SU-E-I-36: Investigation of Geometric Image Distortion Correction Using the Bricks Phantom for Multi-Modality Imaging




To investigate the feasibility of geometric image distortion correction using the LEGO bricks phantom without plastic container, the geometric MR image distortion was evaluated through the procedure of CT to MR image registration

Method and Materials:

Architecturally stable stacked LEGO bricks phantom, 20 cm in diameter, was scanned on a 1.5 T MRI by using T2 FSE sequence and on a 16 slice CT scanner in the sliceslice mode using 120 kVp and 100 mA. The size of each LEGO brick was 31.60 mm2 including four stud 6.47 mm in inner diameter. The space between stud-and-tube couplings of the LEGO bricks were filled with distilled water. The geometric distortion was evaluated based on fiducial arrays and control circles which defined by stud pieces. Control circles were determined by the difference between the diameters of the stud pieces in the MR image and the corresponding diameters of stud pieces in the CT image.


The fiducial arrays of the LEGO bricks without plastic container were easily visualized in the MR and CT images and there was no water leakage detection within one hour. The control circles were identified and registered. The magnitude of geometric distortion in MR image was gradually increased from near the isocenter to off-center regions of the magnet, maximum 3%. These results are in good agreement with the standard phantom result.


The LEGO are inexpensive, good physical accuracy and easy to construct. The bricks are injection molded in Acrylonitrile butadiene styrene (ABS) and are the geometric tolerance with quite tight. However, plastic container for filling with a solution limits clinical applications in terms of flexibility of phantom design. We measured the geometric MR image distortion using the LEGO bricks phantom precisely without plastic container and it can be easily customized for multimodality imaging.