Phantom Design for Distortion Correction of MR Images

AGNETIC resonance imaging (MRI) provides an excellent modality for distinguishing different tissues in the human body, which is essential for medical applications. When MRI is used for stereotactic treatment planning, its geometric accuracy is crucial. Previous studies have been conducted to correct the distortion caused by nonlinearity of the MRI scanner’s magnetic gradient fields by imaging a cubic phantom [1], [2] and defining distortion correction functions based on the distorted appearance its surfaces. Correct mathematical handling of the distortion correction function required that the cube was centered about the magnetic isocenter, which is defined as the common center of the three magnetic gradient fields and is not very accurately known. New 3Tesla MRI systems have a larger bore, making the previous phantom design impractically small for probing the field nonlinearity in the periphery of the bore, as the phantom cannot be scaled up due to constraints related to weight and cost of manufacturing. We are introducing a new phantom design using a different approach, which can be built to a larger size, improves accuracy of distortion characterization and reduces cost.