(Saturday, 4/7/2018)
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Purpose: Development of hybrid MR/CT compatible phantom and tissue-equivalent materials on each MR and CT image was purposed.
Methods: To accomplish our purpose, we designed the essential requirements and developed the hybrid MR/CT compatible phantom in this study. Total 12 different tissue-equivalent materials both for each MR and CT image was developed using various chemical component. The uniformity of each sample was calculated. The developed phantom was designed to equip 14 plugs which contained various tissue equivalent materials. Measurement using the developed phantom were done using 3.0-T scanner with 32-channel and Somatom Sensation 64. For MR image, T1 and T2 measurement was performed. The HU on CT depending on the amount of K₂CO₃ which was applied in tissue-equivalent materials to modulate HU on CT and its fitted curve are conducted.
Results: The maximum percentage difference of HU value on CT image by adding K₂2CO₃3 was 3.31%. Also, the uniformity of each tissue was evaluated by calculating %PIU of MR image, which was 82.18% ±1.87 with 83% of the acceptance value and the average of circular-shaped ROIs on CT image for all sample was within ±5 HU. The T1-T2 measurement data was compared with reference data and the average of percentage difference was 2.86% and -13.37% for T1- and T2 relaxation time, respectively. With the 5% of tolerance for percentage difference, 10 measurement data among 24 was acceptable and tissue-equivalent materials of liver was acceptable as tissue-equivalent materials.
Conclusion: A hybrid MR/CT compatible phantom for image acquisition of MR and CT was designed and investigated the relation between MR and CT image for MR-only based radiotherapy in terms of target delineation and radiation dose calculation. In addition, various tissue-equivalent materials for both MR and CT image to be inserted into the developed phantom were described in this study.
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