A clinically viable technique of fat suppression for abdomen and pelvis

Novel rapid fat suppression strategy with spectrally selective pulses

Short repetition time gradient echo sequences are gaining popularity in clinical applications such as dynamic contrast enhancement imaging, cardiac imaging, and MR angiography. Performing fat suppression in these sequences is usually time consuming and often somewhat ineffective, due to the relatively short T(1) and long T(2) of fat. A novel rapid fat suppression strategy using spectrally selective pulses is introduced and compared with clinically popular sequences such as fat presaturated fast field echo (FFE) and turbo field echo (TFE) and binomial water-selective spatial-spectral excitation (SSE, or SPSP excitation) FFE. The new strategy combines fat presaturation with low-order binomial water-selective SSE pulses in a TFE sequence. This enables the use of a long echo train length to decrease exam time, but without creation of excess fat signal contamination of the resultant images. The fat nullification is also more reliable as fat signals in central k-space data are suppressed twice. An implementation of this strategy is compared with traditional methods in both phantom and human studies, confirming that the new technique provides strong fat suppression with few artifacts despite the short scan duration.

Susceptibility artifact reduction in fat suppression

Strong fat signal in regions where a large susceptibility difference exists, for instance at the interface between air and tissue near the maxillary sinus, may not be eliminated by currently available fat suppression techniques without sacrificing the overall quality of the images. In this article, we show that this fat signal, which appears as a susceptibility artifact, can be significantly reduced by using an optimized presaturation pulse with sharp edges and a broad bandwidth, while causing minimal disturbance of the water signal. Several optimized presaturation pulses can be reproduced by the Fourier coefficients provided in the Appendix.

STIR imaging of synthetic vascular graft infection

Nine patients with suspected prosthetic vascular graft infection were studied with axial spin echo (SE) and short TI inversion recovery (STIR) magnetic resonance imaging. Images were assessed for presence and extent of abnormality. All patients had either surgical (8/9) or bacteriologic (6/9) confirmation of infection. STIR images better defined the extent of infection and had greater fat-fluid contrast than SE images in 6/9 studies. In 3 cases with peri-graft fluid alone, T2-weighted images had slightly greater contrast, although the STIR images were still diagnostic. STIR imaging can offer improved accuracy in evaluation of suspected prosthetic graft infection when used in conjunction with SE techniques.