Phase Of Respiration Cycle Research Articles

Cerebral oxygenation during locomotion is modulated by respiration

In the brain, increased neural activity is correlated with increases of cerebral blood flow and tissue oxygenation. However, how cerebral oxygen dynamics are controlled in the behaving animal remains unclear. We investigated to what extent cerebral oxygenation varies during locomotion. We measured oxygen levels in the cortex of awake, head-fixed mice during locomotion using polarography, spectroscopy, and two-photon phosphorescence lifetime measurements of oxygen sensors. We find that locomotion significantly and globally increases cerebral oxygenation, specifically in areas involved in locomotion, as well as in the frontal cortex and the olfactory bulb. The oxygenation increase persists when neural activity and functional hyperemia are blocked, occurred both in the tissue and in arteries feeding the brain, and is tightly correlated with respiration rate and the phase of respiration cycle. Thus, breathing rate is a key modulator of cerebral oxygenation and should be monitored during hemodynamic imaging, such as in BOLD fMRI.

An Active Self-Driven Piezoelectric Sensor Enabling Real-Time Respiration Monitoring.

In this work, we report an active respiration monitoring sensor based on a piezoelectric-transducer-gated thin-film transistor (PTGTFT) aiming to measure respiration-induced dynamic force in real time with high sensitivity and robustness. It differs from passive piezoelectric sensors in that the piezoelectric transducer signal is rectified and amplified by the PTGTFT. Thus, a detailed and easy-to-analyze respiration rhythm waveform can be collected with a sufficient time resolution. The respiration rate, three phases of respiration cycle, as well as phase patterns can be further extracted for prognosis and caution of potential apnea and other respiratory abnormalities, making the PTGTFT a great promise for application in long-term real-time respiration monitoring.

In vivo measurements of structure/electrode position changes during respiration for Electrical Impedance Tomography

For pulmonary applications of EIT systems, the electrodes are placed around the chest in a 2D ring, and the images are reconstructed based on the assumptions that the object is rigid and the measured resistivity change in EIT images is only caused by the actual resistivity change of tissue. Structural changes are rarely considered. Previous studies have shown that structural changes which result in tissue/organ and electrode position change tend to introduce artifacts to EIT images of the thorax. Since EIT reconstruction is an ill-posed inverse problem, any inaccurate assumptions of object may cause large artifacts in reconstructed images. Accurate information on structure/electrode position changes is necessary to understand factors contributing to the measured resistivity changes and to improve EIT reconstruction algorithm. In this study, in vivo structure/electrode position changes from a healthy male volunteer are investigated during respiration cycle at two levels, the nipple line level and the level approximately 5 cm below. For each level, sixteen fiduciary markers are equally spaced around the surface, the same as the electrode placement for EIT measurements. A MR scanner with respiration-gated ability is used to acquire images of the thorax. MR thoracic images are prospectively acquired corresponding temporally to specific time periods within respiration cycle (FRC, mid tidal volume, tidal volume). The chest expansions in anterior-posterior and lateral directions and inside tissue/organ position changes are then analyzed. The electrode position changes corresponding to different phases of respiration cycle are also measured.

SU-FF-J-34: Video-Surface-Guided Respiratory Motion Correction for 3D Static CT Images

Purpose: Three-dimensional (3D) static CT images of structures in the thorax and abdomen constantly suffer from artifacts caused by periodic respiratory motion. This study presents a novel method to correct respiratory motion for 3D CT images by correlating CT images with dynamic body surface models in which physiologic motion of body surface is recorded with the aid of a 3D video imaging system. Method and Materials: We introduce a new dynamic CT imaging technique that utilizes a commercially available high-speed 3D camera system to gather magnitude and frequency information of respiration cycle by acquiring the motion of body surface. A dynamic body surface model is built to record 3D surface geometry and texture information at different phases of respiration cycle. Retrospective gating technique is then adopted to correlate or register CT images with the dynamic body surface model. Multiple skin markers shown on CT and video surface images are used for verification of the dynamic model. Results: In this study, motion artifacts were remarkable reduced and accurate 4D CT datasets were generated for the further use by planning systems. Conclusion: Quantifying internal anatomy motion as a function of respiration cycle is important in conformal radiotherapy, especially for lung and breast tumors. Compared to conventional 3D CT, four-dimensional CT (4D CT) techniques present overwhelming advantage on imaging objects undergoing periodic motion. The feasibility of 4D CT techniques based on a 3D video imaging system has been demonstrated in this work. Correlating these images with the dynamic body surface models reduced respiratory motion artifacts for 3D CT images. Conflict of Interest: Partially supported by the camera company.