FORBILD

BAVARIAN CENTER OF EXCELLENCE FOR MEDICAL IMAGING AND IMAGE PROCESSING

I.2 Dedicated Head Scanner with aan Area Detector

Field of work:

Project I.2 aims at developing appropriate reconstruction algorithms for spiral cone-beam CT systems. Reconstruction algorithms for single- and multi-slice CT systems with few detector rows are well known and generally available. In modern CT systems the measured slices, typically four, are assumed to be parallel, due to the negligible cone angle (up to 0.5°). The demand for higher volume coverage at decreasing scan time can be met by new CT systems with significantly more than four slices. These cone-beam CT scanners require new classes of reconstruction algorithms due to the non-negligible cone angle. None of the existing cone-beam reconstruction algorithms are suitable for medical CT. They either require to completely scan the patient (from head to toe), or the reconstruction time is too long. Thus cone-beam reconstruction algorithms suitable for medical CT must be developed. To evaluate the different reconstruction algorithms a data base of new virtual 3D phantoms was generated in a first step. It contains a mathematical definition of each phantom which can be used by simulation tools to produce virtual CT raw data. Three new reconstruction algorithms have been developed and implemented. The first results, based on reconstructions of the virtual phantoms, are very promising. Cone-beam artifacts are nearly eliminated and the reconstruction time is comparable to what is used in today`s CT scanners. Further steps will concentrate on the evaluation of cone-beam reconstruction and the definition of customer requirement specifications for a dedicated head scanner.