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.

Optimisation of radiological protection for operators working with fluoroscopically guided procedures has to be performed during the procedure, under varying and difficult conditions. The aim of the present study was to evaluate the impact of a system for real-time visualisation of radiation dose rate on optimisation of occupational radiological protection in fluoroscopically guided procedures. Individual radiation dose measurements, using a system for real-time visualisation, were performed in a cardiology laboratory for three cardiologists and ten assisting nurses. Radiation doses collected when the radiation dose rates were not displayed to the staff were compared to radiation doses collected when the radiation dose rates were displayed. When the radiation dose rates were displayed to the staff, one cardiologist and the assisting nurses (as a group) significantly reduced their personal radiation doses. The median radiation dose (Hp(10)) per procedure decreased from 68 to 28 μSv (p = 0.003) for this cardiologist and from 4.3 to 2.5 μSv (p = 0.001) for the assisting nurses. The results of the present study indicate that a system for real-time visualisation of radiation dose rate may have a positive impact on optimisation of occupational radiological protection. In particular, this may affect the behaviour of staff members practising inadequate personal radiological protection.

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.

Abstract131 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 À 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

Doses to the eyes of interventional clinicians can exceed 20 mSv. Various protective devices can afford protection to the eyes with the final barrier being protective eyewear. The protection provided by lead glasses is difficult to quantify, and the majority of dosimeters are not designed to be worn under lead glasses. This study has measured dose reduction factors (DRFs) equal to the ratio of the dose with no protection, divided by that when lead glasses are worn. Glasses have been tested in X-ray fields using anthropomorphic phantoms to simulate the patient and clinician. DRFs for X-rays incident from the front vary from 5.2 to 7.6, while values for orientations reminiscent of clinical practice are between 1.4 and 5.2. Results suggest that a DRF of two is a conservative factor that could be applied to personal dosimeter measurements to account for the dose reduction provided by most types of lead glasses.