Report from ASNR: MR angiography works in pediatric vascular abnormalities

The vascular nature of most head and neck anomalies can usually be assessed clinically. When this is not possible, catheter angiography remains the reference standard for both the definitive diagnosis of the vascular nature and the delineation of vascular anatomy.

But angiography presents risk problems for pediatric patients, and the search for a noninvasive technique is a worthwhile goal, said Dr. Paul D. Griffiths at the American Society of Neuroradiology meeting in Washington DC on Tuesday. Griffiths and colleagues from the University of Sheffield and the Sheffield Teaching Hospitals in the U.K. report that MR digital subtraction angiography may be the answer.

The researchers studied 12 consecutive children (ages two days to 16 years) with known or suspected vascular abnormalities. They performed routine MR and time-of-flight MRA, supplemented with MR DSA.

MR DSA consisted of projectional thick-slice (6 to 10 cm) acquisitions before and during the administration of gadolinium. A slice-selective spoiled fast gradient-echo sequence was used and performed in three orthogonal planes with a frame rate of one per second and, more recently, at 0.8 frame/sec.

MR DSA was performed successfully in all 12 cases and was useful in distinguishing high-flow (six cases) from low-flow (five) and avascular lesions (one). Only two of the high-flow lesions were suspected to be vascular in nature at the time of imaging. Delineating low-flow lesions increases confidence to biopsy.

The final diagnoses included arteriovenous malformation (five patients), hemangioma (two), choroidal angiomas associated with Sturge-Weber syndrome (two), Burkitt's lymphoma (one), and one patient with two suprahyoid neck masses without histologic diagnoses at present.
MR DSA had significant influence on patient management without recourse to catheter angiography, Griffiths said.

Parallel development of radial sliding window projection imaging now has been performed with intracranial AVM. This has allowed acquisitions with 0.7-mm spatial resolution and a frame rate of over 150 per second.
Current spatial and temporal limitations of MR DSA should subside as the technology advances, Griffiths said, adding that using a radial projection sequence gives a refresh rate of 185 frames per second.