Tierärztliche Hochschule Hannover Entwicklung von Methoden zur ...

7 Summary
Jurriaan Schulman
SUMMARY
Development of Methods for Quality Assurance and Analysis of Density Measurements of
Implant and Bone Structures in µCT.
One of the main goals of this study was the evaluation of the image quality characteristics of
the micro-CT scanner „XtremeCT“ (Scanco Medical AG; Brüttisellen, Schweiz). In
particular, by analysis of the most important image quality parameters, the suitability of the
XtremeCT for both small animal imaging as well as for in vivo studies of degradable
magnesium implants in a rabbit model were to be evaluated. It was to be assessed if, and
using which scan parameters, selected magnesium alloys as well as a peri-implant bone
formation can be optimally imaged with the XtremeCT. Also, the question was to be
answered whether and how a density calibration can be accomplished with the XtremeCT,
which reliably allows quantitative conclusions about a changing implant density. Finally, the
question was to be answered whether a lower mean photon energy than currently achievable
with the XtremeCT scanner would result in better image quality regarding the imaging of
peri-implant bone formation and degradable implants.
Custom phantoms were developed and established which were to guarantee a long-term and
continuous high image quality with the XtremeCT Scanner. Phantoms were constructed for
measuring image noise, CT number homogeneity and linearity as well as low contrast
resolution. Also, a method was established which used hydroxylapatite or bone meal coated
magnesium implants to simulate peri-implant bone formation. Lastly, phantoms were made
for measuring the density of both degradable implants as well as hydroxylapatite, bone meal
and rabbit tibiae. In the context of this work the magnesium alloys LAE442, ZEK100, AX30
and MgCa0,8%, as well as prepared explanted rabbit tibiae, were investigated. To evaluate
the influence of a mean photon energy of 28 keV on the imaging of peri-implant bone and
degradable implants with µCT, phantom measurements with coated implants and density
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