A segmented k‐space velocity mapping protocol for quantification of renal artery blood plow during breath‐holding

Abstract

Two important prerequisites for MR velocity mapping of pulsatile motion are synchronization of the sequence execution to the time course of the flow pattern and robustness toward loss of signal in complex flow fields. Synchronization is normally accomplished by using either prospective ECG triggering or so-called retrospective gating. However, if the studied vessel moves periodically in space as a result of respiratory motion, as in the case of renal arteries, a second synchronization with respect to the vessel motion in space may be necessary. One method to overcome this problem is to use the segmented k-space technique, in which the entire data acquisition can be made within a breath-hold by the sampling of several phase-encoding lines within a small time window during each heart cycle. The aim of this study was to investigate the performance of a segmented k-space velocity mapping protocol for renal artery flow determination. The protocol uses 16 phase-encoding lines per heart beat during 16 heart cycles and gives a temporal velocity resolution of 160 msec. Comparison with a conventional ECG-triggered velocity mapping protocol was made in phantoms as well as in volunteers. In our study, both methods showed sufficient robustness toward complex flow in a phantom model. In comparison with the ECG technique, the segmentation technique reduced vessel blurring and pulsatility artifacts caused by respiratory motion, and average flow values obtained in vivo in the left renal artery agreed between the two methods studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood flow measurements with magnetic resonance phase velocity mapping

“…Consequently, the acquisi tion can be performed in seconds instead of min utes, with high temporal and spatial resolution [60][61][62][63][64]. If velocity-encoding gradients are added to the regular sequence, the flow velocity can be measured rapidly.…”

Renal artery blood flow: quantification with breath-hold or respiratory triggered phase-contrast MR imaging

“…Respiratory motion, which causes the renal arteries to move during data acquisition, appears to be a considerable source of error in these measurements [20,21,22]. Synchronization with respect to respiratory motion, along with cardiac triggering, seems to be necessary to obtain accurate, reproducible flow data [22,23].…”

Ultrafast Flow Quantification With Segmented k-Space Magnetic Resonance Phase Velocity Mapping

“…TGE has shown better flow behavior and is, therefore, more promising for reliable ultrafast flow quantification with relatively disturbed flow and significant vessel motion (e.g., coronary arteries). 9,10,14,20,25 In addition, previous in vitro and clinical studies 2,10,11,14,19,20,23,25,28,29 evaluating both EPI and TGE techniques for PVM have indicated that TGE is generally superior in terms of temporal and (sub-millimeter…”