2025 SIECVI共识声明：介入超声心动图医师的辐射防护

Abstract

The interventional echocardiographer (IE) plays a crucial role in structural heart interventions, yet faces significant risks from ionizing radiation, often greater than those encountered by the primary interventional cardiologist (IC). This elevated exposure is due to the IE's close proximity to the patient's head and, consequently, to the X-ray source, combined with a general lack of dedicated protective equipment designed for their position. Despite growing awareness of radiation safety in the catheterization lab, the specific protection needs of IEs remain under-recognized. Recent studies have shown that IEs can receive up to 11 times more radiation than ICs during procedures guided by transesophageal echocardiography (TEE), such as transcatheter edge-to-edge repair or left atrial appendage closure. These findings, together with the recent reduction in recommended dose thresholds for deterministic effects like contact formation, emphasize the urgent need to implement effective protective measures. Radiation exposure can be significantly reduced by following the core principles of radiation safety: time, distance, and shielding. Key strategies include optimizing the IE's position based on expected fluoroscopic projections, using dedicated mobile or ceiling-mounted shields, adopting lightweight personal protective equipment, and encouraging the use of low-dose imaging protocols. Ongoing education and training, targeted not only at IEs but also at ICs, is essential to reinforce safe practices and promote a culture of radiation awareness. Technological innovations offer promising solutions. New shielding systems like the Eggnest® and Rampart® have demonstrated effective protection for staff near the patient's head. Disposable radiation-reducing drapes and the development of robotic systems for remote TEE manipulation may further enhance safety without compromising workflow or image quality. Advances in imaging hardware and software also support dose reduction without sacrificing clinical effectiveness. Finally, computational dosimetry methods may soon allow for more accurate and individualized exposure monitoring, overcoming the limitations of conventional dosimeters. In summary, improving radiation protection for IE must become a priority. A combination of strategies is necessary to ensure long-term safety and sustainability in this rapidly evolving field.

Keywords: Interventional echocardiography, occupational exposure, radioprotection, structural heart interventions

INTRODUCTION

In recent years, significant progress in cardiovascular medicine has occurred alongside the rapid development of cardiac ultrasound technology. Percutaneous therapeutic options for structural heart disease have expanded dramatically, with most interventions performed under fluoroscopic and echocardiographic guidance.

During the procedures, the interventional echocardiographer (IE) is required to frequently manipulate the transesophageal

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Address for correspondence: Dr. Giacomo Ingallina, Cardiovascular Imaging Unit, IRCCS San Raffaele, Milan, Italy. E-mail: g.ingallina@hotmail.com

This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License (CC BY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

For reprints contact: WKHRPMedknow_reprints@wolterskuwer.com

Submitted: 30-Sep-2025

Published: 31-Dec-2025

How to cite this article: Ingallina G, Moreo A, Colombo PE, Casadei F, Spanò F, Belli O, et al. Radioprotection for interventional echocardiographers: A consensus statement of the Italian Society of Echocardiography and Cardiovascular Imaging. J Cardiovasc Echography 2025;35:427-33.

Ingallina, et al.: Radioprotection for interventional echocardiographers

echocardiography (TEE) probe. As a result, the IE is positioned near the patient's head in close proximity to the X-ray source. [1-3]

Long-term occupational radiation exposure has been known to pose several health risks to interventional cardiologist (IC). Despite the increasing awareness of the amount of radiation, the importance of radiation safety for the IE seems still not a priority for most cardiac catheterization laboratories or hybrid operating rooms.[1]

IC has always been guided by fluoroscopy, and the focus on radiation exposure has led to the development of effective monitoring and fixed protection systems. These protections are installed to the right of the operating table where the IC is located. The IE, both due to the proximity to the X-ray source and the absence of dedicate protection equipment, is subjected to high levels of radiation exposure up to 11-fold higher than the IC underlying the importance to look for protective solutions.[4,5]

Recently, lower dose thresholds have been indicated following the detection of damages like cataracts even for low-dose exposures.[6]

The increased number of structural heart interventions (SHIs) performed with TEE guidance, combined with the reduction in operator exposure thresholds, makes it necessary to study appropriate solutions in terms of educational recommendations and equipment to protect the IE.

# BASIC RADIATION PRINCIPLES

X-ray imaging is based on the differential absorption of X-ray photons as they pass through the body and reach a detector. When an X-ray beam is emitted from the source, it penetrates various tissues, which attenuate the radiation to different extents depending on their density and atomic composition.

Denser structures, such as bones and calcifications, absorb more X-rays and appear as bright areas on the final image, whereas less dense tissues, such as soft tissues and fluids, allow more radiation to pass through and appear darker. The X-ray photons that are not absorbed reach the detector, which converts them into an electrical signal to generate a radiographic image. This process provides real-time visualization of anatomical structures and medical devices, making it essential for guiding interventional procedures. However, the interaction of X-rays with tissues also leads to radiation exposure, posing potential health risks to both patients and healthcare personnel.

# PHOTOELECTRIC EFFECT AND COMPTON SCATTERING

When X-rays interact with matter, they can be absorbed or scattered, primarily through two mechanisms: the photoelectric effect and Compton scattering.[7]

$\bullet$ Photoelectric effect: This occurs when an X-ray photon transfers all its energy to an inner-shell electron in an atom, ejecting it from the atom and leaving behind a

vacancy. This vacancy is then filled by an electron from a higher energy level, releasing secondary characteristic radiation. The photoelectric effect is more prevalent at lower X-ray energies and in materials with high atomic numbers, such as bone and iodine contrast agents. The photoelectric effect occurs within the X-ray beam, enhancing image contrast but also increasing localized radiation absorption, which may raise the risk of tissue damage

$\bullet$ Compton scattering: In this interaction, an X-ray photon collides with an outer-shell electron, transferring part of its energy to the electron and ejecting it from the atom. The remaining photon is deflected at an angle and continues traveling with reduced energy. Compton scattering is dominant at higher X-ray energies and in soft tissues, producing scattered radiation that degrades image quality and contributes to occupational exposure.

For IE, Compton scattering represents the primary radiation hazard. During fluoroscopic procedures, scattered radiation originates from the patient's body and propagates in multiple directions, including toward healthcare personnel. Because the IE is positioned near the area of the patient irradiated by the X-ray source, IE is significantly exposed to scattered radiation.

BIOLOGICAL EFFECTS

Radiation exposure can lead to biological effects classified into two main categories: deterministic effects and stochastic effects. The distinction between these effects is crucial for understanding the risks associated with occupational radiation exposure.

Deterministic effects (threshold effects): These effects occur only when radiation exposure exceeds a specific dose threshold. Above this threshold, the severity of the effect increases with dose. Deterministic effects result from significant damage to a large number of cells, leading to functional impairment of tissues or organs. Examples include radiation-induced skin injuries, cataracts, bone marrow suppression, and sterility. Recent evidence suggests that cataracts can develop even at lower doses than previously thought, leading to stricter exposure limits for the lens of the eye.[6]

Stochastic effects (probability-based effects): These effects have no dose threshold, meaning they can occur even at low levels of radiation exposure. The probability of occurrence increases with dose, but the severity of the effect remains independent of the dose. Radiation-induced DNA damage leads to stochastic effects. The principal stochastic effect is cancer, with risk assessments predominantly derived from research on Hiroshima and Nagasaki survivors. Recent studies aim to assess risks at lower doses, including research on radiation-exposed workers and children undergoing computed tomography (CT) scans. Some CT studies suggest a slight increase in cancer risk at doses of a few tens of millieverts (mSv). However, these findings are debated due to methodological issues such as reverse causation and confounding by indication. Caution

Ingallina, et al.: Radioprotection for interventional echocardiographers

is advised when interpreting low-dose risk data.[8,9] For IEs, chronic low-dose exposure over years could increase the risk of malignancies, particularly brain tumors, hematological cancers, and thyroid cancer.

RADIATION DOSIMETRY

Radiation exposure is quantified using specific dosimetric parameters to assess the potential biological effects on different tissues and organs. Two key concepts in radiation protection are equivalent dose and effective dose, both measured in Sieverts.

$\bullet$ Equivalent dose (H): This metric accounts for the type of radiation and its potential biological damage. Since different types of radiation have varying levels of ionization potential, a radiation weighting factor (wR) is applied to the absorbed dose (measured in gray, Gy). The equation is:

$$H=D\times wR$$

Where D is the absorbed dose and wR is the weighting factor. For X-rays, wR is 1, so the absorbed dose equals the effective dose. Equivalent dose is the most appropriate quantity for use in setting limits on tissue doses to prevent tissue reactions (deterministic effects).

An example of an equivalent dose threshold is the International Commission on Radiological Protection (ICRP) recommendation to lower the annual limit on the equivalent dose to the lens of the eye for occupational exposures to 20 mSv, averaged over 5 years, with no year exceeding 50 mSv, due to evidence showing sensitivity of eye's lens to opacities at lower doses.

$\bullet$ Effective dose (E): The effective dose considers both the type of radiation and the varying sensitivity of different organs to radiation. It is calculated as:

$$E=\Sigma(HT\times wT)$$

Where HT is the equivalent dose for a specific organ and wT is the tissue wR, which reflects the organ's radiosensitivity (e.g., bone marrow and lungs have higher wT values than muscle or skin). The effective dose provides a measure of overall risk for stochastic effects, allowing for comparison of different types of radiation exposure across the body.

In occupational settings, effective dose is used to assess whole-body exposure, while equivalent dose is crucial for monitoring specific organ risks, such as the eye lens, hands, or thyroid. It is a valuable metric for optimizing worker and public protection, setting control criteria, and demonstrating compliance. Its use assumes a linear nonthreshold dose– response relationship at low doses or rates, equivalence of acute and chronic low-level exposures, and equivalence of internal and external exposures.

For IE, understanding these metrics is essential for implementing dose-reduction strategies, such as optimizing procedural techniques and using protective equipment.

For workers who are exposed to radiation, their dose is typically estimated by giving them one or more personal

dosimeters. These devices are worn during work and allow for accurate monitoring of each individual's exposure.

Usually, the dosimeter used to measure the effective dose is placed on the chest, following ICRP guidelines. In addition, separate dosimeters are used to measure the dose to the lens of the eye and to the extremities – these are typically worn on the wrist or as a ring.

OCCUPATIONAL RADIATION EXPOSURE RISKS AND DOSE LIMITS

Cath lab staff accumulate significant lifetime radiation exposure in the range of 50–200 mSv, corresponding to a whole-body dose equivalent of 2500–10,000 chest X-rays with a projected professional lifetime attributable excess cancer risk of 1 in 100.[10]

The occupational hazards associated with radiation exposure in cardiac catheterization laboratory personnel are well documented. Research has demonstrated that prolonged exposure to radiation correlates with increased incidences of cancer, cataracts, hypertension, hyperlipidemia, endothelial dysfunction, accelerated vascular aging, and early-onset atherosclerosis when compared to individuals not routinely exposed to radiation.[10-15] Consequently, concerns regarding these health risks have grown, prompting the implementation of protective measures, with a primary focus on safeguarding IC.

In 2007, the ICRP established specific dose limits for occupational radiation exposure. These included an effective dose limit of 20 mSv per year, averaged over 5-year periods, with a maximum of 50 mSv in any single year. In addition, the equivalent dose limits were set at 500 mSv annually for the skin, hands, and feet, and 150 mSv per year for the eye lens.[10] However, emerging evidence suggested that cataract formation could occur at lower exposure levels than previously assumed. In response, the ICRP revised its guidelines in 2011, reducing the equivalent dose limit for the lens to 20 mSv per year, averaged over 5 years, with no single year exceeding 50 mSv. This change underscored the critical need for enhanced eye protection.[11]

These recommendations are consistent with the European Council Directive 2013/59/Euratom, introduced in 2013, as summarized in Table 1.[12]

Italian legislation has aligned with the European directive (2013/59/Euratom) since July 2020, applying the same limits and thereby reducing the lens dose limit for exposed workers by seven times.[16]

RADIATION EXPOSURE FOR INTERVENTIONAL ECHOCARDIOGRAPHER

Despite the increased use of imaging techniques involving ionizing radiation, overall occupational exposure to ionizing radiation among doctors has decreased in the past two decades.

Ingallina, et al.: Radioprotection for interventional echocardiographers

|Type of limit|Value| |---|---| |Effective dose|20 mSv per year, averaged over defined periods of 5 years with no single year exceeding 50 mSv| |Effective dose in pregnancy|1 mSv to the embryo/fetus during the remainder of pregnancy| |Annual equivalent dose in Lens of the eye|20 mSv/year, averaged over defined periods of 5 years with no single year exceeding 50 mSv| |Skin|500 mSv| |Hands and feet|500 mSv|

However, this reduction is not observed for cardiologists, who experience exposure levels two to three times higher than those of radiologists.[17]

Recent studies have raised concerns about the radiation exposure IE during SHI, highlighting the need for improved protective measures.

Salaun et al. found on 30 various SHIs that IEs were exposed to significantly higher radiation doses than IC when only standard shielding on the right side was used.[18]

McNamara et al. confirmed that during left atrial appendage occlusion (LAAO) and transcatheter edge-to-edge repair (TEER) procedures, IEs were exposed to 3-fold and 11-fold higher radiation doses than IC, respectively.[4]

Furthermore, Crowhurst et al. discovered in around 100 procedures among transcatheter aortic valve implantation, LAAO, and TEER that radiation doses to IEs were comparable to primary implanters and higher than secondary operators. However, the addition of a ceiling-suspended shield identical to that used by the implaner led to an 82% reduction in radiation exposure to the TEE operator.[5]

The slightly different results of these three studies can be attributed to variations in operating room setups, including differences in the fluoroscopy unit's C-arm configuration, staff positioning, and shielding arrangements [Figure 1].

To estimate the risk to operators during different procedures, it is essential to understand where Compton scattering is most significant. The position of the X-ray tube greatly influences the distribution of scattered radiation, with the highest scatter occurring in areas closest to the source (backscatter). According to the inverse square law, radiation intensity decreases proportionally to the square of the distance from the source – meaning that doubling the distance from the patient beam entry point results in a fourfold reduction in exposure.[19]

In interventional cardiology, fluoroscopic projections are typically named based on the position of the X-ray detector

 Figure 1: (a-c) Overhead illustration depicting the positions of the interventional echocardiographer and interventional cardiologist in relation to the patient across different cardiac catheterization lab setup for structural heart interventions

relative to the patient's chest. For example, in a left anterior oblique (LAO) projection, the detector is positioned to the patient's left, while the X-ray tube is located beneath the table on the right side. Consequently, operators standing on the patient's right are exposed to higher levels of scattered radiation. Conversely, in right anterior oblique (RAO) projections, greater scatter radiation occurs on the left side of the patient.[19]

A similar pattern is observed in cranial and caudal projections. Caudal projections, in particular, generate increased scatter toward the head of the table, posing a higher radiation risk to operators positioned near the patient's head – such as the IE and anesthesiologist.

Moreover, avoiding steep angulations can reduce scattered radiation. Steep lateral angles, such as pronounced cranial or caudal views, increase the beam path length within the patient, resulting in greater patient exposure and therefore greater scatter. Paying close attention to the angulation and placing the C-arm in 0° to 20° angulation will result in a more than 3-fold reduction in the amount of radiation scattered during fluoroscopic acquisition. Hence, LAO projections with angles >40° are particularly concerning for IC positioned on the right side of the table.[20]

While the positioning of IC and anesthesiologists in the operating room follows a standardized setup, the IE is typically located either at the patient's head or on their left side. The IE's position relative to the X-ray source significantly affects radiation exposure and should be adjusted according to the fluoroscopic projections most commonly used during the procedure. For instance, during LAAC – which extensively uses RAO projections – remaining on the patient's left side could lead to significantly higher radiation exposure for the IE compared to other staff members.

Finally, the fluoroscopy settings are typically managed by the IC. However, the adoption of a low radiation protocol, such as reducing frame rates from 15 to 7.5 or 3.5 frames per second and switching the default fluoroscopy dose setting from normal to low, have been shown to effectively reduce radiation exposure for patients and medical staff.[21]

Ingallina, et al.: Radioprotection for interventional echocardiographers

It is important to note that interventional radiology staff work in a diffuse radiation field that can vary a lot depending on the location, especially since they are often very close to the patient. This makes it quite challenging to measure actual exposure accurately.

For instance, to monitor exposure to the extremities, a personal dosimeter is typically worn on the wrist – but the radiation field at the wrist can be quite different from what reaches the fingertips. Because of this, dose estimates usually include correction factors to better reflect the true exposure.

STRATEGIES TO REDUCE RADIATION EXPOSURE RISK

IE can reduce radiation exposure following the cardinal principles of radiation safety: time, distance, and shielding. This involves minimizing exposure time, increasing the distance from the radiation source, and maximizing the use of appropriate shielding. The objective is to maintain radiation exposure in accordance with the "As Low As Reasonably Achievable (ALARA)" principle.

To minimize radiation exposure time, it is essential to limit the number of IEs in the operating room. A control room with monitors for fluoroscopy and TEE, along with a large window viewing the operating room to follow the procedure in real time, can serve as an efficient solution. This allows staff training while minimizing radiation exposure time. Only IE directly involved in the procedure or those who are completing the final part of their training program should be permitted to remain near the patient's head during the procedure. Moreover, implementing a shift rotation among IEs can help reduce individual exposure times.

Doubling the distance from a radiation source cuts exposure to one-fourth of the original dose, as per the inverse square law. Therefore, small increases in distance very significantly reduce exposure. This is especially true near the radiation source: moving from 50 to 70 cm is more effective than moving from 100 to 120 cm. However, close proximity to the patient, along with table and X-ray tube positioning, is necessary for IE to manipulate TEE probe during the procedure.

Since the highest levels of scattered radiation occur on the side of the X-ray tube – at the beam entry point on the patient – the IE's position should be carefully planned based on the fluoroscopic projections anticipated during the procedure [Figures 1 and 2].

For example, procedures such as LAAO and tricuspid TEER rely heavily on RAO projections, in which the X-ray tube is located on the patient's left side. In these cases, the IE should ideally be positioned at the patient's head, away from the primary scatter zone on the patient's left side. Conversely, for procedures such as mitral TEER, which typically do not require RAO projections, the IE may safely stand either at the head or on the patient's left side. In procedures such as paravalvular leak closure, where optimal fluoroscopic projections vary case

 by case, the IE's position should be carefully chosen based on the specific projections decided during preoperative assessment to guide the intervention.

Shielding can reduce X-ray occupational radiation exposure caused by scatter and is essential when maintaining distance from the X-ray tube during TEE manipulation is not possible. Shielding includes both personal protective devices (PPD) and laboratory shielding.

PPD is essential for safety. The adoption of lightweight lead aprons, or alternatively, a two-piece wraparound apron comprising a skirt and vest, may mitigate orthopedic problems associated with the extended use of traditional, heavier protective aprons exceeding 7 kg in weight.[10]

To reduce exposure to the lens and extremities, anti-X glasses or anti-X gloves may be worn.

Catheterization laboratories are outfitted with movable ceiling-mounted upper-body leaded acrylic shields and lower-body lead skirts positioned on the right side of the table, where the IC or implanting team typically stands. The shield should be as close as possible to the patient to stop the scatter at the source for the greatest degree of attenuation. These protections reduce scatter radiation by approximately 80%-90%.

However, the catheterization laboratories were not designed with IE in mind.

IE and anesthesiology team, often located near the patient's head, may not benefit as effectively from these fixed protections and frequently rely on mobile lead shields.

Mobile ceiling-mounted leaded acrylic shields provide effective protection for the IE without hindering C-arm mobility. In comparison, mobile shields on wheels can be heavy, challenging to reposition, may obstruct the manipulation of the TEE probe, and might need to be removed during procedures due to interference with C-arm movement, which

Ingallina, et al.: Radioprotection for interventional echocardiographers

 can limit their effectiveness [Figure 3]. The practical efficacy of supplementary ceiling-mounted lead protection for shielding interventionalists has been demonstrated by Crowhurst et al., showing an approximate 80% reduction in radiation exposure during SHI.[5]

Finally, proper training of IE is essential to minimize radiation exposure in the operating room. Staff should be educated on the principles of protection – including optimal positioning, use of shielding, and adherence to the ALARA principle. Training sessions and evaluations of dosimeter results have shown to effectively reduce radiation exposure.[22] The training program should actively involve even the IC, emphasizing the importance of adopting low-radiation protocols whenever possible, and raising awareness about the increased exposure for IE associated with steep projections. A well-informed team is more likely to adopt effective strategies that reduce unnecessary exposure.

INNOVATIONS AND FUTURE PROSPECTIVE

A novel approach to enhancing staff safety involves the use of dedicated shielding systems, such as the Eggnest® (Egg Medical, Inc.). The Eggnest is a lead-equivalent enclosure that surrounds the patient, effectively reducing scatter radiation in all directions – including toward the head of the table, where the IE and anesthesiologist are typically positioned. Studies have demonstrated that this system can significantly reduce whole-body radiation exposure for the entire procedural team, without compromising patient access or procedural workflow, and without requiring additional shielding [Figure 3d].[23]

The Rampart™ M1128 system (Rampart IC, LLC) is another staff protection device designed for cath-lab procedures. It consists of a mobile barrier positioned between the operator and the radiation field, which attenuates scatter radiation using a combination of lead-equivalent acrylic panels and soft shielding materials engineered to protect staff members

[Figure 3f]. This system has proven to be highly effective for ICs, though it has not yet been evaluated for the protection of IEs.[24]

Another protective strategy involves the use of disposable radiation drapes placed directly on the patient's skin. These drapes contribute to reducing radiation exposure to staff while maintaining patient safety.[24]

In response to these challenges, a novel robotic system has recently been developed to remotely manipulate the TEE probe. The remote control robotic (RCR) system for TEE represents a promising solution in the context of SHI. This innovative RCR system was evaluated through in vitro testing to assess its performance, with particular emphasis on the quality and reproducibility of the images produced.[24]

One of the most promising future directions for minimizing staff exposure in interventional cardiology is the advancement of techniques aimed at reducing radiation emissions from the imaging equipment itself. In recent years, both software- and hardware-based innovations have enabled substantial reductions in patient radiation doses while preserving image quality. These advancements include improved radiation filtration systems and advanced image postprocessing techniques that reduce noise in low-dose images.

Finally, the implementation of more efficient detectors holds the potential to further reduce radiation exposure, thereby enhancing safety for both patients and healthcare personnel. Efforts are also underway to develop more precise methods for assessing occupational exposure, such as those investigated in the computational dosimetry initiative (Personal Online Dosimetry Using computational Methods Project – European Commission Concert). This approach enables dose estimation without the use of personal dosimeters, instead relying on the spatial positioning of individual staff members – tracked by a system of cameras – and the simulation of radiation fields using Monte Carlo methods [Figure 4].[24]

Ingallina, et al.: Radioprotection for interventional echocardiographers

![a\nb\nFigure 4: (a and b) Simulated and real-life computational dosimetry (Podium Project) (courtesy Filip Vanhavere [SCK-CEN, Belgium])\n](1/parseimages/figure4907af2b7da44185b1e3aa6d8e029e49_0_1.png)

CONCLUSIONS

The IE plays a crucial role in SHIs, yet faces significant risks from ionizing radiation, often greater than those encountered by the primary IC.

Despite growing awareness of radiation safety in the catheterization lab, the specific protection needs of IEs remain under-recognized. Improving radiation protection for IE must become a priority. A combination of targeted education, optimized procedural planning, improved shielding strategies, and innovative technologies is necessary to ensure long-term safety and sustainability in this rapidly evolving field of SHI.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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