© Z. You et al., Published by EDP Sciences, 2025

1 Introduction

Fluoroscopic guidance techniques in cardiac catheterization interventions require the use of X-rays, which can produce a certain amount of radiation (Behan et al., 2010). Due to the particularity of this kind of interventional procedure, the operator and nurse need to be exposed to radiation throughout the process (Monzen et al., 2017). Currently, these professionals are the highest dose-exposed group of radiologists (Zhang et al., 2011). With the increasing number of cardiac catheterization interventions in China, there’s a corresponding rise in radiation doses received by these individuals, leading to emerging radiation-related occupational health concerns (Rajaraman et al., 2016; Uwineza et al., 2019; Ma et al., 2021). Emphasizing radiation protection has become crucial in cardiac catheterization interventions (Liu et al., 2018). The scattering and invisibility of radiation and the dynamic angles of the digital subtraction angiography (DSA) machine during these interventions result in varying radiation doses across different locations within the cardiac catheterization room and the radiation doses to the operator and nurses are dynamically changing. This study aims to analyze radiation dose levels in 22 specific areas under eight projection angles of the DSA machine, offering radiation protection strategies for operators and nurses.

2 Material and methods

The brand of DSA machine used in this study was PHILIPS, model number UNIQ FD20, X-ray tube model number MRC 200 0407; one standard manikin simulating the patient and two ordinary manikins simulating the first operator and the second operator were used; the radiation dosemeter brand is RAYCAN, the model was RadTarger, and the calibrated radiation unit was μSv; the brand of radiation protective clothing used was KangHun lead-free radiation protective clothing, and the lead equivalent was 0.5 mmPb; the brand of ceiling suspension lead screen and under- operating table lead curtain used was Huaren, and the lead equivalent was 0.5 mmPb.

In this study, the DSA machine acquisition mode was set to cine acquisition CardFixed, the tube voltage was 73 kV, the acquisition frame rate was 15 fps/s, and the vision of the flat-panel receiver was 20 × 20 cm. The projection angles of the DSA machine used in the study are divided into 8 types, namely: (1) The right front oblique position (RAO 30°); (2) The liver position (RAO 30° CAU 20°); (3) The right shoulder position (RAO 30° CRA 20°); (4) The head position (CRA 30°); (5) The left shoulder position (LAO 45°CRA 20°); (6) The left front oblique position (LAO 45°); (7) The spider position (LAO 45° CAU 20°); (8) The foot position (CAU 30°).

The patient’s manikin was placed on the midline of the operating table to simulate the conventional thoracoabdominal position of the patient in the cardiac catheterization interventions. A parallel line of the longitudinal axis of the body was drawn 10 cm medial to the left anterior axillary line of the patient manikin, and a parallel line of the transverse axis was drawn 20 cm below the left shoulder, and a steel ball of approximately 1 cm³ in size was placed at the intersection of the two lines and set as the heart center. Perform the following at each projection angle, lower the flat-panel receiver and the operating table to the lowest point and move the operating table so that the central area of the heart, i.e., the steel ball, is in the center of the vision of the flat-panel receiver. The first operator manikin was placed close to the operating table in the usual puncture standing area for cardiac catheterization interventions, i.e., the patient’s right radial artery puncture position, and the second operator manikin was placed close to the operating table in the position of the DSA machine operating panel, and both operator manikin were routinely wear radiation protective clothing, In addition, the ceiling suspension lead screen is close to the first operator manikin, and the lower edge is close to the operating table. This placement method has been proven to have a better radiation protection effect (Fetterly et al., 2011).

In this study, the floor of the cardiac catheterization room was gridded by different partition lines, dividing the room into a total of 22 areas, see Figure 1, where area (11) and area (15) are set as the first operator and second operator standing areas.

Radiation dose collection method is as follows: the center of each area, 1.6m height position set as a measurement point, a total of 22 measurement points, in the measurement point at the placement of the radiation dosimeter, the DSA machine using the cine mode release 5 times, each release 10s, to be radiation dosimeter stabilized to take the value, each area to collect to 5 dose values. In order to prevent overloading of the x-ray tube, the next area radiation dose collection is started again at an interval of 1 minute, each projection angle can be collected to 110 radiation dose, a total of 880 radiation dose values can be collected.

All data in this study were processed in SPSS 26.0, and the radiation dose of the 22 areas under each projection angle conformed to normal distribution by Kolmogorov–Smirnov test, described by mean ± sem. One-way analysis of variance (ANOVA) was used for comparison of radiation dose values in 22 areas at the same projection angle and for comparison of radiation dose values in the same area at different projection angles, Under the same projection angle, the comparison of radiation dose in the 2 areas was performed by independent sample t-test. p < 0.05 was considered a statistically significant difference.

Fig. 1 Partitioning of the cardiac catheterization room.

3 Results

The radiation dose of 22 areas under 8 projection angles is shown in Figure 2.

Among them, an analysis of the radiation dose in 22 areas with 8 projection angles revealed that the lowest radiation dose (p < 0.05)was found in the areas (19) in the right anterior oblique position (RAO 30°), liver position (RAO 30°CAU 20°), right shoulder position (RAO 30°CRA 20°), and foot position (CAU 30°); the lowest radiation doses (p < 0.05) was found in the area (18) in the left shoulder position (LAO 45°CRA 20°) and the spider position (LAO 45°CAU 20°); the lowest radiation dose (p < 0.05) was found in the areas (21) in the left anterior oblique position (LAO 45°); the lowest radiation dose (p < 0.05) was found in the areas (20) in the cephalic position (CRA 30°); the highest radiation dose (p < 0.05)was found in the areas (7) in the right anterior oblique position (RAO 30°), liver position (RAO 30°CAU 20°), right shoulder position (RAO 30°CRA 20°), and head position (CRA 30°); the highest radiation dose (p < 0.05)was found in the areas (8) in the left anterior oblique position (LAO 45°), left shoulder position (LAO 45°CRA 20°), spider position (LAO 45°CAU 20°) and foot position (CAU 30°), as shown in Figure 3.

Analysis of the radiation dose in area (7) and area (11) shows that the radiation dose in area (7) is greater than the radiation dose in area (11) at all projection angles (p < 0.05). When analyzing the radiation dose in area (11) and area (15), it was found that the radiation dose in area (15) was greater than that in area (11) at all projection angles (p < 0.05), as shown in Figure 4.

In the analysis of the radiation dose in area (11) and area (15) at eight projection angles, it was found that area (11) had the highest radiation dose (p < 0.05) in the cephalic position (CRA 30°), and area (15) had the highest radiation dose (p < 0.05) in the left anterior oblique position (LAO 45°), as shown in Figure 5.

In the analysis of the radiation dose in area (7) and area (8) under each projection angle, it was found that the radiation dose in area (7) was greater than that in area (8) at the RAO projection angle (p < 0.05); while the radiation dose in area (8) was greater than that in area (7) at the LAO projection angle (p < 0.05), as shown in Figure 6.

Fig. 2 Radiation dose of 22 areas under 8 projection angles.

Fig. 3 Highest and lowest radiation doses areas under 8 projection angles.

Fig. 4 Comparison of radiation dose in area (7), area (11) and area (15) under 8 projection angles.

Fig. 5 Comparison of radiation dose under different projection angles for area (11) and area (15).

Fig. 6 Comparison of radiation dose in area 7 and area 8 under 8 projection angles.

4 Discussion

During cardiac catheterization interventions, the use of X-rays is indispensable, leading to radiation exposure among operators and nurses. Several studies have highlighted that in specific regions, the annual radiation doses received by these professionals exceed the thresholds recommended by the ICRP (Domienik et al., 2016; D’Avino et al., 2019). Moreover, there have been instances where operators and nurses have manifested radiation-induced health complications (Papp et al., 2017; Lee et al., 2021), emphasizing the imperative to monitor and ensure their occupational safety.

The duration of exposure is a primary factor influencing the radiation dose during cardiac catheterization interventions. However, the dynamic nature of the procedure, characterized by the continuous adjustment of the DSA machine’s C-arm angle, results in variable radiation doses across the operating room. This variability implies that professionals positioned at different locations are subjected to distinct radiation doses. Notably, while an operator’s position is relatively static, nurses have the flexibility to move around, leading to differential exposure.

Our data indicates that the radiation doses are consistently lowest in areas (18)–(21), situated at the extremity of the operating table. This observation can be rationalized by the inverse square law of radiation (Zhao et al., 2017), suggesting that these areas, being most distant from the X-ray source and shielded by equipment, are least exposed.

The study delineated that the radiation doses in the highest radiation dose areas (7) and (8) are contingent on the projection angle. Specifically, the radiation dose in area (8) surpasses that in area (7) at the LAO angle and vice versa for the RAO angle. This variation can be attributed to the interplay between the X-ray tube’s orientation, the operating table, and the specific area under consideration. To optimize safety, it is advisable for nurses to preferentially occupy low-radiation areas like area (18)–(21), and avoid standing in areas of high-radiation like area (7) and (8). Furthermore, strategic placement of equipment and consumables in these low radiation dose areas can minimize the necessity for nurses to traverse high-radiation areas.

Areas (11) and (15) were demarcated as the standard operational areas for the first and second operators, respectively. Typically, a ceiling-suspended lead screen is positioned between area (7) and the first operator, serving as a radiation barrier. Our findings corroborate the efficacy of this screen in substantially attenuating the radiation exposure of the first operator, consistent with prior research (Jia et al., 2017). However, the second operator, despite being more distal to the X-ray tube, often registers higher radiation doses, contrary to the results of previous studies (Ullery et al., 2014). This anomaly is attributed to the suboptimal coverage offered by the under-table lead curtain, which inadequately shields the second operator’s area, and that the operating table cannot be lowered to the lowest point due to the limitations of the X-ray tube at some projection angle, resulting in the lead curtain under the operating table overhanging from the floor, and the scattering of radiation can be leaked through the gap between the lead curtain and the floor, resulting in a higher dose of radiation for the second operator than for the first operator. This result reminds us to pay more attention to the radiation dose of the second operator and to take better radiation protection measures, such as extending the length and width of the lead curtain under the operating table to adapt to changes in the position of the operating table or designing radiation protection equipment for use by the second operator in order to minimize the radiation dose to the second operator.

Our comprehensive analysis underscored that the radiation doses vary with projection angles. The first operator’s area registers the peak dose at the head position (CRA 30°), while the second operator’s area is most exposed at the left anterior oblique position (LAO 45°). These dose variations are influenced by specific machine configurations and the relative positioning of protective barriers. To mitigate radiation risks, operators can judiciously minimize exposure durations at these specific angles and harness advanced features of the DSA machine, such as screen freeze and virtual collimation, or design radiation protection equipment on the left side of the operating table to reduce the radiation dose to the operator.

The researchers have developed a DSA machine radioprotective cabin, which can significantly reduce the radiation dose from the four elevations around the operating table, including the radiation dose of the first operator and second operator standing areas. Thus, solving the problem of high radiation dose to the second operator pointed out in this study, and at the same time, the cabin also reduced the radiation dose in the area at the end of the operating table. Combined with the fact that the area at the end of the operating table is the area with the lowest radiation dose as pointed out in this study (Liu et al., 2023). The effect of the cabin in reducing the radiation dose during cardiac catheterization interventions can be comprehensively explored in a follow-up study.

The results of the radiation dose analysis in this study provide radiation protection suggestions to operators and nurses, but more importantly, any radiation protection suggestions must be accepted and cooperated with by operators and nurses in order to achieve the best radiation protection effect, and this accepted and cooperation is related to the hospital’s training and system, but due to the rapid updating of radiation protection measures in cardiac catheterization interventions, the training progress and system of most hospitals are relatively backward. resulting in less-than-optimal radiation protection measures for operators and nurses (Bertho and Geryes, 2023). In the researcher’s follow-up study, research on attitudes toward radiation protection in cardiac catheterization interventions will be prioritized.

5 Conclusion

In this study, the researchers investigated the radiation dose levels in various areas of the cardiac catheterization room during cardiac catheterization interventions. Our results showed that nurses should choose the area at the end of the operating table to stand during the intervention, as well as the equipment and supplies in the cardiac catheterization room should also be placed in this area to avoid higher radiation exposure for nurses. The radiation doses of the first and second operators remind us to pay more attention to the radiation exposure of the second operator, and to improve the radiation protection measures of the DSA machine in a timely manner, also in the cephalic (CRA 30°) and left anterior oblique (LAO 45°) positions, the operator needs to take additional measures to minimize the increase in radiation dose.

5.1 Limitation

The cardiac catheterization room in which this study was conducted is not generalized, and the different layouts of facilities in different cardiac catheterization room lead to possible differences in radiation dose from this study. In subsequent studies, the distribution of radiation dose in cardiac catheterization rooms with different layouts will be analyzed, and simulations will be used to explore the patterns, so that standards for the placement of cardiac catheterization room equipment supplies and standing areas for operators and nurses can be developed, and the probability of radiation-related occupational illnesses occurring in operators and nurses can be reduced.

Funding

Scientific research project of Hunan Provincial Health Commission, 202212013945. Natural Science Foundation of Hunan Province, 2021JJ40489. Hunan Province General Colleges and Universities Teaching Reform Research Fund, HNJG-2021-0635; China Vocational Education Teachers’ Teaching Innovation Team Research Project. ZH2021070301

Conflicts of interest

All authors have made significant contributions, and all authors declare no conflict of interest.

Data availability statement

The research data associated with this article are included within the article.

Author contribution statement

Ze You, Yaqing Liu: the conceived idea, research design, manuscript writing, figure drafting. Chunyan Li, Aizhao Hu, Xun Liu, Wu Li: data collection, critical review. Fenggang Liu, Li Liao: data analysis and interpretation, manuscript writing and revision, proofreading, supervised whole process of study. All authors read and approved the final manuscript.

Ethics approval

The ethic of this research (CCI-24-0418) has been approved by IRB of The First Affiliated Hospital of University of South China. The authors declare that this research does not involve human or animal experiments, all data used in this research were obtained from currently physical experiments. Hence, no informed consent was signed.

References

All Figures

	Fig. 1 Partitioning of the cardiac catheterization room.
In the text

	Fig. 2 Radiation dose of 22 areas under 8 projection angles.
In the text

	Fig. 3 Highest and lowest radiation doses areas under 8 projection angles.
In the text

	Fig. 4 Comparison of radiation dose in area (7), area (11) and area (15) under 8 projection angles.
In the text

	Fig. 5 Comparison of radiation dose under different projection angles for area (11) and area (15).
In the text

	Fig. 6 Comparison of radiation dose in area 7 and area 8 under 8 projection angles.
In the text