Non-Lead Protective Aprons for the Protection of Interventional Radiology Physicians from Radiation Exposure in Clinical Settings: An Initial Study

Radiation protection/evaluation during interventional radiology (IVR) poses a very important problem. Although IVR physicians should wear protective aprons, the IVR physician may not tolerate wearing one for long procedures because protective aprons are generally heavy. In fact, orthopedic problems are increasingly reported in IVR physicians due to the strain of wearing heavy protective aprons during IVR. In recent years, non-Pb protective aprons (lighter weight, composite materials) have been developed. Although non-Pb protective aprons are more expensive than Pb protective aprons, the former aprons weigh less. However, whether the protective performance of non-Pb aprons is sufficient in the IVR clinical setting is unclear. This study compared the ability of non-Pb and Pb protective aprons (0.25- and 0.35-mm Pb-equivalents) to protect physicians from scatter radiation in a clinical setting (IVR, cardiac catheterizations, including percutaneous coronary intervention) using an electric personal dosimeter (EPD). For radiation measurements, physicians wore EPDs: One inside a personal protective apron at the chest, and one outside a personal protective apron at the chest. Physician comfort levels in each apron during procedures were also evaluated. As a result, performance (both the shielding effect (98.5%) and comfort (good)) of the non-Pb 0.35-mm-Pb-equivalent protective apron was good in the clinical setting. The radiation-shielding effects of the non-Pb 0.35-mm and Pb 0.35-mm-Pb-equivalent protective aprons were very similar. Therefore, non-Pb 0.35-mm Pb-equivalent protective aprons may be more suitable for providing radiation protection for IVR physicians because the shielding effect and comfort are both good in the clinical IVR setting. As non-Pb protective aprons are nontoxic and weigh less than Pb protective aprons, non-Pb protective aprons will be the preferred type for radiation protection of IVR staff, especially physicians.

Although physicians should wear protective aprons, the IVR physician may not tolerate wearing one for long procedures because protective aprons are generally heavy. In fact, orthopedic problems are increasingly reported in IVR physicians due to the strain of wearing heavy aprons during IVR [26][27][28].
Recently, non-lead (Pb) protective aprons (lighter weight, composite materials) have been developed [29,30]. Although non-Pb protective aprons are more expensive than Pb protective aprons, the former protective aprons weigh less. Furthermore, non-Pb protective aprons are environmentally friendly. Pb toxicity is obviously not in play. Thus, non-Pb protective aprons are optimal. However, whether the protective performance of non-Pb aprons is sufficient in the IVR clinical setting is unclear. Furthermore, the optimal Pbequivalent of protective aprons, 0.25-and 0.35-mm Pb-equivalents, is unclear in the IVR clinical setting.
This study compared the ability of non-Pb and Pb protective aprons (0.25-and 0.35-mm Pb-equivalents) to protect physicians from scatter radiation in a clinical setting (cardiac catheterizations, including percutaneous coronary intervention, PCI) using an electric personal dosimeter (EPD). Physician comfort levels in each apron during procedures were also evaluated.
The purpose of this initial study was to demonstrate the effectiveness of non-lead protective aprons for the protection of IVR physicians from radiation exposure in clinical settings.
For radiation measurements, physicians wore two EPDs (PDM-117, Hitachi-Aloka, Taitoku, Japan): One inside a personal protective apron at the chest, and one outside a personal protective apron at the chest. Figure 1 indicates the position of each EPD in the clinical setting (cardiac catheterizations, including PCI). We evaluated external (average dose of exterior EPDs at the chest) and internal doses (average dose of interior EPDs at the chest). The radiation shielding effects (%) of the protective aprons were also determined as follows: Radiation shielding effects (%) = (1 − inside dose/outside dose) × 100. The radiation shielding effects (%) of the protective aprons were also determined as follows: Radiation shielding effects (%) = (1 − inside dose/outside dose) × 100.

Cardiac Catheterization
Radiation exposure (external and internal radiation dose) for the two physicians during more than 50 cardiac catheterizations (including PCI) with the four types of protective apron were measured randomly at Akita Medical Center (Akita, Akita, Japan) ( Table 1). We did not establish inclusion or exclusion criteria for this initial study. During each procedure, physicians were at liberty to choose any of the four types of protective apron. In this study, an additional lead acrylic protection device was also used, if possible, during procedures ( Figure 2). Physician comfort levels in each protective apron during cardiac catheterizations procedures (including PCI) were also determined through interviews.
This study was approved by the Ethics Committee of Akita Cerebrospinal and Cardiovascular Center (Akita Medical Center). We also evaluated the radiation dose indicator (cumulative air karma [AK]) and fluoroscopy time undergoing cardiac catheterizations, including PCI. Physician comfort levels in each protective apron during cardiac catheterizations procedures (including PCI) were also determined through interviews.
The procedures (cardiac catheterizations, including PCI) were performed using a digital cine X-ray single-plane system (Infinix Celeve-i, Toshiba, Ohtawara, Japan) with a 7-inch mode flat-panel detector, an acquisition (cine) rate of 15 frames/s, and pulsed fluoroscopy (15 pulses/s). This study was approved by the Ethics Committee of Akita Cerebrospinal and Cardiovascular Center (Akita Medical Center). We also evaluated the radiation dose indicator (cumulative air karma [AK]) and fluoroscopy time undergoing cardiac catheterizations, including PCI.

Results
The X-ray procedure details used in cardiac catheterizations (including PCI) are shown in Table 1. Table 2 summarizes the findings of this clinical study. Although the radiationshielding effect of the 0.35-mm Pb protective apron was the best (98.9%) among the four types, physician comfort was the worst (very poor) because this protective apron was the heaviest. Conversely, although physician comfort in the non-Pb 0.25-mm Pb-equivalent protective apron was highest (excellent) among the types because the protective apron was the lightest, the radiation shielding effect was the worst (96.1%). The performance (both the shielding effect (98.5%) and comfort (good)) of the non-Pb 0.35-mm-Pb-equivalent protective apron was good in the clinical setting. The radiationshielding effects of the 0.35-mm Pb and non-Pb 0.35-mm-Pb-equivalent protective aprons were very similar. The extent of physician comfort when wearing the non-Pb 0.35-mm-Pb-equivalent protective apron was similar to that when wearing the non-Pb 0.25-mm-Pbequivalent protective apron. Thus, non-Pb 0.35-mm Pb-equivalent protective aprons may be more suitable in providing radiation protection for IVR physicians. Thus, we recommend that IVR physicians should wear the non-Pb 0.35-mm-Pb-equivalent protective apron.

Discussion
In X-ray examination, radiation protection/evaluation of physicians and patients is significant. Although the wide acceptance of IVR procedures, such as PCI, has led to increasing numbers of interventions being performed, radiation exposures from IVR are conclusively higher, exposing both the IVR staff and the patient to high radiation doses. [31][32][33][34][35][36][37][38][39].
A protective apron is inevitably heavy but should be worn by all staff working in catheterization suites. The protective aprons increase the risk of musculoskeletal disorders. Careful selection of a personal protective apron is thus important [55,56].
As non-lead aprons consist of composite materials, mainly W and Sn, they are approximately 20% lighter than lead aprons [29,30]. In the phantom study, the performance of these non-Pb and Pb protective aprons was similar for scattered X-rays [30]. However, whether the performance (both shielding effect and comfort) of non-Pb aprons is sufficient in the clinical setting (cardiac catheterizations including PCI) is unclear. In this study, the radiation protection provided by non-Pb and Pb protective aprons in clinical IVR settings are compared. As a result, we demonstrated the effectiveness of non-Pb protective aprons for the protection of IVR physicians from radiation exposure in clinical IVR settings.
Namely, our results showed that the performance (both shielding effect and comfort) of the non-Pb 0.35-mm Pb-equivalent protective apron was good in the clinical setting (cardiac catheterizations including PCI). Thus, non-Pb 0.35-mm Pb-equivalent protective aprons may be more suitable in providing radiation protection for IVR physicians.
For procedures during which non-lead protective aprons were worn, the mean external dose tended to be lower than that when lead protective aprons were worn (non-lead protective aprons 142.6 or 123.9 µSv; lead protective aprons 166.4 or 209.2 µSv, Table 2). Moreover, the cumulative AK was higher (non-lead protective aprons 1345.7 or 1345.3 mGy, lead protective aprons 1037.2 or 812.3 mGy, Table 1) and the fluoroscopy time longer (nonlead protective aprons 34.5 or 31.7 min, lead aprons 30.4 or 21.2 min, Table 1). The probable explanation is that an additional, lead-containing, acrylic protection device was employed during many procedures featuring non-lead protective aprons. Thus, if the cumulative AK was higher, the external dose was lower because the non-apron device shielded staff from scattered radiation. We did not evaluate the effect of the non-apron device because the shielding effect (%) is relative.
Possible ergonomic improvements include the use of a two-part protective apron (that separately protects the chest and waist). This would distribute the protective apron weight more equally across the shoulders and waist, possibly reducing the risk of musculoskeletal pain [56].

Limitation
This was an initial study of non-Pb protective apron use in clinical settings. A controlled comparison of four groups (wearing non-Pb and Pb protective aprons; 0.25-and 0.35-mm-Pb-equivalents), with statistical evaluation, is necessary.

Conclusions
This study compared the protective performance of Pb and non-Pb aprons of 0.25-mm and 0.35-mm Pb-equivalents in the clinical setting (cardiac catheterizations including PCI). Non-Pb 0.35-mm Pb-equivalent protective aprons may be more suitable for providing radiation protection for IVR physicians because the shielding effect and comfort are both good in the clinical setting.
As non-Pb protective aprons are nontoxic and weigh less than Pb protective aprons, and IVR staff mainly receive doses from scattered X-rays, non-Pb protective aprons will be the preferred type for radiation protection of IVR staff, especially physicians.  Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.