Introduction

Lead protective apparel for x-ray shielding such as lead aprons, thyroid shield, gonad shield and gauntlets is an example for personnel protective equipment. The purpose is to keep occupational exposures to radiation within the appropriate limits and as low as reasonably achievable (ALARA).

The lead is leaded impregnated vinyl or rubber with a shielding equivalent given in millimeters of lead. Some aprons use a combination of lead and other attenuation material to make the apron lighter while maintaining an equivalent shielding ability. The lead-impregnated vinyl apron usually has a nylon fabric as finished outer materials.

Everybody knows that the radiation exposure may cause deterministic and stochastic effects. However, it is not always possible to estimate stochastic effect on organism.

A non-stochastic or deterministic effect has a severity that is dependent on dose and have a threshold level for which no effect will be seen. Meanwhile, the stochastic effect occurs by chance, generally occurring without a threshold level of dose, and the severity is independent of the dose, such as cancer and genetic effects.

Type and criteria of Lead Protective Aprons in X-Ray

Lead protective aprons should be provided to all staff who carrying out X-ray procedures where the aprons:

1. Must have minimum attenuation of 0.35 mm lead (Pb) for the front section and not less than 0.25 mm lead (Pb) for the remaining parts.
2. Should be designed to cover at least:
   1. The front part of the body from the throat down to and including the knees, the entire breast bone and shoulder
   2. The sides of the body of not more than 10 cm below the armpit to at least half way down the thigh; and
   3. The back from the shoulder blades down to and including the knees.

The philosophy of keeping doses as low as reasonably achievable (ALARA) must be used to establish the rejection criteria. With ALARA, reasonable can be defined as ringgit amount spent to prevent a given dose. This has not been used in medical health physics; however, it is practice in the nuclear power industry only.

Purpose for Reject Analysis

The purpose of reject analysis is to provide a rationale for the rejection of lead apron for use by x-ray facility operators and to present the basis on which the criteria was developed for radiation purposes.

Testing of Lead Aprons

All lead aprons should be tested for shielding integrity once received from the vendor and subsequently in 12-18 month intervals. Each apron should be labeled and not be removed. Using fluoroscopy on a floating top table performs testing. This test will not measure lead equivalence but it will quickly show faults, holes and apron deterioration. If there is any doubt about apron, it should be withdrawn from use until further advice is obtained. All the result received should be documented for future reference.

Lead aprons should never be folded. Crack in the lead lining can develop at the fold, reducing the useful life of apron. Any item displaying break or crack in the lead lining should be replaced.

Criteria for Rejection Lead Apron

Based on the cost of replacing lead apron and estimated radiation dose received from the defect, it is suggested that lead aprons should be replaced if the defect is greater than 15mm2. If the defect is clearly not over a critical organ then the lead apron can be used, provided the clearly marked location of defect with size and other details should be documented.

If the defect is not in critical organs, which are along the seam, overlapped areas or at the back of the lead aprons, it should be subject to a less conservative rejection criterion. In these cases, it is suggested that lead aprons are replaced if the defect is greater than 670 mm2.

Thyroid shields should be replaced if the defect is greater than 11mm2.

The other commons examples criteria for rejection of lead aprons are;

1. Multiple small holes and cracks
2. Large hole or cracks
3. Wearing out or thinning of the lead
4. Velcro not in working order

Care and Use of Lead Aprons

Lead apron should be checked fluoroscopically at least on annual basis of their shielding integrity. Rejecting lead apron depends on the location, area size and number of flaws. It is best to keep the number of flaws to a minimum.

For storage purposes, the lead apron should be hung up by the shoulder or on an approved apron hanger. Aprons should never be folded or creased. If possible, do not lay or store aprons on the flat surface.

For cleaning purposes, clean daily and deodorize by scrubbing with a soft bristle brush. Never use products containing bleach. Rinse thoroughly with water to remove the residue. Hang it to dry. Do not put in washing machine or dry clean lead aprons.

References

1. Rejection Criteria For Defects on Lead Apparel Used in Radiation Protection of X-ray Workers
   http://www.bccdc.ca/NR/rdonlyres/A5EB891B-7BC4-442D-A6ED-864438FAF9EF/0/RejectionCriteriaforLeadApparel.html
2. How Protective Are The Lead Aprons We Use Against Ionizing Radiation?
   http://www.dirjournal.org/sayilar/42/buyuk/pdf_DIR_412.html
3. The Use and Care of Lead Protective Equipment
   www.ncradiation.net
4. Lambert K, McKeon T. Inspection of lead aprons: criteria for rejection. Health Phys. 2001;80:S67–9