Direct Injection Conrast Enhanced MRA

Greg Brown
Royal Adelaide Hospital MRI Unit
29 September 2001

The standard CE-MRA approach relies on a venous injection of contrast agent with physiological dilution and transport to the target vessels.  Another group of techniques use a direct injection of suitable concentration to fill the target vessels with contrast.
Conservative researchers employed the method to create direct MR venography (1), while others developed direct intra-arterial CE-MRA. (IACEMRA).  Direct injection CE-MRA has obvious application in the development of interventional MR [ii],[iii] but it has been used initially to supplement equivocal X-ray DSA.
The only human studies comparing intra-arterial direct CEMRA (IACEMRA) with arterial X-ray DSA were published by two independent Australian groups.[iv],[v]
Laboratory and animal studies described two technical approaches (injected solution fully replacing blood, or using physiological flow to further dilute the injected solution) but there were discrepancies on the target concentration [vi],[vii]The concentration of injected concentration was thought to be of critical importance for successful direct CE-MRA, but the T1 response of the sequences used mean that a broad range of concentrations, 10 60 mM (dilutions of 1:50 and 1:8), give almost equal results.
This range means that direct MRA with a 1:10 solution and fast hand injections ( 3 6 cc/sec) will deliver effective results in all vessels outside the Aorta. Commercial contrast agents are not approved for direct arterial injection, but the safe use of intra-arterial Magnevist for X-ray angiography[viii],[ix] and CT angiography[x] has been reported.
From Taylor & Brown, Proc ISMRM 2000- 66

[i] Li W,David V, Goldfarb J, Kaplan R, Edelmane R. Low-doise gadolinium enhanced three dimensional peripheral MR venography.1998 Proc. ISRM 842
[ii] Bos C,Bakker CJ, Smits HF, Viergever MA. Catheter Injection of Contrast Agent: Application in MR-Guided Endovascular Interventions 1999 Proc ISMRM 1893
[iii] Omary RA, Frayne R, Unal O, Korosec FR, Mistretta CA, Strother CM Magnetic Resonance-Guided Angioplasty of Renal Artery Stenosis in a Pig Model: A feasibility Study. 1999 Proc ISMRM 576
[iv] Tello R, Mitchell P, Melhem E, Witte D, Thomson K. Interventional angiography with conventional 1.5-T magnet: Work in progress. Australasian Radiology 1999 43: 435-439
[v] Taylor D,Brown G. Intra-Arterial Contrast Enhanced MRA (IA-CEMRA)2000 Proc. ISMRM 466
[vi] Bos C, Bakker CJ, Viergever MA. In Situ Administration if Contrast Agent in MR Angiography. 1999 Proc ISMRM 1894
[vii] Frayne R, Omary R, Unal O, Grist T, Strother C, MRA with intra-arterial administration of contrast 1999 Proc. ISMRM 1885
[viii] Schild H, Weber W, Boeck E et al. Gadolinium-DTPA (Magnevist) as contrast medium ofor arterial DSA.Rofo Fortsch Geb Rontgenstr.neuen Bildgeb Verhauf. 1994 160:218-221
[ix] Kaufman J, Geller S, Waltman A. Renal insufficiency: Gadopentate dimeglumine as a radiographic contrast agent during peripheral vascular investigational procedures. Radiology 1996 198:579-581
[x] Kawano T. Ishijima H. Nakajima T. Aoki J. Endo K. Gd-DTPA: a possible alternative contrast agent for use in CT during intraarterial administration. Journal of Computer Assisted Tomography. 1999 23(6):939-40