Presentation Application of an imaging plate for estimating the uncertainty in direct organ measurements due to a variation of the detector placement

Kurihara, Osamu  ,  K.Kanai  ,  M.Hirota  ,  Tani, Kotaro  ,  Eunjoo, Kim

2015-04-21
Description
The uncertainty of a quantified activity amount due to a variation of the detector location is one of the concerned issues in direct organ measurements. The authors proposed a new usage of an imaging plate (IP) technique for estimating this uncertainty. This method needs only to set an array of regions of interest (ROIs) on a latent image obtained from the IP; each of the ROIs corresponds to an active area of the detector to be used. This work benchmarked the method through an experiment using a realistic torso phantom containing an 241Am liver source. The latent image of the source was obtained by irradiating the IP (20 x 40 cm2) from the anterior surface of the phantom. The phantom was also measured with a HPGe detector with an active area of 70 mm in diameter. As a result, the comparison in the response between the IP and the HPGe detector was made for six of 144 circular ROIs arranged on the latent image, showing in a good correlation (r2= 0.994). This suggested that the uncertainty of concern in the present measurement with the HPGe detector was inherited from the dispersion of counts on the latent image: 8.2% of the 144 ROIs. Although a practical use of the IP in the direct organ measurements still has difficulties (e.g., a fading effect), the IP would be a useful tool not only for optimizing the detector location, but also for avoiding possible underestimations of the activity amount due to inappropriate locations of the detector by visual confirmation.
International Conference on Individual Monitoring of Ionising Radiation 2015(iM2015)

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