title: Blood tracer kinetics in the arterial tree.
abstract: Evaluation of blood supply of different organs relies on labeling blood with a suitable tracer. The tracer kinetics is linear: Tracer concentration at an observation site is a linear response to an input somewhere upstream the arterial flow. The corresponding impulse response functions are currently treated empirically without incorporating the relation to the vascular morphology of an organ. In this work we address this relation for the first time. We demonstrate that the form of the response function in the entire arterial tree is reduced to that of individual vessel segments under approximation of good blood mixing at vessel bifurcations. The resulting expression simplifies significantly when the geometric scaling of the vascular tree is taken into account. This suggests a new way to access the vascular morphology in vivo using experimentally determined response functions. However, it is an ill-posed inverse problem as demonstrated by an example using measured arterial spin labeling in large brain arteries. We further analyze transport in individual vessel segments and demonstrate that experimentally accessible tracer concentration in vessel segments depends on the measurement principle. Explicit expressions for the response functions are obtained for the major middle part of the arterial tree in which the blood flow in individual vessel segments can be treated as laminar. When applied to the analysis of regional cerebral blood flow measurements for which the necessary arterial input is evaluated in the carotid arteries, present theory predicts about 20% underestimation, which is in agreement with recent experimental data.
authors.affiliation: Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Elias
authors.initials: E
authors.lastname: Kellner
authors.affiliation: Siemens AG, Healthcare Sector, Erlangen, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Gall
authors.affiliation: Fraunhofer MEVIS, Institute for Medical Image Computing, Bremen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Günther
authors.affiliation: Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Reisert
authors.affiliation: Department of Neuroradiology, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Irina
authors.initials: I
authors.lastname: Mader
authors.affiliation: Gruss Magnetic Resonance Research Center, Department of Radiology, Albert Einstein College of Medicine, New York, New York, United States of America.
authors.forename: Roman
authors.initials: R
authors.lastname: Fleysher
authors.affiliation: Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Valerij G
authors.initials: VG
authors.lastname: Kiselev
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology*; D001921:Brain / Q000098:blood supply / Q000502:physiology; D002339:Carotid Arteries / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D013113:Spin Labels
chemical_list: D013113:Spin Labels