Retrobulbar magnetic resonance angiography using binomial off-resonant rectangular (BORR) pulse

A novel spectrally selective fat saturation pulse design with robustness to B0 and B1 inhomogeneities: A demonstration on 3D T1-weighted breast MRI at 3 T

PURPOSE

Spectrally selective fat saturation (FatSat) sequence is commonly used to suppress signal from adipose tissue. Conventional SINC-shaped pulses are sensitive to B₀ off-resonance and B₁⁺ offset. Uniform fat saturation with large spatial coverage is especially challenging for the body and breast MRI. The aim of this study is to develop spectrally selective FatSat pulses that offer more immunity to B₀/B₁⁺ field inhomogeneities than SINC pulses and evaluate them in bilateral breast imaging at 3 T.

MATERIALS AND METHODS

Optimized composite pulses (OCP) were designed based on the optimal control theory with robustness to a targeted B₀/ B₁⁺ conditions. OCP pulses also allows flexible flip angles to meet different requirements. Comparisons with the vendor-provided SINC pulses were conducted by numerical simulation and in vivo scans using a 3D T₁-weighted (T₁w) gradient-echo (GRE) sequence with coverage of the whole-breast.

RESULTS

Simulation revealed that OCP pulses yielded almost half of the transition band and much less sensitivity to B₁⁺ inhomogeneity compared to SINC pulses with B₀ off-resonance within ±200 Hz and B₁⁺ scale error within ±0.3 (P < 0.001). Across five normal subjects, OCP FatSat pulses produced 25-41% lower residual fat signals (P < 0.05) with 27-36% less spatial variation (P < 0.05) than SINC.

CONCLUSION

In contrast to conventional SINC-shaped pulses, the newly designed OCP FatSat pulses mitigated challenges of wide range of B₀/ B₁⁺ field inhomogeneities and achieved more uniform fat suppression in bilateral breast T₁w imaging at 3 T.

Neuroimaging in the Diagnostic Evaluation of Eye Pain

Ocular or eye pain is a frequent complaint encountered not only by eye care providers but neurologists. Isolated eye pain is non-specific and non-localizing; therefore, it poses significant differential diagnostic problems. A wide range of neurologic and ophthalmic disorders may cause pain in, around, or behind the eye. These include ocular and orbital diseases and primary and secondary headaches. In patients presenting with an isolated and chronic eye pain, neuroimaging is usually normal. However, at the beginning of a disease process or in low-grade disease, the eye may appear "quiet," misleading a provider lacking familiarity with underlying disorders and high index of clinical suspicion. Delayed diagnosis of some neuro-ophthalmic causes of eye pain could result in significant neurologic and ophthalmic morbidity, conceivably even mortality. This article reviews some recent advances in imaging of the eye, the orbit, and the brain, as well as research in which neuroimaging has advanced the discovery of the underlying pathophysiology and the complex differential diagnosis of eye pain.