Category: Diagnostic Imaging
Author’s Name: David Platten
Published: Oct 08, 2010
An ImageJ macro that determines the slice thickness of a helical CT scan by analysing a directory of DICOM images from a helical scan through a thin gold disc phantom or very small metal bead.
The macro expects a directory of DICOM images from a helical scan run through a thin metal disc or a very small metal bead. The reconstruction interval should be around 1/10 of the slice thickness. For example, if the reconstructed slice thickness is 3 mm then you need to set the reconstruction interval to 0.3 mm.
The phantom can be a thin gold disc embedded in a Perspex rod, similar to the one that ImPACT uses. Alternatively the method may work by scanning through a small metal bead, provided that the bead is much smaller than the reconstructed slice thickness.
Calculates the FWHM by finding the bead or disc position then measuring the CT# of it. The FWHM is taken as the difference between min and max CT# values. Note – this may not be a correct assumption for your scan! Note – this will only work well if the contrast between the bead or disc CT # and background is high – use a very small bead / disc roi to help with this.