Comparative evaluation of radiation shielding zero gravity vs lead apron in coronary angiography and percutaneous coronary intervention

Abstract

Introduction

Ensuring safety from radiation in catheterization labs is critical due to the cumulative nature of radiation exposure. This study compares the effectiveness of Zero Gravity (ZG) and conventional Lead Apron shields in coronary angiography and percutaneous coronary intervention.

Methods

Over six months, radiation exposure was assessed for two operators performing angiography procedures. One operator used a Lead Apron, while the other used the Zero Gravity system. Radiation was measured using Thermoluminescent Dosimeters (TLDs). Procedural characteristics, fluoroscopy time, and contrast dose were recorded. Feedback on Lead Apron use was collected using the Oswestry Low Back Pain Disability Questionnaire.

Results

Each operator performed 63 procedures with similar characteristics. Zero Gravity showed no significant difference in whole-body radiation exposure (De) compared to the Lead Apron (0.349 mSv vs. 0.346 mSv). However, Zero Gravity resulted in a lower external skin dose (Ds) compared to the Lead Apron (0.314 mSv vs. 0.339 mSv). Most cardiologists reported minimal disability from using Lead Aprons.

Discussion

Zero Gravity and Lead Apron provide comparable whole-body radiation protection, with Zero Gravity slightly reducing skin exposure. While ZG does not significantly alter overall radiation exposure, it may reduce ergonomic issues associated with Lead Aprons.

Conclusion

Zero Gravity provides comparable whole-body radiation protection to Lead Aprons and reduces skin exposure. Further research is needed to address long-term impacts and enhance protective strategies in catheterization labs.

1. Introduction

Ensuring safety in the catheterization laboratory environment is paramount for both staff and patients. Despite the invisible nature of radiation, its potential risks necessitate unwavering attention to proper protective measures. Established standards for radiation protection, as defined by the Society for Cardiac Angiography and Intervention, emphasize that minimizing exposure reduces the risk of biological interactions with absorbed energy. Notably, is no known level of ionizing radiation that can be considered a permissible or absolutely safe dose. Radiation exposure is cumulative, and the absence of a ‘washout’ phenomenon underscores the need for continuous vigilance. While participants in the cardiac catheterization laboratory exposure, they are duty-bound to minimize risks for themselves and others. The primary source of radiation is the X-ray beam emitted from the under-table X-ray tube, which travels through the patient and onto the image intensifier [1].

Each cardiac catheterization laboratory should adopt a radiation safety policy tailored to its specific needs and implement it effectively. This policy should encompass routine monitoring of personnel radiation exposure, continuous education programs to enhance personnel awareness of radiation safety and its associated risks. Additionally, it should mandate the use of protective equipment by all personnel and establish procedures to ensure the safety of all equipment, Including checks on X-ray dose output, the integrity of Lead Aprons, and thyroid shields.

The standard radiation protection strategy in the angiography suite typically involves the use of a conventional Lead Apron (typically 0.5 mm thick), along with a thyroid shield, and lead eyeglasses [2]. Lead Aprons should contain a 0.5-mm-thick lead lining and require proper care to ensure longevity. Cracks or tears in the lead lining are often the result from careless handling or improper storage. To assess Lead Aprons integrity, a fluoroscopy examination should be conducted at least once a year, and documentation regarding the condition of each Apron should be maintained. Each Lead Apron should be appropriately identified, using a number, color, or name. Aprons should be long enough to cover the long bones (femur) and extend to or just below the knee.

The Zero Gravity (ZG), developed by CFI Medical Solutions in Fenton, Michigan, USA, is a radiation protection system consisting of an overhead-suspended Lead suit with a curved Lead acrylic head shield. It utilizes a ceiling-mounted monorail arrangement to provide radiation protection while allowing motion in all three spatial axes. This system effectively alleviates the weight from the operator's body [3,4]. Although Zero Gravity has demonstrated efficacy minimizing radiation exposure among operators, specific data pertaining to neurovascular procedures are currently unavailable.

Our objective is to prospectively assess the performance of the ZG system in the cardiac catheterization lab by comparing the radiation exposure of physicians utilizing ZG Versus conventional Lead Apron protection.

2. Methods

The study was conducted in the cardiology catheterization lab at a tertiary care center. The aim was to assess radiation exposure of two primary operators in catheterization labs performing angiography procedures. Two different shields were used during the study period: Lead Apron and Zero Gravity. The study was done over six months, and active participation was ensured by two operators. Both were equipped with protective eyeglasses and thyroid shields. One operator consistently wore a Lead Apron, while the other opted for the Zero-Gravity protection shield throughout all angiography procedures. Radiation exposure was quantified by employing Thermoluminescent Dosimeters (TLDs), which were constantly worn by both operators during each procedure. These TLDs placed on the chest under the shield allowed for the real-time measurement of radiation absorption over the study duration. Upon the completion of the study period, the TLDs were collected. The data derived from these dosimeters were examined to evaluate the radiation levels experienced by each operator when utilizing their respective protection shields. In addition, a validated questionnaire ‘Oswestry Low Back Pain Disability’ (Appendix A) was distributed to multiple operators (N = 22) to gather a broader perspectives on the usability, comfort and effectiveness of Lead Apron shield. The responses collected were then analyzed to explore their insights into the perceived benefits and challenges associated with the use of these shields. Approval to conduct the study was obtained from HMC IRB (MRC-01-20-352).

3. Statistical analysis

Normal continuous variables are presented as mean ± standard deviation (SD), while skewed variables are described as median and interquartile range (IQR). Categorical variables are presented as proportions. Between-group comparisons for continuous or ordinal variables were conducted using the student t-test, Mann–Whitney U test, or ANOVA, as appropriate. Categorical variables were compared using the χ2 test or Fisher's exact test, as appropriate. Stata/SE version 14.2 was employed for data analysis, with statistical significance set at p < 0.05.

4. Results

Each operator performed 63 procedures during the study period. Procedural characteristics were similar for both operators. Most of the cases was done via radial approach, there was no statistically significant differences found in access types, procedure complexity, total fluoroscopy time, and contrast dose (Table 1). The operator who used the Zero-Gravity shield used magnification size of 25 while the operator who used Lead Apron used 20. The fluoroscopy pulse rate (P/S) used both operators was 7.5.

Table 1.

Comparison of radiation exposure and procedure characteristics between Zero Gravity and Lead Apron Protection shields in cardiac catheterization.

	Zero Gravity	Lead Apron	P-value
Number of cases	63	63
Access type:
Femoral	4	5	0.729
Radial	59	58
Complexity
Diagnostic angiogram	19	26	0.241
Single-vessel PCI	37	28
Two-vessel PCI	7	7
Three-vessel PCI	0	2
Total fluoroscopy time (min) per case Median, IQR	7.4 (4.9–11.5)	7 (3.1–10.3)	0.481
Contrast dose (ml) per case Median, IQR	100 (48–120)	80 (45–120)	0.642

Table 2 displays the measured radiation exposure doses for De (External whole body equivalent dose at tissue depth of 10 mm), Ds (External Skin equivalent dose at tissue depth of 0.07 mm), and Dx (External equivalent dose to the extremities, including hands and feet). The values for Dx were consistently recorded as 0.000 mSv for both Zero Gravity and Lead Apron, indicating negligible exposure to the extremities during the study. For De, the radiation exposure dose for operators using Zero Gravity was 0.349 mSv, while for those using Lead Apron, it was 0.346 mSv. Similarly, for Ds, the radiation exposure dose with Zero Gravity was 0.314 mSv, and with Lead Apron, it was 0.339 mSv.

Table 2.

Comparison of Radiation Exposure Doses (mSv) for Zero Gravity and Lead Apron Protection Shields in Cardiac Catheterization by two operators.

	Zero Gravity	Lead Apron
De (mSv)*	0.349	0.346
Ds (mSv)*	0.314	0.339
Dx (mSv)*	0.000	0.000

De: External whole body equivalent dose (at tissue depth of 10 mm).

Ds: External Skin equivalent dose (At tissue depth of 0.07 mm).

Dx: External equivalent dose to the extremities (hand & feet).

5. Oswestry Low Back Pain Disability Questionnaire

The analysis of responses from 22 participating cardiologists who used conventional Lead Apron shields, revealed varying levels of disability associated with low back pain. The majority (45 %) reported minimal disability, with a score of 0 %. Additionally, 14 % showed minimal to moderate disability, with scores ranging from 2 % to 7 %. A small proportion (9 %) fell into the moderate disability category, scoring 9 % to 20 %. These findings suggest that, in the context of this study, most cardiologists experience low levels of disability associated with low back pain.

6. Discussion

This study aimed to prospectively compare the efficacy of two radiation protection modalities, Zero Gravity and Lead Apron, used during coronary angiography procedures in the cardiac catheterization lab. Our data analysis revealed no significant difference in the external whole body radiation exposure between the two operators using Zero Gravity vs Lead Apron during coronary angiography procedures. However, external skin radiation exposure was lower with Zero Gravity. Measurement of radiation absorption, conducted through cumulative radiation exposure over 6 months using Thermo-luminescent Dosimeters (TLDs), showed a similar fluoroscopy pulse rate. However, there was some difference in magnification size used by two operators.

A key strength of our study is the consistency of the procedural conditions for both operators, which assures that any observed differences in radiation exposure can be attributed to the type of shield used rather than other variables. There was no statistical difference in the fluoroscopy rate or contrast dose used by the operators, and both performed the same number of procedures. Additionally, the operators had similar demographic characteristics: both are in their late forties, with BMI ranging from 23 to 25, and each had >10 years of experience in the field. These factors further minimized potential confounding variables, ensuring a fair comparison of the two shielding modalities. One limitation of our study is that the TLDs used measured cumulative radiation exposure over six months rather than daily exposure. However, we believe this does not affect our findings, as the cumulative measurement captures overall exposure accurately and aligns with our study's primary objective of comparing the two shielding modalities over a prolonged period under real-world conditions.

Similar studies such as the one by Jose Salcido-Rios MD et al. indicated that the use of a suspended lead suit during coronary angiography was associated with marked reductions in head-level physician radiation doses [5]. Another study by Ryan D Madder et al., observed that the utilization of suspended lead and robotics were observed to result in significantly less radiation exposure to the chest and head of operating physicians during PCI. [6]. Notably, these studies focused exclusively on head and chest radiation exposure only. In contrast to our study, Jose Salcido-Rios et al. concentrated on approximately two-thirds of coronary angiography procedures performed with Zero Gravity. Our study stands out by measuring whole-body radiation exposure, and we ensured that procedural conditions were similar for both operators.

Additionally, a study by Federica Zanca et al. found that the ZG systems have a great potential to significantly reduce operator dose through the creation of a nearly zero-radiation work environment [7]. However, in this study an anthropomorphic mannequin not a human was used simulating an operator and radiation measurement was done using TLDs which were inserted into the head and into the eye bulbs of the mannequin, while electronic dosimeters were positioned on the temple and at the level of the thyroid.

Recently Maher Rabah et al. studied the efficacy of radiation shielding system in the cardiac catheterization laboratory to provide comprehensive protection that obviates the need for personal Lead Aprons. In this study, the Protego™ shield system was used, providing excellent radiation exposure protection to the physician operator, without the need for personal Lead Aprons and has the potential to reduce catheterization laboratory occupational health hazards [8]. These findings align with our observation of reduced skin exposure using ZG systems.

Our study uniquely contributes to the field by comparing ZG and LA in real-world scenarios, emphasizing whole-body exposure. By ensuring similar procedural conditions—including fluoroscopy rates, contrast dose, and number of procedures—and accounting for comparable operator demographics, we minimized potential confounding variables. These findings underscore the potential of advanced radiation protection modalities to mitigate occupational hazards, particularly for operators in high-radiation environments.

7. Conclusion

In summary, the integration of Zero Gravity suits in coronary angiography did not yield a significant disparity in whole-body radiation exposure when compared to conventional Lead Aprons. Nevertheless, there was a notable reduction in skin radiation exposure with the use of Zero Gravity. It is crucial to acknowledge the potential drawbacks of protective garments, particularly the risk of orthopedic injuries, including spinal injuries over an extended period. Consequently, further research in this field is recommended to gain a deeper understanding of these concerns and develop effective solutions.

CRediT authorship contribution statement

Omnia Tajelsir Abdalla Osman: Writing – review & editing, Writing – original draft, Visualization, Methodology, Investigation, Funding acquisition, Conceptualization. Sara Al Balushi: Writing – review & editing, Validation, Software, Project administration, Methodology, Investigation, Formal analysis, Data curation. Salaheddin Omran Arafa: Supervision, Project administration, Methodology, Investigation, Conceptualization. Murad Al Khani: Supervision, Project administration, Methodology, Investigation, Conceptualization. Jassim Al Suwaidi: Supervision, Resources, Project administration, Funding acquisition. Fahad Alkindi: Writing – review & editing, Validation, Supervision, Project administration, Methodology, Investigation, Funding acquisition, Conceptualization.

Ethical statement

This study (Study No. MRC-01-20-352) was approved by the Institutional Review Board (IRB) of the Medical Research Center at Hamad Medical Corporation in Qatar. The research involved data collected from thermoluminescent dosimeters (TLDs) worn by operators during procedures. No patient data or human subjects were involved, and therefore no informed consent was required. The study adhered to institutional guidelines for occupational safety and radiation exposure monitoring.

Declaration of Generative AI and AI-assisted technologies in the writing process

During the preparation of this work the authors used ChatGPT/OpenAI in order to improve readability and language of the work only. After using this ChatGPT/OpenAI, the authors reviewed and edited the content as needed and take full responsibility for the content of the publication.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.