Albert Hsiao MD, PhD, Presenter: Nothing to Disclose

Shreyas Shreenivas Vasanawala MD, PhD, Abstract Co-Author: Research support, General Electric Company Consultant, Zimmer Holdings, Inc Consultant, ArthroCare Corporation

Jeffrey A. Feinstein MD, Abstract Co-Author: Nothing to Disclose

V Mohan Reddy, Abstract Co-Author: Nothing to Disclose

Frandics Pak Chan MD, PhD, Abstract Co-Author: Nothing to Disclose

Accurate and precise quantification of blood flow is essential in the management of patients who undergo complex surgical repairs for congenital heart disease. By capturing a velocity vector field, 4D-phase contrast (PC) MRI obviates the need for precise positioning of multiple cut planes required by the 2D approach. We sought to assess the consistency of 4D-PC relative to 2D-PC, and whether the overall acquisition time may be abbreviated by using 4D-PC in patients who undergo Y-graft Fontan repair for single ventricle.

Three patients, 3 to 4 years of age, underwent 5 clinical MRI studies under general anesthesia after surgical placement of Y-grafts for their cavopulmonary connections. 2D-PC measurements were taken at 9 points along the Fontan circuit, followed by a 2D-accelerated tetrahedral velocity-encoded 4D-PC acquisition over the chest. 2D-PC and 4D-PC data were processed with QFlow (Medis) and in-house developed software, respectively. Consistency of the two methods was evaluated by comparing inflow and outflow along the Fontan circuit. A total of 45 pairs of 2D/4D flow measurements and 20 pairs of 2D/4D flow fractions were compared. Data acquisition times for multiple localizer and 2D-PC sequences were also compared against the 4D-PC sequence.

45 pairs of flow measurements ranged from 0 to 2.5 L/min. Bland-Altman limits of agreement ranged from -0.26 to 0.22 L/min with a mean difference of -0.02 L/min. 20 pairs of flow fractions ranged from 34% to 81%. Bland-Altman limits of agreement ranged from -8 to 10% with a mean difference of 1%. The maximum inflow-outflow discrepancies for 2D and 4D measurements were 32% and 19%, respectively, while the average discrepancies were 10% and 5%. The average 2D and 4D acquisition times were 27 min and 10 min.

2D and 4D flow measurements and flow fractions were well-correlated, while total acquisition time for 4D-PC was less than half that for 2D-PC. 4D-PC flow measurements were also more internally consistent than 2D-PC. Therefore, 4D-PC is a valuable tool for evaluating patients with complex heart repairs.

4D-PC is an effective and accurate technique for the assessment of blood flow, and may significantly shorten overall anesthesia time when interrogation of multiple vessels is required.

Hsiao, A, Vasanawala, S, Feinstein, J, Reddy, V, Chan, F, Effectiveness of 4D-Phase Contrast MRI in the Assessment of Complex Flow after Y-graft Fontan Repair.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11014401.html