Liu Jian-Hung, Jeng Geng-Shi, Wu Tung-Ke, Li Pai-Chi
Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan.
IEEE Trans Ultrason Ferroelectr Freq Control. 2006 Sep;53(9):1590-6. doi: 10.1109/tuffc.2006.1678187.
Echocardiography (ECG) is routinely used in the clinical diagnosis of cardiac function. The anatomy of the mouse is similar to that of the human, and thus murine ECG has become an effective tool for the assessment of small animal models of human cardiac diseases. Unfortunately, clinical ultrasonic imaging systems are not suitable for murine cardiac imaging due to their limited spatial and temporal resolutions. Murine ECG requires a spatial resolution better than 100 pim, which mandates the use of high-frequency, ultrasonic imaging (i.e., >20 MHz). High-frequency transducer arrays currently are not available, and so such systems use the mechanical scanning of a single-element transducer for which the frame rate is insufficient for directly monitoring the rapid beating of a mouse heart, and thus retrospective image reconstruction is necessary. This paper presents a high-frequency, ultrasonic imaging system for murine cardiac imaging. Two scanning methods have been developed. One is based on ECG triggering and is called the block scanning mode, in which the murine cardiac images from the isovolumic contraction and isovolumic relaxation phases are retrospectively reconstructed within a relatively short data acquisition time using the ECG R-wave as the trigger to the imaging system. The other method is the line scanning mode based on ECG gating, in which both ECG and ultrasound scan lines are continuously acquired over a longer time, enabling images during the entire cardiac cycle to be obtained. It is demonstrated here that the effective frame rate is determined by the pulse repetition frequency and can be up to 2 kHz in the presented system.
超声心动图（ECG）常用于心脏功能的临床诊断。小鼠的解剖结构与人类相似，因此小鼠超声心动图已成为评估人类心脏疾病小动物模型的有效工具。不幸的是，临床超声成像系统由于其有限的空间和时间分辨率，不适用于小鼠心脏成像。小鼠超声心动图需要优于100微米的空间分辨率，这就要求使用高频超声成像（即>20MHz）。目前尚无高频换能器阵列，因此此类系统使用单元素换能器的机械扫描，其帧率不足以直接监测小鼠心脏的快速跳动，因此需要进行回顾性图像重建。本文介绍了一种用于小鼠心脏成像的高频超声成像系统。开发了两种扫描方法。一种基于心电图触发，称为块扫描模式，其中使用心电图R波作为成像系统的触发信号，在相对较短的数据采集时间内回顾性重建等容收缩期和等容舒张期的小鼠心脏图像。另一种方法是基于心电图门控的线扫描模式，其中在较长时间内连续采集心电图和超声扫描线，从而获得整个心动周期的图像。本文证明有效帧率由脉冲重复频率决定，在所提出的系统中可达2kHz。
