An evaluation using computer simulation of two methods of slice profile determination in MRI

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Abstract
In test object measurements of slice profiles in MR imaging the two methods usually utilised (ramp and wedge techniques) each have their own advantages and disadvantages. Whereas the ramp method yields immediate slice profiles from the images it is only capable of accuracy (errors 5% or less) where the plate thickness is more than a factor of 2.5 to 3 times less than the FWHM slice thickness. This leads to problems for thin slices, particularly since the effects of noise become more severe for thin plates. In the case of the ramp method no difficulties exist with thin slices except that the requirement for numerical differentiation leads to an increased sensitivity to noise. For the same slice thickness the wedge method is approximately twice as sensitive to noise as the ramp method using a 1 mm plate. In both methods it is highly desirable to average several lines in the image to obtain a profile-a facility which usually does not exist in commercial imaging apparatus.