Renal Artery Flow Measurement on 2D Cine Phase Contrast Sequence

Cine PC can non-invasively measure renal artery blood flow.A 2D cine PC sequence can also be performed after gadolinium-enhanced MRA to take advantage of the increased SNR provided by paramagnetic contrast agents [34]. Using cardiac gating and breath-holding, cine phase contrast offers both high spatial and temporal resolution [35]. Flow volume data per unit time as well as a velocity-time curve for a region of interest can be derived from phase contrast images (Fig. 21). The re

Table 3. General guide for grading renal artery stenoses

Grade

3D Gd MRA

3D PC MRA

Recommendation

Normal

Normal

Normal

Leave alone, medication

Mild stenosis

Stenosis

Normal

Leave alone, medication

Moderate stenosis

Stenosis

+/- dephasing

DSA + pressure measurement

Severe stenosis

Stenosis

+ dephasing

Angioplasty

Occluded

occlusion

Occlusion

Surgery or Medicine

Steps For Kidney Clearance
Fig. 21. Flow measurement with 2D cine phase contrast obtained post gadolinium. Note the difference between the flow profile of the normal right and high grade stenotic left renal artery

sults from this technique show high accuracy and excellent correlation with flow measurements in animal models and indirect techniques such as clearance of p-aminohippurate [36] and 133Xenon washout measurements [37]. On PC-flow curves, the characteristic changes of significant renal artery stenosis include delay and sometimes complete loss of the early systolic peak with reduction in renal capillary resistance [38]. A renal flow index less than 1.5 ml/min/cm3 predicts successful outcome of revasculization [30].

Combining cine PC data with MR angiography reduces interobserver variability on stenosis grading [38]. Cine PC may be useful for follow-up of patients with metallic stents. Although susceptibility artifacts from the stent may impair assessment of vessel patency on traditional CE MRA, cine PC detection of decreased flow beyond the stent may help to detect stenosis within the stent [39]. Cine PC renal blood flow measurements obtained before and after pharmacologic intervention provides even more physiological data. For example, an ACE inhibitor will dramatically reduce flow to the ischemic kidney but has only a minor and symmetrical effect when stenoses are not hemo-dynamically significant [4]. However, different studies have reported controversial results in evaluating the significance of ACE inhibitors [40]. Fur ther experiments are needed to clarify their usefulness and accuracy.

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  • James Shaw
    Is inhance 3d velocity a phase contrast sequence?
    7 years ago

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