The Improvement of In vivo XRF Lead Measurement System

Abstract

<p>¹⁰⁹Cd induced K-XRF has been used for in vivo lead measurement for about two decades. The improvement of this system has been emphasized recently due to the increasing understanding of the low level lead exposure. In this work, a cloverleaf detector system is used to improve the minimum detectable limit (MDL) for the in vivo measurement of lead in bone. This system consists of four 8mm radius detectors which are placed closely with a space of 2mm between neighboring ones. We measured some bare phantoms and phantoms in leg phantom which simulates the in vivo measurement and found that the MDL is greatly improved by using the cloverleaf system and a stronger source. The effect of the geometries is also discussed. An overall MDL ratio of about 0.278 is obtained by using the cloverleaf system compared to the conventional system for the in vivo measurement, which means a decreasing of MDL from about 10 micro g/(g bone mineral) to about 2.78 micro g/(g bone mineral).</p> <p>Two sets of phantoms also have been investigated due to the different calibration lines for these two sets of phantoms for the same lead measurement system. The results indicate that the compositions of these two sets of phantoms, which are supposedly the same, are greatly different. Since they were both made of "plaster of Paris", we can conclude that not all the plaster of Paris has the same composition. Hence the materials need to be measured before they are used to make the calibration phantoms.</p>