The use of out-of-plane high Z patient shielding for fetal dose reduction in computed tomography: Literature review and comparison with Monte-Carlo calculations of an alternative optimisation technique.

When performing CT examinations on pregnant patients, great effort should be dedicated towards optimising the exposure of the mother and the conceptus. For this purpose, many radiology departments use high-Z garments to be wrapped around the patient's lower abdomen for out-of-plane organ shielding to protect the fetus. To assess their current protection efficiency, we performed a literature review and compared the efficiencies mentioned in the literature to Monte-Carlo calculations of CT protocols for which the overall scan length was reduced. We found 11 relevant articles, all of them reporting uterus exposure due to CT imaging performed for exclusion of pulmonary embolism, one of the leading causes of peripartum deaths in western countries. Uterus doses ranged between 60 and 660 µGy per examination, and relative dose reductions to the uterus due to high-Z garments were between 20 and 56%. Calculations showed that reducing the scan length by one to three centimetres could potentially reduce uterus dose up to 24% for chest imaging, and even 47% for upper abdominal imaging. These dose reductions were in the order of those achieved by high-Z garments. However, using the latter may negatively influence the diagnostic image quality and even interfere with the automatic exposure control system thus increasing patient dose if positioned in the primary beam, for example in the overranging length in helical acquisition. We conclude that efforts should be concentrated on positioning the patient correctly in the gantry and optimising protocol parameters, rather than using high-Z garments for out-of-plane uterus shielding

An overview on extremity dosimetry in medical applications

Some activities of EURADOS Working Group 9 (WG9) are presently funded by the European Commission (CONRAD project). The objective of WG9 is to promote and co-ordinate research activities for the assessment of occupational exposures to staff at workplaces in interventional radiology (IR) and nuclear medicine. For some of these applications, the skin of the fingers is the limiting organ for individual monitoring of external radiation. Therefore, sub-group 1 of WG9 deals with the use of extremity dosemeters in medical radiation fields. The wide variety of radiation field characteristics present in a medical environment together with the difficulties in measuring a local dose that is representative for the maximum skin dose, usually with one single detector, makes it difficult to perform accurate extremity dosimetry. Sub-group 1 worked out a thorough literature review on extremity dosimetry issues in diagnostic and therapeutic nuclear medicine and positron emission tomography, interventional radiology and interventional cardiology and brachytherapy. Some studies showed that the annual dose limits could be exceeded if the required protection measures are not taken, especially in nuclear medicine. The continuous progress in new applications and techniques requires an important effort in radiation protection and trainin

An overview of the use of extremity dosemeters in some European countries for medical applications

Some medical applications are associated with high doses to the extremities of the staff exposed to ionising radiation. At workplaces in nuclear medicine, interventional radiology, interventional cardiology and brachytherapy, extremities can be the limiting organs as far as regulatory dose limits for workers are concerned. However, although the need for routine extremity monitoring is clear for these applications, no data about the status of routine extremity monitoring reported by different countries was collected and analysed so far, at least at a European level. In this article, data collected from seven European countries are presented. They are compared with extremity doses extracted from dedicated studies published in the literature which were reviewed in a previous publication. The analysis shows that dedicated studies lead to extremity doses significantly higher than the reported doses, suggesting that either the most exposed workers are not monitored, or the dosemeters are not routinely worn or not worn at appropriate position

Comparison of organ doses and image quality between CT and flat panel XperCT scans in wrist and inner ear examinations

The aim of this study was to evaluate and compare organ doses delivered to patients in wrist and petrous bone examinations using a multislice spiral computed tomography (CT) and a C-arm cone-beam CT equipped with a flat-panel detector (XperCT). For this purpose, doses to the target organ, i.e. wrist or petrous bone, together with those to the most radiosensitive nearby organs, i.e. thyroid and eye lens, were measured and compared. Furthermore, image quality was compared for both imaging systems and different acquisition modes using a Catphan phantom. Results show that both systems guarantee adequate accuracy for diagnostic purposes for wrist and petrous bone examinations. Compared with the CT scanner, the XperCT system slightly reduces the dose to target organs and shortens the overall duration of the wrist examination. In addition, using the XperCT enables a reduction of the dose to the eye lens during head scans (skull base and ear examinations

Intraoperative 2D C-arm and 3D O-arm in children: a comparative phantom study.

Exposure to ionizing radiation is a concern for children during intraoperative imaging. We aimed to assess the radiation exposure to the paediatric patient with 2D and 3D imaging. To evaluate the radiation exposure, patient absorbed doses to the organs were measured in an anthropomorphic phantom representing a five-year-old child, using thermoluminescent dosimeters. For comparative purposes, organ doses were measured using a C-arm for one minute of fluoroscopy and one acquisition with an O-arm. The cone-beam was centred on the pelvis. Direct and scattered irradiations were measured and compared (Student's <i>t</i> -test). Skin entrance dose rates were also evaluated. All radiation doses were expressed in µGy. Direct radiation doses of pelvic organs were between 631.22 and 1691.87 for the O-arm and between 214.08 and 737.51 for the C-arm, and were not significant (p = 0.07). Close scattered radiation on abdominal organs were between 25.11 and 114.85 for the O-arm and between 8.03 and 55.34 for the C-arm, and were not significant (p = 0.07). Far scattered radiation doses on thorax, neck and head varied from 0.86 to 6.42 for the O-arm and from 0.04 to 3.08 for the C-arm, and were significant (p = 0.02). The dose rate at the skin entrance was 328.58 µGy.s <sup>-1</sup> for the O-arm and 1.90 with the C-arm. During imaging of the pelvis, absorbed doses for a 3D O-arm acquisition were higher than with one minute fluoroscopy with the C-arm. Further clinical studies comparing effective doses are needed to assess ionizing risks of the intraoperative imaging systems in children

An overview on extremity dosimetry in medical applications

Some activities of EURADOS Working Group 9 (WG9) are presently funded by the European Commission (CONRAD project). The objective of WG9 is to promote and co-ordinate research activities for the assessment of occupational exposures to staff at workplaces in interventional radiology (IR) and nuclear medicine. For some of these applications, the skin of the fingers is the limiting organ for individual monitoring of external radiation. Therefore, sub-group 1 of WG9 deals with the use of extremity dosemeters in medical radiation fields. The wide variety of radiation field characteristics present in a medical environment together with the difficulties in measuring a local dose that is representative for the maximum skin dose, usually with one single detector, makes it difficult to perform accurate extremity dosimetry. Sub-group 1 worked out a thorough literature review on extremity dosimetry issues in diagnostic and therapeutic nuclear medicine and positron emission tomography, interventional radiology and interventional cardiology and brachytherapy. Some studies showed that the annual dose limits could be exceeded if the required protection measures are not taken, especially in nuclear medicine. The continuous progress in new applications and techniques requires an important effort in radiation protection and training

Extremity ring dosimetry intercomparison in reference and workplace fields

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

An overview of the use of extremity dosemeters in some European countries for medical applications

Some medical applications are associated with high doses to the extremities of the staff exposed to ionising radiation. At workplaces in nuclear medicine, interventional radiology, interventional cardiology and brachytherapy, extremities can be the limiting organs as far as regulatory dose limits for workers are concerned. However, although the need for routine extremity monitoring is clear for these applications, no data about the status of routine extremity monitoring reported by different countries was collected and analysed so far, at least at a European level. In this article, data collected from seven European countries are presented. They are compared with extremity doses extracted from dedicated studies published in the literature which were reviewed in a previous publication. The analysis shows that dedicated studies lead to extremity doses significantly higher than the reported doses, suggesting that either the most exposed workers are not monitored, or the dosemeters are not routinely worn or not worn at appropriate positions