Danias P G, Stuber M, Botnar R M, Kissinger K V, Edelman R R, Manning W J
Department of Medicine, Charles A. Dana Research Institute and the Harvard-Thorndike Laboratory, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA.
AJR Am J Roentgenol. 1999 Apr;172(4):1061-5. doi: 10.2214/ajr.172.4.10587147.
Diaphragmatic navigators are frequently used in free-breathing coronary MR angiography, either to gate or prospectively correct slice position or both. For such approaches, a constant relationship between coronary and diaphragmatic displacement throughout the respiratory cycle is assumed. The purpose of this study was to evaluate the relationship between diaphragmatic and coronary artery motion during free breathing.
A real-time echoplanar MR imaging sequence was used in 12 healthy volunteers to obtain 30 successive images each (one per cardiac cycle) that included the left main coronary artery and the domes of both hemidiaphragms. The coronary artery and diaphragm positions (relative to isocenter) were determined and analyzed for effective diaphragmatic gating windows of 3, 5, and 7 mm (diaphragmatic excursions of 0-3, 0-5, and 0-7 mm from the end-expiratory position, respectively).
Although the mean slope correlating the displacement of the right diaphragm and the left main coronary artery was approximately 0.6 for all diaphragmatic gating windows, we also found great variability among individual volunteers. Linear regression slopes varied from 0.17 to 0.93, and r2 values varied from .04 to .87.
Wide individual variability exists in the relationship between coronary and diaphragmatic respiratory motion during free breathing. Accordingly, coronary MR angiographic approaches that use diaphragmatic navigator position for prospective slice correction may benefit from patient-specific correction factors. Alternatively, coronary MR angiography may benefit from a more direct assessment of the respiratory displacement of the heart and coronary arteries, using left ventricular navigators.
膈肌导航器常用于自由呼吸状态下的冠状动脉磁共振血管造影，用于门控或前瞻性校正层面位置，或两者兼用。对于此类方法，假定在整个呼吸周期中冠状动脉和膈肌位移之间存在恒定关系。本研究的目的是评估自由呼吸期间膈肌与冠状动脉运动之间的关系。
对12名健康志愿者使用实时平面回波磁共振成像序列，以获取连续30幅图像（每个心动周期一幅），这些图像包括左冠状动脉主干和双侧膈肌圆顶。确定并分析冠状动脉和膈肌位置（相对于等中心），以获得3、5和7毫米的有效膈肌门控窗（分别为从呼气末位置开始膈肌移动0 - 3、0 - 5和0 - 7毫米）。
尽管对于所有膈肌门控窗，右膈肌位移与左冠状动脉主干位移的平均斜率约为0.6，但我们也发现个体志愿者之间存在很大差异。线性回归斜率从0.17到0.93不等，r²值从0.04到0.87不等。
自由呼吸期间冠状动脉与膈肌呼吸运动之间的关系存在很大的个体差异。因此，利用膈肌导航器位置进行前瞻性层面校正的冠状动脉磁共振血管造影方法可能受益于针对患者的校正因子。或者，冠状动脉磁共振血管造影可能受益于使用左心室导航器对心脏和冠状动脉呼吸位移进行更直接的评估。
