Supplementary material #2
Registration error due to non-rigid transformation of solid
components of the RF surface coils
Purpose
The implemented 3D B-Spline transform non-rigidly deforms solid structures, e.g. the preamplifier units
of the RF surface coils. This leads to a falsified appearance of the solid structures in the combined
µ-maps generated by the algorithm.
Materials and Methods
To quantify the influence of this registration error on the PET emission data of the NEMA phantom
scan, the attenuation template of the RF surface coil obtained by the flat CT scan was non-rigidly
registered by the algorithm while the solid preamplifier units of the coil were only rigidly transformed.
This was performed by segmenting the preamplifier units out of the attenuation template prior to the
non-rigid transformation and by a separate rigid transformation of the preamplifier units. The PET
scan with the RF surface coil was then reconstructed with the modified combined µ-map (acronym:
NEMA_COIL_FLAT_NON-RIGID_SOLID).
Results
Axial slices of the µ-maps corresponding to the PET reconstructions NEMA_COIL_FLAT_NONRIGID and NEMA_COIL_FLAT_NON-RIGID_SOLID are displayed in Fig. S2(A,B). An axial average intensity projection of the absolute deviation (%) of the PET data of NEMA_COIL_FLAT_NONRIGID from NEMA_COIL_FLAT_NON-RIGID_SOLID is shown by Fig. S2(C). The error due to
the non-rigid deformation of the solid preamplifier units of the RF surface coil is rather small with
maximum deviations of up to 4 % in the immediate vicinity of the solid components of the RF surface
coils. No influence of the registration error on the rest of the phantom volume was measured.
Fig. S2. (A) Axial slice of the µ-map corrresponding to NEMA_COIL_FLAT_NON-RIGID. (B)
Axial slice of the µ-map corresponding to NEMA_COIL_FLAT_NON-RIGID-SOLID. The geometrically rigid preamplifier units are not deformed by the transformation. (C) Axial average intensity
projection over the whole phantom (80 slices) of the absolute deviation (%) of PET emission data of NEMA_COIL_FLAT_NON-RIGID from NEMA_COIL_FLAT_NON-RIGID_SOLID. Local
maximum deviations of up to 4 % were measured in the immediate vicinity of the high attenuating
components of the RF surface coil.
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