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Higher patient doses through X-ray imaging procedures

Published:November 12, 2020DOI:https://doi.org/10.1016/j.ejmp.2020.10.017

      Highlights

      • Patient doses in the range of a few tens of mSv are not uncommon.
      • Cumulative doses from multiple X-ray procedures may lead to doses over 100 mSv.
      • Lack of optimization by users despite better technology is important contributor.
      • Technological solutions are showing great promise for the future.
      • One important advance that is coming up is that of monochromatic X-ray source.

      Abstract

      Medical imaging using X-rays has been one of the most popular imaging modalities ever since the discovery of X-rays 125 years ago. With unquestionable benefits, concerns about radiation risks have frequently been raised. Computed tomography (CT) and fluoroscopic guided interventional procedures have the potential to impart higher radiation exposure to patients than radiographic examinations. Despite technological advances, there have been instances of increased doses per procedure mainly because of better diagnostic information in images. However, cumulative dose from multiple procedures is creating new concerns as effective doses >100 mSv are not uncommon. There is a need for action at all levels. Manufacturers must produce equipment that can provide a quality diagnostic image at substantially lesser dose and better implementation of optimization strategies by users. There is an urgent need for the industry to develop CT scanners with sub-mSv radiation dose, a goal that has been lingering. It appears that a new monochromatic X-ray source will lead to replacement of X-ray tubes all over the world in coming years and will lead to a drastic reduction in radiation doses. This innovation will impact all X-ray imaging and will help dose reduction. For interventional procedures, the likely employment of robotic systems in practice may drastically reduce radiation exposures to operators- but patient exposure will still remain an issue. Training needs always need to be emphasized and practiced.

      Keywords

      1. Introduction

      Since their discovery 125 years ago, X-rays have been at the core of some of the most popular imaging modalities in medicine. This is evident from the 3.6 billion X-ray exams that were performed annually worldwide according to the 2008 United Nations Scientific Committee on Effects of Atomic Radiation (UNSCEAR) report [

      United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). 2008 Report to the General Assembly: Annex B Exposures of the Public and Workers from Various Sources of Radiation. vol. I. 2010.

      ]. Current estimates are not yet available from UNSCEAR, but it is expected that between 4 and 5 billion X-ray exams are performed annually across the globe, implying that nearly 13 million imaging exams every single day of the year are performed using X-rays. No other medical imaging modality matches this level of use. While the utility of X-rays in diagnosis, follow-up, and management of many diseases (through interventional guidance) has been unquestionable, concern about radiation risks have frequently been raised [
      • Rehani M.M.
      Challenges in radiation protection of patients for the 21st century.
      ,
      • Rehani M.M.
      • Srimahachota S.
      Skin injuries in interventional procedures.
      ,

      Food and Drug Administration (FDA). Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging n.d. https://www.fda.gov/radiation-emitting-products/radiation-safety/initiative-reduce-unnecessary-radiation-exposure-medical-imaging.

      ]. Concerns regarding radiation risk have centered on both tissue reactions (earlier called deterministic effects) and stochastic effects [

      International Commission on Radiological Protection. Annals of the ICRP: Publication 103. Proc 31st World Nucl Assoc Annu Symp 2006 2007.

      ,
      • Rehani M.M.
      ICRP and IAEA actions on radiation protection in computed tomography.
      ]. These concerns have led to improvements in imaging technology and the proposal of a variety of solutions to optimize and justify the use of X-rays in medical imaging [
      • Rehani M.M.
      Challenges in radiation protection of patients for the 21st century.
      ,
      • Kachelrieß M.
      • Rehani M.M.
      Is it possible to kill the radiation risk issue in computed tomography?.
      ,

      M.M. Rehani T. Berris International Atomic Energy Agency study with referring physicians on patient radiation exposure and its tracking: a prospective survey using a web-based questionnaire BMJ Open 2012;2. 10.1136/bmjopen-2012-001425.

      ].
      Despite being the most frequent imaging modality, radiography involves a relatively small radiation dose per exam, typically ranging from a fraction of a mSv of effective dose (E) to 3 mSv. Furthermore, the dose in radiographic examination has decreased by nearly an order of magnitude in the last half a century, as shown in Table 1 which was taken from an earlier paper [
      • Rehani M.M.
      Challenges in radiation protection of patients for the 21st century.
      ]. However, some computed tomography (CT) and interventional procedures using fluoroscopy are associated with a relatively higher E (a few tens of mSv). This and increasing patient radiation doses are primarily due to many fold increases in diagnostic information [
      • Rehani M.M.
      • Szczykutowicz T.P.
      • Zaidi H.
      CT is still not a low-dose imaging modality.
      ]. Previously, in 1970′s, the CT scan used to be 10 mm slices scan with about 10 mm inter-slice gap. Now there are increasingly thinner and thinner slices and volume scanning with no gap thus giving images that have much more information so as not to miss a lesion or abnormality in the body [

      Tsapaki V, Rehani M, Saini S. Radiation Safety in Abdominal Computed Tomography. Semin Ultrasound, CT MRI 2010;31. https://doi.org/10.1053/j.sult.2009.09.004.

      ]. The cost of this increased information is increased radiation dose. Per exam, dose in CT has varied from about a mSv to about 15 mSv. Recent studies have shown that with the use of multiphase CT imaging and recurrent imaging, much higher doses are being received by some patients [

      S. Rastogi R. Singh R. Borse P.V. Zujic D. Segota A. Diklic et al. Use of Multiphase CT Protocols in 18 Countries: Appropriateness and Radiation Doses Can Assoc Radiol J = J l’Association Can Des Radiol 2020:846537119888390. 10.1177/0846537119888390.

      ,
      • Rehani M.M.
      • Yang K.
      • Melick E.R.
      • Heil J.
      • Šalát D.
      • Sensakovic W.F.
      • et al.
      Patients undergoing recurrent CT scans: assessing the magnitude.
      ], as discussed later. Also, the use of CT for performing interventions has led to as much as 100 mSv in a single procedure [
      • Arellano R.
      • Yang K.
      • Rehani M.M.
      Analysis of patients receiving ≥100 mSv during a computed tomography intervention.
      ]. Relatively high doses both in CT and interventional procedures are becoming a focus of recent attention.
      Table 1Trends in average effective doses resulting from selected diagnostic medical examinations in countries in Health Care Level 1, as per UNSCEAR data

      United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). 2008 Report to the General Assembly: Annex B Exposures of the Public and Workers from Various Sources of Radiation. vol. I. 2010.

      ,
      • Rehani M.M.
      Challenges in radiation protection of patients for the 21st century.
      .
      ExaminationAverage effective dose per examination in millisieverts in years
      1970–19791980–19901991–19961997–2007
      Chest radiography0.250.140.140.07
      Abdominal X-ray1.91.10.530.82
      Mammography1.810.510.26
      CT scan1.34.48.87.4
      Angiography9.26.8129.3
      This paper being part of the 125th year celebration of discovery of X-rays by Roentgen, the paper deals only with doses from X-ray procedures and thus excludes nuclear medicine studies.

      2. Dosimetric quantities

      For stochastic risks, E is the most appropriate quantity to date [
      • Martin C.J.
      • Harrison J.D.
      • Rehani M.M.
      Effective dose from radiation exposure in medicine: past, present, and future.
      ]. One must distinguish between dose per exam, collective dose, and cumulative dose as otherwise it leads to confusion. Dose per exam is rather easy to understand if one confines oneself to a single dose quantity. Medical physicists can use dozens of metrics to infer dose, starting from machine related operating parameters like, mAs and indirectly kVp as the minimum, then going to CTDIvol, dose length product (DLP), size specific dose estimates (SSDE) and finally effective dose (E). There are several dose quantities for different imaging modalities that have been agreed upon by ICRU and IAEA [

      IAEA. IAEA TRS 457_Dosimetry in dignostic radiology: Code of Practice. 2007.

      ,
      • Zoetelief J.
      • Dance D.R.
      • Drexler G.
      • Järvinen H.
      • Rosenstein M.
      • Allisy-Roberts P.
      • et al.
      ICRU 74_Patient dosimetry for X rays used in medical imaging.
      ]. They range from description of machine output to dose at the entrance of the patient, to organ doses and to finally the effective dose (E). None of these quantities are perfect as they each pertain to a small piece of what we need for holistic dose information. Physicians obviously get confused if presented with such a number of different dose metrices. Thus, despite the limitations of E, it remains the best single descriptor and has been used the most despite being the most argued quantity [
      • Martin C.J.
      • Harrison J.D.
      • Rehani M.M.
      Effective dose from radiation exposure in medicine: past, present, and future.
      ]. E was initially derived for a standard/ reference sized person, and newer developments are suggesting patient-specific E [
      • Martin C.J.
      • Harrison J.D.
      • Rehani M.M.
      Effective dose from radiation exposure in medicine: past, present, and future.
      ]. In future, if a better alternative becomes available, things may be different.
      The average dose per exam (commonly expressed in E) when multiplied by population provides collective dose to the population (as person-sievert) and has been used extensively by organizations dealing with population dose such as UNSCEAR, European Commission, and many national organizations. In this review paper, we will focus on protection of the individual rather than the population and thus will not deliberate further on collective doses. For the individual patient, the cumulative dose, which is the sum of doses from different exams, is used. Once again, this becomes feasible mainly with E. When the sum of effective doses from CT exams for example, is done, then it becomes the cumulative effective dose (CED) [
      • Rehani M.M.
      • Yang K.
      • Melick E.R.
      • Heil J.
      • Šalát D.
      • Sensakovic W.F.
      • et al.
      Patients undergoing recurrent CT scans: assessing the magnitude.
      ,
      • Rehani M.M.
      • Hauptmann M.
      Estimates of the number of patients with high cumulative doses through recurrent CT exams in 35 OECD countries.
      ]. For interventional procedures, kerma-area-product (KAP) and estimation of E using appropriate coefficients is practiced to indicate stochastic risk. Peak skin dose is the most appropriate dose quantity for tissue reactions, but an inability to have electronic peak skin dose estimate available in most fluoroscopy machines precludes the use of this quantity. Kerma at the interventional reference point (Ka,r) is thus far the most easily available dose metric in angiography machines and most recommendations for tissue reactions are based on Ka,r.

      3. High doses in CT

      The development and implementation of multidetector-row computed tomography (MDCT) in the 1990′s represented a significant evolution in CT [
      • Kalender W.A.
      • Seissler W.
      • Klotz E.
      • Vock P.
      Spiral volumetric CT with single-breath-hold technique, continuous transport, and continuous scanner rotation.
      ,
      • Rehani M.M.
      • Kalra M.K.
      • McCollough C.H.
      • Nagel H.D.
      • Collins L.
      • Kalender W.
      Managing patient dose in multi-detector computed tomography(MDCT). ICRP Publication 102.
      ]. As opposed to the previous generation of CT’s with a single-detector-row (SDCT), the MDCT’s rotate-rotate approach with expanded detector arrays allowed for volumetric acquisition of entire organs. These could be performed with high spatial resolution and within the time of a single breath hold, at least for chest CT. This provided many benefits, including reduced motion-based artifacts (common in children, trauma patients, or cardiac imaging), decreased quantity of required contrast medium (thus reducing potential kidney damage), and thinner slice acquisition. MDCT however represented a trade-off between enhanced diagnostic capability and increased radiation exposure for increased information. This compromise can be seen in the comparison of SDCT and MDCT doses in Table 2.
      Table 2Effective doses for various CT examination using single detector CT (SDCT) and multi-detector (MDCT) systems, taken from ICRP P102
      • Rehani M.M.
      • Kalra M.K.
      • McCollough C.H.
      • Nagel H.D.
      • Collins L.
      • Kalender W.
      Managing patient dose in multi-detector computed tomography(MDCT). ICRP Publication 102.
      .
      ExaminationsEffective dose (mSv) SDCTEffective dose (mSv) MDCT
      Abdomen and pelvis17.214.4
      Liver/kidney8.711.5
      Aorta, abdominal7.610.3
      Coronary CTA10.5
      Brain2.82.8
      Face and sinuses1.10.8
      Face and neck2.02.0
      Chest6.25.7
      Pelvis8.87.2
      Aorta, thoracic5.86.7
      Pulmonary vessels3.65.4
      Cervical spine2.12.9
      Lumbar spine2.78.1
      A number of contributing factors have identified why MDCT scanners are prone to delivering higher radiation doses to patients. These include the existence of dose inefficiencies in early 4-MDCT systems, actions that lead to higher doses to address image noise in thinner slices during 3D imaging of thinner slices, and a newfound ease in acquiring greater scan volumes and multiple contrast phases. On the technical side, unnecessarily high patient dose occurred in part due to overbeaming (beam geometries larger than the detector width), comparably shorter X-ray source-to-patient distance, and overlapping beams. In addition, the MDCT’s use of narrow collimation caused a decrease in geometric efficiency and thus an increase in image noise and was countered through the use of increased dose [
      • Rehani M.M.
      • Kalra M.K.
      • McCollough C.H.
      • Nagel H.D.
      • Collins L.
      • Kalender W.
      Managing patient dose in multi-detector computed tomography(MDCT). ICRP Publication 102.
      ]. Use of higher than needed image quality, with a preference for crisp images rather than those with some noise present, has also contributed to the higher CT doses [
      • Rehani M.M.
      • Szczykutowicz T.P.
      • Zaidi H.
      CT is still not a low-dose imaging modality.
      ,
      • Padole A.M.
      • Sagar P.
      • Westra S.J.
      • Lim R.
      • Nimkin K.
      • Kalra M.K.
      • et al.
      Development and validation of image quality scoring criteria (IQSC) for pediatric CT: a preliminary study.
      ]. As such, radiologists must be willing to use images with some noise (salt and pepper appearance) [
      • Padole A.M.
      • Sagar P.
      • Westra S.J.
      • Lim R.
      • Nimkin K.
      • Kalra M.K.
      • et al.
      Development and validation of image quality scoring criteria (IQSC) for pediatric CT: a preliminary study.
      ].
      There are limited clinical studies demonstrating change in patient dose for a defined exam. A longitudinal analyses of radiation dose data was undertaken on adult patients undergoing repeat identical and clinically indicated thoracoabdominal CT examinations [
      • Mileto A.
      • Nelson R.C.
      • Larson D.G.
      • Samei E.
      • Wilson J.M.
      • Christianson O.
      • et al.
      Variability in radiation dose from repeat identical CT examinations: longitudinal analysis of 2851 patients undergoing 12,635 thoracoabdominal CT scans in an academic health system.
      ]. The investigators noted trend toward global reduction in size specific dose estimates (SSDE) values, despite widespread variations in the radiation dose absorbed by each patient undergoing identical repeat thoracoabdominal CT protocols.
      In another study, 1695 paediatric chest CT examinations conducted over 7 years were analyzed [
      • Esser M.
      • Hess S.
      • Teufel M.
      • Kraus M.S.
      • Schneeweiß S.
      • Gatidis S.
      • et al.
      Radiation dose optimization in pediatric chest CT: major indicators of dose exposure in 1695 CT scans over seven years.
      ]. The median volume CT dose index (CTDI; mGy), effective dose (E; mSv) and size-specific dose estimate (SSDE; mGy) were investigated in the different years of the observation time and decrease was demonstrated through regression curves. Although it is difficult to state how much percent change in radiation dose has actually occurred, scattered reports indicate changes in clinical settings largely under controlled observations during the past two decades. The observations are also available from ACR Dose Index Registry (ACR-DIR) but there is lack of a cohesive reporting to demonstrate quantitatively the magnitude of change.
      For many years, the focus in radiation doses from CT exams has been placed on individual exam dose, which has been decreasing substantially over the years [
      • Rehani M.M.
      • Szczykutowicz T.P.
      • Zaidi H.
      CT is still not a low-dose imaging modality.
      ]. For example, the drastic increase in computational power since the 1970′s has allowed a switch from filtered back projection to iterative reconstruction of CT images in CT systems worldwide. In these systems, the noise reduction facilitated by iterative reconstruction has allowed patient dose reductions of 26–50% per exam compared to traditional filtered back projection systems [
      • Klink T.
      • Obmann V.
      • Heverhagen J.
      • Stork A.
      • Adam G.
      • Begemann P.
      Reducing CT radiation dose with iterative reconstruction algorithms: the influence of scan and reconstruction parameters on image quality and CTDIvol.
      ]. Meanwhile, dual-energy CT has allowed improved image quality per dose over traditional systems by utilizing two different tube potentials to provide increased CNR with comparable dose [
      • Yu L.
      • Primak A.N.
      • Liu X.
      • McCollough C.H.
      Image quality optimization and evaluation of linearly mixed images in dual-source, dual-energy CT.
      ]. Not only have these technologies allowed for reduced dose per exam when used alone, they have also facilitated an improved diagnostic ability when performing dedicated low-dose CT exams via modulation of tube current, potential, or pitch [
      • Padole A.
      • Ali Khawaja R.D.
      • Kalra M.K.
      • Singh S.
      CT radiation dose and iterative reconstruction techniques.
      ].
      Despite these advances in per-exam dose, cumulative doses to individual patients have reached such a high level that radiation risks can no longer be ignored [
      • Rehani M.M.
      • Yang K.
      • Melick E.R.
      • Heil J.
      • Šalát D.
      • Sensakovic W.F.
      • et al.
      Patients undergoing recurrent CT scans: assessing the magnitude.
      ,
      • Rehani M.M.
      • Hauptmann M.
      Estimates of the number of patients with high cumulative doses through recurrent CT exams in 35 OECD countries.
      ,
      • Rehani M.M.
      • Melick E.R.
      • Alvi R.M.
      • Doda Khera R.
      • Batool-Anwar S.
      • Neilan T.G.
      • et al.
      Patients undergoing recurrent CT exams: assessment of patients with non-malignant diseases, reasons for imaging and imaging appropriateness.
      ,
      • Brambilla M.
      • Vassileva J.
      • Kuchcinska A.
      • Rehani M.M.
      Multinational data on cumulative radiation exposure of patients from recurrent radiological procedures: call for action.
      ]. A large study on 2.5 million patients who underwent 4.8 million CT exams found that 1.33% of patients received CEDs ≥ 100 mSv with an overall median CED of 130.3 mSv, and a maximum of 1185 mSv during a period between 1 and 5 years [
      • Rehani M.M.
      • Yang K.
      • Melick E.R.
      • Heil J.
      • Šalát D.
      • Sensakovic W.F.
      • et al.
      Patients undergoing recurrent CT scans: assessing the magnitude.
      ]. Although the vast majority (72–86%) of patients were > 50 years of age, nearly 20% (13.4 to 28%) were ≤ 50 years. The paper concluded that we are in an unprecedented era where patients undergoing multiple CT exams during a short span of 1 to 5 years are not uncommon and a sizable fraction among them are below 50 years of age. The investigators further reported their results from a single institution and found that 9.6% of patients exhibited non-malignant conditions, with 1.4% of the patients ≤ 40 years old [
      • Rehani M.M.
      • Melick E.R.
      • Alvi R.M.
      • Doda Khera R.
      • Batool-Anwar S.
      • Neilan T.G.
      • et al.
      Patients undergoing recurrent CT exams: assessment of patients with non-malignant diseases, reasons for imaging and imaging appropriateness.
      ]. More than half of the CT exams were unrelated to follow-up of a primary chronic disease. Imaging guidelines and appropriateness use criteria are not available for many conditions, however, this study identified many of them. Wherever guidelines are available, they tend to be for initial work-up and diagnosis. As such, there is a lack of guidance on serial CT imaging. These studies thus provide characteristics of the population of patients with CED ≥ 100 mSv.
      Further, the minimum time to accrue 100 mSv was a single day at all four institutions included in the study. This had been previously unreported prior to this author’s finding in 2019 [
      • Rehani M.M.
      • Yang K.
      • Melick E.R.
      • Heil J.
      • Šalát D.
      • Sensakovic W.F.
      • et al.
      Patients undergoing recurrent CT scans: assessing the magnitude.
      ].
      The most important message of these papers was that there is an urgent need for the industry to develop CT scanners with sub-mSv radiation dose, a goal that has been lingering [
      • Kachelrieß M.
      • Rehani M.M.
      Is it possible to kill the radiation risk issue in computed tomography?.
      ,
      • Rehani M.M.
      • Yang K.
      • Melick E.R.
      • Heil J.
      • Šalát D.
      • Sensakovic W.F.
      • et al.
      Patients undergoing recurrent CT scans: assessing the magnitude.
      ,
      • Rehani M.M.
      • Melick E.R.
      • Alvi R.M.
      • Doda Khera R.
      • Batool-Anwar S.
      • Neilan T.G.
      • et al.
      Patients undergoing recurrent CT exams: assessment of patients with non-malignant diseases, reasons for imaging and imaging appropriateness.
      ].
      In another study, the authors estimated the number of patients receiving high doses in 35 OECD (Organization for Economic Co-operation and Development) countries [
      • Rehani M.M.
      • Hauptmann M.
      Estimates of the number of patients with high cumulative doses through recurrent CT exams in 35 OECD countries.
      ]. They found patients receiving CED ≥ 100 mSv amounted to 0.21% of the population. Expressed as per 1000 population, the values ranged from 0.51 for Finland to 2.94 for the US, a nearly six-fold difference. Countries with >2 patients with CED ≥ 100 mSv in a 5-yr period per 1000 population were: Belgium, France, Iceland, Japan, Korea, Luxembourg, Portugal, Turkey, and US.

      4. Tracking and assessment of high doses in different disease conditions

      The review of the various aspects involved in tracking a patient’s radiation exposure to obtain a lifelong record of radiation dose of individual patient is available [
      • Rehani M.M.
      Patient radiation exposure and dose tracking: a perspective.
      ]. Description of how tracking has helped the process of justification and optimization was done by taking the case reports in the day-to-day setting of a paeditric hospital [
      • Seuri R.
      • Rehani M.M.
      • Kortesniemi M.
      How tracking radiologic procedures and dose helps: experience from Finland.
      ]. For a detailed view of various aspects of tracking, readers are referred to other publications, as those are outside the scope of the current paper [

      M.M. Rehani T. Berris International Atomic Energy Agency study with referring physicians on patient radiation exposure and its tracking: a prospective survey using a web-based questionnaire BMJ Open 2012;2. 10.1136/bmjopen-2012-001425.

      ,

      Rehani MM. Tracking of examination and dose: Overview. Radiat Prot Dosimetry 2015;165. https://doi.org/10.1093/rpd/ncv026.

      ,
      • Rehani M.M.
      • Berris T.
      Templates and existing elements and models for implementation of patient exposure tracking.
      ,
      • Rehani M.
      • Frush D.
      Tracking radiation exposure of patients.
      ,
      • Rehani M.M.
      • Frush D.
      • Berris T.
      • Einstein A.J.
      Patient radiation exposure tracking : Worldwide programs and needs – Results from the first IAEA survey.
      ,
      • Mercuri M.
      • Rehani M.M.
      • Einstein A.J.
      Tracking patient radiation exposure: challenges to integrating nuclear medicine with other modalities.
      ,
      • Rehani M.M.
      • Berris T.
      Radiation exposure tracking: survey of unique patient identification number in 40 countries.
      ].
      In the previous years, many studies have reported high cumulative doses to patients not only from CT but other exams as well, and they are reviewed in a recent paper [
      • Brambilla M.
      • Vassileva J.
      • Kuchcinska A.
      • Rehani M.M.
      Multinational data on cumulative radiation exposure of patients from recurrent radiological procedures: call for action.
      ]. The results of those papers are summarized here in Table 3, taken from [
      • Brambilla M.
      • Vassileva J.
      • Kuchcinska A.
      • Rehani M.M.
      Multinational data on cumulative radiation exposure of patients from recurrent radiological procedures: call for action.
      ]. These high cumulative doses have been discussed in detail across several different categories e.g. cardiac disease, end stage kidney disease, Crohn’s disease, Endovascular aortic repair (EVAR) as reviewed in paper [
      • Brambilla M.
      • Vassileva J.
      • Kuchcinska A.
      • Rehani M.M.
      Multinational data on cumulative radiation exposure of patients from recurrent radiological procedures: call for action.
      ]. Although publications reviewed in this paper showed that some patients undergoing recurrent radiological procedures can receive CED between 50- over 1000 mSv or in some cases more, it is unknown whether this was restricted only to these disease categories or widespread among patients overall. To assess the population health aspect of high doses the studies mentioned above [
      • Rehani M.M.
      • Yang K.
      • Melick E.R.
      • Heil J.
      • Šalát D.
      • Sensakovic W.F.
      • et al.
      Patients undergoing recurrent CT scans: assessing the magnitude.
      ,
      • Rehani M.M.
      • Melick E.R.
      • Alvi R.M.
      • Doda Khera R.
      • Batool-Anwar S.
      • Neilan T.G.
      • et al.
      Patients undergoing recurrent CT exams: assessment of patients with non-malignant diseases, reasons for imaging and imaging appropriateness.
      ,
      • Brambilla M.
      • Vassileva J.
      • Kuchcinska A.
      • Rehani M.M.
      Multinational data on cumulative radiation exposure of patients from recurrent radiological procedures: call for action.
      ] evaluated patients undergoing CT exams at multiple hospitals across several countries.
      Table 3Cumulative radiation exposure and patients with CED > 100 mSv
      • Brambilla M.
      • Vassileva J.
      • Kuchcinska A.
      • Rehani M.M.
      Multinational data on cumulative radiation exposure of patients from recurrent radiological procedures: call for action.
      .
      AuthorConditionN. PtsX-ray proceduresAge (years) Mean or Median §Patients with CED > 50 mSvPatients with CED > 100 mSvFollow-up (years)
      Chen 2010
      • Chen J.
      • Einstein A.J.
      • Fazel R.
      • Krumholz H.M.
      • Wang Y.
      • Ross J.S.
      • et al.
      Cumulative exposure to ionizing radiation from diagnostic and therapeutic cardiac imaging procedures: A population-based analysis.
      Pts with Cardiac Imaging90,121Only Cardiac Procedures51.13173 (3.5%)#75 (0.08%)^3
      Einstein 2010
      • Einstein A.J.
      • Weiner S.D.
      • Bernheim A.
      • Kulon M.
      • Bokhari S.
      • Johnson L.L.
      • et al.
      Multiple testing, cumulative radiation dose, and clinical indications in patients undergoing myocardial perfusion imaging.
      Pts with myocardial perfusion scan1097All medical imaging procedures62.2344 (31.4%)20
      Stein 2010
      • Stein E.G.
      • Haramati L.B.
      • Bellin E.
      • Ashton L.
      • Mitsopoulos G.
      • Schoenfeld A.
      • et al.
      Radiation exposure from medical imaging in patients with chronic and recurrent conditions.
      Cardiac disease8656All medical imaging procedures65.9533 (6.2%)3
      Kaul 2010
      • Kaul P.
      • Medvedev S.
      • Hohmann S.F.
      • Douglas P.S.
      • Peterson E.D.
      • Patel M.R.
      Ionizing radiation exposure to patients admitted with acute myocardial infarction in the United States.
      Acute myocardial infarction64,071All medical imaging procedures64.9§1060 (1.7%)°---
      Eisenberg 2011
      • Eisenberg M.J.
      • Afilalo J.
      • Lawler P.R.
      • Abrahamowicz M.
      • Richard H.
      • Pilote L.
      Cancer risk related to low-dose ionizing radiation from cardiac imaging in patients after acute myocardial infarction.
      Acute myocardial infarction82,861Only Cardiac Procedures63.2§15,090 (18%)*1
      Lawler 2011
      • Lawler P.R.
      • Afilalo J.
      • Eisenberg M.J.
      • Pilote L.
      Exposure to low-dose ionizing radiation from cardiac imaging among patients with myocardial infarction.
      Acute myocardial infarction11,427Only Cardiac Procedures68.0§825 (7.2%)*°1
      Kinsella 2010
      • Kinsella S.M.
      • Coyle J.P.
      • Long E.B.
      • McWilliams S.R.
      • Maher M.M.
      • Clarkson M.R.
      • et al.
      Maintenance hemodialysis patients have high cumulative radiation exposure.
      Hemodialysis100All medical imaging procedures58.926 (26%)13 (13%)*3.4 median
      De Mauri 2011
      • De Mauri A.
      • Brambilla M.
      • Chiarinotti D.
      • Matheoud R.
      • Carriero A.
      • De Leo M.
      Estimated radiation exposure from medical imaging in hemodialysis patients.
      Hemodialysis106All medical imaging procedures65.317 (16%)3.0 median
      Coyle 2011
      • Coyle J.
      • Kinsella S.
      • McCarthy S.
      • MacWilliams S.
      • McLaughlin P.
      • Eustace J.
      • et al.
      Cumulative ionizing radiation exposure in patients with end stage kidney disease: A 6-year retrospective analysis.
      Hemodialysis244All medical imaging procedures52.756 (23%)4.0 median
      Kidney Transplant150All medical imaging procedures45.712 (8%)
      De Mauri 2012
      • De Mauri A.
      • Brambilla M.
      • Izzo C.
      • Matheoud R.
      • Chiarinotti D.
      • Carriero A.
      • et al.
      Cumulative radiation dose from medical imaging in kidney transplant patients.
      Kidney Transplant92All medical imaging procedures52.426 (28%)11 (12%)4.1 median
      Desmond 2012
      • Desmond A.N.
      • McWilliams S.
      • Maher M.M.
      • Shanahan F.
      • Quigley E.M.
      Radiation exposure from diagnostic imaging among patients with gastrointestinal disorders.
      Crohn’s354All medical imaging procedures3255 (16%)*15
      Levi 2009
      • Levi Z.
      • Fraser A.
      • Krongrad R.
      • Hazazi R.
      • Benjaminov O.
      • Meyerovitch J.
      • et al.
      Factors associated with radiation exposure in patients with inflammatory bowel disease.
      Crohn’s

      Ulcerative Colitis
      199

      125
      All medical imaging procedures (no Interventional)3923 (7%)5.5

      5.0
      Kroeker 2011
      • Kroeker K.I.
      • Lam S.
      • Birchall I.
      • Fedorak R.N.
      Patients with IBD are exposed to high levels of ionizing radiation through CT scan diagnostic imaging: a five-year study.
      Crohn’s371All medical imaging procedures4027 (7%)12(3%)*5
      Butcher 2012
      • Butcher R.O.
      • Nixon E.
      • Sapundzieski M.
      • Filobbos R.
      • Limdi J.K.
      Radiation exposure in patients with inflammatory bowel diseaseprimum non nocere?.
      Crohn’s127All medical imaging procedures (458 (6%)11.2
      Estay 2015
      • Estay C.
      • Simian D.
      • Lubascher J.
      • Figueroa C.
      • O’Brien A.
      • Quera R.
      Ionizing radiation exposure in patients with inflammatory bowel disease: are we overexposing our patients?.
      Crohn’s82All medical imaging procedures3616 (20%)9.6
      Chatu 2013
      • Chatu S.
      • Poullis A.
      • Holmes R.
      • Greenhalgh R.
      • Pollok R.C.G.
      Temporal trends in imaging and associated radiation exposure in inflammatory bowel disease.
      Crohn’s217All medical imaging procedures3129 (13%)8.3
      Jung 2013
      • Jung Y.S.
      • Il Park D
      • Kim E.R.
      • Kim Y.H.
      • Lee C.K.
      • Lee S.H.
      • et al.
      Quantifying exposure to diagnostic radiation and factors associated with exposure to high levels of radiation in korean patients with inflammatory bowel disease.
      Crohn’s777All medical imaging procedures29249 (35%)15
      Fuchs 2011
      • Fuchs Y.
      • Markowitz J.
      • Weinstein T.
      • Kohn N.
      • Choi-Rosen J.
      • Levine J.
      Pediatric inflammatory bowel disease and imaging-related radiation: are we increasing the likelihood of malignancy?.
      Crohn’s171All medical imaging procedures11 (pediatric)14 (8%)5.3
      Sauer 2011
      • Sauer C.G.
      • Kugathasan S.
      • Martin D.R.
      • Applegate K.E.
      Medical radiation exposure in children with inflammatory bowel disease estimates high cumulative doses.
      Crohn’s86All medical imaging procedures12 (pediatric)6 (7%)3.5
      Huang 2011
      • Huang J.S.
      • Tobin A.
      • Harvey L.
      • Nelson T.R.
      Diagnostic medical radiation in pediatric patients with inflammatory bowel disease.
      Crohn’s

      Ulcerative Colitis

      Indeterminate colitis
      61

      32

      12
      All medical imaging procedures11§ (pediatric)6 (6%)5
      Brambilla 2015
      • Brambilla M.
      • Cerini P.
      • Lizio D.
      • Vigna L.
      • Carriero A.
      • Fossaceca R.
      Cumulative radiation dose and radiation risk from medical imaging in patients subjected to endovascular aortic aneurysm repair.
      EVAR71All medical imaging procedures7471 (100%)66 (93%)1.8
      *CED > 30 mSv; # CED > 60 mSv; *CED > 75; ^CED > 150 mSv; ° per admission after acute myocardial infarction; § Median.

      5. High doses in interventional procedures

      Interventional procedures attempt to minimize the invasiveness of various medical procedures through application of an assortment of medical imaging guidance. Interventional procedures avoid open surgical procedures by using live imaging modalities, such as fluoroscopy, to guide fine instruments to the target site [
      • Murphy T.P.
      • Soares G.M.
      The evolution of interventional radiology.
      ]. While its inception began in the cardiac field, the applicability of interventional procedures now spans the whole of medicine. Given its noninvasive focus and reduced rate of post-operative complications, the use of interventional procedures continues to grow among both patients and providers. Despite a host of modalities available for guidance, the predominant imaging method is fluoroscopy [
      • Jones A.K.
      • Dixon R.G.
      • Collins J.D.
      • Walser E.M.
      • Nikolic B.
      Best practice guidelines for CT-guided interventional procedures.
      ].
      The US Food and Drug Administration (FDA) stipulates that fluoroscopy equipment provided with automatic exposure rate control (AERC), shall not be operable at any combination of tube potential and current that will result in an air kerma rate exceeding 88 mGy per minute at the measurement point specified in standard []. If provided, when a high level mode of operation is activated, the limit is doubled to 176 mGy/min [].
      Typical dose rates reported for fluoroscopic imaging range from around 17 mGy/min for thin tissues or small patients, to 44 mGy/min for more standard tissues and patient sizes [
      • Bushberg J.
      The essential physics of medical Imaging.
      ].
      As per National Council of Radiation Protection and Measurements (NCRP) Report 168, a FGI procedure should be classified as a potentially-high radiation dose procedure if >5% of cases result in Ka,r exceeding 3 Gy or PKA exceeding 300 Gy cm2 [

      NCRP. NCRP Report No. 168, Radiation Dose Management for Fluoroscopically-Guided Interventional Medical Procedures. n.d.

      ]. Although those patients in the median and lower percentiles undergoing PCI were not imaged with an air kerma quite near the 3 Gy threshold, they most certainly underwent a variety of pre-procedural diagnostic imaging given their condition.
      High doses in interventional procedures are common but the focus has been on tissue reactions and injuries, as injuries have continued to be reported ever since the early 1990′s [
      • Rehani M.M.
      • Srimahachota S.
      Skin injuries in interventional procedures.
      ,
      • Srimahachota S.
      • Udayachalerm W.
      • Kupharang T.
      • Sukwijit K.
      • Krisanachinda A.
      • Rehani M.
      Radiation skin injury caused by percutaneous coronary intervention, report of 3 cases.
      ,
      • Tsapaki V.
      • Rehani M.M.
      I perform more than 100 interventional procedures every year but have never seen radiation-induced skin injury: am I missing something?.
      ,
      • Tsapaki V.
      • Balter S.
      • Cousins C.
      • Holmberg O.
      • Miller D.L.
      • Miranda P.
      • et al.
      The international atomic energy agency action plan on radiation protection of patients and staff in interventional procedures: achieving change in practice.
      ,
      • Kostova-Lefterova D.
      • Vassileva J.
      • Rehani M.M.
      Lessons from two cases of radiation induced skin injuries in fluoroscopic procedures in Bulgaria.
      ]. There are well established guidelines by various organizations to avoid injuries [

      NCRP. NCRP Report No. 168, Radiation Dose Management for Fluoroscopically-Guided Interventional Medical Procedures. n.d.

      ,

      NCRP. Statement No. 11 – Outline Of Administrative Policies For Quality Assurance And Peer Review Of Tissue Reactions Associated With Fluoroscopically-Guided Interventions. 2014.

      ,
      • Cousins C.
      • Miller D.L.
      • Bernardi G.
      • Rehani M.M.
      • Schofield P.
      • Vañó E.
      • et al.
      International Commission on Radiological Protection. ICRP PUBLICATION 120: Radiological protection in cardiology.
      ,
      • ICRP
      Avoidance of Radiation Injuries from Medical Interventional Procedures. ICRP Publication 85.
      ,
      • Rehani M.M.
      • Miller D.L.
      • Baliyan V.
      High dose fluoroscopically guided procedures in patients: radiation management recommendations for interventionalists.
      ] including action before, during and after the procedure. Monitoring of kerma at the reference point (Ka,r) is the crucial indicator for possible tissue injury. Most literature on radiation induced skin injury comes from experience with injuries in radiotherapy (high energy X-rays or gamma rays). Thus the precise dose–effect correlation with fluoroscopic X-rays is not established [
      • Tsapaki V.
      • Balter S.
      • Cousins C.
      • Holmberg O.
      • Miller D.L.
      • Miranda P.
      • et al.
      The international atomic energy agency action plan on radiation protection of patients and staff in interventional procedures: achieving change in practice.
      ,
      • Balter S.
      • Miller D.L.
      Patient skin reactions from interventional fluoroscopy procedures.
      ,
      • Rehani M.M.
      What makes and keeps radiation risks associated with CT a hot topic?.
      ]. Values between 3 and 5 Gy of Ka,r have been used by most organizations and institutions for following up patients, but injuries are rarely observed below 9 Gy of Ka,r or in some cases even higher. This is so as Ka,r is not skin dose but is cumulative air kerma when the tube may be rotating and operating in different views. The skin dose will vary with position of the tube as dose gets distributed over different parts of the body as the view changes. On the other hand, Ka,r is at the fixed reference point. Depending upon thickness of the patient, Ka,r may lie on patient skin, below the skin of a few cm away from the skin in air towards the X-ray tube. Multiple procedures on the same patient may require higher dose if the gap between procedures is of several weeks. These aspects are discussed at length in other publications and readers are referred to those [
      • Balter S.
      • Miller D.L.
      Patient skin reactions from interventional fluoroscopy procedures.
      ,
      • Balter S.
      • Hopewell J.W.
      • Miller D.L.
      • Wagner L.K.
      • Zelefsky M.J.
      Fluoroscopically guided interventional procedures: a review of radiation effects on patients’ skin and hair.
      ,
      • Jaschke W.
      • Bartal G.
      • Martin C.J.
      • Vano E.
      Unintended and accidental exposures, significant dose events and trigger levels in interventional radiology.
      ,
      • Tsapaki V.
      • Faruque G.M.
      • Lim S.T.
      • Ngo Minh H.
      • Nwe N.
      • Sharma A.
      • et al.
      Status of radiation protection in various interventional cardiology procedures in the Asia Pacific region.
      ].
      Somehow the emphasis on stochastic risk in interventional procedures has not received adequate attention in the past. It is true that tissue injuries have been observed, they are serious in some patients, and need definite preventive actions as treatment options are either not available or are not easy, but keeping stochastic risks out of considerations is not appropriate. Stochastic risks in interventional procedures have mainly been emphasized in children, in light of their longer life expectancy.
      One reason why stochastic risk has not received comparable attention in previous years is that effective dose in interventional procedure has been considered relatively low, around 9–17 mSv for some of the common interventional procedures [
      • Pantos I.
      • Patatoukas G.
      • Katritsis D.G.
      • Efstathopoulos E.
      Patient radiation doses in interventional cardiology procedures.
      ]. Thus, not even in the most extreme cases was patient dose expected to be near 100 mSv. However, a recent paper reviewing all the interventional procedures at a major hospital for the past 9 years [
      • Li X.
      • Hirsch J.A.
      • Rehani M.M.
      • Ganguli S.
      • Yang K.
      • Liu B.
      Radiation effective dose above 100 mSv from fluoroscopically guided intervention: frequency and patient medical condition.
      ] found that among 46,491 procedures across 25,253 patients, 1011 patients (4%) had CEDs of >100 mSv. Thus, the percent of patients exceeding 100 mSv is not small. The median value of the CED in this cohort was 177 mSv.
      Another common understanding was that these procedures are involving older patients and if the procedures are repeated, they are spaced apart by more than a year. It was pointed out by [
      • Li X.
      • Hirsch J.A.
      • Rehani M.M.
      • Ganguli S.
      • Yang K.
      • Liu B.
      Radiation effective dose above 100 mSv from fluoroscopically guided intervention: frequency and patient medical condition.
      ] that the majority (about 90%) of patients had their procedures within 12 months, and 10.7% were under 40 years of age. For patients whose age at first procedure was 40 years or younger, the dominant medical disorder was chronic disease of the torso (54.6%) and the percentage of cancer was low (11.1%). Thus, it will be wrong to assume that one is dealing primarily with patients of advanced ages and that doses in the range of 100 mSv are only accumulated over a long period. This is despite the fact that overall, for the entire patient cohort receiving >100 mSv (not only those age 40 years or less), medical disorders included cancer (36.7%), chronic disease of the torso (30.0%), internal bleeding (24.8%), trauma (4.6%), organ transplant (3.2%) and cerebrovascular disease (0.7%). Thus, trauma rather than cancer was the dominant cause for interventional procedure in younger aged patients.
      The above paper rightly highlights that although the benefits of successful diagnosis and therapeutic treatment largely outweigh the aforementioned risks in the palliative care of patients under serious trauma or illness, all risks, including the radiation risk associated with fluoroscopic guided interventional procedures, warrant continued attention.

      6. CT guided interventional procedures

      While many interventional procedures can be performed under fluoroscopic guidance, ultrasound (US) or magnetic resonance imaging (MRI) guidance, many require CT guidance especially for interventions that require access to anatomically challenging locations and those requiring better image quality. Typical examples include: biopsy, drainage, myelography, and ablation [
      • Arellano R.
      • Yang K.
      • Rehani M.M.
      Analysis of patients receiving ≥100 mSv during a computed tomography intervention.
      ,
      • Sarti M.
      • Brehmer W.P.
      • Gay S.B.
      Low-dose techniques in CT-guided Interventions.
      ].
      Unlike CT fluoroscopy that involves somewhat lower doses, CT guided interventions require much higher doses, sometime delivering as much as 100 mSv or more in a single procedure [
      • Arellano R.
      • Yang K.
      • Rehani M.M.
      Analysis of patients receiving ≥100 mSv during a computed tomography intervention.
      ]. In their study, the authors found 33 patients who underwent 37 CT-guided interventions, each resulting in ≥ 100 mSv. Procedures included ablations (15), myelograms (8), drainages (7), biopsies (6) and other (1). The dose for individual procedures ranged from 100.2 to 235.5 mSv with mean and median doses of 125.7 mSv and 111.8 mSv, respectively. Six patients (18%) were less than 50 years of age. There are situations when an individual patient may require multiple interventions, each involving over 100 mSv during the period of a few weeks or months.

      7. Newer technology and impact of technology on radiation doses in interventional procedures

      A number of advancements in fluoroscopy systems have and will allow patient exposures to decrease while maintaining and in many cases even improving the image quality and thus the quality of an intended intervention. Such advancements include electroanatomic 3D mapping systems and nonfluoroscopic magnetic guidance systems, which utilize micro-Tesla strength magnetic fields and specialized mapping catheters to provide interventional catheter localization and guidance (typically done via fluoroscopy), and 3D anatomical reconstruction without any need for ionizing radiation [
      • Bhakta D.
      • Miller J.M.
      Principles of electroanatomic mapping.
      ,
      • Scaglione M.
      • Ebrille E.
      • Di Clemente F
      • Gaita F.
      • Bradfield J.S.
      Catheter ablation of atrial fibrillation without radiation exposure using A 3D mapping system.
      ]. Multiple randomized trials have demonstrated the significant benefits that newer, nonionizing catheter localization systems offer, such as reductions in fluoroscopy time and radiation exposure by 70% and 83% respectively [
      • Earley M.J.
      • Showkathali R.
      • Alzetani M.
      • Kistler P.M.
      • Gupta D.
      • Abrams D.J.
      • et al.
      Radiofrequency ablation of arrhythmias guided by non-fluoroscopic catheter location: a prospective randomized trial.
      ].
      Furthermore, pre-recorded fluoroscopic cine loops may be used in conjunction with a magnetic guidance system to reduce procedure duration by 22% and interventional exposure by 82% [
      • Thibault B.
      • Mondésert B.
      • Macle L.
      • Dubuc M.
      • Dyrda K.
      • Talajic M.
      • et al.
      Reducing radiation exposure during CRT implant procedures: single-center experience with low-dose fluoroscopy settings and a sensor-based navigation system (mediguide).
      ]. However, while the new non-ionizing methods are potentially beneficial options, their cost may be prohibitive to some healthcare systems. Thus, in order to prevent greater disparity between healthcare systems, fluoroscopic advancements that have already shown some significant level of integration are also important to consider. Automatic positioning systems reduce the fluoroscopic time (and thus patient exposure) needed to achieve optimal viewing of relevant anatomies using preset views and collimator configurations [
      • Nickoloff E.L.
      • Lu Z.F.
      • Dutta A.
      • So J.
      • Balter S.
      • Moses J.
      Influence of flat-panel fluoroscopic equipment variables on cardiac radiation doses.
      ].

      8. Lack of optimization by user despite better technology

      Despite advancements such as dual-energy sources or digital flat panel detectors that allow potential dose reductions of up to 30–60% [
      • Lee T.-Y.
      • Chhem R.K.
      Impact of new technologies on dose reduction in CT.
      ], studies increasingly show that these technologies are often being used to acquire images of higher quality than necessary for diagnosis. At the user-level, technologists at many institutions are relied on to select imaging parameters, which introduces a significant amount of variability in image quality and patient exposure [
      • Szczykutowicz T.P.
      • Bour R.
      • Ranallo F.
      • Pozniak M.
      The current state of CT dose management across radiology: well intentioned but not universally well executed.
      ]. This individual-level variability has been supported by the finding that sites lacking a dedicated medical physicist and specialist imaging team are less likely to use existing “Dose Check” features [
      • Szczykutowicz T.P.
      • Bour R.
      • Ranallo F.
      • Pozniak M.
      The current state of CT dose management across radiology: well intentioned but not universally well executed.
      ]. The concept of diagnostic reference level has been used to achieve optimization of protection [
      • Vassileva J.
      • Rehani M.
      • Kostova-Lefterova D.
      • Al-Naemi H.M.
      • Al Suwaidi J.S.
      • Arandjic D.
      • et al.
      A study to establish international diagnostic reference levels for paediatric computed tomography.
      ,
      • Salama D.H.
      • Vassileva J.
      • Mahdaly G.
      • Shawki M.
      • Salama A.
      • Gilley D.
      • et al.
      Establishing national diagnostic reference levels (DRLs) for computed tomography in Egypt.
      ] despite some concerns about limitation of the concept [
      • Einstein A.J.
      • Pascual T.N.
      • Mercuri M.
      • Karthikeyan G.
      • Vitola J.V.
      • Mahmarian J.J.
      • et al.
      INCAPS Investigators Group. Current worldwide nuclear cardiology practices and radiation exposure: results from the 65 country IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS).
      ,
      • Roch P.
      • Célier D.
      • Dessaud C.
      • Etard C.
      • Rehani M.M.
      Long-term experience and analysis of data on diagnostic reference levels: the good, the bad, and the ugly.
      ]. Unfortunately, cases of variable and higher exposure have not been confined to abnormal patient attenuation or nonstandard cases. A recent study [
      • Padole A.M.
      • Sagar P.
      • Westra S.J.
      • Lim R.
      • Nimkin K.
      • Kalra M.K.
      • et al.
      Development and validation of image quality scoring criteria (IQSC) for pediatric CT: a preliminary study.
      ] examining image quality among the most frequent pediatric CT exams found that 16–40% of the CT images assessed were of higher than necessary quality acquired with higher settings (kVp, mAs) leading to higher radiation dose for adequate diagnostic interpretation. Similar issues have also been identified in other studies [
      • Shah R.
      • Gupta A.K.
      • Rehani M.M.
      • Pandey A.K.
      • Mukhopadhyay S.
      Effect of reduction in tube current on reader confidence in paediatric computed tomography.
      ,
      • Rehani M.M.
      Radiological protection in computed tomography and cone beam computed tomography.
      ,
      • AlSuwaidi J.S.
      • AlBalooshi L.G.
      • AlAwadhi H.M.
      • Rahanjam A.
      • ElHallag M.A.
      • Ibrahim J.S.
      • Rehani M.M.
      Continuous monitoring of CT dose indexes at Dubai Hospital.
      ] and in fluoroscopy. Despite newer fluoroscopy systems incorporating higher sensitivity flat panel detectors (FPDs) and intentional dose-reduction features such as automatic brightness control (ABC), multiple studies have found no statistically significant reduction in patient doses from the use of FPDs over traditional image intensifiers (IIs) for typical fluoroscopic procedure dose rates (e.g. as in coronary angiography) – 31 Gy cm2 (II) vs 33 Gy cm2 (FPD) [
      • Bogaert E.
      • Bacher K.
      • Lapere R.
      • Thierens H.
      Does digital flat detector technology tip the scale towards better image quality or reduced patient dose in interventional cardiology?.
      ], 31.2 Gy cm2 vs 33.4 Gy cm2 (FPD) [
      • Trianni A.
      • Bernardi G.
      • Padovani R.
      Are new technologies always reducing patient doses in cardiac procedures?.
      ], and 30 Gy cm2 (II) vs 31 Gy cm2 (FPD) [
      • Tsapaki V.
      • Kottou S.
      • Kollaros N.
      • Dafnomili P.
      • Kyriakidis Z.
      • Neofotistou V.
      Dose performance evaluation of a charge coupled device and a flat-panel digital fluoroscopy system recently installed in an interventional cardiology laboratory.
      ]. Additionally, no significant differences in image quality between a FPD and II in the fluoroscopy mode (p = 0.26) were found [
      • Bogaert E.
      • Bacher K.
      • Lapere R.
      • Thierens H.
      Does digital flat detector technology tip the scale towards better image quality or reduced patient dose in interventional cardiology?.
      ], and that in cinegraphy mode, where the FPD did exhibit intrinsically superior performance over the II exposure settings, were instead programmed for optimized image quality over reduced patient dose. While these exposure parameters can be changed to accomplish the user’s objective, operators’ uncertainty in how to balance image quality and dose makes them reluctant to adjust these parameters outside of their default values.
      Beyond the user-level, important obstacles have been identified at the organization level by personnel responsible for oversight of radiation dose optimization, including resistance to change, limited resources, complex organizational structure, and variations in CT equipment and protocol [
      • Whitebird R.R.
      • Solberg L.I.
      • Bergdall A.R.
      • López-Solano N.
      • Smith-Bindman R.
      Barriers to CT dose optimization: the challenge of organizational change.
      ].

      9. Future directions

      The greatest hope on patient dose management always remains from technology that continues to improve and of course actions at the level of users and operators play important role [
      • Rehani M.M.
      Challenges in radiation protection of patients for the 21st century.
      ,
      • Kachelrieß M.
      • Rehani M.M.
      Is it possible to kill the radiation risk issue in computed tomography?.
      ,
      • Lell M.M.
      • Kachelrieß M.
      Recent and upcoming technological developments in computed tomography: high speed, low dose, deep learning.
      ,

      Vano E. Challenges for managing the cumulative effective dose for patients. Br J Radiol 2020:20200814. https://doi.org/10.1259/bjr.20200814.

      ,

      Vano E. Recurrent imaging procedures with ionising radiation on the same patient. Should we pay more attention? J Radiol Prot Off J Soc Radiol Prot 2020;40:E14–7. https://doi.org/10.1088/1361-6498/ab7fbb.

      ]. There is an urgent need for the industry to develop CT scanners with sub-mSv radiation dose, a goal that has been lingering [
      • Rehani M.M.
      • Yang K.
      • Melick E.R.
      • Heil J.
      • Šalát D.
      • Sensakovic W.F.
      • et al.
      Patients undergoing recurrent CT scans: assessing the magnitude.
      ]. The upcoming technological advances in CT technology are listed in recent papers [
      • Kachelrieß M.
      • Rehani M.M.
      Is it possible to kill the radiation risk issue in computed tomography?.
      ,
      • Lell M.M.
      • Kachelrieß M.
      Recent and upcoming technological developments in computed tomography: high speed, low dose, deep learning.
      ]. They essentially fall in 6 categories: More powerful X-ray tubes, thicker prefilters, in a filter changer; use of tunable tube voltage settings; AEC not only to include mA modulation but also kV and filter thickness modulation; adaptive bow-tie filters; photon counting detector technology and use of deep learning [
      • Kachelrieß M.
      • Rehani M.M.
      Is it possible to kill the radiation risk issue in computed tomography?.
      ,
      • Lell M.M.
      • Kachelrieß M.
      Recent and upcoming technological developments in computed tomography: high speed, low dose, deep learning.
      ]. One of the important advances that is coming up is that of monochromatic X-ray source [Silver E, Shulman S, Rehani MM. A New Compact Source of Monochromatic X-Rays for High Quality, Low Dose, Medical Imaging, under publication]. It appears that this advance will lead to replacement of X-ray tubes all over the world in coming years and will lead to drastic reduction in radiation doses as only X-ray energies that are needed for image formation shall be generated by the X-ray tube and others that unnecessarily add to radiation dose (despite filtration) will be avoided. This innovation will impact all X-ray imaging not only CT and thus will help dose reduction in interventional fluoroscopy as well. For interventional procedures, robotic systems are likely to be implemented into practice which may drastically reduce radiation exposures to operators, but patient exposure will still remain an issue [
      • Chehab M.A.
      • Brinjikji W.
      • Copelan A.
      • Venkatesan A.M.
      Navigational tools for interventional radiology and interventional oncology applications.
      ]. On the contrary, this may result in complacency on the part of operator resulting in higher patient doses [
      • Mendelsohn D.
      • Strelzow J.
      • Dea N.
      • Ford N.L.
      • Batke J.
      • Pennington A.
      • et al.
      Patient and surgeon radiation exposure during spinal instrumentation using intraoperative computed tomography-based navigation.
      ]. The operator dose can be reduced by as much as 95% as the operator navigates the catheter sitting away from the X-ray source at a console either located in a lead shielded cabin in the room or outside the room at usual console. Training needs are perpetual and this always needs to be emphasized and practiced [
      • Rehani M.M.
      • Pauwels R.
      • Rehani B.
      Evaluation of medical physics training in radiology residency in 67 countries.
      ].

      References

      1. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). 2008 Report to the General Assembly: Annex B Exposures of the Public and Workers from Various Sources of Radiation. vol. I. 2010.

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