PPT Slide
Helical mode :
- Images reconstructed at intervals of 1/10 the slice thickness
- Mean CT number is used to create the profile
The disk has contrast of 160 HU @ 2.5 mm slice thickness and pitch =1.0
The contrast of the disk varies with slice width and scanning pitch
Z-Sensitivity Measurement Techniques
Notes:
- In the spiral mode images are reconstructed at intervals equal to 1/10 of the slice thickness, and the mean CT number in a region of interest within the disk is used to produce the Slice Sensitivity Profile.
- The ramp phantom is still used for axial mode scanning
- The Tungsten disk has a contrast of about 190 Hounsfield Units at slice thickness of 2.5mm and pitch of 1.0.
The slice sensitivity profile and object contrast vary with slice width and scanning pitch, The next speaker will cover these issues, As you can see from these two profiles the contrast of the disk reduces by one third when slice thickness is doubled from 2.5 to 5mm.