title: Transfer function analysis of respiratory and cardiac pulsations in human brain observed on dynamic magnetic resonance images.
abstract: Magnetic resonance (MR) imaging provides a noninvasive, in vivo imaging technique for studying respiratory and cardiac pulsations in human brains, because these pulsations can be recorded as flow-related enhancement on dynamic MR images. By applying independent component analysis to dynamic MR images, respiratory and cardiac pulsations were observed. Using the signal-time curves of these pulsations as reference functions, the magnitude and phase of the transfer function were calculated on a pixel-by-pixel basis. The calculated magnitude and phase represented the amplitude change and temporal delay at each pixel as compared with the reference functions. In the transfer function analysis, near constant phases were found at the respiratory and cardiac frequency bands, indicating the existence of phase delay relative to the reference functions. In analyzing the dynamic MR images using the transfer function analysis, we found the following: (1) a good delineation of temporal delay of these pulsations can be achieved; (2) respiratory pulsation exists in the ventricular and cortical cerebrospinal fluid; (3) cardiac pulsation exists in the ventricular cerebrospinal fluid and intracranial vessels; and (4) a 180-degree phase delay or inverted amplitude is observed on phase images.
authors.affiliation: Department of Biomedical Imaging and Radiological Sciences, School of Medicine, National Yang-Ming University, and Department of Radiology, Taipei Veterans General Hospital, Taipei 112, Taiwan. yhkao@ym.edu.tw
authors.forename: Yi-Hsuan
authors.initials: YH
authors.lastname: Kao
authors.forename: Wan-Yuo
authors.initials: WY
authors.lastname: Guo
authors.forename: Adrain Jy-Kang
authors.initials: AJ
authors.lastname: Liou
authors.forename: Ting-Yi
authors.initials: TY
authors.lastname: Chen
authors.forename: Chau-Chiun
authors.initials: CC
authors.lastname: Huang
authors.forename: Chih-Che
authors.initials: CC
authors.lastname: Chou
authors.forename: Jiing-Feng
authors.initials: JF
authors.lastname: Lirng
mesh_terms: D001921:Brain / Q000098:blood supply* / Q000502:physiology*; D002555:Cerebrospinal Fluid / Q000502:physiology; D002560:Cerebrovascular Circulation; D019295:Computational Biology; D017352:Echo-Planar Imaging / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008955:Models, Cardiovascular; D008959:Models, Neurological; D011673:Pulsatile Flow; D015656:Respiratory Mechanics