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

The out-of-plane contact shield and mA-modulation - the effect on fetal absorbed dose

The effect of patient shielding on fetal radiation dose was evaluated in computed tomography pulmonary angiography with the out-of-plane shield visible in the localizer but absent in the scan range in chest computed tomography (CT). An anthropomorphic phantom with additional prosthetic pregnancy belly was scanned with different CT scanners using clinical imaging protocols and radiophotoluminescence dosemeters (GD-352 M). The out-of-plane shield decreased the fetal absorbed radiation dose with Siemens Somatom go.Up, Canon Aquilion Prime SP and Canon Aquilion One scanners. The decrease was 3.9%-39.4% (0.01-0.09 mGy). With GE Optima the shield increased the fetal dose by 100% (0.23 mGy), with Canon Aquilion One and GE Optima scanners the abdomen dose increase was 17.5% and 36.4%, respectively (0.61 and 1.38 mGy). Applying an out-of-plane shield outside the scanned volume may increase the fetal radiation dose during CT when using tube current modulation, depending on the make and model of the CT scanner.

Simulation of the shielding effect of lead apron undergoing chest CT scan

Lead aprons are used to reduce radiation dose to patients. As the distance between the lead apron and the edge of the scan range increases, organ dose is expected to decrease, but with increasing scattered radiation dose in the body. By simulation, this work aims at estimate whether the organ dose increases due to the scattered radiation in the body with lead apron. A standard-sized male and a female phantom is used to simulate organ doses of chest scans in various lead apron shielding situations. Simulations in this work considered different distance between the edge of the 0.35-mm lead apron and the edge of the scan range. For the female phantom, the dose to the gonads was significantly reduced (56% on average), but not as much as men (78% on average). However, the amount of dose reduction is small for male and female phantoms (0.0082 mGy/100 mAs and 0.0160 mGy/100 mAs).

Is It Appropriate to Completely Eliminate Contact Shielding during CT Examination? A Discourse Based on Experimental Findings

OBJECTIVE

Through the integration of experimental data and literature, this study examines whether complete elimination of contact shielding during CT examination is warranted, with a particular focus on potential impacts to children's thyroid and pregnant women, as well as limitations associated with contact shielding. Methods: The thermoluminescent dosimeter (TLD) tablets were inserted into the phantom's five organs and tissues. Select fixed exposure, automatic exposure control (AEC), and use contact shielding combined into four experimental modes, with scanning of the phantom's four parts. Obtain the absorbed dose measurements within or outside the FOV. Statistical analysis was conducted using SPSS software. Results: (1) The AEC significantly reduces dose within and outside the FOV, with a dose reduction of 40%-60%. (2) The application of contact shielding outside the FOV significantly reduced the dose adjoin the FOV. (3) Both the use of AEC mode and contact shielding can effectively minimize the dose, with a reduction of 50-80%. (4) The shielding within the FOV may introduce image artifacts or interfere with AEC, the implementation of contact shielding outside FOV provides little reduction in radiation exposure risk through previous literature. (5) Contact shielding exhibits certain drawbacks in all aspects. Conclusion: The utilization of AEC mode in clinical CT should be widely adopted to minimize patient radiation exposure. In general, contact shielding both inside and outside the FOV should be avoided during exposure. However for children under 12 years old with thyroid gland examination, contact shielding could maximally reduce external radiation and may be appropriate. Pregnant women require careful evaluation when considering the use of contact shielding. Contact shielding should not be entirely abandoned.

THE EFFECT OF OUT-OF-PLANE PATIENT SHIELDING ON CT RADIATION EXPOSURE AND TUBE CURRENT MODULATIONS: A PHANTOM STUDY ACROSS THREE VENDORS

The aim of this study was to evaluate how out-of-plane patient shielding affects radiation exposure parameters and tube current modulation on different vendors' computed tomography (CT) scanners. Helical CT scans were performed using two homogenous phantoms to mimic patient attenuation. Four CT scanners from three vendors were investigated by varying the distance of the patient shield from the border of the imaging volume. Scans were performed with a shield placed before and after the localizer. Changes in volume computed tomography dose index (CTDIvol), dose-length product (DLP) and tube current-time products were studied. Out-of-field lead shield increased the CTDIvol and DLP values for each scanner at least for one scan setting when the shield was present in the localizer. The most notable changes were recorded with >1.3 pitch values when the shield was closest to the scanned volume (2.5 cm), and the scan direction was towards the shield. The usage of patient shields in the localizer CT scans can disturb TCM even when placed 7.5 cm away from the edge of the scan.

Systematic literature review on the benefit of patient protection shielding during medical X-ray imaging: Towards a discontinuation of the current practice

PURPOSE

Patient shielding during medical X-ray imaging has been increasingly criticized in the last years due to growing evidence that it often provides minimal benefit and may even compromise image quality. In Europe, and as also shown in a short assessment in Switzerland, the use of patient shielding is inhomogeneous. The aim of this study was to systematically review recent literature in order to assess benefits and appraise disadvantages related to the routine use of patient shielding.

METHODS

To evaluate benefits and disadvantages related to the application of patient shielding in radiological procedures, a systematic literature review was performed for CT, radiography, mammography and fluoroscopy-guided medical X-ray imaging. In addition, reports from medical physics societies and authorities of different countries were considered in the evaluation.

RESULTS

The literature review revealed 479 papers and reports on the topic, from which 87 qualified for closer analysis. The review considered in- and out-of-plane patient shielding as well as shielding for pregnant and pediatric patients. Dose savings and other dose and non-dose related effects of patient shielding were considered in the evaluation.

CONCLUSIONS

Although patient shielding has been used in radiological practice for many years, its use is no longer undisputed. The evaluation of the systematic literature review of recent studies and reports shows that dose savings are rather minimal while significant dose- and non-dose-related detrimental effects are present. Consequently, the routine usage of patient protection shielding in medical X-ray imaging can be safely discontinued for all modalities and patient groups.

European consensus on patient contact shielding

Patient contact shielding has been in use for many years in radiology departments in order to reduce the effects and risks of ionising radiation on certain organs. New technologies in projection imaging and CT scanning such as digital receptors and automatic exposure control systems have reduced doses and improved image consistency. These changes and a greater understanding of both the benefits and the risks from the use of shielding have led to a review of shielding use in radiology. A number of professional bodies have already issued guidance in this regard. This paper represents the current consensus view of the main bodies involved in radiation safety and imaging in Europe: European Federation of Organisations for Medical Physics, European Federation of Radiographer Societies, European Society of Radiology, European Society of Paediatric Radiology, EuroSafe Imaging, European Radiation Dosimetry Group (EURADOS), and European Academy of DentoMaxilloFacial Radiology (EADMFR). It is based on the expert recommendations of the Gonad and Patient Shielding (GAPS) Group formed with the purpose of developing consensus in this area. The recommendations are intended to be clear and easy to use. They are intended as guidance, and they are developed using a multidisciplinary team approach. It is recognised that regulations, custom and practice vary widely on the use of patient shielding in Europe and it is hoped that these recommendations will inform a change management program that will benefit patients and staff.

European consensus on patient contact shielding

Patient contact shielding has been in use for many years in radiology departments in order to reduce the effects and risks of ionising radiation on certain organs. New technologies in projection imaging and CT scanning such as digital receptors and automatic exposure control (AEC) systems have reduced doses and improved image consistency. These changes and a greater understanding of both the benefits and the risks from the use of shielding have led to a review of shielding use in radiology. A number of professional bodies have already issued guidance in this regard. This paper represents the current consensus view of the main bodies involved in radiation safety and imaging in Europe: European Federation of Organisations for Medical Physics, European Federation of Radiographer Societies, European Society of Radiology, European Society of Paediatric Radiology, EuroSafe Imaging, European Radiation Dosimetry Group (EURADOS), and European Academy of DentoMaxilloFacial Radiology (EADMFR). It is based on the expert recommendations of the Gonad and Patient Shielding (GAPS) Group formed with the purpose of developing consensus in this area. The recommendations are intended to be clear and easy to use. They are intended as guidance, and they are developed using a multidisciplinary team approach. It is recognised that regulations, custom and practice vary widely on the use of patient shielding in Europe and it is hoped that these recommendations will inform a change management program that will benefit patients and staff.

European consensus on patient contact shielding

Patient contact shielding has been in use for many years in radiology departments in order to reduce the effects and risks of ionising radiation on certain organs. New technologies in projection imaging and CT scanning such as digital receptors and automatic exposure control (AEC) systems have reduced doses and improved image consistency. These changes and a greater understanding of both the benefits and the risks from the use of shielding have led to a review of shielding use in radiology. A number of professional bodies have already issued guidance in this regard. This paper represents the current consensus view of the main bodies involved in radiation safety and imaging in Europe: European Federation of Organisations for Medical Physics, European Federation of Radiographer Societies, European Society of Radiology, European Society of Paediatric Radiology, EuroSafe Imaging, European Radiation Dosimetry Group (EURADOS), and European Academy of DentoMaxilloFacial Radiology (EADMFR). It is based on the expert recommendations of the Gonad and Patient Shielding (GAPS) Group formed with the purpose of developing consensus in this area. The recommendations are intended to be clear and easy to use. They are intended as guidance, and they are developed using a multidisciplinary team approach. It is recognised that regulations, custom and practice vary widely on the use of patient shielding in Europe and it is hoped that these recommendations will inform a change management program that will benefit patients and staff.

Neurocritical Care of the Pregnant Patient

Purpose of review

To summarize recent changes in management and emerging therapies for pregnant neurocritical care patients.

Recent findings

Diagnostic and treatment options for managing neurologic emergencies in pregnant patients have expanded with both greater understanding of the effects of imaging modalities and medications on pregnancy and application of standard treatments for non-pregnant patients to pregnant populations. Specifically, this includes cerebrovascular diseases (pregnancy-associated ischemic stroke, pregnancy-associated intracerebral hemorrhage, cerebral venous sinus thrombosis), post-maternal cardiac arrest care, seizures and status epilepticus, myasthenia gravis, and fetal somatic support in maternal death by neurologic criteria.

Summary

With the exception of direct abdominal computed tomography (CT), most imaging studies are reasonably safe in pregnancy. When emergent imaging is needed to prevent maternal morbidity or mortality, any CT sequence with or without contrast is appropriate to pursue. Though new safety data on antiplatelets, antihypertensives, thrombolytics, and antiepileptic drugs have increased options for disease management in pregnancy, unfractionated and low-molecular weight heparin remain the safest options for anticoagulation. Early studies on hypothermia, ketamine, and immunomodulating therapies in pregnancy are promising. In myasthenia gravis, new data on adjunct devices may allow more patients to undergo safe vaginal delivery, avoiding cesarean section and the associated risk of crisis. When difficult decisions regarding preterm delivery arise, recent outcome studies can help inform discussion. Lastly, when the feared complication of maternal death by neurologic criteria occurs, fetal somatic support may help to save at least one life.

Use of out-of-field contact shielding on patients in medical imaging: A review of current guidelines, recommendations and legislative documents

The use of patient contact-shielding has become a topic of intensive scientific debate. While it has been common practice during the last decades, some studies have questioned the efficiency of using such shielding while others have highlighted the inconsistencies in its application. The objective of this work is to review current recommendations and legislative documents on the use of out-of-field shielding in X-ray imaging, including those from national authorities and from international and national organisations and professional bodies. The review, performed within the framework of the activities of EURADOS Working Group 12, covers available recommendations on use of contact shielding in adult, pregnant and paediatric patients in general radiography, fluoroscopy, computed tomography, mammography and dental radiology. It includes a comprehensive search of 83 documents from 32 countries and 6 international organisations over the last 39 years. In general, using shielding is recommended only under two conditions: if it does not compromise the diagnostic task and the performance of the procedure and/or if it reassures the patient and comforters that they are appropriately protected against potentially harmful effects of radiation. There are very few specific regulatory requirements to use shielding in a particular imaging modality, although they may consider use of shielding either as part of good radiological practice or as requirements for availability of protective or ancillary tools, without further specification of their use. There is a wide variety of positions among documents that recommend out-of-field shielding, those that do not recommend it and those that are not specific. Therefore, evidence-based consensus is still needed to ensure best and consistent practice.

Patient shielding: The need for a European consensus statement

Contact shielding has been in widespread use for the last 60-70 years aiming to protect against genetic effects, cancer, and other detriment. Since 2012, studies have begun to appear in the literature that question the continued use of such shielding, especially when radiographic technology has changed so much over the intervening period This literature has culminated in several professional bodies such as the American Association of Physicists in Medicine (AAPM) and the British Institute of Radiology (BIR) issuing guidance and statements recommending against the continued routine use of patient contact shielding. Many professional societies have also endorsed these statements. National statements on the matter continue to be produced. It is notable however that the major European bodies involved in diagnostic radiology and radiation safety have not to date issued a statement on patient shielding. This commentary looks at reasons for that and argues that it is now time for a European consensus statement on patient shielding. It is the authors belief that there are advantages to building on the work done by the AAPM and BIR, using the opportunity to amplify the statements, propagate the intent of the original statements, refine the message to deal with questions that have arisen since their publication. Α working group, Gonad and Patient Shielding (GAPS) has been formed by members from a) the European Federation of Organisations for Medical Physics (EFOMP), b) the Eurosafe Imaging initiative of the European Society of Radiology (ESR), c) the European Federation of Radiographers Societies (EFRS), d) EURADOS and e) the BIR to produce a joint statement on the proper application of patient shielding in diagnostic and interventional radiology.

TO USE OR NOT USE PATIENT SHIELDING ON PREGNANT WOMEN UNDERGOING CT PULMONARY ANGIOGRAPHY: A PHANTOM STUDY

Pregnancy increases the risk of pulmonary embolism. Computed tomography pulmonary angiography (CTPA) is used for diagnosis. CT generates ionising radiation, and thus, abdominal shielding may be used. This phantom study investigated the effects of patient shielding and scan length reduction on the fetal and maternal ionising radiation dose from CTPA. The absorbed dose to the fetus was measured using thermoluminescent dosemeters. Estimated effective doses to the pregnant patient were based on the dose-length products. Shielding increased both the effective dose to the patient by 47% and the mean absorbed dose to the fetus (0.10 vs. 0.12 mGy; p < 0.001) compared with unshielded standard CTPA, as it affected the automatic exposure control. Shielded short CTPA marginally lowered only the mean fetal absorbed dose (0.03 vs. 0.02 mGy; p = 0.018). Shortening the scan reduced the fetal absorbed dose most effectively by 70% (0.10 vs. 0.03 mGy; p = 0.006), compared with the standard unshielded scan. Shielding modestly reduces fetal radiation dose but may compromise automatic exposure control, possibly increasing the maternal and fetal radiation dose. Shortening the scan is beneficial, assuming anatomical coverage is secured.

Investigation and diagnostic imaging of suspected pulmonary embolism during pregnancy and the puerperium: A review of the literature

Pulmonary embolism (PE) is a leading cause of maternal mortality with women at increased risk of PE during pregnancy and the early postpartum period. Clinical assessment of suspected PE during pregnancy is challenging as signs and symptoms associated with PE overlap with physiological changes of pregnancy. Clinical tests and rules commonly used to assess pre-test probability of PE were historically not well validated in the pregnant population. The challenges of clinical assessment in the pregnant and postpartum population result in a lowered threshold for diagnostic imaging. Computed tomographic pulmonary angiography (CTPA) and nuclear medicine lung scintigraphy or ventilation/perfusion (V/Q) scans are the main types of diagnostic imaging for suspected PE. Both methods are associated with small levels of ionising radiation exposure to mother and foetus. Accuracy of the diagnostic imaging tests is paramount. Haemodynamic changes of pregnancy, including increased heart rate, increased blood volume and altered flow velocity in the pulmonary arteries, may influence the quality of imaging. This comprehensive review examines the literature and evidence for the investigation and diagnostic imaging of suspected pulmonary embolism during pregnancy with CTPA and V/Q. Clinical decision-making tools, biomarkers and diagnostic imaging during pregnancy and postpartum will be considered with a focus on diagnostic accuracy and yield, radiation dose exposure (maternal-foetal) and protocol modifications. Current practice guideline recommendations and recent literature on diagnostic pathways are also presented.

Patient Shielding in Diagnostic Imaging: Discontinuing a Legacy Practice

OBJECTIVE

Patient shielding is standard practice in diagnostic imaging, despite growing evidence that it provides negligible or no benefit and carries a substantial risk of increasing patient dose and compromising the diagnostic efficacy of an image. The historical rationale for patient shielding is described, and the folly of its continued use is discussed.

CONCLUSION

Although change is difficult, it is incumbent on radiologic technologists, medical physicists, and radiologists to abandon the practice of patient shielding in radiology.