Although the use of iron oxide as tracer is essential for magnetic particle imaging and iron is one of the major trace elements in the human body, the injection of iron oxide into the human body involves some severe risks. If a critical mass of iron is exceeded, the reaction of iron with peroxides can cause the emergence of free radicals which are toxic for the human body. Therefore the exact knowledge of the injected iron concentration is essential for medical applications. Photometry and atomic absorption spectroscopy are techniques currently used for the determination of the iron concentration, although both bring along the disadvantage that the probes have to be prepared effortful.

Measurements with micro Computed Tomography (Micro-CT) were introduced as a new approach for the determination of the iron oxide concentration of ferrofluids. A phantom and evaluation software have been designed which enable the user to determine the concentration without the chemical altering of the ferrofluid. In future, micro-CT measurements could determine the iron oxide concentration of superparamagnetic iron oxide based ferrofluids in lymph nodes without depending on invasive techniques as histologic staining.