Medical personnel involved in abdominal angiography are exposed not only to direct radiation but also scattered radiation from inspection tables, patients, image intensifiers, and the beam-limiting system (collimator), among others. Japanese standard JISZ4831 prescribes protective coats of at least 0.25mm lead equivalent, which is the uniform thickness of lead equivalent. The most commonly used protective coats are 0.25mm Pb, 0.35mm Pb, or 0.5mm Pb in thickness. The weight of a typical protective coat is about 3kg. While some coats weigh up to 6kg, wearing such heavy coats becomes physically burdensome as inspection time increases. The trade-off between physical burden and protection was considered by analyzing the X-ray intensity distribution and attenuation rate of scattered radiation in each position assumed by the medical staff. In the case of inspections performed at an x-ray tube voltage of 80kV, it may be possible to reduce the weight of the lead rubber apron by about 33%. Namely, the lead thickness can be reduced uniformly by 0.20mm Pb at 70cm and 0.05mm Pb at 100cm, when the shielding capability of a 0.25mm thick Pb layer is accepted as the standard at 40cm above the gonad position. The same range of permeated X-ray dose for the gonad position may be reduced as well. In the case of 110kV, when the lead thicknesses are 0.30mm Pb at 40cm and 70cm, and 0.10mm Pb at 100cm, it is possible to reduce the weight of the lead rubber apron by about 28%.
