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F R Korosec

Publications and source records attributed to F R Korosec.

40 records · Page 3Linked to original sources
PubMedDate not supplied

A complex-difference phase-contrast technique for measurement of volume flow rates.

Magnetic resonance (MR) phase-difference methods work well for measuring volumetric flow rates when the vessel diameter is large compared with the in-plane voxel dimensions. For small vessels (eg, coronary arteries), partial-volume effects introduce substantial errors in the measured volume flow rate. To correctly measure flow rates through a voxel, both the fraction of the voxel containing moving spins and the phase shift imparted to those spins must be known. The authors propose a flow measurement method that combines information obtained with both the complex-difference and phase-difference processing techniques and thereby provides the fractional volume occupied by the moving spins and the phase of those spins. The complex-difference flow map method proposed results in improved accuracy of MR phase-contrast flow measurements in the presence of partial-volume effects.

Blood Flow Velocity↗
PubMedDate not supplied

Effects of through-plane myocardial motion on phase-difference and complex-difference measurements of absolute coronary artery flow.

We have previously reported on a complex-difference (CD) flow measurement technique that produces more accurate results than the phase-difference (PD) flow measurement technique due to the greater immunity of the former method to partial volume effects. We report here on some of the ways in which through-plane myocardial motion affects the accuracy of absolute coronary artery flow measurements obtained using the PD and CD techniques. We also discuss motion correction schemes that can be applied to the PD and CD processing methods to improve their accuracy. Computer simulations have been performed to assess the magnitude of the errors associated with these flow measurement techniques when they are applied to small vessels that are attached to a moving background. Laminar and plug flow, with and without complete background suppression, have been considered. Experiments with a moving vessel phantom have been conducted to test the performance of the PD and CD flow measurement techniques in circumstances similar to those simulated. The simulations and the experiments showed that, after corrections for through-plane motion are made, the CD method generally yields more accurate flow results than the PD method. As shown by the simulations, however, both methods yield compromised results due to subtle saturation effects that occur when the direction of myocardial motion is opposite the direction of blood flow. Unvalidated PD and CD measurements of coronary artery flow waveforms in human volunteers are presented to illustrate the magnitude of the proposed through-plane motion effects in vivo.

Blood Flow Velocity↗
PubMedDate not supplied

Combined MRI and MRA for limb salvage planning.

Magnetic resonance angiography (MRA) was performed in two patients with primary bone neoplasms being staged for differing types of limb-salvage procedures. A gated two-dimensional (2D) phase contrast MRA sequence that is capable of variable velocity encoding throughout the cardiac cycle was used to acquire the MRA images. The resulting cardiac phase images were added with a matched filter algorithm to create a single high signal-to-noise ratio image. An SE MR image in the same plane and field of view was then added to the MRA image. This displayed the relationship of vascular and stationary tissues within a composite picture: a "2D combined angiographic-stationary tissue" image. The anatomy represented gave information equivalent to conventional angiography. While this technique is not an ideal 3D rendering, it is easier to use. Along with other SE sequences acquired as needed for staging, it provides a complete preoperative evaluation of a tumor bed or donor site for a vascularized graft harvest.

Adolescent↗