Improved quantification and mapping of anomalous pulmonary venous flow with four-dimensional phase-contrast MRI and interactive streamline rendering.
BACKGROUND
Cardiac MRI is routinely performed for quantification of shunt flow in patients with anomalous pulmonary veins, but can be technically-challenging to perform. Four-dimensional phase-contrast (4D-PC) MRI has potential to simplify this exam. We sought to determine whether 4D-PC may be a viable clinical alternative to conventional 2D phase-contrast MR imaging.


METHODS
With institutional review board approval and HIPAA-compliance, we retrospectively identified all patients with anomalous pulmonary veins who underwent cardiac MRI at either 1.5 Tesla (T) or 3T with parallel-imaging compressed-sensing (PI-CS) 4D-PC between April, 2011 and October, 2013. A total of 15 exams were included (10 male, 5 female). Algorithms for interactive streamline visualization were developed and integrated into in-house software. Blood flow was measured at the valves, pulmonary arteries and veins, cavae, and any associated shunts. Pulmonary veins were mapped to their receiving atrial chamber with streamlines. The intraobserver, interobserver, internal consistency of flow measurements, and consistency with conventional MRI were then evaluated with Pearson correlation and Bland-Altman analysis.


RESULTS
Triplicate measurements of blood flow from 4D-PC were highly consistent, particularly at the aortic and pulmonary valves (cv 2-3%). Flow measurements were reproducible by a second observer (ρ = 0.986-0.999). Direct measurements of shunt volume from anomalous veins and intracardiac shunts matched indirect estimates from the outflow valves (ρ = 0.966). Measurements of shunt fraction using 4D-PC using any approach were more consistent with ventricular volumetric displacements than conventional 2D-PC (ρ = 0.972-0.991 versus 0.929).


CONCLUSIONS
Shunt flow may be reliably quantified with 4D-PC MRI, either indirectly or with detailed delineation of flow from multiple shunts. The 4D-PC may be a more accurate alternative to conventional MRI.
Department of Radiology, University of California, San Diego, California, USA.
Albert
A
Hsiao
Department of Radiology, Stanford University, Stanford, California, USA.
Ufra
U
Yousaf
Department of Radiology, Stanford University, Stanford, California, USA.
Marcus T
MT
Alley
Department of Electrical Engineering and Computer Science, University of California, Berkeley, California, USA.
Michael
M
Lustig
Department of Radiology, Stanford University, Stanford, California, USA.
Frandics Pak
FP
Chan
Department of Radiology, Stanford University, Stanford, California, USA.
Beverley
B
Newman
Department of Radiology, Stanford University, Stanford, California, USA.
Shreyas S
SS
Vasanawala
D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001783:Blood Flow Velocity; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007223:Infant; D018810:Magnetic Resonance Angiography / Q000379:methods*; D015588:Observer Variation; D011667:Pulmonary Veins / Q000002:abnormalities* / Q000473:pathology / Q000503:physiopathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014584:User-Computer Interface; D055815:Young Adult
flow; pulmonary; shunt; structural; veins