BaSO4-loaded agarose: A construction material for multimodality imaging phantoms

Rationale and Objectives. Phantom studies are an important part of the eval uation of imaging techniques; however, presently available phantom construc tion materials are not adequate for studies involving both magnetic resonan ce (MR) imaging and computed tomography (CT), The purpose of this study was to design a phantom construction material useful for multimodality imaging experiments. Materials and Methods. Iodinated contrast agent or BaSO4 was added during t he formation of agarose gels. Both CT and MR imaging were performed, and T1 and T2 values and CT numbers (in Hounsfield units) were obtained for multi ple combinations of contrast material and agarose. Results. The T2 values of agarose gels span the range of those values found in biologic tissues. Phantoms containing iodinated contrast agent were not stable; contrast agent diffused across concentration gradients. BaSO4-load ed agarose phantoms were stable, however, and varying barium concentrations produced phantoms that spanned the range of CT numbers found in biologic t issues. Addition of BaSO4 did not substantially alter T1 or T2 values of ag arose gels. Agarose concentration had only a small effect on the CT numbers of BaSO4 suspensions. Conclusion. BaSO4-loaded agarose is an effective material for construction of multimodality imaging phantoms. It provides adequate signal intensity fo r MR imaging and attenuation for CT, with independently variable contrast i n both modalities.