Meetings » 2nd CTUG Meeting » Development of new phantoms for the physical assessment of multi-slice CT scanners

Development of new phantoms for the physical assessment of multi-slice CT scanners

Dr SA Sassi, N Keat, MA Lewis, JF Carden, S Edyvean

ImPACT, St George's Hospital, London


PURPOSE: Multi-Slice scanners offer a wide range of slice thicknesses and scan combinations, which should be catered for in developing phantoms for the assessment of these scanners. With nearly two decades of experience in developing physical phantoms for CT scanner assessment at ImPACT, we embarked on developing new phantoms suitable for the assessment of Multi-Slice scanners.

METHODS: Quad-Slice scanners have up to four times more volume coverage per rotation than Single Slice scanners scanned at the same pitch. This needs to be reflected in the extra length of the phantoms required. They also offer a wider range of slice thicknesses between 0.5mm and 10mm requiring consistently high contrast for widely variable partial volume averaging. The new phantoms can be divided into two categories; water filled phantoms for noise and uniformity measurements, and inserts, which fit into existing CTDI phantoms for high contrast spatial resolution and slice sensitivity measurements. The high contrast spatial resolution insert is a 0.1mm diameter 140mm long tungsten wire cast in Perspex. The z-sensitivity insert is a 6mm diameter 0.05mm thick tungsten disk embedded in Perspex.

RESULTS: The phantoms and the individual inserts provide the tools for the physical assessment of spiral and axial CT image quality including image noise, uniformity, high contrast spatial resolution and slice sensitivity. Preliminary evaluation data has been obtained from single slice GE CT/i scanner and a GE Lightspeed QX/i Multi-Slice scanner.

CONCLUSION: The new phantoms meet the increased demands of spiral Multi-Slice CT on phantom design, particularly z-axis length and uniformity.

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