Quantitative MRA may eliminate need for follow-up catheter-based angiography
Researchers at Rush University Medical Center in Chicago found that quantitative MR angiography (QMRA) is a promising screening tool to detect in-stent stenosis with high sensitivity and specificity, according to a study available online that will appear in the March issue of Stroke.
QMRA is a flow-analysis system that uses traditional MRI to produce a 3D model of the vasculature and quantify vessel blood flow. The procedure is non-invasive and no contrast is needed.
Shyam Prabhakaran, MD, section head of cerebrovascular disease and neurological critical care at Rush, and colleagues conducted a retrospective review of 14 patients who underwent stent placement for cerebral aneurysm or intracranial stenosis. All patients had a QMRA scan performed within one year after stent placement and a follow-up diagnostic angiography study performed within one month of the QMRA scan. An interventional neurologist reviewed all angiograms for presence of greater than 50 percent in-stent stenosis.
The study found that low blood flow as measured by QMRA at sites of intracranial stent placement was significantly associated with in-stent stenosis by catheter-based angiography. As a screening tool to predict greater than 50 percent in-stent stenosis, QMRA was 100 percent sensitive. In other words, QMRA was able to detect narrowing of stented arteries in all cases where invasive angiography showed greater than 50 percent stenosis.
"Given the potentially deadly consequences of in-stent stenosis, a test with high sensitivity and an acceptably low false-positive rate is desirable," Prabhakaran said. "In addition, none of the patients with normal QMRA results had stenosis on angiography, suggesting that patients with normal QMRA results may not require follow-up catheter-based angiography."
Due to the small sample size of the study, the authors suggest larger prospective studies to confirm their findings.
QMRA is a flow-analysis system that uses traditional MRI to produce a 3D model of the vasculature and quantify vessel blood flow. The procedure is non-invasive and no contrast is needed.
Shyam Prabhakaran, MD, section head of cerebrovascular disease and neurological critical care at Rush, and colleagues conducted a retrospective review of 14 patients who underwent stent placement for cerebral aneurysm or intracranial stenosis. All patients had a QMRA scan performed within one year after stent placement and a follow-up diagnostic angiography study performed within one month of the QMRA scan. An interventional neurologist reviewed all angiograms for presence of greater than 50 percent in-stent stenosis.
The study found that low blood flow as measured by QMRA at sites of intracranial stent placement was significantly associated with in-stent stenosis by catheter-based angiography. As a screening tool to predict greater than 50 percent in-stent stenosis, QMRA was 100 percent sensitive. In other words, QMRA was able to detect narrowing of stented arteries in all cases where invasive angiography showed greater than 50 percent stenosis.
"Given the potentially deadly consequences of in-stent stenosis, a test with high sensitivity and an acceptably low false-positive rate is desirable," Prabhakaran said. "In addition, none of the patients with normal QMRA results had stenosis on angiography, suggesting that patients with normal QMRA results may not require follow-up catheter-based angiography."
Due to the small sample size of the study, the authors suggest larger prospective studies to confirm their findings.