Based on the imaging photoplethysmography (iPPG) and blind source separation (BSS) theory the author put forward a method for non-contact heartbeat frequency estimation. Using the recorded video images of the human face in the ambient light with Webcam, we detected the human face through software, separated the detected facial image into three channels RGB components. And then preprocesses i.e. normalization, whitening, etc. were carried out to a certain number of RGB data. After the independent component analysis (ICA)'theory and joint approximate diagonalization of eigenmatrices (JADE) algorithm were applied, we estimated the frequency of heart rate through spectrum analysis. Taking advantage of the consistency of Bland-Altman theory analysis and the commercial Pulse Oximetry Sensor test results, the root mean square error of the algorithm result was calculated as 2. 06 beat/min. It indicated that the algorithm could realize the non-contact measurement of heart rate and lay the foundation for the re- mote and non-contact measurement of multi-parameter physiological measurements.
Algorithms ; Face ; Heart Rate ; Humans ; Monitoring, Physiologic ; methods ; Oximetry ; Photoplethysmography ; Software ; Video Recording

Objective:To explore the clinical application value of the dual-layer detector spectral CTA in evaluation of brain perfusion impairment in patients with acute ischemic stroke.Methods:Clinical and imaging data of 35 patients with acute ischemic stroke in Weihai Central Hospital from March 2020 to October 2020 were reviewed retrospectively. All patients underwent head and neck spectral CTA examination and dynamic cerebral perfusion CT examination with dual-layer detector spectral CT. The iodine density map and effective atomic number map were reconstructed using CTA data, and the iodine density and effective atomic number, as well as the cerebral blood volume (CBV) and cerebral blood flow (CBF) values of the hypoperfusion area and the contralateral side were measured and compared; the areas of brain hypoperfusion regions were measured. Pearson′s correlation coefficient was used to analyze the correlation between iodine density values and CBV values, iodine density values and CBF values, effective atomic number values and CBV values, effective atomic number values and CBF values, as well as hypoperfusion area shown on CTA images and displayed on CTP-CBF map.Results:Of all the 35 patients, the iodine density value [(0.22±0.07) mg/ml], effective atomic number value (7.38±0.05), CBV value [(1.9±0.7) ml/100 g] and CBF value [(15.1±5.9) ml/(100 g·min)] of the hypoperfusion area were significantly lower than those of the healthy side [iodine density value (0.44±0.10) mg/ml, effective atomic number value (7.52±0.06), CBV value (3.4±0.7) ml/100 g, CBF value (57±27) ml/(100 g·min); t values were -14.7, -14.5, -11.2, -9.7, respectively, all P<0.001]. No significant difference was found between the hypoperfusion area shown on spectral CTA [(2 292±1 393) mm 2] and shown on CTP-CBF map [(2 290±1 359) mm 2] ( t=-0.076, P=0.944). There was a positive correlation between iodine density value and CBV (affected side: r=0.350, P=0.039, healthy side: r=0.551, P=0.001); a positive correlation was also found between effective atomic number value and CBV (affected side: r=0.488, P=0.003, healthy side: r=0.552, P=0.001); and there was a strong positive correlation between the hypoperfusion area on CTA and that on CTP-CBF ( r=0.993, P<0.001). Conclusion:Dual-layer detector spectral CTA can provide the “one-stop” assessement including head and neck vascular evaluation, as well as the hypoperfution area measument, which can be an alternative rapid method for evaluation of patients with acute ischemic stroke.