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Tips for non-contrast MRA

Application Tip
van Essen, Marco Philips Healthcare • Netherlands
Geerts, Liesbeth Philips Healthcare • Netherlands

In the past few years, new developments have spurred the use of non-CE MRA. Philips MR scanners provide two robust sequences for non-contrast MR angiography: TRANCE and B-TRANCE.

The tips are based on the most recent insights.


TRANCE involves the acquisition and subtraction of systolic and diastolic images using a 3D-TSE sequence. In a diastolic image both arteries and veins are bright. In a systolic image, arteries appear dark due to dephasing of the signal in the fast flowing blood, and veins are bright. So, in the subtracted image only the arteries are visible.

 
In B-TRANCE a volume-selective IR prepulse is used in combination with 3D B-TFE readout. The IR prepulse is applied for background suppression, while the use of a delay between application of the IR prepulse and the readout allows for inflow of unaffected blood.

Tip 1: Setting flowcomp in TRANCE

In diastole, use flowcomp = Yes

In systole, use flowcomp = Sensitized

Sensitized flowcomp is sensitive to acceleration in flow, so helps improve nulling in arteries, making it a very robust method for arteries. Note that background suppression will be best if a fixed TE and water fat shift (WFS) is used in both acquisitions.

 Flowcomp NO Flowcomp Yes and Sensitized
Flowcomp NO
Flowcomp Yes and Sensitized

Tip 2: Best flip angle in TRANCE depends on vessel size

The flip angle of the refocusing pulses determines the relative contributions of spin echoes and stimulated echoes, and therefore strongly influences the flow sensitivity of the sequence.

The large vessels, such as the popliteal artery, are better depicted with a high flip angle, whereas smaller branch vessels are better depicted at lower flip angle. Generally, the optimum flip angle to depict both larger and smaller vessels ranges between 90° and 120°.

 

 
Reference

P Storey, IP Atanasova, RP Lim, J Xu, D Kim, Q Chen, VS Lee
Tailoring the Flow Sensitivity of Fast Spin-Echo Sequences for
Non-contrast Peripheral MR Angiography

Magnetic Resonance in Medicine 64:1098–1108 (2010)

Tip 3: Set turbo direction in TRANCE

To reduce pulsation artifacts and to decrease scan time it is advised to use Turbo direction Radial instead of Y.

 Turbo direction Y Turbo direction Radial
Turbo direction Y
Turbo direction Radial

Tip 4: Patient positioning for imaging calf veins

Good imaging of calf veins requires careful positioning of the patient to avoid pressure on the calf that may restrict blood flow in the veins. Positioning the patient prone can be an alternative to positioning the patient supine with the calves hanging free.

Tip 5: Tailoring TI in B-TRANCE

The choice of inversion time (TI) determines how much and how far fresh blood enters into the imaging volume. However, TI also influences background suppression – this is optimal around a TI value of about 400 ms. The user can use TI to control the preferred balance between vessel visibility and background suppression.

Below, in the image on the right the distal renal arteries are better visualized, but the background signal is increased compared to the image on the left.

 B-TRANCE with TI 450 ms TI 600 ms TI 800 ms
B-TRANCE with TI 450 ms
TI 600 ms
TI 800 ms

Tip 6: REST positioning in B-TRANCE of renal arteries

Image quality in B-TRANCE imaging can be degraded by ghosting of abdominal fat. To avoid this ghosting signal we recommend positioning a REST slab on the abdominal wall, over the subcutaneous fat. The REST slab parallel to the imaging volume is used to suppress venous blood.

"New" planning: REST slab on abdominal wall
 Source Source
Source
Source
 Thin MIP <br>
 Thin MIP <br>
Thin MIP
"Old" planning: REST on adrenal cortex
Thin MIP
"New" planning: REST on abdominal wall


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Application Tip
Achieva 1.5T, Achieva 3.0T
B-TRANCE, mra, non-CE MRA, Non-contrast MRA, Peripheral MRA, Renal arteries, TRANCE, Vascular
 

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