# Lead Equivalence of Various Materials for Narrow X-ray Beams Table 4.7 (1)

Example of using the table

In the example which follows we have converted all imperial units to SI units.

Assume you have a 150 kV x-ray source.

Assume you have a 23 cm (9 inch) thick standard brick of 1.6 density (i.e. 1.6 kg/m3 or 100 lb/ft3)

The table shows that the lead equivalence under these conditions is 2 mm lead.

It can be shown that 2 mm of lead (at 150 kV) will provide two TVL (10th value layers) which is 10-2 transmission. (TVL / TVT is explained in the glossary section of this site).

So the 23 cm standard brick (1.6 density) will provide the same shielding as using 2 mm of lead, which will provide a 10-2 reduction of x-ray dose rate on the safe side of the shield for a 150 kV tube.

Note that the above deviation is for educational purposes only. That said, modern literature indicates that the TVL for 150 KV x-rays is 0.95 mm which is practically 1 mm. Therefore the above analysis would work in a real world situation.

Physics is, hopefully, simple. Physicists are not

– Edward Teller -