Gkotsis Dimosthenis E, Bherwani Anand, Kapsalaki Eftychia Z, Bishop Courtney J, Schwarz Adam J
From the GE HealthCare, Pharmaceutical Diagnostics, London, United Kingdom (D.E.G., A.B., C.J.B., A.J.S.); Radiology Department, Diagnostic Center Euromedica, Athens, Greece (E.Z.K.); and Department of Radiology, University of Thessaly, School of Medicine, Larissa, Greece (E.Z.K.).
Invest Radiol. 2025 May 7. doi: 10.1097/RLI.0000000000001205.
The objective of this study is to derive a contrast agent-specific theoretical framework to optimize acquisition parameters for contrast-enhanced magnetic resonance imaging (MRI) based on the physiochemical properties of gadolinium-based contrast agents, focusing on fast spoiled gradient recalled echo sequences. The goal is to enhance the lesion-to-background contrast for improved diagnostic sensitivity in clinical applications.
Signal equations for fast spoiled gradient recalled echo sequences were derived for nonenhancing and enhancing tissues using gadoterate meglumine and gadobutrol, characterized by distinct longitudinal (r1) and transverse (r2/r*2) relaxivities. Simulations were conducted at 2 field strengths, 1.5T and 3.0T, and various scenarios were considered, including hypothetical lesions with T1 ratios ranging from 1.1 to 1.8. The signal behavior was analyzed across a range of initial conditions, including different spin densities and field-strength dependent variations in tissue relaxation times. The optimal flip angle and repetition time combinations were determined to maximize contrast. In vivo validation was performed on 2 patients undergoing contrast-enhanced MRI of the brain, using the proposed acquisition parameters.
The modeling and simulations revealed that the flip angle that maximizes signal intensity for a contrast-enhancing lesion (Ernst angle) differs from the flip angle that maximizes T1-dependent contrast between lesion and healthy tissue in unenhanced MRI (Pelc angle) and also differs from the flip angle that maximizes the same in contrast-enhanced MRI. The theoretical simulations indicated possible contrast gains of 24%-28% using optimized parameters. The in vivo acquisitions demonstrated contrast gains of 19%-44% for a diffuse enhancing lesion and 91% for a weakly enhancing focal lesion, when comparing the optimized acquisition parameters to manufacturer's default settings.
Adjusted repetition time and flip angle values, derived using the proposed framework, improved the image contrast between healthy and diseased tissues, enhancing the visualization of abnormalities. This approach can be used to optimize routine clinical MRI protocols and balance scan time with contrast enhancement. This may translate to more precise lesion detection, potentially leading to earlier and more accurate diagnosis or treatment monitoring in clinical practice.
本研究的目的是基于钆基造影剂的物理化学性质，推导一种针对造影剂的理论框架，以优化基于快速扰相梯度回波序列的对比增强磁共振成像（MRI）的采集参数。目标是提高病变与背景的对比度，以提高临床应用中的诊断敏感性。
使用钆特醇和钆布醇，针对非增强和增强组织推导快速扰相梯度回波序列的信号方程，其特征在于具有不同的纵向（r1）和横向（r2/r*2）弛豫率。在1.5T和3.0T这两种场强下进行模拟，并考虑了各种情况，包括T1比率范围为1.1至1.8的假设病变。在一系列初始条件下分析信号行为，包括不同的自旋密度和组织弛豫时间的场强依赖性变化。确定最佳翻转角和重复时间组合以最大化对比度。使用建议的采集参数对2名接受脑部对比增强MRI的患者进行体内验证。
建模和模拟显示，使增强病变的信号强度最大化的翻转角（恩斯特角）不同于在未增强MRI中使病变与健康组织之间基于T1的对比度最大化的翻转角（佩尔茨角），也不同于在对比增强MRI中使相同对比度最大化的翻转角。理论模拟表明，使用优化参数可能使对比度提高24%-28%。与制造商的默认设置相比，体内采集显示，对于弥漫性增强病变，对比度提高了19%-44%，对于弱增强局灶性病变，对比度提高了91%。
使用所提出的框架得出的调整后的重复时间和翻转角值，改善了健康组织与病变组织之间的图像对比度，增强了异常的可视化。这种方法可用于优化常规临床MRI方案，并在扫描时间与对比增强之间取得平衡。这可能转化为更精确的病变检测，有可能在临床实践中实现更早、更准确的诊断或治疗监测。
