CORONARY FLOW AND FLOW RESERVE IN CANINES USING MR PHASE DIFFERENCE AND COMPLEX DIFFERENCE PROCESSING

Coronary artery disease continues to be the leading cause of death for adults in the United States. Magnetic resonance imaging (MR) has the potential to dramatically impact the diagnosis of heart disease by non invasively providing a wide range of anatomic and physiologic informat ion. Previous research has shown that coronary flow, one component of a complete examination, can be accurately measured in the left anterio r descending artery in vivo. The current work validates MR flow measur ements in canine circumflex arteries using transit time ultrasound as a standard. The circumflex artery experiences greater in-plane motion and is a more stringent test for flow measurement accuracy, This work also compares two methods of processing MR velocity data, phase differ ence and complex difference techniques, and examines the sources of er ror present in the animal validation model, Phase difference processin g with a 30% magnitude threshold best matched the mean ultrasound flow values (30% PD = 1.04 x US + 1.49, r = 0.94), but it was very sensiti ve to vessel boundary identification. The complex difference process w as less sensitive to vessel boundary identification and correlated wel l with the transit time ultrasound despite systematic underestimations . The reasons for the discrepancies are shown to stem from a number of possible sources including variability of the ultrasound standard, lo w signal-to-noise ratios in the MR images, sensitivity of the MR techn ique to vessel boundary identification, and motion artifacts in the im ages.