@misc{oai:repo.qst.go.jp:00071322,
 author = {Kawaguchi, Hiroshi and Hirano, Yoshiyuki and Yoshida, Eiji and Suga, Mikio and Shiraishi, Takahiro and Tanimoto, Katsuyuki and Kimura, Yasuyuki 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 菅 幹生 and 白石 貴博 and 谷本 克之 and 木村 泰之 and 小畠 隆行 and 伊藤 浩 and 山谷 泰賀},
 month = {Nov},
 note = {Several MRI-based attenuation correction methods have been reported for PET/MRI. The accuracy of the attenuation map (mu-map) from an MRI image depends on correctness of the segmentation of tissue and the attenuation coefficients to be assigned (mu-values). However, an MRI image does not reflect the attenuation of radiation and inaccurate assignment of mu-values affects the quantitative assessment of functional images of PET. Although installation of a transmission scan function on the PET/MRI can provide an accurate mu-map, it restricts the design of the scanner, increases the manufacturing cost and takes additional scanning time. In this study, we proposed an MRI-based mu-value estimation method with a non-rotational radiation source to construct the proper mu-map for PET/MRI. The proposed method uses the accurately segmented tissue map, the partial path length of each tissue, and detected intensities of attenuated radiation from a fixed-position radiation source which usually rotates around the subject to obtain the mu-map with the tomographic procedure. According to the Lambert-Beer law, attenuated intensity is described as the function of partial path length and mu-values of every tissue. The partial path length could be estimated by the simulation of fixed-point radiation with the same scanner geometry using the known tissue map from MRI. The mu-values of every tissue could be estimated by inverting the function. The simulation results, based upon measurement data, showed the averaged errors between mu-values of the conventional transmission scan and our proposed method were 2.3%, 18.6% and -11.1% for brain, bone and soft tissue other than brain, respectively. Although there were over- and under-estimations for bone and soft tissue, respectively, the present method is able to estimate the brain mu-value accurately and that strongly affects the quantitative value of PET images because of the large volumetric ratio of the brain., IEEE NSS/MIC/RTSD 2013},
 title = {A MRI-Based PET Attenuation Correction with mu-Values Measured by a Fixed-Position Radiation Source},
 year = {2013}
}