@article{oai:repo.qst.go.jp:00047324,
 author = {Kawaguchi, Hiroshi and Hirano, Yoshiyuki and Yoshida, Eiji and Kershaw, Jeffrey and Shiraishi, Takahiro and Suga, Mikio and Ikoma, Yoko and Obata, Takayuki and Ito, Hiroshi and Yamaya, Taiga and 川口 拓之 and 平野 祥之 and 吉田 英治 and Ｋｅｒｓｈａｗ Ｊｅｆｆｒｅｙ and 白石 貴博 and 菅 幹生 and 生駒 洋子 and 小畠 隆行 and 伊藤 浩 and 山谷 泰賀},
 issue = {Part B},
 journal = {Nuclear Instruments & Methods in Physics Research Section A},
 month = {Sep},
 note = {Several MRI-based attenuation correction methods have been reported for PET/MRI; these methods are expected to make efficient use of high-quality anatomical MRIs and reduce the radiation dose for PET/MRI scanning. The accuracy of the attenuation map (mu-map) from an MRI depends on the accuracy of tissue segmentation and the attenuation coefficients to be assigned (mu-values). In this study, we proposed an MRI-based mu-value estimation method with a non-rotational radiation source to construct a suitable mu-map for PET/MRI. The proposed method uses an accurately segmented tissue map, the partial path length of each tissue, and detected intensities of attenuated radiation from a fixed-position (rather than a rotating) radiation source to obtain the mu-map. We estimated the partial path length from a virtual blank scan of fixed-point radiation with the same scanner geometry using the known tissue map from MRI. The mu-values of every tissue were estimated by inverting a linear relationship involving the partial path lengths and measured radioactivity intensity. Validation of the proposed method was performed by calculating a fixed- point data set based upon real a real transmission scan. The root-mean-square error between the mu-values derived from a conventional transmission scan and those obtained with our proposed method were 2.4+/1.4%,
17.4+/-9.1% and 6.6+/-4.3% for brain, bone and soft tissue other than brain, respectively. Although the error estimates for bone and soft tissue are not insignificant, the method we propose is able to estimate the brain mu-value accurately and it is this factor that most strongly affects the quantitative value of PET images because of the large volumetric ratio of the brain.},
 pages = {156--161},
 title = {A proposal for PET/MRI attenuation correction with mu-values measured using a fixed-position radiation source and MRI segmentation},
 volume = {734},
 year = {2013}
}