Accuracy the Spatial Position of Gold Markers in MR Images

Tufve Nyholm¹, Joakim Jonsson¹, Magnus G. Karlsson¹, Mikael Karlsson¹

MR has potential to replace CT as basis for radiotherapy of prostate cancer. To be able to use the MR images for patient positioning at treatment, the position of the internal gold markers needs to be correct in the MR images. A phantom was created and scanned to evaluate the dependence between the apparent position and relevant sequence parameters. It was found that use of 2D sequences introduces errors in the position, and that the apparent marker position is dependent on the tissue type surrounding the marker. The apparent position is not dependent on band-width or frequency encoding direction.