A study of MDL improvement for the in vivo measurement of lead in bone

Cd-109 induced K XRF has been used for in vivo lead measurement for about two decades. Recently, the need for improvement of this system has been emphasized due to an increased understanding of low-level lead exposure. The conventional XRF bone-lead measurement system includes a 25 mm radius HPGe detector and one set of electronics. In this work, a cloverleaf detector system is investigated. This system consists of four 8 mm radius detectors and four sets of electronics. We measured bare plaster of Paris phantoms and phantoms in a soft tissue equivalent leg phantom to represent in vivo measurement. A Monte Carlo simulation for XRF measurement was also used to simulate this system. We compared both the experimental results and the simulation and found that the minimum detectable limit (MDL) is greatly improved by using the cloverleaf system and a stronger source. The effect of geometry is also discussed. An overall MDL ratio of about 0.3 (experimental value 0.278 +/- 0.016 and simulation value 0.273) is obtained by using the cloverleaf system compared to the conventional system for in vivo measurement, which means a decrease of MDL from about 6-10 to about 2-3 mug/(g bone mineral). (C) 2003 Elsevier B.V. All rights reserved.