MR Angiography at 3T in the follow-up of coiled cerebral aneurysms:

to use Gadolinium or not?

Paolo Vezzulli

ESNR-ESONR Exams 2010 Session

Fellowship in Neuroradiology

XIX Symposium Neuroradiologicum Bologna, 6th October 2010

3D-TOF MRA at 3.0T yields images with a higher quality than that of 1.5 T TOF-MRA in terms of better spatial resolution and better delineation of vessel walls (Gibbs GF, AJNR 2004).

Intermodality agreement between 3D-TOF MRA at 3.0T and DSA is excellent (k=0.86 in Urbach H, Neuroradiology, 2008 and k=0.86 in Ferrè JC Eur Radiol, 2009).

The sensitivity of TOF-MRA compared with DSA for detection of residual aneurysms ranged from 71 to 97% and specificity from 89 to 100% (Ferré JC Eur Radiol, 2009)

3D-TOF limitations: turbulent and slow residual flow in a coiled aneurysm may result in signal loss,

because of intravoxel dephasing and spin saturation (particularly in large remnants) (Ozsarlak O, Neuroradiology 2004; Yamada, N, AJNR 2004; Atlas SW, 4th Ed 2008).

susceptibility artifacts due to coil packing : related to distortion of local B0 field and to eddy currents (Hartmann J, AJNR, 1997; Roy D, AJNR 1997; Weber B Eur Radiol, 2001). 3T could lead to greater coil-related artifacts (Majoie CB, AJNR 2005).

intra- or extra-luminal blood-clot interpreted as flow (Kahara VJ, AJNR 1999; Gauvrit, AJNR 2005)

DSA 3D TOF CE-MRA

More precise detection of slow flow in CE-MRA may improve evaluation of residual patency in treated large and giant aneurysms and better definition of the distal branch arteries (AnzaloneN, AJNR 2000, Cottier JP, AJNR 2003, Pierot L, AJNR 2006)

spin saturation effect can be eliminated by Gd-injection (T1-shortening effects of flowing blood from 1.2 sec down to 50-100 ms) (Cottier JP, AJNR 2003; Atlas SW, 4th Ed 2008)

use of ultra-short TE in CE-MRA reduce signal loss related to transverse dephasing (Anzalone N, AJNR 2000; Anzalone N, Invest Radiol 2008; Atlas SW, 4th Ed 2008). The use of short TE (<2.5 msec) reduced artifacts (Gonner F, AJNR 2005; Walker MT, AJNR 2005).

CE-MRA

CE-MRA is at least equivalent to DSA (Agid R, AJNR 2208; Gauvrit JY, Stroke 2006) for characterization of aneurysm remnants after coiling (sens. 86.8%; spec. 91.9% Kwee TC, Neuroradiology 2007): contrast filling within coils is more clearly seen with CE-MRA.

CE-MRA was preferred over DSA in 91% of the “helmet type” remnants (Agid R, AJNR 2008, Farb RI, Neuroradiology 2005) and seems to be highly sensitive to predict early aneurysm recanalization (Gauvrit JY, AJNR 2005)

3D-TOF MRA and CE-MRA perform comparably at 3.0T for evaluation of intracranial aneurysms (Nael K, AJNR 2006; Wilkstrom J, Acta Radiol 2008; k=0.71 in Sprengers MES, AJNR 2009), The sensitivityof TOF-MRA and CE-MRA is 75%, the specificity of TOF-MRA is 98% and of CE-MRA is 97%, with good correlation with DSA for both techniques (Sprengers MES, AJNR 2009)

Use of contrast material has no additional value in the evaluation of occlusion status… (Majoie CB, AJNR 2005)

…nor in the evaluation of parent or branch vessel patency

(Majoie CB, AJNR 2005)

3D-TOF CE-MRA 3D-TOF CE-MRA

NPV for incomplete occlusion at 6-month follow-up are the same for TOF and CE-MRA; PPV of CE-MRA was somewhat lower than that of TOF

(Sprengers MES, AJNR 2009)

Increased conspicuity of contrast enhancement should be associated with increased intravascular signal compared to background (Merkle EM, Acad Radiol 2007)

CE-MRA AT 3.OT

CE-MRA 1.5T3D-TOF 3T3D-TOF 1.5TDSA

TOF-MRA follow-up of coiled aneurysms is better at 3T than at 1.5T; nevertheless, greater definition of residual patency is achieved with ultrafast CE-MRA at 1.5T

TOF-MRA at 3 T was preferred to TOF-MRA at 1.5 T in 37.9% of cases CE-MRA at 1.5T was preferred to TOF-MRA at 3T in 10.3% of cases

“…we noted a benefit of CE-MRA at 1.5 T compared to 3D TOF-MRA at both 1.5 T and 3 T…”

(Anzalone N, Invest Radiol 2008)

44 patients (14♀ e 30♂ - mean age 56y, range 38-74y)46 aneurysms (40 small, 6 large); mean interval between coiling and MRA: 25 months (1d-36m)

30

8

71

ICA

A-Co A

Basilar artery

MCA

To compare unenhanced 3DTOF MRA and CEMRA at 3T for the evaluation of coiled

aneurysms

3D TOF MRA (10’) - TR 23, TE 3.5, FOV 250, SENSE factor 2.5, 180 slices, voxel size 0.5 x 0.5 x 1 mm

3D CEMRA (24”) - TR 5.9, TE 1.8, FOV 220, SENSE factor 3, 50 slices, voxel size 0.43 x 0.43 x 0.4 mm Gd-BOPTA 0.1mmol/kg + 25ml flush of the 0.9% saline injected at a 1.8ml/sec rate.Source images, 3D reconstructions MIP and VR were evaluated

3T Philips Intera

Coil Artifacts3D TOF: 5 aneurysms CEMRA: 0

aneurysms

Patency (Roy-Raymond classification)

CEMRA

3D TOF 18

19

8

8

20

19

CEMRA

3D TOF

3D TOF

CEMRA3D TOF

DSA post DSA postCEMRA

CEMRA3D TOF

CEMRA3D TOF CEMRA

CEMRA

DSA postDSA postDSA pre

CEMRA3D TOF CEMRA

CEMRA

DSA post

DSA post

DSA post

CE MRA3D TOF

CEMRA3D TOF CEMRA

Our data confirm that follow-up with CEMRA of coiled aneurysms at 3T is feasible.

CEMRA demonstrated the presence of residual patency at neck not evident at TOF MRA in 1 case.

Moreover it demonstrated to be less sensitive to the presence of artifacts and better showed the residual patency (30.7% of cases;

p=0.001)

“…the real advantage of CE-MRA over TOF acquisitions is in the demonstration of small type 1 remnants; however, such remnants are not considered treatable by most interventionists. We do not

yet know how many of these residual aneurysms will grow to become treatable, and consequently, we do not really know how

relevant the advantage of CE-MRA actually is from a clinical perspective…”

“…3D TOF MRA without contrast is generally accurate and closely correlates with the findings of contrast-enhanced techniques…”

but “…in several cases contrast enhancement aided the visualization of small remnants and uncovered a larger neck

remnant or filling of the coil pack that was not anticipated on the noncontrast MRA technique…”

FUTURE PERSPECTIVES

Von Morze C, J Magn Reson Imag, 2007

7T-9T

Time-Resolved 3D-MRA (3D-TRICKS/TREAT) ?

Blood-Pool Contrast Medium (BPCM)

BPCM, due to prolonged blood-retention time resulting in increased relaxivity, overcomes false neck remnant in CE-MRA (GD-enhancement of the organized thrombus) and shows sharper definition of parent vessel. (Kau T, AJNR 2009).

BPCE-MRA shows higher sensitivity (91.7% vs. 87.5%) and higher specificity (92.3% vs. 76.9%) compared with TOF-MRA (Kau T, AJNR 2009).

Drawback: venous contaminations in

steady-state acquisitions (FP)

Thank you