Relationship between patient exposure and measurement precision in dual-photon absorptiometry of the spine.

Computer simulations and experimental studies were performed to investigate the relationship between patient exposure and measurement precision in dual-photon absorptiometry (DPA). Systems employing 153Gd, K-edge filtered x-rays and dual-kV x-rays were analysed. The results indicate that, except for added exposure due to beam-profile overlap between scan lines, currently available systems are capable of operating at or near the limits of statistical precision per unit of patient exposure. They further indicate that there are no major advantages in exposure requirements for x-ray systems as compared to 153Gd systems.