Cardiac, respiratory, and patient body motion artifacts degrade the image quality and quantitative accuracy of the nuclear medicine imaging which may lead to incorrect diagnosis, unnecessary treatment and insufficient therapy. We present a new miniaturized system including joint micro electromechanical (MEMS) accelerometer and gyroscope sensors for simultaneous extraction of cardiac and respiratory signals. We employ two tri-axial joint MEMS sensors for selecting an optimal trigger point in a cardiac and respiratory cycle. The 6-axis motion sensing helps to detect candidate features for cardiac and respiratory gating in Positron emission tomography (PET) imaging. The aim of this study was to validate MEMS-derived signals against traditional Real-time Position Management (RPM) and electrocardiography (ECG) measurement systems in 4 healthy volunteers. High agreement and correlation were found between cardiac and respiratory cycle intervals. These promising first results warrant for further investigations.
IntroductionIn cardiac and oncologic Positron emission tomography (PET)/computed tomography (CT) imaging, cardiac, respiratory, and patient body motions may impair the image quality and the quantitative accuracy of heart imaging [1][2][3]. To reduce motion-related inaccuracies, cardiac and respiratory gating methods are the most common approaches applied in clinical PET imaging [4]. Simultaneous respiratory and cardiac gating, namely dual gating, can reduce motion-related inaccuracies and correspondingly imaging resolution in cardiac PET and oncological applications [5]. Cardiac gating is accomplished by an electrocardiography (ECG) measurement system, while respiratory gating can be performed by external devices such as spirometry, elastic belts (consisting of pressure or load cell sensors) monitors or using optical techniques including a camera and laser sensor that track chest wall or abdomen displacement [3,6,7]. However, respiratory gating devices have been considered for only research purposes due to the need for complex logistics and long data processing which may increase patient discomfort and be laborious for the clinicians [2,3]. Additionally, ECG is able to show only electrical activity of the heart and still fails to trace the instantaneous mechanical state of the heart due to the stirring movements of the myocardium [8]. Thus, these challenges complicate PET imaging protocols and create a serious demand for simultaneous recording of cardiac and respiratory signals in dual gating. Recently, new techniques based on bioimpedance [2, 9] and accelerometers [10] have been suggested for concurrent acquisition of both respiratory and cardiac signals in oncologic and cardiac PET imaging. However, there is still space to optimize these methods, especially in terms of technology, accuracy, and patient comfort. We present a new framework based upon tri-axial microelectromechanical (MEMS) accelerometer and gyroscope sensors to extract cardiac and respiratory signals. Our main objective in this study is t...