RESUMO
PURPOSE: To develop and demonstrate the feasibility of a silent respiratory navigator technique for prospective triggering, which was incorporated into a three-dimensional radial zero-echo-time sequence for respiratory navigated silent abdominal imaging. METHODS: A nonselective hard excitation radiofrequency pulse was used for the navigator sequence with a derated readout gradient, to avoid generation of high levels of acoustic noise. The acquired navigator signals were processed in real time and used for prospective triggering of the zero-echo-time sequence. Ten healthy volunteers were scanned using the proposed and conventional techniques at 1.5 T. An acoustic noise measurement with A-weighted continuous equivalent sound pressure level was also performed. RESULTS: The sound pressure-level values of the background noise, zero-echo-time imaging, conventional, and silent navigators were 68.3, 68.4, 102.5, and 69.4 dBA, respectively. Excellent correlation with correlation coefficients greater than 0.9 was observed between the bellows signals and displacement values calculated from the navigators. Sharpness of the portal vein of both conventional and silent navigator-triggered images was significantly higher than those of nontriggered images. CONCLUSIONS: The silent navigator-triggered zero-echo-time technique is feasible and might improve image quality and workflow of abdominal MRI of patients who are prone to acoustic noise. Magn Reson Med 79:2170-2175, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
Assuntos
Abdome/diagnóstico por imagem , Imageamento Tridimensional , Imageamento por Ressonância Magnética , Acústica , Algoritmos , Artefatos , Voluntários Saudáveis , Humanos , Interpretação de Imagem Assistida por Computador , Movimento (Física) , Oscilometria , Pressão , Reprodutibilidade dos Testes , Respiração , Processamento de Sinais Assistido por ComputadorRESUMO
The silent navigator technique utilizes a non-selective excitation and an appropriate respiratory waveform generation method is necessary for an accurate motion detection. We compared three methods for silent navigator waveform generation. The profile generation method with coil selection (prof-selection) resulted in a high cross correlation with bellows signals and a large respiration amplitude. The prof-selection method should be used for silent navigator waveform generation.