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Abstract：
BACKGROUND: Three-dimensional (3D) contrast-enhanced magnetic resonance angiography (CEMRA) is routinely used for vascular evaluation. With existing techniques for CEMRA, diagnostic image quality is only obtained during the first pass of the contrast agent or shortly thereafter, whereas angiographic quality tends to be poor when imaging is delayed to the equilibrium phase. We hypothesized that prolonged blood pool contrast enhancement could be obtained by imaging with a balanced T1 relaxation-enhanced steady-state (bT1RESS) pulse sequence, which combines 3D balanced steady-state free precession (bSSFP) with a saturation recovery magnetization preparation to impart T1 weighting and suppress background tissues. An electrocardiographic-gated, two-dimensional-accelerated version with isotropic 1.1-mm spatial resolution was evaluated for breath-hold equilibrium phase CEMRA of the thoracic aorta and heart.
METHODS: The study was approved by the institutional review board. Twenty-one subjects were imaged using unenhanced 3D bSSFP, time-resolved CEMRA, first-pass gated CEMRA, followed by early and late equilibrium phase gated CEMRA and bT1RESS. Nine additional subjects were imaged using equilibrium phase 3D bSSFP and bT1RESS. Images were evaluated for image quality, aortic root sharpness, and visualization of the coronary artery origins, as well as using standard quantitative measures.
RESULTS: Equilibrium phase bT1RESS provided better image quality, aortic root sharpness, and coronary artery origin visualization than gated CEMRA (P < 0.05), and improved image quality and aortic root sharpness versus unenhanced 3D bSSFP (P < 0.05). It provided significantly larger apparent signal-to-noise and apparent contrast-to-noise ratio values than gated CEMRA and unenhanced 3D bSSFP (P < 0.05) and provided ninefold better fluid suppression than equilibrium phase 3D bSSFP. Aortic diameter and main pulmonary artery diameter measurements obtained with bT1RESS and first-pass gated CEMRA strongly correlated (P < 0.05).
CONCLUSIONS: We found that using bT1RESS greatly prolongs the useful duration of blood pool contrast enhancement while improving angiographic image quality compared with standard CEMRA techniques. Although further study is needed, potential advantages for vascular imaging include eliminating the current requirement for first-pass imaging along with better reliability and accuracy for a wide range of cardiovascular applications.
METHODS: The study was approved by the institutional review board. Twenty-one subjects were imaged using unenhanced 3D bSSFP, time-resolved CEMRA, first-pass gated CEMRA, followed by early and late equilibrium phase gated CEMRA and bT1RESS. Nine additional subjects were imaged using equilibrium phase 3D bSSFP and bT1RESS. Images were evaluated for image quality, aortic root sharpness, and visualization of the coronary artery origins, as well as using standard quantitative measures.
RESULTS: Equilibrium phase bT1RESS provided better image quality, aortic root sharpness, and coronary artery origin visualization than gated CEMRA (P < 0.05), and improved image quality and aortic root sharpness versus unenhanced 3D bSSFP (P < 0.05). It provided significantly larger apparent signal-to-noise and apparent contrast-to-noise ratio values than gated CEMRA and unenhanced 3D bSSFP (P < 0.05) and provided ninefold better fluid suppression than equilibrium phase 3D bSSFP. Aortic diameter and main pulmonary artery diameter measurements obtained with bT1RESS and first-pass gated CEMRA strongly correlated (P < 0.05).
CONCLUSIONS: We found that using bT1RESS greatly prolongs the useful duration of blood pool contrast enhancement while improving angiographic image quality compared with standard CEMRA techniques. Although further study is needed, potential advantages for vascular imaging include eliminating the current requirement for first-pass imaging along with better reliability and accuracy for a wide range of cardiovascular applications.
摘要：
背景：三维（3D）对比增强MR血管造影（CEMRA）常规用于血管评估。利用CEMRA的现有技术，诊断图像质量仅在造影剂的第一次通过期间或此后不久获得，而当成像延迟到平衡阶段时，血管造影质量往往较差。我们假设，通过使用平衡的T1弛豫增强稳态（bT1RESS）脉冲序列成像可以获得延长的血池对比增强，将3D平衡稳态自由进动（bSSFP）与饱和恢复磁化准备相结合，以赋予T1加权并抑制背景组织。心电图（ECG）门控，对于胸主动脉和心脏的屏气平衡阶段CEMRA，评估了具有各向同性1.1mm空间分辨率的2D加速版本。主体本研究获得IRB批准。21名受试者使用未增强的3DbSSFP成像，时间分辨CEMRA,第一次通过门控CEMRA，其次是早期和晚期平衡阶段门控CEMRA和bT1RESS。另外9名受试者使用平衡相3DbSSFP和bT1RESS成像。评估图像质量，主动脉根部锐度，以及冠状动脉起源的可视化，以及使用标准的定量措施。
结果：平衡阶段bT1RESS提供了更好的图像质量，主动脉根部锐度，和冠状动脉起源的可视化比门控CEMRA（P<0.05），与未增强的3DbSSFP相比，提高了图像质量和主动脉根部清晰度（P<0.05）。与门控CEMRA和未增强的3DbSSFP相比，它提供了明显更大的表观信噪比和表观对比度（P<0.05），并且比平衡相3DbSSFP提供了九倍的更好的流体抑制。bT1RESS和首过门控CEMRA获得的主动脉直径和主肺动脉直径测量结果密切相关（P<0.05）。
结论：我们发现，与标准CEMRA技术相比，使用bT1RESS大大延长了血池对比度增强的有用持续时间，同时改善了血管造影图像质量。虽然还需要进一步的研究,血管成像的潜在优势包括消除了当前对首次成像的要求，以及为广泛的心血管应用提供更好的可靠性和准确性。
结果：平衡阶段bT1RESS提供了更好的图像质量，主动脉根部锐度，和冠状动脉起源的可视化比门控CEMRA（P<0.05），与未增强的3DbSSFP相比，提高了图像质量和主动脉根部清晰度（P<0.05）。与门控CEMRA和未增强的3DbSSFP相比，它提供了明显更大的表观信噪比和表观对比度（P<0.05），并且比平衡相3DbSSFP提供了九倍的更好的流体抑制。bT1RESS和首过门控CEMRA获得的主动脉直径和主肺动脉直径测量结果密切相关（P<0.05）。
结论：我们发现，与标准CEMRA技术相比，使用bT1RESS大大延长了血池对比度增强的有用持续时间，同时改善了血管造影图像质量。虽然还需要进一步的研究,血管成像的潜在优势包括消除了当前对首次成像的要求，以及为广泛的心血管应用提供更好的可靠性和准确性。
