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

Open AccessPublished:January 11, 2022DOI:https://doi.org/10.1016/j.ejmp.2021.12.016

      Highlights

      • Systematic literature review on patient’s dose savings when using patient shielding.
      • Patient shielding can be safely abandoned.
      • Unsystematic use of patient shielding in Switzerland.

      Abstract

      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.

      Keywords

      Introduction

      The urgent need of a consensus concerning the use of patient shielding in Europe was addressed in an article by Gilligan and Damilakis [
      • Gilligan P.
      • Damilakis J.
      Patient shielding: the need for a European consensus statement.
      ]. The authors referred briefly to advantages and disadvantages of the use of patient shielding and addressed the need of harmonization of practices among European countries [
      • Gilligan P.
      • Damilakis J.
      Patient shielding: the need for a European consensus statement.
      ]. This article corroborates previous publications addressing the same topic [
      • Marsh R.M.
      • Silosky M.
      Patient shielding in diagnostic imaging: discontinuing a legacy practice.
      ] as well as surveys showing the unsystematic use of patient shielding [
      • Safiullah S.
      • Patel R.
      • Uribe B.
      • Spradling K.
      • Lall C.
      • Zhang L.
      • et al.
      Prevalence of protective shielding utilization for radiation dose reduction in adult patients undergoing body scanning using computed tomography.
      ,
      • Argyropoulou M.I.
      • Alexiou G.A.
      • Xydis V.G.
      • Adamsbaum C.
      • Chateil J.-F.
      • Rossi A.
      • et al.
      Pediatric minor head injury imaging practices: results from an ESPR survey.
      ,
      • Shanley C.
      • Matthews K.
      A questionnaire study of radiography educator opinions about patient lead shielding during digital projection radiography.
      ]. Several national authorities as well as societies of radiologists, medical physicists and radiographers suggest to abandon the practice of patient shielding in radiological examinations, among of which the Italian [

      SIRM A, FASTER. POSIZIONE DI AIFM, SIRM E FASTeR SULL’USO DEI DISPOSITIVI DI PROTEZIONE INDIVIDUALE. 2020.

      ] and the American Association of Physicists in Medicine [

      AAPM. AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding. PP 32-A. 2019.

      ], the British Institute of Radiology [

      Radiology BIo. Guidance on using contact shielding on patients for diagnostic radiology applications; 2020.

      ], the Danish, Finnish, Icelandic, Norvegian and Swedish authorities [

      NSRP. Nordic guidelines for dose reduction to radiosensitive organs of the patient in conventional radiography and fluoroscopy; 2019.

      ]. Based on articles – published mainly between 1992 and 2012 – the German recommendations advise to use patient shielding only during some CT examinations and pelvis radiography. Moreover, the German recommendations specify that for fluoroscopy-guided procedures patient shielding can be used only when it is guaranteed that it stays out of the primary beam [

      Strahlenschutzkommission. https://www.ssk.de/SharedDocs/Beratungsergebnisse/2018/2018-12-13Patienten.html. wwwsskde2018.

      ]. Overall, most of these recommendations and national guidelines are based on selected publications that somehow represent the current state of knowledge and research. Furthermore, even among a single country or region there is currently a wide variety of recommendations and legislative documents on the use of out-of-field shielding [
      • Candela-Juan C.
      • Ciraj-Bjelac O.
      • Sans Merce M.
      • Dabin J.
      • Faj D.
      • Gallagher A.
      • et al.
      Use of out-of-field contact shielding on patients in medical imaging: A review of current guidelines, recommendations and legislative documents.
      ].
      In order to emphasize this situation we performed a survey about the current practice in Switzerland within the framework of this study. The usage of patient shielding in radiological examinations in Switzerland is addressed in article 24 of the Ordinance for X-rays [

      Affairs FDoH. Radiological Protection Ordinance (RPO). 2017.

      ]. According to this legislation, the authorization holder must provide adequate shielding for patients, but it is up to the health institution to judiciously regulate its use. The Federal Office of Public Health (FOPH) as the supervisory authority in the field of radiation protection introduced in 2003 (revised in 2018) a specific guideline “Directive R-09-02” aiming to harmonize the use of patient radiation shielding [

      BAG. Wegleitung R-09-02: Schutzmittel für Patienten, Personal und Dritte in der Röntgendiagnostik.: BAG; 2018.

      ]. Unfortunately, this directive leaves space for different practices, as the formulation does not legally oblige the institutions to use patient shielding. Switzerland is a small country, with less than 10 million population but has four official languages (share of population: German speaking 63%, French speaking 23%, Italian speaking 8% and Romansh speaking 0.5%) [

      Switzerland. www.eda.admin.ch/. https://wwwedaadminch/aboutswitzerland/en/home/gesellschaft/sprachen/die-sprachen---fakten-und-zahlenhtml.

      ]. On a smaller scale – compared to entire Europe -, the practice of use of patient shielding shows a great variety also in Switzerland. As an example, Fig. 1 presents the inhomogeneous use of in- and out-of-plan abdominal shielding during CT examinations of pregnant women. All details about this sub-study are given in the supplemental material. Similar to other attempts all over Europe, the Swiss Society of Radiobiology and Medical Physics (SSRMP) published a report, based on selected scientific publications, showing that the use of patient shielding has a negligible effect on patient dose and other techniques should be used for an efficient patient protection [

      SSRMP. Report on the use of patient shielding in radiological procedures, report 21. 2020.

      ].
      Figure thumbnail gr1
      Fig. 1Inhomogeneous use of out-of-plan and in-plane fetus shielding during CT examinations: in-plane shielding during CT examinations to pregnant patients is used rarely and only in ¼ of German-speaking centers, while out-of-plane shielding is used more frequently for CT examinations in the German- and Italian-speaking regions.
      Despite all these facts, to the best of our knowledge, there is still no systematic literature review available, which investigates the benefits of patient protection means with respect to recent technical developments and the current state of the equipment present in European radiology departments and institutes. It was the aim of this study to evaluate the benefits and disadvantages from different type of patient shielding, considering scientific evidence based on systematic literature review of articles published in the past decade.

      Methods

      In order to assess the benefits and negative effects of patient protection means applied in radiological examinations, a systematic literature review of recent publications was performed. The literature review focused on peer-reviewed scientific original articles listed in the PubMed database that were published during the past 10 years (publication date January 1st 2010 – December 31st 2020) and title and abstract are available. Further inclusion criteria for the analysis were: (a) addressing benefits and/or negative effects of patient protection means for both pediatric and/or adult patients, (b) all X-ray based modalities (CT, fluoroscopy, radiography and mammography) that are available in radiological departments were considered but also including fluoroscopy application in other disciplines, e.g. cardiology, urology etc.). Articles were excluded if the investigated dose reduction due to patient shielding were related to applications in nuclear medicine, dental medicine or radiotherapy. Details of the literature search are summarized in Table 1. Results of the search were cleaned for duplicates based on PMID, and title and abstract were screened independently by two reviewers for eligibility in full text analysis. Reports from medical physics societies and reviews on the same topic were checked for references listed and included in the review if they met the inclusion criteria.
      Table 1PubMed search strategy with number of publications retrieved.
      Search criteria
      #1“radiation protection”[MeSH Terms]

      AND

      “apron” [All Fields] OR “aprons” [All Fields])
      172
      #2*“radiation protection”[MeSH Terms]

      AND

      “shield” [All Fields] OR “shielded” [All Fields] OR “shielding” [All Fields] OR “shieldings” [All Fields] OR “shields” [All Fields]
      (758)
      #3#2 AND

      “radiology” [MeSH Terms] OR “radiology” [All Fields] OR “radiography” [MeSH Terms] OR “radiography” [All Fields] OR “radiology s” [All Fields]
      371
      #4#2 AND

      “cardiologi” [All Fields] OR “cardiologie” [All Fields] OR “cardiology” [MeSH Terms] OR “cardiology” [All Fields] OR “cardiology s” [All Fields]
      49
      #5#2 AND

      “urologie” [All Fields] OR “urology” [MeSH Terms] OR “urology” [All Fields] OR “urology s” [All Fields]
      14
      #6#2 AND

      “orthopaedic” [All Fields] OR “orthopedics” [MeSH Terms] OR “orthopedics” [All Fields] OR “orthopedic” [All Fields] OR “orthopaedical” [All Fields] OR “orthopedical” [All Fields] OR “orthopaedics” [All Fields]
      23
      #7#2 AND

      “fluoroscopy” [MeSH Terms] OR “fluoroscopy” [All Fields] OR “fluoroscopies” [All Fields]
      92
      Total of publications721
      Total of publications (excluding duplicates)479
      *not included in the review process.

      Results

      In total, the literature search in PubMed resulted in 721 relevant articles (479 after cleaning for duplicates). After screening of title and abstract 410 articles were not included in the full text analysis. The most frequent reasons for exclusion were that the article was not patient oriented (220), not radiology oriented (nuclear medicine (30), radiation therapy (28), dental medicine (25)) or the dose reduction due to the protective means was not investigated (43). There were three review articles found that met the inclusion criteria [

      Karami V ZM, Shams N, Saki Malehi A. Gonad Shielding during Pelvic Radiography: A Systematic Review and Meta-analysis. Arch Iran Med. 2017:113-23.

      ,
      • Mehnati P.
      • Malekzadeh R.
      • Sooteh M.Y.
      Use of bismuth shield for protection of superficial radiosensitive organs in patients undergoing computed tomography: a literature review and meta-analysis.
      ,
      • Poon R.
      • Badawy M.K.
      Radiation dose and risk to the lens of the eye during CT examinations of the brain.
      ]. Analysis of these reviews in combination with cross references from the national guidelines [

      SIRM A, FASTER. POSIZIONE DI AIFM, SIRM E FASTeR SULL’USO DEI DISPOSITIVI DI PROTEZIONE INDIVIDUALE. 2020.

      ,

      AAPM. AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding. PP 32-A. 2019.

      ,

      Radiology BIo. Guidance on using contact shielding on patients for diagnostic radiology applications; 2020.

      ,

      NSRP. Nordic guidelines for dose reduction to radiosensitive organs of the patient in conventional radiography and fluoroscopy; 2019.

      ,

      Strahlenschutzkommission. https://www.ssk.de/SharedDocs/Beratungsergebnisse/2018/2018-12-13Patienten.html. wwwsskde2018.

      ,

      ACR. Breast Imaging Statement on Radiation Received to the Thyroid from Mammography; 2012.

      ] revealed twelve more publications that were also included in the full text analysis [
      • Marsh R.M.
      • Silosky M.
      Patient shielding in diagnostic imaging: discontinuing a legacy practice.
      ,
      • Safiullah S.
      • Patel R.
      • Uribe B.
      • Spradling K.
      • Lall C.
      • Zhang L.
      • et al.
      Prevalence of protective shielding utilization for radiation dose reduction in adult patients undergoing body scanning using computed tomography.
      ,
      • Abuzaid M.M.E.W.
      • Haneef C.
      • Alyafei S.
      Thyroid shield during brain CT scan: dose reduction and image quality evaluation.
      ,
      • Marcusohn E.
      • Postnikov M.
      • Musallam A.
      • Yalonetsky S.
      • Mishra S.
      • Kerner A.
      • et al.
      Usefulness of pelvic radiation protection shields during transfemoral procedures-operator and patient considerations.
      ,

      Martus JE HM, Grice JV, Stutz CM, Schoenecker JG, Lovejoy SA, Mencio GA. Radiation exposure during operative fixation of pediatric supracondylar humerus fractures: is lead shielding necessary? J Pediatr Orthop. 2018:249–53.

      ,
      • Musallam A.
      • Volis I.
      • Dadaev S.
      • Abergel E.
      • Soni A.
      • Yalonetsky S.
      • et al.
      A randomized study comparing the use of a pelvic lead shield during trans-radial interventions: Threefold decrease in radiation to the operator but double exposure to the patient.
      ,
      • Phelps A.S.
      • Gould R.G.
      • Courtier J.L.
      • Marcovici P.A.
      • Salani C.
      • MacKenzie J.D.
      How much does lead shielding during fluoroscopy reduce radiation dose to out-of-field body parts?.
      ,
      • Pyka M.
      • Eschle P.
      • Sommer C.
      • Weyland M.S.
      • Kubik R.
      • Scheidegger S.
      Effect of thyroid shielding during mammography: measurements on phantom and patient as well as estimation with Monte Carlo simulation.
      ,
      • Smith J.R.
      • Marsh R.M.
      • Silosky M.S.
      Is lead shielding of patients necessary during fluoroscopic procedures? A study based on kyphoplasty.
      ,
      • Strauss K.J.
      • Gingold E.L.
      • Frush D.P.
      Reconsidering the value of gonadal shielding during abdominal/pelvic radiography.
      ,
      • Tsai Y.-S.
      • Liu Y.-S.
      • Chuang M.-T.
      • Wang C.-K.
      • Lai C.-S.
      • Tsai H.-M.
      • et al.
      Shielding during x-ray examination of pediatric female patients with developmental dysplasia of the hip.
      ,
      • Raissaki M.
      • Perisinakis K.
      • Damilakis J.
      • Gourtsoyiannis N.
      Eye-lens bismuth shielding in paediatric head CT: artefact evaluation and reduction.
      ].
      The findings for each type of patient shielding are summarized in Table 2, Table 3, Table 4, Table 5 together with the respective literature referencing and presented according to:
      • Imaging modality (CT, radiography, mammography, fluoroscopy)
      • Body region exposed to primary radiation (i.e. head, thorax, abdomen, etc.)
      • Specific organ-at-risk (i.e. eye lenses, breast, gonads, etc.)
      • Location (i.e. in- or out-of-plane)
      Table 2Summary of the literature review for CT examinations.
      Examined body partPatient protection shieldingDose reduction range due to the usage of protective shieldingDetrimental effects due to the usage of protective shieldingConclusive statement
      HeadThyroid protection (out-of-plane)
      • Abuzaid M.M.E.W.
      • Haneef C.
      • Alyafei S.
      Thyroid shield during brain CT scan: dose reduction and image quality evaluation.
      ,
      • Tsai Y.-S.
      • Liu Y.-S.
      • Chuang M.-T.
      • Wang C.-K.
      • Lai C.-S.
      • Tsai H.-M.
      • et al.
      Shielding during x-ray examination of pediatric female patients with developmental dysplasia of the hip.
      ,
      • Liebmann M.
      • Lüllau T.
      • Kluge A.
      • Poppe B.
      • von Boetticher H.
      Patient radiation protection covers for head CT scans – a clinical evaluation of their effectiveness.
      Range of absolute dose reduction 0.09–0.88 mGy, range of relative dose reduction 17.9% to 44.7%Image qualityDiscontinue routine patient shielding
      Thyroid protection (in-plane)
      • Catuzzo P.
      • Aimonetto S.
      • Fanelli G.
      • Marchisio P.
      • Meloni T.
      • Mistretta L.
      • et al.
      Dose reduction in multislice CT by means of bismuth shields: results of in vivo measurements and computed evaluationRiduzione della dose mediante l’utilizzo di protezioni in bismuto: risultati di misure in vivo e valutazione delle immagini.
      ,
      • Chang K.-H.
      • Lee W.
      • Choo D.-M.
      • Lee C.-S.
      • Kim Y.
      Dose reduction in CT using bismuth shielding: measurements and Monte Carlo simulations.
      ,
      • Lee K.L.W.
      • Lee J.
      • Lee B.
      • Oh G.
      Dose reduction and image quality assessment in MDCT using AEC (D-DOM & Z-DOM) and in-plane bismuth shielding.
      ,
      • Gbelcova L.
      • Nikodemova D.
      • Horvathova M.
      Dose reduction using bismuth shielding during paediatric CT examinations in Slovakia.
      ,
      • Hoang J.K.
      • Yoshizumi T.T.
      • Choudhury K.R.
      • Nguyen G.B.
      • Toncheva G.
      • Gafton A.R.
      • et al.
      Organ-based dose current modulation and thyroid shields: techniques of radiation dose reduction for neck CT.
      Range of absolute dose reduction 0.16 to 56 mGy, range of relative dose reduction −6% to 48%, range of E reduction: 0.8 to 1.5 mSv
      Breast shield (out-of-plane)
      • Liebmann M.
      • Lüllau T.
      • Kluge A.
      • Poppe B.
      • von Boetticher H.
      Patient radiation protection covers for head CT scans – a clinical evaluation of their effectiveness.
      Range of absolute dose reduction for thyroid between 0.04 and 0.19 mGyPotential dose increase due to overscanDiscontinue routine patient shielding
      Eyes protection (in-plane)
      • Poon R.
      • Badawy M.K.
      Radiation dose and risk to the lens of the eye during CT examinations of the brain.
      ,
      • Raissaki M.
      • Perisinakis K.
      • Damilakis J.
      • Gourtsoyiannis N.
      Eye-lens bismuth shielding in paediatric head CT: artefact evaluation and reduction.
      ,
      • Kim J.-S.
      • Kwon S.-M.
      • Kim J.-M.
      • Yoon S.-W.
      New organ-based tube current modulation method to reduce the radiation dose during computed tomography of the head: evaluation of image quality and radiation dose to the eyes in the phantom study.
      ,
      • Nikupaavo U.
      • Kaasalainen T.
      • Reijonen V.
      • Ahonen S.-M.
      • Kortesniemi M.
      Lens dose in routine head CT: comparison of different optimization methods with anthropomorphic phantoms.
      ,
      • Wang J.
      • Duan X.
      • Christner J.A.
      • Leng S.
      • Grant K.L.
      • McCollough C.H.
      Bismuth shielding, organ-based tube current modulation, and global reduction of tube current for dose reduction to the eye at head CT.
      ,
      • Schmidt S.A.
      • Gruenke T.
      • Beer M.
      • Wunderlich A.P.
      Frequency and diagnostic implications of image artifacts by eye-lens shielding in head CT.
      ,
      • Kosaka H.
      • Monzen H.
      • Amano M.
      • Tamura M.
      • Hattori S.
      • Kono Y.
      • et al.
      Radiation dose reduction to the eye lens in head CT using tungsten functional paper and organ-based tube current modulation.
      ,
      • Hakim A.
      • Vulcu S.
      • Dobrocky T.
      • Z'Graggen W.J.
      • Wagner F.
      Using an orbit shield during volume perfusion CT: is it useful protection or an obstacle?.
      ,
      • Catuzzo P.
      • Aimonetto S.
      • Fanelli G.
      • Marchisio P.
      • Meloni T.
      • Mistretta L.
      • et al.
      Dose reduction in multislice CT by means of bismuth shields: results of in vivo measurements and computed evaluationRiduzione della dose mediante l’utilizzo di protezioni in bismuto: risultati di misure in vivo e valutazione delle immagini.
      ,
      • Chang K.-H.
      • Lee W.
      • Choo D.-M.
      • Lee C.-S.
      • Kim Y.
      Dose reduction in CT using bismuth shielding: measurements and Monte Carlo simulations.
      ,
      • Lee K.L.W.
      • Lee J.
      • Lee B.
      • Oh G.
      Dose reduction and image quality assessment in MDCT using AEC (D-DOM & Z-DOM) and in-plane bismuth shielding.
      ,
      • Gbelcova L.
      • Nikodemova D.
      • Horvathova M.
      Dose reduction using bismuth shielding during paediatric CT examinations in Slovakia.
      ,
      • Huggett J.
      • Mukonoweshuro W.
      • Loader R.
      A phantom-based evaluation of three commercially available patient organ shields for computed tomography X-ray examinations in diagnostic radiology.
      ,
      • Lin M.-F.
      • Chen C.-Y.
      • Lee Y.-H.
      • Li C.-W.
      • Gerweck L.E.
      • Wang H.
      • et al.
      Topogram-based tube current modulation of head computed tomography for optimizing image quality while protecting the eye lens with shielding.
      ,

      Lee YH YS, Lin YK, Glickman RD, Chen CY, Chan WP. Eye shielding during head CT scans: dose reduction and image quality evaluation. Acad Radiol 2020. p. 1523–30.

      ,
      • Ciarmatori A.
      • Nocetti L.
      • Mistretta G.
      • Zambelli G.
      • Costi T.
      Reducing absorbed dose to eye lenses in head CT examinations: the effect of bismuth shielding.
      Range of absolute dose reduction 2 to 144 mGy, range of relative dose reduction 2% to 70%Orbit shields can cause significant artefacts, significant HU increase, increasing image noise, unhygienicDiscontinue routine patient shielding
      NeckThyroid shield (in-plane)
      • Lee Y.H.
      • Park E.-T.
      • Cho P.K.
      • Seo H.S.
      • Je B.-K.
      • Suh S.-i.
      • et al.
      Comparative analysis of radiation dose and image quality between thyroid shielding and unshielding during CT examination of the neck.
      ,
      • Inkoom S.P.A.
      • Raissaki M.
      • Perisinakis K.
      • Schandorf C.
      • Fletcher J.J.
      • Damilakis J.
      Paediatric neck multidetector computed tomography: the effect of bismuth shielding on thyroid dose and image quality.
      Range of relative dose reduction 3.4% to 47%Significant changes in HU, image qualityDiscontinue routine patient shielding
      Breast shield (out-of-plane)
      • Chung J.-J.
      • Cho E.-S.
      • Kang S.M.
      • Yu J.-S.
      • Kim D.J.
      • Kim J.H.
      Usefulness of a lead shielding device for reducing the radiation dose to tissues outside the primary beams during CT.
      No organ reduction estimations
      ChestSurround-apron (out-plane)
      • Weber N.
      • Monnin P.
      • Elandoy C.
      • Ding S.
      A model-based approach of scatter dose contributions and efficiency of apron shielding for radiation protection in CT.
      ,
      • Yu L.
      • Bruesewitz M.R.
      • Vrieze T.J.
      • McCollough C.H.
      Lead shielding in pediatric chest CT: effect of apron placement outside the scan volume on radiation dose reduction.
      ,
      • Foley S.J.
      • McEntee M.F.
      • Achenbach S.
      • Brennan P.C.
      • Rainford L.S.
      • Dodd J.D.
      Breast surface radiation dose during coronary CT angiography: reduction by breast displacement and lead shielding.
      ,
      • Iball G.R.
      • Brettle D.S.
      Organ and effective dose reduction in adult chest CT using abdominal lead shielding.
      Range of absolute dose reduction 0.003 to 0.013 mGy, range of relative dose reduction –6.5% to 77.6%, E reduction: 4%Dose increase, artifacts, risk of backscatter inside the apron, positioning, patient repositioningDiscontinue routine patient shielding
      Fetal protection for pregnant (out-of-plane)
      • Ryckx N.
      • Sans-Merce M.
      • Schmidt S.
      • Poletti P.-A.
      • Verdun F.R.
      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.
      ,
      • Danova D.
      • Keil B.
      • Kästner B.
      • Wulff J.
      • Fiebich M.
      • Zink K.
      • et al.
      Reduction of uterus dose in clinical thoracic computed tomography.
      ,
      • Chatterson L.C.
      • Leswick D.A.
      • Fladeland D.A.
      • Hunt M.M.
      • Webster S.T.
      Lead versus bismuth-antimony shield for fetal dose reduction at different gestational ages at CT pulmonary angiography.
      ,
      • Chatterson L.C.
      • Leswick D.A.
      • Fladeland D.A.
      • Hunt M.M.
      • Webster S.
      • Lim H.
      Fetal shielding combined with state of the art CT dose reduction strategies during maternal chest CT.
      Range of absolute dose reduction 0.02 to 0.09 mGy, range of relative dose reduction 20% to 56%,Possible artefacts, uncomfortable for patients especially in the later stages of pregnancy, possible problems with vena cava and blood circulation due to the heavy aprons, unhygienicDiscontinue routine patient shielding
      Breast shields (in-plane)
      • Catuzzo P.
      • Aimonetto S.
      • Fanelli G.
      • Marchisio P.
      • Meloni T.
      • Mistretta L.
      • et al.
      Dose reduction in multislice CT by means of bismuth shields: results of in vivo measurements and computed evaluationRiduzione della dose mediante l’utilizzo di protezioni in bismuto: risultati di misure in vivo e valutazione delle immagini.
      ,
      • Colletti P.M.
      • Micheli O.A.
      • Lee K.H.
      To shield or not to shield: application of bismuth breast shields.
      ,
      • Wang J.
      • Duan X.
      • Christner J.A.
      • Leng S.
      • Yu L.
      • McCollough C.H.
      Radiation dose reduction to the breast in thoracic CT: comparison of bismuth shielding, organ-based tube current modulation, and use of a globally decreased tube current.
      ,
      • Midgley S.M.
      • Einsiedel P.F.
      • Langenberg F.
      • Lui E.H.
      • Heinze S.B.
      Assessment of patient dose and image quality for cardiac CT with breast shields.
      ,
      • Revel M.-P.
      • Fitton I.
      • Audureau E.
      • Benzakoun J.
      • Lederlin M.
      • Chabi M.-L.
      • et al.
      Breast dose reduction options during thoracic CT: influence of breast thickness.
      ,

      Kotiaho AMA, Nikkinen J, Nieminen MT. Comparison of organ-based tube current modulation and bismuth shielding in chest CT: effect on the image quality and the patient dose. Radiat Prot Dosimetry2019. p. 42–8.

      ,
      • Lambert J.W.
      • Gould R.G.
      Evaluation of a Net dose-reducing organ-based tube current modulation technique: comparison with standard dose and bismuth-shielded acquisitions.
      ,
      • Abadi S.
      • Mehrez H.
      • Ursani A.
      • Parker M.
      • Paul N.
      Direct quantification of breast dose during coronary CT angiography and evaluation of dose reduction strategies.
      ,
      • Rupcich F.
      • Badal A.
      • Popescu L.M.
      • Kyprianou I.
      • Gilat Schmidt T.
      Reducing radiation dose to the female breast during CT coronary angiography: a simulation study comparing breast shielding, angular tube current modulation, reduced kV, and partial angle protocols using an unknown-location signal-detectability metric.
      ,
      • Einstein A.J.
      • Elliston C.D.
      • Groves D.W.
      • Cheng B.
      • Wolff S.D.
      • Pearson G.D.N.
      • et al.
      Effect of bismuth breast shielding on radiation dose and image quality in coronary CT angiography.
      ,
      • Chang K.-H.
      • Lee W.
      • Choo D.-M.
      • Lee C.-S.
      • Kim Y.
      Dose reduction in CT using bismuth shielding: measurements and Monte Carlo simulations.
      ,
      • Lee K.L.W.
      • Lee J.
      • Lee B.
      • Oh G.
      Dose reduction and image quality assessment in MDCT using AEC (D-DOM & Z-DOM) and in-plane bismuth shielding.
      ,
      • Saba V.
      • Keshtkar M.
      Targeted radiation energy modulation using Saba shielding reduces breast dose without degrading image quality during thoracic CT examinations.
      ,
      • Alonso T.C.
      • Mourão A.P.
      • Santana P.C.
      • da Silva T.A.
      Assessment of breast absorbed doses during thoracic computed tomography scan to evaluate the effectiveness of bismuth shielding.
      Range of absolute dose reduction 0.23 to 31.8 mGy, range of relative dose reduction 12.4% to 57%, E reduction: 0.27 mSvPossible artefacts, CT number inaccuracy, increased image noise, unhygienicDiscontinue routine patient shielding.
      Abdomen/ PelvisBreast shield (out-of-plane)
      • Chung J.-J.
      • Cho E.-S.
      • Kang S.M.
      • Yu J.-S.
      • Kim D.J.
      • Kim J.H.
      Usefulness of a lead shielding device for reducing the radiation dose to tissues outside the primary beams during CT.
      Range of relative dose reduction 16.2% to 26%
      Fetal protection for pregnant women (in plane)
      • Moore W.
      • Bonvento M.J.
      • Lee D.
      • Dunkin J.
      • Bhattacharji P.
      Reduction of fetal dose in computed tomography using anterior shields.
      Range of absolute dose reduction 3.6 to 4.8 mGy, range of relative dose reduction 16.2% to 26%Potential artifactsDiscontinue routine patient shielding.
      Lower limbsGonads protection (in-plane)
      • Choi J.W.
      • Lee S.Y.
      • Kim J.H.
      • Jin H.
      • Lee J.
      • Choi Y.H.
      • et al.
      Iterative metallic artifact reduction for in-plane gonadal shielding during computed tomographic venography of young males.
      Absolute dose reduction 5 mGy, relative dose reduction 61%Artifacts, patient collaboration needed, patient discomfort, time consuming, hygieneDiscontinue routine patient shielding.
      Table 3Summary of the literature review for mammography examinations.
      Examined body partPatient protection shieldingDose reduction due to the usage of protective shieldingDetrimental effects due to the usage of protective shieldingConclusive statement
      Mammography examinationContralateral breast
      • Ali R.M.K.M.
      • Mercer C.E.
      • Tootell A.K.
      • Hogg P.
      Impact of contralateral breast shielding on the risk of developing radiation-induced cancer from full-field digital mammography screening.
      Absolute dose reduction 29 μSvDiscontinue routine patient shielding
      Thyroid protection (out-of-plane)
      • Pyka M.
      • Eschle P.
      • Sommer C.
      • Weyland M.S.
      • Kubik R.
      • Scheidegger S.
      Effect of thyroid shielding during mammography: measurements on phantom and patient as well as estimation with Monte Carlo simulation.
      ,
      • Sechopoulos I.
      • Hendrick R.E.
      Mammography and the risk of thyroid cancer.
      ,

      ACR. Breast Imaging Statement on Radiation Received to the Thyroid from Mammography; 2012.

      Range of absolute dose reduction 16–187 μGyDisplacementDiscontinue routine patient shielding
      Table 4Summary of the literature review for radiography examinations.
      Examined body partPatient protection shieldingDose reduction due to the usage of protective shieldingDetrimental effects due to the usage of protective shieldingConclusive statement
      ThoraxGonads apron (out-of-plane)

      AAPM. AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding. PP 32-A. 2019.

      ,
      • Matyagin Y.V.
      • Collins P.J.
      Effectiveness of abdominal shields in chest radiography: a Monte Carlo evaluation.
      Absolute dose reduction: 0.035 μGy, relative dose reduction: 4%Discontinue routine patient shielding
      Shielding (out-of-plane)
      • Hawking N.G.
      • Sharp T.D.
      Decreasing radiation exposure on pediatric portable chest radiographs.
      -abstract only
      Relative dose reduction: 20%No statement
      BrainThyroid
      • Patcas R.
      • Signorelli L.
      • Peltomaki T.
      • Schatzle M.
      Is the use of the cervical vertebrae maturation method justified to determine skeletal age? a comparison of radiation dose of two strategies for skeletal age estimation.
      Absolute dose reduction: 1.73 μSvDiscontinue routine patient shielding
      Abdomen/ Pelvis/ HipGonads protection (in-plane)

      Karami V ZM, Shams N, Saki Malehi A. Gonad Shielding during Pelvic Radiography: A Systematic Review and Meta-analysis. Arch Iran Med. 2017:113-23.

      ,
      • Tsai Y.-S.
      • Liu Y.-S.
      • Chuang M.-T.
      • Wang C.-K.
      • Lai C.-S.
      • Tsai H.-M.
      • et al.
      Shielding during x-ray examination of pediatric female patients with developmental dysplasia of the hip.
      ,
      • Lee M.C.
      • Lloyd J.
      • Solomito M.J.
      Poor utility of gonadal shielding for pediatric pelvic radiographs.
      ,
      • Larson A.N.
      • Schueler B.A.
      • Dubousset J.
      Radiation in spine deformity.
      ,
      • Kaplan S.L.
      • Magill D.
      • Felice M.A.
      • Xiao R.
      • Ali S.
      • Zhu X.
      Female gonadal shielding with automatic exposure control increases radiation risks.
      Range of relative dose reduction: 16–67%Increase of dose to other organs, misplacement, positioning, obscuring anatomical structuresDiscontinue routine patient shielding
      Gonads protection (out-of-plane)

      Karami V ZM, Shams N, Saki Malehi A. Gonad Shielding during Pelvic Radiography: A Systematic Review and Meta-analysis. Arch Iran Med. 2017:113-23.

      ,
      • Lee M.C.
      • Lloyd J.
      • Solomito M.J.
      Poor utility of gonadal shielding for pediatric pelvic radiographs.
      ,
      • Larson A.N.
      • Schueler B.A.
      • Dubousset J.
      Radiation in spine deformity.
      ,
      • Fauber T.
      Gonadal shielding in radiography: a best practice?.
      Range of relative dose reduction: 26.4%Dose increase, misplacement, positioning, hygieneDiscontinue routine patient shielding
      Table 5Summary of the literature review for fluoroscopy-guided procedures.
      Examined body partPatient protection shieldingDose reduction range due to the usage of protective shieldingDetrimental effects due to the usage of protective shieldingConclusive statement
      HeartPelvis shielding (out-of-plane)
      • Musallam A.
      • Volis I.
      • Dadaev S.
      • Abergel E.
      • Soni A.
      • Yalonetsky S.
      • et al.
      A randomized study comparing the use of a pelvic lead shield during trans-radial interventions: Threefold decrease in radiation to the operator but double exposure to the patient.
      ,
      • Marcusohn E.
      • Postnikov M.
      • Musallam A.
      • Yalonetsky S.
      • Mishra S.
      • Kerner A.
      • et al.
      Usefulness of pelvic radiation protection shields during transfemoral procedures-operator and patient considerations.
      Increase of patient doseDiscontinue routine patient shielding
      Spine (kyphoplasty/vertebroplasty)Pelvis shielding (out-of-plane)
      • Smith J.R.
      • Marsh R.M.
      • Silosky M.S.
      Is lead shielding of patients necessary during fluoroscopic procedures? A study based on kyphoplasty.
      No dose assessment reportedDiscontinue routine patient shielding
      Orthopedics (displaced supracondylar humerus fracture)Thyroid, torso shielding (out-of-plane)

      Martus JE HM, Grice JV, Stutz CM, Schoenecker JG, Lovejoy SA, Mencio GA. Radiation exposure during operative fixation of pediatric supracondylar humerus fractures: is lead shielding necessary? J Pediatr Orthop. 2018:249–53.

      No dose assessment reportedDiscontinue routine patient shielding
      UteroscopyUterus
      • Nguyen K.K.
      • Schlaifer A.E.
      • Smith D.L.
      • Anderson K.M.
      • Arnold D.C.
      • Heldt J.P.
      • et al.
      In automated fluoroscopy settings, does shielding affect radiation exposure to surrounding unshielded tissues?.
      0.96 mGyIncrease of other organ dosesDiscontinue routine patient shielding
      General fluoroscopyOut-of plane
      • Phelps A.S.
      • Gould R.G.
      • Courtier J.L.
      • Marcovici P.A.
      • Salani C.
      • MacKenzie J.D.
      How much does lead shielding during fluoroscopy reduce radiation dose to out-of-field body parts?.
      No dose assessment reportedDiscontinue routine patient shielding
      Absolute and relative dose reduction ranges as well as the effective dose reduction if reported by the authors are summarized in the third column of each table. The fourth column includes detrimental effects as reported in relevant articles.

      CT examinations

      Various articles discussed the use of contact shielding during CT examinations (Table 2). However, only few estimated dose reductions with out-of-plane shielding with the highest reported dose reduction to be equal to 0.2 mGy [
      • Liebmann M.
      • Lüllau T.
      • Kluge A.
      • Poppe B.
      • von Boetticher H.
      Patient radiation protection covers for head CT scans – a clinical evaluation of their effectiveness.
      ]. Most of the articles reported dose reduction for in-plane shielding estimated either using phantoms or with in-vivo measurements. The authors for the majority of the papers compared the dose reduction with in-plane shielding with other acquisition protocols and techniques to reduce organ doses. It is worth mentioning that the AAPM in its recent publication on bismuth shielding recommended that alternatives methods should be considered and implemented instead of bismuth shielding, as they can provide equivalent dose reduction maintaining the same or improving image quality without other limitations of bismuth shields [

      AAPM. AAPM Position Statement on the Use of Bismuth Shielding for the Purpose of Dose Reduction in CT scanning; 2017.

      ]. The absolute eye dose reduction ranged between 2 and 144 mGy, corresponding to relative dose reductions between 2 and 70%. For eye protection, several authors reported more important dose reductions for the eyes (up to 92%) with gantry tilt so as to keep the eyes outside the primary beam [
      • Poon R.
      • Badawy M.K.
      Radiation dose and risk to the lens of the eye during CT examinations of the brain.
      ,
      • Kim J.-S.
      • Kwon S.-M.
      • Kim J.-M.
      • Yoon S.-W.
      New organ-based tube current modulation method to reduce the radiation dose during computed tomography of the head: evaluation of image quality and radiation dose to the eyes in the phantom study.
      ,
      • Nikupaavo U.
      • Kaasalainen T.
      • Reijonen V.
      • Ahonen S.-M.
      • Kortesniemi M.
      Lens dose in routine head CT: comparison of different optimization methods with anthropomorphic phantoms.
      ] or if this is not possible they suggested organ-based tube current modulation (OBTCM) with comparable eye dose reduction to bismuth shielding and with better image quality [
      • Kim J.-S.
      • Kwon S.-M.
      • Kim J.-M.
      • Yoon S.-W.
      New organ-based tube current modulation method to reduce the radiation dose during computed tomography of the head: evaluation of image quality and radiation dose to the eyes in the phantom study.
      ,
      • Nikupaavo U.
      • Kaasalainen T.
      • Reijonen V.
      • Ahonen S.-M.
      • Kortesniemi M.
      Lens dose in routine head CT: comparison of different optimization methods with anthropomorphic phantoms.
      ,
      • Wang J.
      • Duan X.
      • Christner J.A.
      • Leng S.
      • Grant K.L.
      • McCollough C.H.
      Bismuth shielding, organ-based tube current modulation, and global reduction of tube current for dose reduction to the eye at head CT.
      ]. Other authors reported image artifacts caused by the in-plane shielding and addressed the need for correct positioning and use [
      • Schmidt S.A.
      • Gruenke T.
      • Beer M.
      • Wunderlich A.P.
      Frequency and diagnostic implications of image artifacts by eye-lens shielding in head CT.
      ,
      • Kosaka H.
      • Monzen H.
      • Amano M.
      • Tamura M.
      • Hattori S.
      • Kono Y.
      • et al.
      Radiation dose reduction to the eye lens in head CT using tungsten functional paper and organ-based tube current modulation.
      ]. Especially for CT head perfusion, Hakim et al. recommended not to use in-plane shielding as orbit shields cause significant artefacts appear if included in scan ranges during acquisition of CT perfusion and interfere with the diagnostic utility of whole brain CTP [
      • Hakim A.
      • Vulcu S.
      • Dobrocky T.
      • Z'Graggen W.J.
      • Wagner F.
      Using an orbit shield during volume perfusion CT: is it useful protection or an obstacle?.
      ], while Poon et al. reported changes in CT HU [
      • Poon R.
      • Badawy M.K.
      Radiation dose and risk to the lens of the eye during CT examinations of the brain.
      ]. In-plane shielding use was also studied for breast protection. The absolute breast dose reduction ranged between 0.23 and 31.8 mGy, corresponding to relative dose reductions between 12.4 and 57%. Catuzzo et al. calculated that the effective dose (E) decreased by 0.27 mSv for a breast dose reduction of 12.7 mGy (41%) [
      • Catuzzo P.
      • Aimonetto S.
      • Fanelli G.
      • Marchisio P.
      • Meloni T.
      • Mistretta L.
      • et al.
      Dose reduction in multislice CT by means of bismuth shields: results of in vivo measurements and computed evaluationRiduzione della dose mediante l’utilizzo di protezioni in bismuto: risultati di misure in vivo e valutazione delle immagini.
      ]. Other authors proposed dose reduction with similar effects in dose and image quality (noise, altered HU) with techniques such as tube current reduction [
      • Colletti P.M.
      • Micheli O.A.
      • Lee K.H.
      To shield or not to shield: application of bismuth breast shields.
      ,
      • Wang J.
      • Duan X.
      • Christner J.A.
      • Leng S.
      • Yu L.
      • McCollough C.H.
      Radiation dose reduction to the breast in thoracic CT: comparison of bismuth shielding, organ-based tube current modulation, and use of a globally decreased tube current.
      ], tube voltage reduction [
      • Midgley S.M.
      • Einsiedel P.F.
      • Langenberg F.
      • Lui E.H.
      • Heinze S.B.
      Assessment of patient dose and image quality for cardiac CT with breast shields.
      ,
      • Revel M.-P.
      • Fitton I.
      • Audureau E.
      • Benzakoun J.
      • Lederlin M.
      • Chabi M.-L.
      • et al.
      Breast dose reduction options during thoracic CT: influence of breast thickness.
      ], organ-based tube current modulation OBTCM [

      Kotiaho AMA, Nikkinen J, Nieminen MT. Comparison of organ-based tube current modulation and bismuth shielding in chest CT: effect on the image quality and the patient dose. Radiat Prot Dosimetry2019. p. 42–8.

      ,
      • Lambert J.W.
      • Gould R.G.
      Evaluation of a Net dose-reducing organ-based tube current modulation technique: comparison with standard dose and bismuth-shielded acquisitions.
      ] or for CT coronary angiography gating, reducing the acquisition window for the heart cycle [
      • Abadi S.
      • Mehrez H.
      • Ursani A.
      • Parker M.
      • Paul N.
      Direct quantification of breast dose during coronary CT angiography and evaluation of dose reduction strategies.
      ]. One study reported even increase of doses for breast tissue for identical image quality when in-plane breast shielding was used, while different protocol settings could reduce breast dose maintaining image quality [
      • Rupcich F.
      • Badal A.
      • Popescu L.M.
      • Kyprianou I.
      • Gilat Schmidt T.
      Reducing radiation dose to the female breast during CT coronary angiography: a simulation study comparing breast shielding, angular tube current modulation, reduced kV, and partial angle protocols using an unknown-location signal-detectability metric.
      ]. Moore et al. investigated the efficiency of in-plane shielding for fetal protection [
      • Moore W.
      • Bonvento M.J.
      • Lee D.
      • Dunkin J.
      • Bhattacharji P.
      Reduction of fetal dose in computed tomography using anterior shields.
      ]. They reported dose savings of an average of 4 mGy for different gestation age and tube voltages with no qualitative difference in low contrast detectability; however, as the authors address the image quality evaluation was based on an anthropomorphic phantom.

      Mammography examinations

      Table 3 shows the articles for dose reduction in mammography examinations with the use of shielding. For thyroid gland protection, some dose reduction was observed (between16 μGy and 187 μGy). Most importantly, if thyroid shielding enters the X-ray field, it can cause artefacts that obscure breast tissue and may require mammography repetition [

      ACR. Breast Imaging Statement on Radiation Received to the Thyroid from Mammography; 2012.

      ]. Moreover, it is important to keep in mind that thyroid radiosensitivity decreases with age, thus, for older patients, thyroid shielding would make no sense [

      Radiology BIo. Guidance on using contact shielding on patients for diagnostic radiology applications; 2020.

      ,
      • Pyka M.
      • Eschle P.
      • Sommer C.
      • Weyland M.S.
      • Kubik R.
      • Scheidegger S.
      Effect of thyroid shielding during mammography: measurements on phantom and patient as well as estimation with Monte Carlo simulation.
      ]. Gonadal shielding is no longer recommended as radiation dose reduction is negligible since the X-ray field is far and the gonad exposure is particularly low [

      AAPM. AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding. PP 32-A. 2019.

      ]. When 0.25 mm Pb equiv. shielding is used for contralateral breast protection, a dose reduction from 41.4 to 0.01 μGy was observed [
      • Ali R.M.K.M.
      • Mercer C.E.
      • Tootell A.K.
      • Hogg P.
      Impact of contralateral breast shielding on the risk of developing radiation-induced cancer from full-field digital mammography screening.
      ].

      Radiography examinations

      The effectiveness of patient shielding in radiography examinations is summarized in Table 4. In-plane and out-of-plane shielding was also found to be used for this modality. Many reports conclude that gonad shielding for head/neck/shoulder and extremities radiography can be safely abandoned as the X-ray field is far from the sensitive organs [

      SIRM A, FASTER. POSIZIONE DI AIFM, SIRM E FASTeR SULL’USO DEI DISPOSITIVI DI PROTEZIONE INDIVIDUALE. 2020.

      ,

      AAPM. AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding. PP 32-A. 2019.

      ,

      Radiology BIo. Guidance on using contact shielding on patients for diagnostic radiology applications; 2020.

      ,

      NSRP. Nordic guidelines for dose reduction to radiosensitive organs of the patient in conventional radiography and fluoroscopy; 2019.

      ,

      Strahlenschutzkommission. https://www.ssk.de/SharedDocs/Beratungsergebnisse/2018/2018-12-13Patienten.html. wwwsskde2018.

      ,

      SSRMP. Report on the use of patient shielding in radiological procedures, report 21. 2020.

      ,
      • Candela-Juan C.
      • Ciraj-Bjelac O.
      • Sans Merce M.
      • Dabin J.
      • Faj D.
      • Gallagher A.
      • et al.
      Use of out-of-field contact shielding on patients in medical imaging: A review of current guidelines, recommendations and legislative documents.
      ]. Regarding, abdomen/pelvis radiography, shielding depends on patient gender with in-plane shielding being applied for female patients and out-of-plane shielding for male patients. For pelvic and hip radiography of female patients the shielding happens to be in the X-ray field then AEC cannot be used as the shielding will increase the exposure parameters considering the density of the irradiated structure. Moreover, the positioning of the shielding for ovaries it’s not an easy task, indeed their position is generally unknown. If the shielding is placed, it is not is usually placed centrally above the pubic symphysis; however, according to more recent studies on the ovaries location, the shielding must be positioned laterally [
      • Bardo D.M.E.B.M.
      • Schenk K.
      • Zaritzky M.F.
      Location of the ovaries in girls from newborn to 18 years of age: reconsidering ovarian shielding.
      ]. This information makes ovaries shielding use during pelvis and hip radiographies practically impossible, as the shielding will hide the anatomical region of interest. For the male patient there should be no particular problems, as the gonad shielding is positioned under the pubic symphysis and thus, the shielding should be out but rather close to the acquisition plane. According to a study by Lee et al., pelvic shields were misplaced in 49% of anteroposterior and 63% of frog lateral radiographs and shielding was misplaced for both girls and boys on frog lateral radiographs (misplacement for girls: 76% vs 51% for boys) [
      • Lee M.C.
      • Lloyd J.
      • Solomito M.J.
      Poor utility of gonadal shielding for pediatric pelvic radiographs.
      ]. Moreover, a review that focused on gonad shieling during pelvic radiography showed that shielding for male patients is controversial and stressed out that the current practice of gonad shielding during female pelvic radiography should be no longer considered as an effective method to reduce radiation exposure [

      Karami V ZM, Shams N, Saki Malehi A. Gonad Shielding during Pelvic Radiography: A Systematic Review and Meta-analysis. Arch Iran Med. 2017:113-23.

      ]. Larson et al. proposed posterior-anterior (PA) radiographs instead of anteroposterior (AP) that can significantly reduce exposure to the testes, thyroid, and breast for all routine screening radiographs [
      • Larson A.N.
      • Schueler B.A.
      • Dubousset J.
      Radiation in spine deformity.
      ].

      Fluoroscopy guided procedures

      Patient shielding during fluoroscopy and interventional procedures is quite rare. This is also reflected in the low number of articles investigating and discussing their effectiveness in Table 5. Only one article provided data on organ dose reduction (0.96 mGy) when shielding was used, but addressed the fact that other neighboring tissue doses were more irradiated [
      • Nguyen K.K.
      • Schlaifer A.E.
      • Smith D.L.
      • Anderson K.M.
      • Arnold D.C.
      • Heldt J.P.
      • et al.
      In automated fluoroscopy settings, does shielding affect radiation exposure to surrounding unshielded tissues?.
      ]. The difficulty in positioning correctly the shielding to guarantee that it will stay outside the X-ray field, while X-ray tube constantly moves around the patient; the fact that the shielding is not visible under the sterile drape, and that the procedures are particularly long increasing the risk that the patient moves, make shielding use complicated. On the other hand, special shielding during fluoroscopy and interventional procedures is often used to decrease the radiation exposure of the operator and not that of the patient [
      • Marcusohn E.
      • Postnikov M.
      • Musallam A.
      • Yalonetsky S.
      • Mishra S.
      • Kerner A.
      • et al.
      Usefulness of pelvic radiation protection shields during transfemoral procedures-operator and patient considerations.
      ,
      • Musallam A.
      • Volis I.
      • Dadaev S.
      • Abergel E.
      • Soni A.
      • Yalonetsky S.
      • et al.
      A randomized study comparing the use of a pelvic lead shield during trans-radial interventions: Threefold decrease in radiation to the operator but double exposure to the patient.
      ,
      • Smith J.R.
      • Marsh R.M.
      • Silosky M.S.
      Is lead shielding of patients necessary during fluoroscopic procedures? A study based on kyphoplasty.
      ]. If this kind of shielding is correctly placed, outside the primary beam, the patient exposure remains the same, while in some cases the dose to the operator may decrease or remain the same [
      • Marcusohn E.
      • Postnikov M.
      • Musallam A.
      • Yalonetsky S.
      • Mishra S.
      • Kerner A.
      • et al.
      Usefulness of pelvic radiation protection shields during transfemoral procedures-operator and patient considerations.
      ,
      • Smith J.R.
      • Marsh R.M.
      • Silosky M.S.
      Is lead shielding of patients necessary during fluoroscopic procedures? A study based on kyphoplasty.
      ]. However, there are bad practice when applying patient shielding was proven to increase the dose to the patient and personnel [
      • Musallam A.
      • Volis I.
      • Dadaev S.
      • Abergel E.
      • Soni A.
      • Yalonetsky S.
      • et al.
      A randomized study comparing the use of a pelvic lead shield during trans-radial interventions: Threefold decrease in radiation to the operator but double exposure to the patient.
      ], hide important anatomical details [
      • Marcusohn E.
      • Postnikov M.
      • Musallam A.
      • Yalonetsky S.
      • Mishra S.
      • Kerner A.
      • et al.
      Usefulness of pelvic radiation protection shields during transfemoral procedures-operator and patient considerations.
      ], and increase the risk of infection [
      • Boyle H.
      • Strudwick R.M.
      Do lead rubber aprons pose an infection risk?.
      ]. Collimation, correct use of settings and other methods have been proven more effective to decrease patient dose than patient shielding [
      • Phelps A.S.
      • Gould R.G.
      • Courtier J.L.
      • Marcovici P.A.
      • Salani C.
      • MacKenzie J.D.
      How much does lead shielding during fluoroscopy reduce radiation dose to out-of-field body parts?.
      ].

      Discussion

      This literature review has shown that during the past 10 years a tremendous scientific effort has been made to investigate and quantify the benefit of different shielding techniques in order to optimize patient protection during medical X-ray imaging. In the beginning of this decade the benefit of patient shielding during medical X-ray imaging was almost undisputed, whereas in recent years some of publications began to scrutinize the importance of patient contact shielding used in routine with respect to the emerging technical improvements for almost all X-ray modalities. Options like automated exposure control (mainly for radiography), tube current modulation in z-direction as well as during gantry rotation – the latter initially developed to account for the non-cylindrical shape of the human body but soon developed further towards organ based tube current modulation – did show great potential to significantly decrease patient dose. In combination with iterative reconstruction and other methods of artificial intelligence, it was shown that the X-ray dose can be reduced even further without compromising or even improving image quality. However, it was also shown that the presence of patient shielding might lead to a detrimental effect and even and increase in patient dose when present in the imaged body region. Soon professional societies of physicians and physicists as well as national authorities became aware of these discussions leading to the current dispute about the benefits or disadvantages of routine use of patient protection means.
      Based on the current hot topic debate about the significance of patient shielding, this review not only summarizes the evidence presented in the literature, but also puts it in the context of the technical developments in the same period [
      • Rehani M.M.
      • Nacouzi D.
      Higher patient doses through X-ray imaging procedures.
      ,
      • Malone J.
      X-rays for medical imaging: radiation protection, governance and ethics over 125 years.
      ,

      COCIR. Medical imaging equipment, Age profile and density, 2019 Edition. Brussels: COCIR, European Coordination of the radiological, electromedical and healthcare IT industry; 2019.

      ,
      • Kubo T.
      • Ohno Y.
      • Seo J.B.
      • Yamashiro T.
      • Kalender W.A.
      • Lee C.H.
      • et al.
      Securing safe and informative thoracic CT examinations-progress of radiation dose reduction techniques.
      ]. In addition, non-dose-related aspects are considered in order to evaluate whether patient protection by means of contact shielding should be maintained or discontinued. Our conclusions for each of the investigated shielding type are given in the last column of Table 2, Table 3, Table 4, Table 5 as a brief statement and the reasoning for these recommendations are explained in the following paragraphs.

      Out-of-plane shielding

      The analysis of dose savings for out-of-plane shielding has revealed that absolute values are in the sub-mGy range. The highest value of 0.2 mGy was reported for thyroid protection during head CT-scans and mammography examinations. In case of CT, this number represents a rather low contribution compared to the total dose of a head CT. In addition, out-of-plane shielding does not protect from internal scattering, which is the main contributing source of the radiation dose to internal organs located outside of the field of view (FoV) [

      Radiology BIo. Guidance on using contact shielding on patients for diagnostic radiology applications; 2020.

      ,
      • Matyagin Y.V.
      • Collins P.J.
      Effectiveness of abdominal shields in chest radiography: a Monte Carlo evaluation.
      ,
      • Weber N.
      • Monnin P.
      • Elandoy C.
      • Ding S.
      A model-based approach of scatter dose contributions and efficiency of apron shielding for radiation protection in CT.
      ]. For external scatter, the effectiveness of the shielding depends on its position relative to the beam edge. Ideally, the contact shielding should be placed exactly on the beam edge, which is practically impossible. If the shielding is positioned more than five cm away from the beam edge, the dose reduction is negligible [
      • Weber N.
      • Monnin P.
      • Elandoy C.
      • Ding S.
      A model-based approach of scatter dose contributions and efficiency of apron shielding for radiation protection in CT.
      ,
      • Yu L.
      • Bruesewitz M.R.
      • Vrieze T.J.
      • McCollough C.H.
      Lead shielding in pediatric chest CT: effect of apron placement outside the scan volume on radiation dose reduction.
      ]. Hence, any lowering of the dose due to protocol optimization, e.g. reducing tube current, will have a larger impact than shielding. On the other hand, if high-Z shielding enters the imaging FoV, besides compromising image quality, the X-ray system will drastically increase the output, resulting in higher radiation dose to the patient. This is particularly important for multidetector CT scans due to the corresponding over-ranging and over-beaming effects. According to recent research, these effects might contribute to extended exposure length of up to 83.1 mm for modern CT systems with a beam width of 80 mm in the z-direction. Thus, even when positioned outside of the selected scan range, high-Z material shielding can be exposed by the primary beam, adversely interfering with the imaging.
      For thyroid shielding during mammography it has been reported that misplacement of the shield might have detrimental effects on dose and image quality. Moreover, it is important to keep in mind that thyroid radiosensitivity decreases with age, thus, for older patients- the major part of the patient population for this specific examination, thyroid shielding would have a low impact [

      Radiology BIo. Guidance on using contact shielding on patients for diagnostic radiology applications; 2020.

      ,
      • Pyka M.
      • Eschle P.
      • Sommer C.
      • Weyland M.S.
      • Kubik R.
      • Scheidegger S.
      Effect of thyroid shielding during mammography: measurements on phantom and patient as well as estimation with Monte Carlo simulation.
      ]. Furthermore, thyroid is placed at larger distance than 5 cm from the primary field, thus the dose reduction is negligible.
      If the dose saving due to out-of-plane thyroid shielding is compared to other sources of ionizing radiation, e.g. sources of natural radiation, the maximal savings of 0.2 mGy is even lower than the annual dose received from cosmic radiation. According to the atlas of natural radiation from the European commission the lowest values measured are 0.3 mSv p.a.[
      • Cinelli G.
      • Tollefsen T.
      • Bossew P.
      • Gruber V.
      • Bogucarskis K.
      • De Felice L.
      • et al.
      Digital version of the European Atlas of natural radiation.
      ].
      The application of contact shielding on a routine daily practice include also non-dose-related aspects that have to be taken into consideration: several publications point out that a proper placement in the daily practice is often not possible and/or might lead to significant patient discomfort [
      • Gilligan P.
      • Damilakis J.
      Patient shielding: the need for a European consensus statement.
      ,

      Radiology BIo. Guidance on using contact shielding on patients for diagnostic radiology applications; 2020.

      ,
      • Foley S.J.
      • McEntee M.F.
      • Achenbach S.
      • Brennan P.C.
      • Rainford L.S.
      • Dodd J.D.
      Breast surface radiation dose during coronary CT angiography: reduction by breast displacement and lead shielding.
      ]. In addition, contact shielding might represent a hygienic risk representing a source of bacterial or viral infections [
      • Grogan B.F.
      • Cranston W.C.
      • Lopez D.M.
      • Furbee C.
      • Murray C.K.
      • Hsu J.R.
      Do protective lead garments harbor harmful bacteria?.
      ,
      • Ang L.A.A.
      • Palakodeti S.
      • Mahmud E.
      Bacterial contamination of lead aprons in a high-volume cardiac catheterization laboratory and disinfection using an automated ultraviolet-C radiation system.
      ,

      Feierabend SSG. Potential infection risk from thyroid radiation protection. J Orthop Trauma. 2015:18–20.

      ]. Nowadays, nosocomial infections in combination with increasing bacterial resistance to antibiotic medication and viral infections represent a significant challenge in the clinical daily routine and should be considered when applying patient contact shielding. Although, no article considered the psychological aspects, we can report from our experience that such effects can be either positive or negative since the use of shielding may provoke a false sense of safety to the patient or give the impression that the patient is exposed to great amounts of radiation dose outside the region of interest.
      Overall, the literature analysis has shown that dose savings for all applications of out-of-plane shielding are low in terms of absolute values. Bearing in mind that for stochastic effects such as malignant cancer the absolute organ doses are important, dose savings well in the sub-mGy range could be classified as negligible. Considering the developments made in the field of imaging techniques and non-dose related aspects, we recommend that the routine practice out-of-plane shielding to be discontinued.

      In-plane shielding

      In-plane shielding is mainly applied to protect radiation sensitive and superficial organs, i.e. breast tissue, the thyroid and the eye lenses. This literature review has shown that considerable dose savings have been reported for in-plane shielding, both in relative as well as absolute values. It is noteworthy that most of the reviewed publications report the dose savings for different shielding applications without investigating the dose savings in relation to image quality. In addition, almost all publications mention that in-plane shielding is causing streak artefacts and significantly increase image noise due to beam hardening and photon starvation [
      • Wang J.
      • Duan X.
      • Christner J.A.
      • Leng S.
      • Grant K.L.
      • McCollough C.H.
      Bismuth shielding, organ-based tube current modulation, and global reduction of tube current for dose reduction to the eye at head CT.
      ,
      • Hakim A.
      • Vulcu S.
      • Dobrocky T.
      • Z'Graggen W.J.
      • Wagner F.
      Using an orbit shield during volume perfusion CT: is it useful protection or an obstacle?.
      ,
      • Colletti P.M.
      • Micheli O.A.
      • Lee K.H.
      To shield or not to shield: application of bismuth breast shields.
      ,
      • Wang J.
      • Duan X.
      • Christner J.A.
      • Leng S.
      • Yu L.
      • McCollough C.H.
      Radiation dose reduction to the breast in thoracic CT: comparison of bismuth shielding, organ-based tube current modulation, and use of a globally decreased tube current.
      ]. The issue of visible image artefacts can almost always be solved by introducing a spacer material between patient surface and shield. However, the fact of beam hardening leads to an unpredictable change of Hounsfield units, thereby challenging for any quantitative image analysis, e.g. for coronary CT angiography or iodine quantification [

      Kotiaho AMA, Nikkinen J, Nieminen MT. Comparison of organ-based tube current modulation and bismuth shielding in chest CT: effect on the image quality and the patient dose. Radiat Prot Dosimetry2019. p. 42–8.

      ,
      • Jang H.
      • Hur J.
      • Choi B.W.
      • Im D.J.
      • Hong Y.J.
      • Kim Y.J.
      • et al.
      Effects of bismuth breast shielding on iodine quantification in dual-energy computed tomography: an experimental phantom study.
      ,
      • Einstein A.J.
      • Elliston C.D.
      • Groves D.W.
      • Cheng B.
      • Wolff S.D.
      • Pearson G.D.N.
      • et al.
      Effect of bismuth breast shielding on radiation dose and image quality in coronary CT angiography.
      ]. In addition, if authors conclude that despite the shielding causing higher noise levels a sufficient diagnostic image quality was achieved, then, one has at least to reconsider whether the original protocol would allow for dose savings based on optimized scanning parameters instead of contact in-plane-shielding. Those papers that accounted for comparable image quality often concluded that similar dose savings can be achieved for optimized protocols without the drawback of altered HU units. Moreover, the main disadvantage of the shielding placed inside the X-ray field is that it can significantly obscure anatomy and compromise the diagnosis. In the worst case, it might even require the repetition of the radiological procedure and thus increase patient radiation exposure [
      • Wang J.
      • Duan X.
      • Christner J.A.
      • Leng S.
      • Grant K.L.
      • McCollough C.H.
      Bismuth shielding, organ-based tube current modulation, and global reduction of tube current for dose reduction to the eye at head CT.
      ,
      • Hakim A.
      • Vulcu S.
      • Dobrocky T.
      • Z'Graggen W.J.
      • Wagner F.
      Using an orbit shield during volume perfusion CT: is it useful protection or an obstacle?.
      ,
      • Wang J.
      • Duan X.
      • Christner J.A.
      • Leng S.
      • Yu L.
      • McCollough C.H.
      Radiation dose reduction to the breast in thoracic CT: comparison of bismuth shielding, organ-based tube current modulation, and use of a globally decreased tube current.
      ]. A major concern of in-plane shielding is the fact that it might interfere with all types of automated dose modulation techniques available. And even if the term “unpredictable” might be incorrect, it would require a fundamental understanding of the individual technique itself as well as the particular manufacturer’s implementation in order to account for possible detrimental effects. These considerations are not only true for CT examinations but apply also to modern X-ray systems, where it has been shown that automatic exposure control (AEC) can significantly increase the X-ray output and hence patient dose [
      • Colletti P.M.
      • Micheli O.A.
      • Lee K.H.
      To shield or not to shield: application of bismuth breast shields.
      ].
      Based on the review of recent scientific literature and our analysis about dose- and non-dose related aspects of it is our opinion that the usage of routine contact shielding in medical X-ray imaging can be discontinued. This conclusion is in-line with several national medical physics societies including the American Association of Physicists in Medicine [

      AAPM. AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding. PP 32-A. 2019.

      ,

      AAPM. AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding PP 32-A; 2019.

      ], the Nordic Society for Radiation Protection [

      NSRP. Nordic guidelines for dose reduction to radiosensitive organs of the patient in conventional radiography and fluoroscopy; 2019.

      ] and the Italian association of Medical physicists [

      SIRM A, FASTER. POSIZIONE DI AIFM, SIRM E FASTeR SULL’USO DEI DISPOSITIVI DI PROTEZIONE INDIVIDUALE. 2020.

      ] that suggest to abandon the practice of patient shielding in medical X-ray imaging. The British Institute of Radiology has recently published an evidence-based guideline on why contact shielding for patients is no longer needed during conventional X-rays procedures, CT scans and interventional radiology [

      Radiology BIo. Guidance on using contact shielding on patients for diagnostic radiology applications; 2020.

      ]. To the best of our knowledge, only the German Commission on Radiological Protection still recommends the use of in-plane or out-of-plane organ shielding for CT examinations and the use of gonad shielding for abdomen/pelvis/hip radiographies [

      Strahlenschutzkommission. https://www.ssk.de/SharedDocs/Beratungsergebnisse/2018/2018-12-13Patienten.html. wwwsskde2018.

      ]. However, the possible dose reduction are in the range of sub-mSv for the out-of-plane shielding, while for in-plane shielding other methods have been proved equally efficient as discussed above.
      Lastly, it is also important to mention that discontinuing the use of routine patient shielding may confuse both the healthcare providers, who were used to employ patient shielding for several decades, as well as the patients, who were used to receive a radiation protection shielding – and especially those who undergo repetitive examinations. It is, therefore, crucial that healthcare practitioners are suitably informed about the scientific evidence and understand the complex influence of the shielding on patients’ safety and diagnostic capacity of the imaging. Radiographers and operators must keep up to date with current techniques and technologies in medical imaging. Finally, healthcare providers should be appropriately trained to listen to patients’ concerns and provide adequate information regarding the use of patient shielding, being aware that using patient shielding only to calm the patient may cause more harm than good.

      Conclusions

      With respect to the manifold technical dose optimization strategies, dose savings due to patient shielding are rather negligible in modern medical X-ray imaging, while significant dose- and non-dose-related detrimental effects are present. Thus, the usage of routine patient shielding can be safely discontinued in the large majority of examinations and patient groups.

      Funding

      This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

      Appendix A. Supplementary data

      The following are the Supplementary data to this article:

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