Room: Exhibit Hall | Forum 9
Purpose: To investigate the effect of various pitches and helical interpolation schemes on the slice sensitivity profile (SSP) and compare these variations with corresponding variations in dose requirements for constant image noise.
Methods: The SSPs were measured on a GE 750 HD with a Standard algorithm, a slice thickness of 3.75mm and pitches of 0.516, 0.984, and 1.375. Reconstructions were performed using both the Full and Plus interpolation schemes (called Recon Options). SSPs were measured using an edge method. With the same effective mAs wider SSPs are expected to produce images of less noise, or at the same noise level wider SSPs are expected to require less dose. Thus SSP widths were compared with the relative dose required to produce a given noise level at each pitch. The FWHM, FWTM and area of the SSPs were measured and reported along with noise in a uniform phantom at various dose levels.
Results: Whether the Full or Plus interpolation is used, FWHM, FWTM, and area of the SSP for the three pitches ranked consistently in the following order from smallest to greatest: 0.516, 1.375, 0.984 on the scanner tested. As expected, the dose required to produce equal noise for the three pitches also ranked in the same order from lowest to highest dose: 0.516, 1.375, 0.984. This was true for both Full and Plus reconstructions. However these changes in the SSP for different pitches did not account for all the measured dose variations.
Conclusion: The lowest pitch on this scanner is seen to have the widest SSP and lowest dose requirement, regardless of the choice of interpolation scheme. Higher pitches donâ€™t necessarily lead to lower doses/deteriorated z-resolution on the scanner tested.
Funding Support, Disclosures, and Conflict of Interest: FNR supplies CT protocols to GE Healthcare under a licensing agreement.
Not Applicable / None Entered.