Automated image acquisition of apical four-chamber view with robotic echocardiography

PURPOSE: The purpose of this study is to propose a method for automatically estimating the position and angle of the acoustic window required to acquire the apical four-chamber view in echocardiography. The apical four-chamber view is clinically important, but it requires accurate probe placement near the cardiac apex. Acquisition of the apical four-chamber view is technically challenging because the acoustic window available for transthoracic ultrasound transmission is restricted by the intercostal space, and the cardiac apex and endocardial borders can be difficult to delineate due to rib shadowing and acoustic attenuation caused by the chest wall and subcutaneous tissue. Therefore, this study proposes a method for automatically acquiring cross sectional images without directly detecting the apex. METHODS: The proposed method estimates the apical four-chamber view through a three-step procedure. First, starting from the parasternal long-axis view, the probe is swept obliquely along the body surface while maintaining the mitral valve near the center of the ultrasound image and gradually rotating the probe toward the apical region. This maneuver is continued through the acoustic window where the cardiac apex can be visualized until the mitral valve leaflets are no longer visible. Second, the probe is rotated and angled to visualize the tricuspid valve, mitral valve, and interventricular septum in a single imaging plane. Finally, the probe is tilted and rocked to optimize the apical four-chamber view. RESULTS: Proof-of-concept experiments demonstrated that the proposed framework could estimate probe positions and orientations for acquiring apical four-chamber views without direct apex detection. Across five subjects, the system achieved an image quality score of 68.0% ± 7.6% based on predefined scoring criteria. These preliminary findings suggest the potential feasibility of algorithm-assisted guidance for apical view acquisition in echocardiography. CONCLUSION: This study presented a three-step method to estimate the acoustic window for apical four-chamber acquisition without direct apex detection. A proof-of-concept evaluation in five subjects demonstrated that the proposed method could estimate the target acoustic window and suggested the potential of algorithm-assisted guidance for apical four-chamber view acquisition.