DEVELOPMENT OF PHANTOMS FOR SPIRAL CT

Purpose: This paper reports on the development of a new phantom for sp iral CT. The phantom meets the increased demands on phantom z-axis uni formity in order that objects from the CT slice, immediately above and below the CT slice of interest, do not contribute perturbing informat ion to the reconstructed CT slice. Material and methods: The phantom d epends on formulation of tissue-like materials that can be cast and pr oduced in both geometric and anthropomorphic shapes with sufficient z- axis length to enable unperturbed CT slices of test objects of interes t. These materials are then used to produce a series of test objects o f CT image quality including low contrast samples that do not require volume averaging or mixing of solutions, and that can reflect sub-slic e thickness lest objects and supra-slice thickness test objects. Resul ts: The overall phantom and its individual test objects provides meani ngful tests of spiral CT image quality including slice sensitivity, CT number linearity and tests of high and low contrast resolution. Schem atic designs and actual CT scans are shown. Conclusion: The new spiral phantom appears to meet the increased demands of spiral CT on phantom design, particularly z-axis length, and requirements for low contrast resolution test objects. (C) 1998 Elsevier Science Ltd. All rights re served.