RESUMEN
PURPOSE: Of the myocardial T(1) mapping techniques, the modified Look-Locker inversion recovery (MOLLI) sequence is accurate and highly reproducible. The MOLLI sequence requires patients to hold their breath for 17 heartbeats during the scanning process to minimize respiratory motion-related artifacts. However, some patients are unable to hold their breath because of illness or limited breath-hold capacity. This study, therefore, aimed to develop a robust myocardial T(1) mapping method based on the MOLLI sequence for patients unable to perform voluntary breath-holds. METHODS: This study presents a free-breathing MOLLI (FB-MOLLI) sequence and an optimized reconstruction method to allow myocardial T(1) mapping in vivo without breath-hold. Nine healthy volunteers participated in this study after providing institutionally approved consent. The FB-MOLLI sequence acquires 20 images within 29 heartbeats. The reconstruction program employs a two-step automatic image registration technique and an image selection method inspired by the self-gating cardiac imaging method. RESULTS: Results indicate that the proposed reconstruction method increases the accuracy and reproducibility of free-breathing T(1) measurements significantly (p < 0.001). CONCLUSIONS: The FB-MOLLI method provides a robust tool for clinical application in free-breathing myocardial T(1) mapping, and could greatly facilitate acquisition procedures during routine examinations.
Asunto(s)
Técnicas de Imagen Sincronizada Cardíacas/métodos , Corazón/anatomía & histología , Aumento de la Imagen/métodos , Interpretación de Imagen Asistida por Computador/métodos , Imagen por Resonancia Magnética/métodos , Reconocimiento de Normas Patrones Automatizadas/métodos , Técnicas de Imagen Sincronizada Respiratorias/métodos , Algoritmos , Humanos , Imagenología Tridimensional/métodos , Masculino , Reproducibilidad de los Resultados , Mecánica Respiratoria , Sensibilidad y Especificidad , Técnica de Sustracción , Adulto JovenRESUMEN
PURPOSE: Clinical cardiac MR imaging techniques generally require patients to hold their breath during the scanning process to minimize respiratory motion-related artifacts. However, some patients cannot hold their breath because of illness or limited breath-hold capacity. This study aims to optimize the PROPELLER reconstruction for free-breathing myocardial T1-weighted imaging. METHODS: Eight healthy volunteers (8 men; mean age 26.4 years) participated in this study after providing institutionally approved consent. The PROPELLER encoding method can reconstruct a low-resolution image from every blade because of k-space center oversampling. This study investigated the feasibility of extracting a respiratory trace from the PROPELLER blades by implementing a fully automatic region of interest selection and introducing a best template index to account for the property of the human respiration cycle. RESULTS: Results demonstrated that the proposed algorithm significantly improves the contrast-to-noise ratio and the image sharpness (p < 0.05). CONCLUSIONS: The PROPELLER method is expected to provide a robust tool for clinical application in free-breathing myocardial T1-weighted imaging. It could greatly facilitate the acquisition procedures during such a routine examination.