title: Intra-vascular blood velocity and volumetric flow rate calculated from dynamic 4D CT angiography using a time of flight technique.
abstract: We examine a time of flight (TOF) approach for the analysis of contrast enhanced 4D volumetric CT angiography scans to derive and display blood velocity in arteries. Software was written to divide blood vessels into a series of cross sections and to track contrast bolus TOF along the central vessel axis, which was defined by a user, from 4D CT source data. Time density curves at each vessel cross section were fit with quadratic, Gaussian, and gamma variate functions to determine bolus time to peak (TTP). A straight line was used to plot TTP versus vessel path length for all three functions and the slope used to calculate intraluminal velocity. Software was validated in a simulated square channel and non-pulsatile flow phantom prior to the calculation of blood velocity in the major cerebral arteries of 8 normal patients. The TOF algorithm correctly calculates intra-luminal fluid velocity in eight flow conditions of the CT flow phantom where quadratic functions were used. Across all conditions, in phantoms and in vivo, the success of calculations depended strongly on having a sufficiently long path length to make measurements and avoiding venous contamination. Total blood flow into the brain was approximately 17 % of a normal 5 L cardiac output. The technique was explored in vivo in a patient with subclavian steal syndrome, in the pulmonary arteries and in the iliac artery from clinical 4D CT source data. Intravascular blood velocity and flow may be calculated from 4D CT angiography using a TOF approach.
authors.affiliation: Department of Medical Imaging, St. Michael's Hospital, 30 Bond Street, Toronto, ON, M5B 1W8, Canada, barfettj@smh.ca.
authors.forename: Joseph John
authors.initials: JJ
authors.lastname: Barfett
authors.forename: Nivethan
authors.initials: N
authors.lastname: Velauthapillai
authors.forename: Jorn
authors.initials: J
authors.lastname: Fierstra
authors.forename: Adrian
authors.initials: A
authors.lastname: Crawley
authors.forename: Catherine
authors.initials: C
authors.lastname: Coolens
authors.forename: Andrew
authors.initials: A
authors.lastname: Crean
authors.forename: Jeff
authors.initials: J
authors.lastname: Jaskolka
authors.forename: Paul
authors.initials: P
authors.lastname: Dufort
authors.forename: Timo
authors.initials: T
authors.lastname: Krings
authors.forename: David
authors.initials: D
authors.lastname: Mikulis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000792:Angiography / Q000295:instrumentation / Q000379:methods*; D001783:Blood Flow Velocity; D002536:Cerebral Arteries / Q000000981:diagnostic imaging / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D003287:Contrast Media; D005260:Female; D056973:Four-Dimensional Computed Tomography / Q000295:instrumentation; D006439:Hemodynamics; D006801:Humans; D007083:Iliac Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D011651:Pulmonary Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D011652:Pulmonary Circulation; D011857:Radiographic Image Interpretation, Computer-Assisted; D012039:Regional Blood Flow; D012189:Retrospective Studies; D012986:Software Validation; D013349:Subclavian Steal Syndrome / Q000000981:diagnostic imaging / Q000503:physiopathology; D013997:Time Factors; D014711:Vertebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology
chemical_list: D003287:Contrast Media