collective dose. The present case study shows a large variation in costs per collective dose from different types of occupational radiological protection, used at Skaraborg Hospital in Sweden.

ALIGNING VIDEO-AND STRUCTURED DATA FOR IMAGING OPTIMISATION.

Imaging optimisation can benefit from combining structured data with qualitative data in the form of audio and video recordings. Since video is complex to work with, there is a need to find a workable solution that minimises the additional time investment. The purpose of the paper is to outline a general workflow that can begin to address this issue. What is described is a data management process comprising the three steps of collection, mining and contextualisation. This process offers a way to work systematically and at a large scale without succumbing to the context loss of statistical methods. The proposed workflow effectively combines the video and structured data to enable a new level of insights in the optimisation process.

OPTIMISATION OF OCCUPATIONAL RADIATION PROTECTION IN IMAGE-GUIDED INTERVENTIONS: EXPLORING VIDEO RECORDINGS AS A TOOL IN THE PROCESS.

The overall purpose of this work was to explore how video recordings can contribute to the process of optimising occupational radiation protection in image-guided interventions. Video-recorded material from two image-guided interventions was produced and used to investigate to what extent it is conceivable to observe and assess dose-affecting actions in video recordings. Using the recorded material, it was to some extent possible to connect the choice of imaging techniques to the medical events during the procedure and, to a less extent, to connect these technical and medical issues to the occupational exposure. It was possible to identify a relationship between occupational exposure level to staff and positioning and use of shielding. However, detailed values of the dose rates were not possible to observe on the recordings, and the change in occupational exposure level from adjustments of exposure settings was not possible to identify. In conclusion, the use of video recordings is a promising tool to identify dose-affecting instances, allowing for a deeper knowledge of the interdependency between the management of the medical procedure, the applied imaging technology and the occupational exposure level. However, for a full information about the dose-affecting actions, the equipment used and the recording settings have to be thoroughly planned.

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.

Radiation-induced thyroid stunning: differential effects of (123)I, (131)I, (99m)Tc, and (211)At on iodide transport and NIS mRNA expression in cultured thyroid cells.

UNLABELLED: Recent clinical and experimental data demonstrate that thyroid stunning is caused by previous irradiation and may influence the efficacy of (131)I radiation therapy of thyroid cancer and possibly hyperthyroidism. To avoid stunning, many clinics have exchanged (131)I for (123)I for pretherapeutic diagnostic imaging and dose planning. Furthermore, recent in vitro studies indicate that (131)I irradiation reduces iodide uptake by downregulating the expression of the sodium iodide symporter (NIS). The rationale for this study was therefore to study effects on iodide transport and NIS messenger RNA (mRNA) expression in thyrocytes exposed to both (123)I and (131)I in addition to some other potentially interesting radionuclides. METHODS: Thyrotropin-stimulated thyroid cell monolayers were exposed to 0.5 Gy of (123)I, (131)I, (99m)Tc, or (211)At, all being radionuclides transported via NIS, in the culture medium for 6 h, or to various absorbed doses of (123)I or (131)I for 48 h. NIS mRNA expression was analyzed using quantitative reverse-transcriptase polymerase chain reaction. RESULTS: Iodide transport and NIS mRNA expression were reduced by all radionuclides. At the same absorbed dose, iodide transport was reduced the most by (211)At, followed by (123)I and (99m)Tc (equally potent), whereas (131)I was least effective. The onset of NIS downregulation was rapid (<1 d after irradiation) in cells exposed to (123)I or (211)At and was delayed in cells irradiated with (131)I or (99m)Tc. Iodide transport and NIS expression were recovered only for (211)At. (123)I reduced the iodine transport and the NIS mRNA expression more efficiently than did (131)I at an equivalent absorbed dose, with a relative biological effectiveness of about 5. CONCLUSION: The stunning effect per unit absorbed dose is more severe for (123)I than for (131)I. Despite the lower absorbed dose per unit activity for (123)I than for (131)I, stunning by (123)I cannot be excluded in patients. The degree to which iodide transport capacity and NIS mRNA expression are reduced seems to be related to the biological effectiveness of the type of radiation delivering the absorbed dose to the target, with (211)At (which has the highest relative biological effectiveness) causing the highest degree of stunning per unit absorbed dose in the present study.

Down-regulation of the sodium/iodide symporter explains 131I-induced thyroid stunning.

(131)I radiation therapy of differentiated thyroid cancer may be compromised by thyroid stunning (i.e., a paradoxical inhibition of radioiodine uptake caused by radiation from a pretherapeutic diagnostic examination). The stunning mechanism is yet uncharacterized at the molecular level. We therefore investigated whether the expression of the sodium/iodide symporter (NIS) gene is changed by irradiation using (131)I. Confluent porcine thyroid cells on filter were stimulated with thyroid-stimulating hormone (TSH; 1 milliunit/mL) or insulin-like growth factor-I (IGF-I; 10 ng/mL) and simultaneously exposed to (131)I in the culture medium for 48 h, porcine NIS mRNA was quantified by real-time reverse transcription-PCR using 18S as reference, and transepithelial iodide transport was monitored using (125)I(-) as tracer. TSH increased the NIS expression >100-fold after 48 h and 5- to 20-fold after prolonged stimulation. IGF-I enhanced the NIS transcription at most 15-fold but not until 5 to 7 days. (131)I irradiation (7.5 Gy) decreased both TSH-stimulated and IGF-I-stimulated NIS transcription by 60% to 90% at all investigated time points. TSH and IGF-I stimulated NIS synergistically 15- to 60-fold after 5 days. NIS expression was reduced by (131)I also in costimulated cells, but the transcription level remained higher than in nonirradiated cells stimulated with TSH alone. Changes in NIS mRNA always correlated with altered (125)I(-) transport in cultures with corresponding treatments. It is concluded that down-regulation of NIS is the likely explanation of (131)I-induced thyroid stunning. Enhanced NIS expression by synergistically acting agents (TSH and IGF-I) partly prevents the loss of iodide transport expected from a given absorbed dose, suggesting that thyroid stunning might be pharmacologically treatable.

Reduced iodide transport (stunning) and DNA synthesis in thyrocytes exposed to low absorbed doses from 131I in vitro.

UNLABELLED: Thyroid stunning refers to reduced uptake of (131)I in the thyroid tissue (or tumor) during radioiodine ((131)I) therapy compared with the uptake measured after the previous administration of (131)I for diagnostic purposes. The phenomenon is clinically important, as it can potentially lead to the undertreatment of thyroid cancer or to unnecessarily high absorbed doses in critical organs. Previous clinical and experimental studies indicated that thyroid stunning is absorbed dose dependent. The aim of this study was to investigate the effects of (131)I irradiation on (125)I(-) transport and cell proliferation at low absorbed doses in vitro. METHODS: Primary cultured porcine thyroid cells were grown to form a confluent monolayer of epithelial cells on a filter in a bicameral culture system. The cells were continuously irradiated with (131)I in the culture medium for 48 h to obtain 0.0015-1.5 Gy. At 3 d after irradiation was stopped, the transepithelial iodide transport capacity was evaluated by measuring (125)I(-) transport from the basal chamber compartment to the apical chamber compartment. The effect of (131)I irradiation on DNA synthesis was estimated by pulse labeling with (3)H-thymidine of both subconfluent and confluent cells irradiated with up to 9 Gy. Total DNA content was measured to quantify cell numbers. RESULTS: A statistically significant reduction in (125)I(-) transport was seen at absorbed doses of >or=0.15 Gy, with a 50% reduction at 1.5 Gy, compared with the results observed for nonirradiated control cells. (3)H-Thymidine incorporation was already statistically significantly reduced at absorbed doses of 0.01-0.1 Gy, but 0.15-0.3 Gy did not affect DNA synthesis. However, absorbed doses of >or=1 Gy again resulted in reduced DNA synthesis. A 50% reduction was obtained at 4 Gy. Total DNA measurements revealed a statistically significant reduction in cell numbers at 8 Gy. CONCLUSION: The lowest absorbed dose from (131)I that reduced iodide transport was 0.15 Gy. Because stunning was found at low absorbed doses, it might occur for (131)I treatment not only of thyroid cancer but also of thyrotoxicosis. On the basis of differences in dose responses, radiation-induced thyroid stunning and cell cycle arrest may be independent phenomena.

Biodistribution of free 211At and 125I- in nude mice bearing tumors derived from anaplastic thyroid carcinoma cell lines.

UNLABELLED: Free 211At has been proposed for therapy of anaplastic thyroid carcinoma (ATC). However, no extensive biodistribution study comparing tumor-bearing and nontumor-bearing mice has previously been performed. The aim of this study was to perform a complete evaluation of the biodistribution of 211At, both for normal and ATC-bearing mice. For comparison, the biodistribution of 125I- was simultaneously studied. Dosimetric evaluations were performed to investigate if (211)At can be used for therapy of ATC. METHODS: Athymic nude mice were subcutaneously injected with either of two human ATC cell lines, HTh83 and KAT-4. Tumor-bearing and nontumor-bearing mice were injected intravenously with 0.3 MBq 211At and 0.3 MBq 125I- simultaneously. The mice were sacrificed 4-24 hours after injection, and the activity concentrations in tissues were determined. RESULTS: Except for the thyroid, the concentration of 211At was higher than that of 125I- in the tissues. The uptake of 211At was primarily high in NIS-expressing organs. Furthermore, the absorbed doses to these organs were higher than both tumor types. CONCLUSIONS: The biodistribution of 211At and 125I- differed in this animal model. The higher mean absorbed dose from 211At in several organs than in tumor tissue restricts the possibility of using free 211At for therapy of ATC.