Application of an imaging plate for evaluating the uncertainty in direct organ measurements due to variation in detector location.

In direct organ measurements, there can be uncertainty to the quantified amount of activity due to variations in detector locations. Here, the authors demonstrate a new use of an imaging plate (IP) for evaluating this uncertainty. The method requires only that an array of regions of interest (ROIs) is set on a latent image obtained from the IP; each ROI conforms to an active area of the detector to be used. In this study, the proposed method was tested in an experiment using a realistic torso phantom containing an (241)Am liver source. The latent image of this source was obtained by irradiating the IP (20 × 40 cm(2)) from the anterior surface of the phantom. A comparison of responses between the IP and a high-purity germanium detector was made for 6 of the 144 circular ROIs arranged on the latent image, showing excellent correlation between the two sets of measures. The dispersion of the photostimulated luminescence values of the 144 ROIs was found to be 8.2% (1σ) and 1.09 as a log-normal scattering factor, which was expected to be the same as the uncertainty of concern in the present measurement with the HPGe detector.