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Steady State MRA better reveals true anatomy and improves the evaluation of stenosis

Case Study
Maki, Jeffrey, M.D., Ph.D. University of Washington • USA

Patient history

62-year-old male smoker with suspected aorto-iliac and peripheral vascular occlusive disease presented with accelerating 20 yard left calf claudication underwent a peripheral MRA with Achieva 1.5T at the Puget Sound VA HCS, Seattle, USA.

MR examination

Achieva 1.5T, release 2.6 was used with the 12-channel SENSE Peripheral Vascular Coil.

A blood-pool agent was used.
Single Injection moving table pMRA using 10 mL Ablavar (gadofosveset, Lantheus Medical) injected 5 mL at 1mL/sec and 5 mL at 0.6 mL/sec followed by a 25 mL saline flush at 0.6 mL/sec. 

First pass was triggered at the aortic bifurcation using BolusTrak, with:
- upper station: voxels 1.2 x 2.0 x 2.2 mm, scan time 13 sec
- middle station: voxels 1.2 x 1.8 x 1.8 mm, scan time 13 sec
- lower station: voxels 1.1 x 1.1 x 1.1 mm, scan time 70 sec

Sub-diastolic thigh BP cuffs (60 mm Hg) were applied for the mask and first pass only.
Steady state high resolution imaging was performed in all 3 stations (from lower to upper), with:
- lower station: voxels 0.8 x 0.65 x 0.65 mm, scan time 5:00 min
- middle station: voxels 1.0 x 0.8 x 0.8 mm, scan time 2:47 min
- upper station: voxels 1.0 x 0.9 x 0.9 mm, scan time 4:47 min



ExamCard used:

 First pass - 3 station First pass - zoomed Steady state sub-volume
First pass - 3 station
First pass - zoomed
Steady state sub-volume


In the fused 3-station MIP of the first pass pMRA using Ablavar, the apparent image quality is good in all three stations, without venous contamination.

The zoom-up of the left external iliac/mid left SFA shows occlusion of the left CFA (dashed arrow)

with very poor filling distal to the occlusion (above fuse plane upper-middle station), and what appears to be severe disease of the left SFA with distal reconstitution (arrows).

The subvolume MIP through this same region with much higher spatial resolution and steady state phase where all vessels are filled, clearly demonstrates the focal CFA occlusion (arrowhead) with a disease-free left SFA (arrows).

This represents a case where despite apparent good timing (note left popliteal well filled in first pass), the distal slow retrograde filling of the left SFA during the first pass was mistaken for severe disease.
The new information supported the management to a less invasive left femoral endarterectomy.

 First pass right external iliac-distal CFA
First pass right external iliac-distal CFA


The zoom-up of the right external iliac/distal CFA shows tandem stenoses of the right CFA(arrows). Despite the good image quality, note the difficulty in accurately grading these stenoses given the 1.2 x 2.0 x 2.2 mm spatial resolution.


Coronal source images through the superior and inferior stenoses

 Steady state - superior RCFA stenosis Steady state - inferior RCFA stenosis
Steady state - superior RCFA stenosis
Steady state - inferior RCFA stenosis
 Steady state - superior RCFA stenosis Steady state - inferior RCFA stenosis
Steady state - superior RCFA stenosis
Steady state - inferior RCFA stenosis

Corresponding axial reformations


Then note on the steady state coronal source images through the superior and inferior stenoses, and the corresponding axial reformations (dashed lines in top row images) how well the eccentric plaque and residual lumen are seen (arrows), with the more inferior stenosis being quite high grade.

Diagnosis

Focal left CFA occlusion with slowly reconstituting but essentially normal left SFA and moderate proximal and severe distal right CFA stenoses.

Impact of Ablavar Steady State imaging

The left CFA and SFA images demonstrate that steady state MRA better reveals the true anatomy. First pass imaging accurately detected the focal left CFA occlusion, but also erroneously depicted severe left SFA disease.  Based on this imaging alone, the treatment of choice would be a left fem-pop bypass.  The steady state imaging, however, demonstrated the left SFA to be essentially normal, completely changing the management to a much less invasive left femoral endarterectomy

The right external iliac/distal CFA images show the benefits of steady state imaging in depicting of stenoses in aortioiliac MRA. First pass imaging as performed here as part of a 3 station pMRA study has marginal resolution to accurately resolve the degree of stenosis – a common problem with first pass CE-MRA. The steady state imaging, which can most easily be viewed and evaluated by looking at the combination of the source coronal images and axial reformations, gives much better anatomic detail – not only of the lumen, but also of the underlying plaque (dark structures in arterial lumen).


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Nov 10, 2011

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Case Study
Achieva 1.5T
Release 2
ablavar, stenosis, Vascular
 

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