Development of a voxel phantom of Japanese adult male in upright posture

Sato, Kaoru   ; Noguchi, Hiroshi; Endo, Akira   ; Emoto, Yutaka*; Koga, Sukehiko*; Saito, Kimiaki  

Calculation of specific absorbed fractions (SAFs) used in internal dosimetry requires a human phantom. However, radiation exposure occurs under various postures, which may affect the shape and location of organs. Therefore, it is important to clarify the effect of posture on SAFs. In the present study, a voxel phantom was developed on the basis of CT images in upright posture, and the difference of SAFs between supine and upright postures was investigated. The authors developed the voxel phantom of Japanese adult in supine posture named JM for the evaluation of SAFs of Japanese adult male. The subject, who was employed for the construction of JM, was selected as a volunteer again to obtain the CT images. The developed voxel phantom in upright posture was named JM2. The voxel size of JM2 is 0.98mm0.98mm1mm, which is the same as that of JM. The fine voxels reproduce the shape and location of organs in the body realistically. It is possible to compare directly the change in the shape and location of organs due to the postures between JM and JM2, since the CT images for construction of the both phantoms were obtained from the identical person. This paper describes the physical characteristics of JM and JM2 and discusses the impact of posture on SAFs for photons in selected organs.