Radiation Principles, Protection, and Reporting for Interventional Pulmonology: A World Association of Bronchology and Interventional Pulmonology White Paper

In the past decade, the field of interventional pulmonology has been transformed by the significant increase in the use of advanced imaging modalities and technological guidance for both diagnostic and therapeutic procedures. The advent of these technologies leads the ability to perform more procedures through bronchoscopy. In diagnostics for peripheral pulmonary lesions, for example, advanced technologies such as electromagnetic tracking, virtual endoscopic guidance based on pre-procedural CT scans, novel shape sensing technologies, and multiple other technologies are being used. Whereas the majority of these technologies aim to provide navigation as a stand-alone modality, the vast majority of procedures sees it accompanied or integrated with real-time X-ray imaging. While only a decade ago the portfolio consisted predominantly of basic fluoroscopy guidance, recent advancements have introduced algorithms enabling not only simple two-dimensional (2D) fluoroscopy but also three-dimensional (3D) imaging modalities such as tomosynthesis and cone-beam CT (CBCT). Although access to high-end hybrid operating rooms (ORs) or interventional radiology suites equipped with fixed flat panel CBCT systems is still limited in many countries, the advent of mobile CBCT systems will likely translate into a rapid increase in the use of these devices.

As diverse image-guiding systems become more available to interventional pulmonologists, increasing the use of ionizing radiation, it is crucial to enhance awareness and education about ionizing radiation principles among both patients and hospital staff. Furthermore, there is a pressing need to establish an international reporting standard for consistent and accurate reporting on radiation dose and safety. This would enable standardized and comparable assessment of radiation metrics among studies. This paper aims to (1) refresh our knowledge on the basic principles of ionizing radiation, (2) guide researchers to address radiation dose and safety accurately and consistently in (future) studies, and (3) create awareness and provide practical tips on how to prevent unnecessary exposure to radiation for the safety of our patients, our staff and ourselves.

Ionizing radiation refers to any form of electromagnetic or particle radiation with sufficient energy to remove tightly bound electrons from atoms. Ionizing radiation includes photons, alpha particles, beta particles, and neutrons. In the case of diagnostic X-ray imaging, the elementary ionizing particles that are of interest are photons (X-rays and gamma rays). These photons possess higher energy levels (expressed in the term electronvolt) than photons known from visible light and therefore have different properties while interacting with tissue. In diagnostic, imaging photons are generated in the X-ray tube (Fig. 1). An image is created by summating all the photons at the detector that did not interact with matter. X-ray photons that interact with matter can either be absorbed or scattered. The chance of interaction between a photon and tissue is small but can be optimized for diagnostic imaging by adjusting the number of photons emitted, photon energy, density of tissue, and pathway length. The difference in absorption per tissue is the building block of images and causes the variation in contrast of the image. As an obvious example, air is less dense than bone tissue so it is more likely that photons interact with bone tissue than with air. Upon interaction of photons with tissue, they are scattered in different directions. The scattered portion negatively contributes to image quality as the scattered radiation can also reach the detector but have an unknown trajectory that cannot be fully distinguished from the original radiation beam causing a reduction in image contrast. Therefore, a grid (Fig. 1) is installed between the patient and the detector to prevent incoming scattered radiation from reaching the detector. The radiation that scatters to the side of the X-ray tube is called “back-scattered radiation” and is much more intense than “forward-scattered radiation” (Fig. 1).

The exposure settings of the X-ray imaging system influence the image quality and radiation dose received by the patient. The tube voltage (kilovoltage peak, kVp) and tube electrical current multiplied with the exposure time (milliampere seconds, mAs), respectively, determine the energy the photons will get and the number of photons that are generated. In order for the detector to obtain any signal the photons require adequate energy to allow penetration (i.e., sufficiently high voltage) but also interaction with the tissue (i.e., the voltage should not be too high). To allow the generation of sufficient photons for clinical image quality, the tube electric current should be sufficiently high. Newer fluoroscopy systems have specialized automatic exposure control feedback loops that can adjust the tube kVp and mA to achieve optimal imaging quality (radiation dose vs. imaging quality). As an example, when using specific lung-tailored protocols in larger adult torsos there is a need for higher energy X-ray photons to penetrate the anatomy than in that of a small child’s torso.

There is a general consensus that ionizing radiation negatively affects the human body. X-ray photon and tissue interactions typically do not lead to problematic disruptions at atomic or molecular level. However, dysregulations in the chemical bonds in the DNA can have significant consequences even with a minimal amount of energy. Normally, DNA repair mechanisms will address these damages immediately, or the affected cells undergo apoptosis. However, DNA double-strand breaks or misrepairs can cause mutations in cells that can result in the induction of cancer. It is widely acknowledged that an increase in radiation exposure corresponds to an increased risk for individuals. The risk of developing cancer due to radiation cannot be clinically distinguished from the same type of cancer arising from other causes. Hence, any cancer risk estimates at diagnostic and interventional levels must be treated with caution [1].

The interaction of tissue with radiation can lead to two different effects in the human population:

• 1.

  Deterministic effects: deterministic effects are effects in which the severity of the injury (rather than its probability of occurrence) increases once a threshold dose has been exceeded. Below the threshold, no effect will be apparent. For example, after an interventional procedure where the peak skin dose (PSD) ranges from 2 to 5 Gy, symptoms such as skin erythema may appear within 2 weeks and hair loss (epilation) can occur within two to 8 weeks. Complete recovery from these symptoms is typically expected at the lower threshold skin doses. Higher doses (>5 Gy) will have longer or even permanent consequences.

• 2.

  Stochastic effects: Stochastic effects refer to the probability of an effect occurring (rather than its severity) and increase with dose, e.g., radiation-induced cancer and hereditary effects. There is no defined threshold dose for stochastic effects.

In interventional pulmonology literature, various metrics have been used to report on radiation use. These are not only metrics provided by the system but also metrics that require additional assumptions about the procedure and the patient (including simulation modeling) for accurate calculation. For example, to estimate the effective dose, one must know the specific organs involved and their positioning within the irradiated field. As rotating the C-arm would significantly alter the geometry, this would significantly affect the procedural effective dose measurements. The use of different units and diverse assumptions complicates the comparison of radiation doses between studies, procedures, hospitals, operators, devices, or even personal performance over time. Below is a brief overview of core metrics as commonly referenced in radiation literature.

Modern fluoroscopy systems report the CAK and the DAP as Dose Metrics:

• Cumulative Air Kerma (CAK, in Gy): The total cumulative Kinetic Energy Released in MAtter (KERMA), specifically in air (Air Kerma) is reported for fluoroscopy systems at a specific location known as the interventional reference point (IRP, Fig. 1). It is expressed in Gray (Gy), which is the SI (International System of Units) base unit of absorbed ionizing radiation. The CAK is roughly correlated with the risk of deterministic effects of radiation on biological tissue and reflects the dose received by the skin. It is important to note that the CAK is reported for the entire patient exam, which may have been distributed over the patient surface opposed to delivering it all at one surface location.

• Dose Area Product (DAP, in Gy∙cm²): The DAP is calculated by multiplying the Dose (Gy) by the area of irradiation (cm²). This measurement reflects the absorbed dose within a specific area of tissue that has been irradiated. DAP is measured using an ionization meter placed beyond the X-ray collimators (Fig. 1). DAP is approximately correlative with the risk of stochastic effects, such as cancer, due to radiation exposure in biological tissue. Akin to CAK, fluoroscopy systems also report the total DAP for a patient examination and thus never reflect the dose in a specific organ.

• Effective Dose (ED, in Sv): The ED accounts for the fact that different tissue types exhibit varying levels of sensitivity to the stochastic risk of radiation (reflected in a weighing factor Wt). The ED is expressed in Sieverts (Sv), which is the SI-unit that represents the stochastic health risk of ionizing radiation. The ED is estimated from the DAP using conversion factors. The accuracy of this estimation depends on many factors such as the C-arm angle, collimation used, organ presence in the field of view, type of exam performed, et cetera. The conversion from DAP to effective dose is rarely generalizable across cohorts in non-standardized imaging procedures (i.e., procedures which allow the operator to adjust imaging performed). Due to the multiple variables involved in estimating the effective dose from DAP in X-ray imaging systems such as C-arms and CBCT systems, a significant error margin can be expected in the calculated effective dose [2‒4]. In interventional pulmonology, it should therefore be regarded with caution and only used as a means to allow the risks to be compared with other imaging modalities like PET-CT and CT in a general sense.

• Note that fluoroscopy systems generally only report total CAK and DAP in a procedural summary report. More recent systems may also provide CAK and DAP for every radiation exposure event, including the beam geometry, in a more detailed Radiation Dose Structured Report which the clinical physicist of the hospital can provide. We recommend that conversion from the reported total CAK and DAP to PSD for deterministic risk and ED for stochastic risk is conducted by a physicist.

• Personal Dose Equivalent (in Sv): For occupational radiation protection monitoring, the personal dose equivalent is measured by dosimeter badges. It is used as an estimation of the effective dose of the staff. Depending on the photon energy and position where the badge is worn, the badge may lead to inaccuracies of the actual effective dose received [5].

Radiation exposure does not only occur in healthcare facilities as every human is exposed to background radiation occurring in nature every day. The average annual background radiation level worldwide is estimated to be 2.4 mSv [6]. An example of effective dose estimations that patients are exposed to in diagnostic imaging can be found below in Table 1. Note that the effective dose should not be used for individual patient doses but rather to compare doses across exam types and modalities.

Historically, the use of ionizing radiation in interventional pulmonology primarily involved fluoroscopy as facilitated by either mobile or fixed C-arm systems with only 2D imaging capabilities. Diagnostic applications of fluoroscopy included the assessment of interstitial lung diseases or nodules, as well as the evaluation of diaphragm motility. Therapeutic interventions often involved bronchoscopic lung volume reduction using coils or valves for severe emphysema, airway stents for central airway obstructions, and less frequently brachytherapy as a form of local radiotherapy. Although trans-thoracic needle aspiration has had a consistent place in interventional pulmonology, it has predominantly been performed under CT guidance by (interventional) radiologists.

Advanced X-ray image guidance has garnered significant interest in interventional pulmonology, particularly with the rise of navigation bronchoscopy procedures. The use and development of advanced X-ray imaging techniques has captured the attention of physicians and the health industry worldwide. The available clinical setups nowadays include (advanced) fluoroscopy, tomosynthesis, fixed CBCT systems in hybrid ORs and interventional radiology suites, and mobile CBCT systems capable of 3D imaging. Numerous studies have been published addressing the procedure outcomes utilizing these technologies. However, the associated radiation exposures are often absent, limited or presented in formats that are difficult to interpret, complicating the task of making accurate comparisons. For example, an extensive but non-exhaustive review of the literature on navigation bronchoscopy technologies that included radiation metrics is presented in Table 2. There is considerable variability in how procedures are performed; with physicians balancing the use of 2D fluoroscopy and 3D image acquisition based on their specific needs. Increasing the use of 2D fluoroscopy can lead to fewer 3D acquisitions and vice versa. The adoption of supplementary guidance technologies plays a role in this clinical decision as well. Aside of differences in individual physician preferences in imaging, imaging and guidance systems also have specific requirements that result in different radiation exposures. The limited subset of studies as shown in Table 2 show the radiation exposure variates considerably even in a similar approach and that there is no consistent total radiation exposure difference between fixed and mobile systems with 3D capabilities nor is there a consistent difference in single or multi-modality settings. The considerable variability as caused by individual preference as well as technological background shows multiple variables are needed to understand differences between studies and procedure performance. For example, although the fluoroscopy time and number of CBCT spins are frequently mentioned, it does not linearly correlate with radiation dose. Comparing the number of spins or fluoroscopy time between reports and then taking an “average” CBCT scan or fluoroscopy dose per amount of time leads to an inaccurate estimation of the total dose. An initial CBCT scan at the start of a navigation bronchoscopy procedure might use a wider field of view and higher image quality for airway visualization than subsequent scans that utilize only collimated 3D imaging with lower quality to confirm tool-in-lesion positioning. As highlighted in the study of Verhoeven et al. with precise radiation measures both fluoroscopy time and the number of spins can increase while still decreasing the overall radiation dose [12].

The International Commission on Radiological Protection (ICRP) is an independent, international organization that provides guidance and recommendations on protection against the harmful effects of ionizing radiation. These recommendations are recognized by many countries and adopted into legislation to minimize patient dose and protect employees and citizens against the dangers of uncontrolled use of ionizing radiation. In 2015, ICRP Publication 129 stated that the most important dose index that should be reported and tracked in fluoroscopy and CBCT imaging is the kerma area product, which is in diagnostic X-ray imaging interpreted to be equal in value to the DAP. They conclude that reporting DAP facilitates a direct comparison between 2D examinations such as fluoroscopy and 3D examinations such as 3D CBCT spins. The commission further stated that the effective dose is not a suitable dosimetric quantity for reporting patient doses in fluoroscopic or cone-beam imaging [42].

The radiation dose per procedure is not only determined by the extensive fluoroscopy and 3D image usage but also determined by the patient on the table. The body mass index (BMI) has a strong influence on the radiation dose produced during the procedure, resulting in a significant increase in DAP for overweight (25.0–29.9) and obese (>30) patients compared to healthy weight BMI range (18.5–24.9) [43]. Also increasing patient’s BMI is associated with a significant increase in the physician’s radiation dose during fluoroscopy use [44]. Therefore, it is important to mention the mean/median BMI together with your radiation reports.

Detailed data reporting on radiation exposure is crucial and should, at minimum, include several key metrics to allow meaningful comparison of procedural imaging approaches and study outcomes. For future research involving radiation exposure in interventional pulmonology, we recommend including the information outlined in Table 3.

Engaging in activities that involve the use of ionizing radiation, particularly in clinical settings, demands careful attention to minimize exposure while preserving the quality of diagnostic images. This approach is steadfastly guided by the ALARA principle – As Low As Reasonably Achievable – signifying a dedicated commitment to use the minimum radiation exposure necessary to achieve the precise goals of imaging [45]. While image quality and radiation exposure share a close relationship, it might be inferred that decreasing radiation exposure could potentially compromise image quality, impacting decision-making during procedures. Nonetheless, numerous measures exist to manage radiation exposure without significantly impacting image quality. In general, a reduction of patient dose directly translates to a reduction in dose for the staff.

In the following section, practical tips for interventional pulmonology procedures are listed.

• Critically examine fluoroscopy use, do you need to see your instruments continuously or is intermittent fluoroscopy use also sufficient? Instruct to disengage the fluoroscopy pedal when imaging is no longer relevant.

• Fluoroscopic imaging at multiple imaging angles can help validate the 3D position of instruments but consider using only intermittent instead of continuous imaging while performing the rotation.

• Fluoroscopic imaging in pulsed mode obtains images in short X-ray pulse emissions compared to continuous fluoroscopy. It can significantly reduce radiation exposure while keeping sufficient image fluency [46]. Review your fluoroscopy frame rate; how low can you go without compromising image quality?

• Most 3D imaging systems have a subset of protocols available ranging in radiation dose and image quality; do you need the highest quality at every time point in the procedure or for every patient, or is a lower dose with reduced image quality also sufficient?

• Some hybrid imaging systems allow the acquisition of 3D information through tomosynthesis of fluoroscopy at a limited set of angles rather than performing a full 3D CBCT scan; evaluate the comparative radiation dose of both imaging sequences and assess the imaging quality needed with the least radiation dose.

The radiation emanating from a point source follows the inverse square law, wherein the dose (or dose rate) reduces proportionally to the square of the distance from the source (irradiation from a point source in a spherical fashion). To illustrate, doubling the distance from the radiation “source” (i.e., tube and/or patient) results in a reduction of the radiation dose by approximately a factor of four.

Distance is a very applicable term in radiation protection and is two-fold.

• Patient distancing: as direct X-ray beams traverse patients to reach the detector, physicians are encouraged to adhere to optimal radiographic geometry practices to improve image quality while reducing radiation dose.

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    This entails positioning the patient as close to the image detector as feasible, to minimize the air gap. The detector in most fixed C-arm and CBCT systems can be mechanically lowered, or the table height increased. A high table position reduces the PSD of the patient and increases the field of view without requiring magnification. These adjustments may not always be possible when mobile CBCT is being utilized and “iso-centering” is required to ensure visualization of the target in CBCT images. The height of the table is then mostly adjusted according to how anterior or posterior the target is located. At all times, keep the ergonomic working position of the interventional pulmonologist in mind for evaluating the right position.

  • -

    Posteroanterior projection angles demand the minimal dose (or dose rate) necessary for effective imaging, as this is the smallest distance for the X-ray source to transverse the (least amount/dense) tissue. However, when transitioning to the left anterior oblique or right anterior oblique system orientations and further into lateral orientation, the dose may escalate significantly [47].

• Staff distancing: as scattered radiation emanates from the patient, it is omnidirectional but more potent in the backscattered direction (Fig. 1). It is the greatest radiation exposure source for staff.

  • -

    Every staff member should avoid direct exposure to the primary X-ray beam.

  • -

    Positioning the X-ray tube beneath the patient support is most efficient in terms of radiation protection for the staff. The primary source of staff exposure arises from scattered X-rays emanating back from the patient (back-scattered radiation, Fig. 1). Consequently, the patient serves as a natural shield for staff positioned near the image detector. This protective effect is particularly pronounced as the majority of backscattered radiation tends to be directed towards below the pelvis level, targeting tissue that are less susceptible to X-ray exposure compared to those in the upper part of the staff’s body. The angulation of the C-arm or CBCT to the left or right anterior oblique can significantly increase the scattered dose [47‒49].

  • -

    It is advised to maximize the distance of staff to the X-ray source and limit the presence of staff near the patient. Position yourself in a low-scatter area. For example, it is a common mistake that the operator stands on the side of the X-ray tube during lateral fluoroscopy, which is the area of the most intense back-scattered radiation [48]. In tomosynthesis image acquisitions with prolonged manual spin of the fluoroscopy arm between certain left and right anterior oblique orientations can increase the scatter for staff if they are not distancing.

  • -

    Reconsider your physical location relative to the X-ray source when you dedicated 3D imaging, move away as far as reasonably possible or find proper shielding. As most physician’s find proper shielding during 3D imaging, the main source of occupational radiation dose originates from the 2D fluoroscopy.

An X-ray collimator is a crucial device positioned in close proximity to the X-ray tube to control and confine the area of the X-ray beam horizontally, vertically or circularly (Fig. 1). Collimation primarily serves to limit the radiation exposure only to the specific area of interest and to a lesser extent improves image quality due to a reduction in the number of scattered X-ray photons. Reducing the area reduces the DAP.

• While using fluoroscopy imaging during interventions, the operator mainly focuses on a certain point while the whole field of view is irradiated. Collimation is a useful technique for reducing the radiation exposure of the areas of no interest (Fig. 2).

• In 3D CBCT spins, collimation can also be applied in cranio-caudal orientations, which results in a significant dose saving [14].

There are multiple types of magnifying modes associated with fluoroscopic equipment. Modern systems with flat panel detectors allow for analog magnification by increasing the spatial resolution to obtain a greater level of image detail. An additional magnification feature is also available in some systems and is referred to as digital zooming. Using this mode, the resultant image can be magnified while the inherent resolution properties of the image remain unchanged.

• Analog magnification increases the exposure rate, ensuring that the signal-to-noise ratio of the image is approximately constant regardless of the X-ray pathway length, and density of the anatomical region in the field of view. Therefore, the use of analog magnification should be minimized unless it is specifically necessary for diagnosis.

Irrelevant objects, especially metal objects with a high attenuation coefficient, will trigger the automatic exposure control to increase the dose rate of the X-ray system. These objects in the field of view, such as parts of the navigation systems and blood pressure band connectors, etc., should be removed by either repositioning the object, moving the field of view of the imaging system or collimation of the imaging system.

Protective equipment is available in many forms and includes both shielding and radiation monitoring devices. Radiation exposure is mainly caused by the scattered radiation from the patient. It should be rare for staff to be exposed to the primary X-ray beam.

• Shielding in the form of lead equivalent aprons and thyroid collars is best used for occupational work with image-guided radiation. Lead protective glasses are optional and mainly recommended for interventions with high fluoroscopy workloads where the operator is continually in close proximity to the patient [50].

• Additional shielding in the form of glass screens and table skirts minimizes exposure.

• Depending on local requirements, occupational radiation monitoring devices may be worn at the torso or thyroid level, either beneath or outside lead protective garments. Regular monitoring of these dosimetry devices is essential to track the annual radiation exposure of the operator. This task is typically carried out by the Radiation Safety Officer or Medical Physicist. Precautionary measures must be applied to respect national radiation levels.

The number of shades of gray the human eye can distinguish is greatly affected by the lighting conditions.

• During fluoroscopic examinations, the room lighting should be minimal to enhance the visualization of the gray-scale images on the monitor. Excessive light will decrease the ability of the eye to resolve detail on the monitor which could cause the physician to modify the exposure parameters to increase the brightness of the resultant image. Once again, an increase in the exposure parameters will directly impact on patient’s dose.

• Large display monitors can be used to reduce image magnification and prevent the interventional pulmonologist from leaning in high-risk irradiated fields.

Extra considerations arise when a patient or staff member is pregnant. On top of the practical measures listed above, alternative treatments, additional shielding, or monitoring may be worth considering.

• Pregnant patients: In every patient, the justification for using ionizing radiation should outweigh the risks that radiation exposure may cause. The fetus is more susceptible to radiation effects; it is important to have sufficient reason for using radiation near the fetus and at least additional radiation reduction and optimization measures.

• Staff Pregnancy: Staff working with ionizing radiation should inform hospital authorities to ensure that the fetus is afforded the appropriate level of protection. The local Radiation Safety Officer should be able to assist with more frequent radiation monitoring of the exposure via the use of specialized electronic dosimeters [51].

The above-mentioned practical dose reduction measures can be easily implemented into everyday clinical workflows, however, to further optimize the use of radiation additional measures should also be considered. Training is an important aspect of this clinical implementation of dose reduction measures in the imaging suite, as many interventional pulmonologists have not received a formal radiation safety training during their careers. Any training implemented should include both the operator of the imaging equipment and staff routinely required to be in attendance during these imaging procedures or interventions. Any training package offered should be delivered by educators with both clinical experience and radiation protection/medical physics expertise. The interventional pulmonologists should be made aware of and recognize the situations in which dose reduction measures can be applied and act accordingly. Additionally, further optimization measures can be achieved for complex procedures requiring prolonged fluoroscopic imaging using medium to high output imaging equipment with the presence of radiography support (radiographer, medical imaging technologist, etc.) for these exams. The involvement of radiography support during fluoroscopic applications is a key element in minimizing patient exposure. Not only to keep prioritization and awareness as physicians are often mentally burdened with procedure performance but also as an adept and experienced teams collaborates best. The radiography support can assist the interventional pulmonologists to recognize the situations in which dose reduction measures can be applied, and act accordingly.

The contribution of clinical physicists and other technologists can help the team gain insight into the radiation dose per procedure and strive for lower radiation levels to further implement ALARA principles to minimize risks. The clinical physicist should be involved in the initial setup, periodic quality control and staff education. Incorporating radiation protection into the briefing or debriefing can help ensure that every team member is aware. Dosimeters can provide insights into the radiation doses to which people in the OR are exposed. Real-time dosimeters, which provide dose rates in real-time, are available on the market and are an effective tool for achieving these outcomes. In addition to the operational aspects of optimizing radiation exposure, facilities should also review or benchmark their patient exposures against facilities performing similar procedures or against published literature for that type of examination. By uniformly reporting radiation doses in the literature, a multi-institutional analysis can help individuals improve radiation reduction measures. Additionally, some countries have implemented diagnostic reference levels for specific procedure types. The objective of a diagnostic reference level is to assist in the avoidance of excessive radiation dose to the patient that does not contribute additional clinical information to the medical imaging task. Dose monitoring software that alert when a threshold is exceeded are recommended. Cases where the expected threshold is exceeded can be reviewed to clarify and justify why the dose was excessive and serve as an opportunity to improve practice.

Given the recent advances in image-guided diagnostic procedures in interventional pulmonology, it is inevitable that X-ray imaging will be increasingly used in the interventional pulmonology field over the coming years. This is especially apparent in the increasing demand and interest in peripheral pulmonary nodule procedures where advanced 3D imaging in combination with high-tech navigation systems is developing into the new gold standard. With the increasing use of chest CT scanning and where lung cancer screening programs are being implemented broadly, more (incidental) nodules will be detected requiring tissue diagnosis [52]. Also, new developments for both diagnostics and local therapy will increase and expand the demand for X-ray guided procedures.

To accommodate this need, advanced mobile systems and hybrid imaging systems have become commercially available over recent years. Although these systems yet have lower image quality and longer acquisition time compared to currently available fixed systems, these systems are a solution for sites without 3D image confirmation systems or limited capacity for intervention radiology rooms and may save costs [31, 33]. Furthermore, the fixed CBCT system developments have not reached their technological limits, as there is room for improvement in more advanced fluoroscopy to guide the bronchoscopist to the lesion and give insight into margins for therapy [19]. Accurate tool-in-lesion confirmation requires reliable imaging systems with 3D acquisition capabilities. Software tools for tool-in-lesion reconstruction lack sufficient accuracy at a millimeter level. In local therapeutics such as microwave ablation, accurate 3D imaging and advanced fluoroscopy are essential for the reconfirmation of nodule margins to critical structures, catheter positioning confirmation and post-ablation zone evaluation [30]. Although all these developments will increase the number of 3D acquisitions in our procedures, it is a challenge to limit radiation exposure for both patients and staff.

The use of advanced X-ray image guidance is rapidly increasing. Interventional pulmonologists are encouraged to minimize radiation exposure for both patients and staff, by understanding the physics of radiation and maximizing the use of radiation safety measures according to the ALARA principles. In daily care, the correct interpretation of your own site’s radiation exposure is important in order to apply correct radiation measures and it should be seen as an effort of the total interventional team. All future clinical research using X-ray image guidance in the field of interventional pulmonology should systematically and uniformly report radiation exposure and safety measures to allow interpretation and comparison of different procedures, clinical setups and devices. We also advise future researchers, reviewers, and editors to address radiation safety. To report doses, our advice is that DAP and CAK should be used relative to the patient’s BMI. In conclusion, as the reliance on advanced X-ray imaging continues to grow in interventional pulmonology, it is imperative for the entire interventional team to rigorously apply radiation safety measures in line with ALARA principles, continually monitor and interpret site-specific radiation data and ensure that future research adheres to consistent reporting standards for radiation exposure to enhance safety, comparability, and clinical outcomes.

We would like to thank S. Langereis, PhD, and F. Mammadli, MSc, for providing help in the literature search.

Statement of Ethics is not applicable as this research is based on literature, physics, and published articles.

The authors declare that they have no conflicts of interest in relation to the content or conceptualization of the work reported in this white paper. All authors have completed the ICMJE uniform disclosure form. P.F. Einsiedel, A. Fantin, and D.J. Hall declare no conflict of interest. I.N. Wijma received no personal fees but discloses institutional and departmental research contracts with Innovative Health Initiative (EU fund). R.F. Casal discloses to receive research funding from Intuitive Surgical, Siemens, Johnson & Johnson, as well as consulting fees from Cannon, Intuitive Surgical and Olympus, and payment for presentations/educational events from Siemens. G.Z. Cheng discloses to receive research funding from Intuitive Surgical, consulting fees from Intuitive Surgical, Olympus, Boston Scientific, Pinnicle Biologics, and Biodesix, and payment for presentations/educational events from Cook Medical and Biodesix, participation on a Data Safety Monitoring Board or Advisory Board for LeadOPTIK and Biodesix, and a current executive board membership at the AABIP and ACCP. F.J.F. Herth discloses to receive payment in the past (2018–2022) for presentations/educational events from Pulmonx and Uptake. C.S.H. Ng discloses to receive personal payment for presentations/educational events from Medtronic and Johnson & Johnson. M.A. Pritchett discloses to receive personal payment for consulting fees from Philips, Intuitive, Medtronic, Johnson & Johnson and Noah Medical, payment for research and speaking from Philips, Intuitive, Medtronic and Johnson & Johnson, travel fees from Intuitive, Noah Medical, Johnson & Johnson and Philips, and a current board membership at the Society for Advanced Bronchoscopy. P.L. Shah discloses to receive payment for speaking from Pulmonx, Olympus and Philips. D.P. Steinfort discloses trial related funds from Zidan Medical and Phenomapper Inc. R. Trisolini discloses to receive consulting fees from MSD and Medi-Globe, payment for presentations/educational activities from Pentax, Medi-Globe, AstraZeneca, Eli Lilly, MSD and Amgen, and participation on a Data Safety Monitoring Board or Advisory Board for MSD, Amgen and AstraZeneca. R.L.J. Verhoeven received no personal fees but discloses institutional and departmental research contracts with Pentax medical, AstraZeneca, Johnson & Johnson, Philips, Intuitive, Innovative Health Initiative (EU fund), KWF (national cancer fund), as well as consulting fees from Intuitive, Johnson & Johnson, NLC paid to the institution, travel support from Intuitive and Johnson & Johnson, equipment gifts from Philips Medical, and a current board membership at the Dutch society for Technical Physicians (NVvTG, unpaid). E. H.F.M. Van der Heijden received no personal fees but discloses institutional research grants from Pentax medical, AstraZeneca, Johnson & Johnson, Philips, Intuitive, Innovative Health Initiative (EU fund), KWF (national cancer fund), as well as consulting fees from Intuitive, Johnson & Johnson, NLC paid to the institution, travel support from Intuitive Surgical and Johnson & Johnson; speaker fees paid to institution by Janssen-Cilag, Pentax, Philips, Astra Zeneca, Intuitive, Siemens and Ethicon; equipment gifts from Philips Medical and equipment loans from Pentax Medical and Intuitive, and a current executive board membership at the European Association for Bronchology and Interventional Pulmonology (unpaid).

There were no funding sources for this study.

I.N. Wijma: conceptualization, writing – original draft, reviewing and editing, final approval. R.F. Casal, P.F. Einsiedel, A. Fantin, D.J. Hall, F.J.F. Herth, C.S.H. Ng, M.A. Pritchett, P.L. Shah, D.P. Steinfort, R. Trisolini, R.L.J. Verhoeven, E.H.F.M. van der Heijden, and G.Z. Cheng: conceptualization, writing – review and editing, and final approval.

Endorsed by the European and American Association for Bronchology and Interventional Pulmonology. On behalf of the WABIP ad hoc committee radiation safety white paper: chaired by Erik H.F.M. van der Heijden.

All data are available in the references, as it is based on literature, physics, and published articles.