Misleading changes of the signal intensity on opposed-phase MRI after injection of contrast medium.


OBJECTIVE The effect of opposed-phase imaging on the interpretation of MR contrast studies is highlighted. MATERIALS AND METHODS A model calculation is performed. It demonstrates the change of signal intensity of an average tumor before and after application of Gd-DTPA on an in-phase and an opposed-phase image, depending on the percentage of fat within the voxels. The effect is then demonstrated, using a small cotton stick soaked with water or a solution of contrast agent representing a tumor before and after i.v. application of Gd-DTPA. RESULTS If an average enhancing tumor, which is surrounded by fat, occupies less than 50-60% of the slice thickness, it becomes undetectable on opposed-phase images. The reason is that due to signal cancellation on the opposed image, no signal change or even signal decrease results, while signal increase is visible on the in-phase image. CONCLUSION In those areas of the body where significant partial volume of a tumor with fat may occur (such as for breast tumors growing along ducts, which are surrounded by fat), severe errors can result. Therefore we explicitly warn from using opposed-image sequences for MR contrast studies.


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@article{HeywangKbrunner1996MisleadingCO, title={Misleading changes of the signal intensity on opposed-phase MRI after injection of contrast medium.}, author={S. H. Heywang-K{\"{o}brunner and H . A . De Wolf and M. Deimling and Sabrina Koesling and Hubert H{\"{o}fer and Rolf Peter Spielmann}, journal={Journal of computer assisted tomography}, year={1996}, volume={20 2}, pages={173-8} }