Subtle bone marrow edema assessed by frequency selective chemical shift MRI.

Subtle edema in yellow bone marrow from tumors (14 subjects) and osteomyelitis (9 subjects) were examined by selective nonexcitation (SENEX) water imaging using a short five pulse frequency selective excitation with lipid suppression greater than 96%. Standard spin-echo (SE) proton density-, T1- and T2-weighted images, and fat suppression methods such as short inversion time inversion recovery and also the chemical shift selective Dixon method are discussed in comparison with SENEX. Application of the SENEX method is described and images from four typical cases are demonstrated. Sensitivity to edema is obviously better using the SENEX chemical shift selective method than using other imaging techniques. Improved delineation of abnormal areas in yellow bone marrow is provided by SENEX water imaging in one slice after multislice standard imaging. After shimming, only one SE scan with frequency selective excitation is necessary to get a pure water image.