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Estimation of Slice Sensitivity Profiles Z-direction with Helical CT

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Summary

The purpose of this study is to determine the most appropriate for measuring SSPz (slice sensitivity profiles in the z direction). SSPz was evaluated by three methods using various phantoms: coin-shaped copper and aluminium plate (coin method), an acrylate cylinder and a steel wire (edge method), and small metallic beads (small beads method).
The coin method showed that the table-feed position influenced the peak point of CT value and SSPz. The edge method using an acrylate cylinder had few errors in alignment, and its CT values were similar to those of human internal organs. However, it was difficult to measure the thin slice thickness due to the shape and quality of phantoms. The edge method using a steel wire was effective for measuring in a thin slice thickness. It was, however, inadequate for measuring in a 10mm thickness. The small beads method showed excellent reproduction, and it was influenced by the size of the metallic ball.
We found some causes of measuring error each method, that was useful for measuring the effective slice thickness.

Key words:SSPz, coin method, edge method, small beads method, measuring error

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