Modified Dixon (mDIXON) sequences are valuable tools in pediatric MR as both the T1 gradient echo recalled (mDIXON FFE) and T1 and T2 spin echo (mDIXON TSE) meet the imaging requirements in a wide fetal and pediatric variety of body, musculoskeletal, vascular and neuro applications.

Time, patient motion, uniform fat suppression, and spatial resolution are challenges met with varied degrees of success in all patients, but can be especially difficult to achieve in children. Pediatric patients often require sedation or anesthesia in order to tolerate long exam times without moving and by virtue of their small size images may be signal starved which limits spatial resolution and signal homogeneity.

This educational exhibit will describe the mDIXON FFE and mDIXON TSE sequence techniques and compare and contrast the method with traditional inversion recovery fat saturation sequences STIR (fat nulled inversion recovery) and the SPIR/SPAIR fat saturation sequences.

Traditional images are strictly 2 dimensional as is mDIXON TSE. The mDIXON FFE, a 3 dimensional high-resolution technique may be reconstructed into planes orthogonal to the acquired source image data, with higher spatial resolution and lesion conspicuity than inversion recovery fast/turbo spin echo techniques.

Advantages of mDIXON FFE and mDIXON TSE include allowing for arbitrary timings of the echoes, so are not constrained to in-phase or out-of-phase, as past iterations of mDIXON required, as each sequence specifically includes multi-peak fat spectral modeling, and improved B0 main magnet shimming.

Image quality is also improved in post-gadolinium sequences when the mDIXON FFE method is employed. Conspicuity of lesion enhancement is improved through reliable and homogenous separation of fat signal from the final image. This feature enables more reliable and confident diagnosis or subtle enhancement and is useful in creating 3 dimensional MRA/MRV type reconstructions from a single gadolinium enhanced image acquisition.

The mDIXON FFE and mDIXON TSE sequence techniques are ideally suited to meet the challenges of MR imaging the small anatomic structures and the often subtle areas of signal variation in pathologic processes in childhood disease. High resolution, rapid sequences with homogenous fat suppression prior to and after delivery of gadolinium provide improved imaging in soft tissue and bone musculoskeletal, neuro, body, vascular and fetal MR examinations, providing details of small anatomical structures, homogenous signal some of which are illustrated in the accompanying figures.