Test tool for assessing lead equivalence in protective lead apparels Roshan S Livingstone and Anna Varghese Department of Radiology Christian Medical College, Vellore, S India Vision statement: The Christian Medical college, Vellore seeks to be a witness to the healing ministry of Christ through excellence in education, service and research

Introduction Protective lead‐equivalent (Pb-eq) aprons provide necessary shielding from secondary radiation (scatter). Pb-eq aprons have vinyl/rubber with lead impregnation or made of composite materials (non lead) Use of high tube potentials (kVp) lead to more scatter radiation. Knowledge on Pb-eq is important for radiation protection

Why this is of concern? CT and fluoroscopic images showing defects in lead apparels Arrow showing a dark line indicating fragility. Nonuniformity of material. Manufacturing defect in thyroid collar. Different combination of lead equivalent material A B C D

Checking integrity of apron Aprons are screened using CT/fluoro/radiography to check for integrity before use and as part of the annual quality control procedure Lead equivalence can be assessed using dosimeter Expensive and available only in few centers Requires qualified personnel to interpret A simple method to identify the Pb eq is required for screening purposes

Aim Create awareness to the radiation worker on integrity of radiation protective apparels For new purchases For adequate radiation safety. Develop a simple test tool to test the Pb-eq of radiation protective apparels

Materials and methods Digital images of 0.25 mm and 0.5 mm lead and lead‐free aprons from 6 manufacturers were assessed using a calibrated digital X‐ray unit. Standard protocol non-grid technique Percentage attenuation values of the aprons were determined at 100 kVp, 32 mAs, 100cm using an ionization chamber

Evaluating pixel values Region of interest (ROI) from radiographic images of lead apron, copper step wedge, and 2 mm thick lead (reference). GE Centricity PACS workstation (Milwaukee, USA) The mean pixel value from the apron was matched with corresponding step (thickness of copper) from step wedge to monitor Pb eq The pixel value ratio (PVR) was calculated from mean pixel intensity of the apron and lead block and lead block versus step wedge.

Results Percentage attenuation at 100 kV, 32 mAs 90 % attenuation for 0.25 mm Pb eq 97 % attenuation for 0.5 mm lead or lead‐free aprons. Pixel values – images acquired at 100 kV, 5 mAs 0.25 mm Pbeq apron correspond to 0.8–1.2 mm Cu (4 – 6 steps) 0.5 mm Pbeq aprons correspond to 2.0 –2.8 mm Cu (12 – 14 steps) Pixel value ratio (lead block/copper step) was constant for 0.25mm Pb eq apron (0.5) and for 0.5mm (0.7) Shows consistency of output

Discussion Defects in the aprons include cracks, changes in homogeneity of pb eq, combination of 0.25 mm, and 0.5 mm Pbeq materials. Deterioration of the lead‐impregnated vinyl is manifested as cracks or holes and may not be visible to the naked eye Technique of measuring the attenuation using transmission ionization chamber is standard, but expensive. An alternative method is discussed in this study – copper step wedge Both lead and lead free (composite bilayer: bismuth-antimony- barium) gives similar attenuation (96 – 98%)

Discussion Pixel values increased with increase in the thickness of copper step wedge indicating a corresponding increase in Pb eq in aprons. The simple test tool is affordable and is validated in this study. Calibrated radiographic unit and standard protocols for acquiring images should be selected

Conclusion It is suggestive that aprons be screened for its integrity from the time of purchase using computed tomography (CT), fluoroscopy, or radiography. It is recommended that this simple test tool could be used for checking lead equivalence as part of periodic quality control (or) if any variation in contrast is seen in the image during screening. Livingstone et al Ijri 28:2; 2018

Disclosure – No funding involved Conflict of interest - NIL