Quantitative Magnetic Resonance Angiography Research Articles

405 The Impact of Cerebral Revascularization on Pial Collateral Flow in Patients With Moyamoya Disease Using Quantitative Magnetic Resonance Angiography

INTRODUCTION: Moyamoya disease (MMD) is a chronic steno-occlusive disease primarily of the anterior circulation leading to significant pial collateralization. Changes in the distribution of intracranial blood flow after revascularization surgery are not well understood. METHODS: We conducted a retrospective chart review of 46 patients with unilateral MMD who underwent cerebral revascularization from 2011-2019. Patients who underwent pre- and post- QMRA NOVA were included in the study. Flow was measured at the M1 segment of the middle cerebral artery (MCA), P2 segment of the posterior cerebral artery (PCA), and A2 segment of the anterior cerebral artery (ACA). Pial collaterals were defined as the sum of (A2+P2) flow. Total hemispheric flow was calculated as (M1+PCA+A2) pre-operatively and (M1+PCA+A2+Bypass) post-operatively, with the incorporation of the bypass graft. RESULTS: A total of 46 patients with unilateral MMD underwent revascularization with pre and post QMRA. Total intracranial flow at baseline prior to revascularization was lower in the side of disease (214.9 ml/min vs. 269.1 ml/min). Total intracranial flow at baseline after revascularization remained lower on the ipsilateral side of disease with an increased flow in the contralateral healthy side (211.7 ml/min vs 286.1 ml/min). Pre-bypass there was a higher flow through pial collaterals on the ipsilateral diseased side (183 ml/min) than the contralateral healthy side (135 ml/min). Post-bypass this difference in pial flow between ipsilateral and contralateral sides decreased from 48 ml/min to 22 ml/min (p = 0.02). Collateral ratio decreased significantly (0.46 preoperatively vs. 0.18 postoperatively) (P < 0.01). CONCLUSIONS: The results of this study quantitatively confirm that direct cerebral revascularization decreases collateral stress in patients with moyamoya disease.

691 Correlation of Cerebral Arteriovenous Malformation Flow Measured by Quantitative Magnetic Resonance Angiography and MR-detected Arteriovenous Malformation Microhemorrhage

INTRODUCTION: Intracranial hemorrhage (ICH) significantly contributes to morbidity and mortality in cerebral arteriovenous malformations (AVM) patients, with a history of prior hemorrhage being the most significant predictor of a future hemorrhage. Recently, silent microhemorrhage as detected on magnetic resonance imaging (MRI) has been proposed as a potential risk factor for future hemorrhage in AVM patients. Recent data suggests that silent microhemorrhage is associated with higher nidal velocity measured through color-coded DSA, raising the question of correlation between flow and microhemorrhage. METHODS: All unruptured AVM patients with a baseline QMRA with noninvasive optimal vessel analysis (NOVA) and gradient echo or susceptibility-weighted MRI were retrospectively reviewed (2004-2022). AVM flow was calculated from the aggregate flow within primary arterial feeders relative to their contralateral counterparts. A review of the MRI determined the presence of microhemorrhages. Descriptive statistics, the X2 test, and a binomial logistic regression were performed to test the association of demographics, clinical, and AVM features with microhemorrhage. RESULTS: The study consisted of ninety patients, with fifty microhemorrhage-positive and forty microhemorrhage-negative patients. The presence of venous anomaly (varix, ectasia, aneurysm) is independently predictive of microhemorrhage (OR = 2.444, p = 0.050), and a compact AVM nidus trended towards independent negative predictability of microhemorrhage (OR =.462, p = 0.081). Calculated AVM flow trends higher in the microhemorrhage-positive group with the median flow 407 mL/min vs. 238 mL/min, and a trend towards predicting presence of microhemorrhage (OR = 1.375, p = 0.106). CONCLUSIONS: Patients with AVM-associated venous anomalies have an increased likelihood of AVM microhemorrhage. Higher AVM flow and a diffuse AVM nidus trend towards a higher likelihood of AVM microhemorrhage. These findings demonstrate the possible relationship between higher AVM flow and risk of future bleeding.

Impact of Cerebral Revascularization on Pial Collateral Flow in Patients With Unilateral Moyamoya Disease Using Quantitative Magnetic Resonance Angiography.

Moyamoya disease (MMD) is a chronic steno-occlusive disease of the intracranial circulation that depends on neoangiogenesis of collateral vessels to maintain cerebral perfusion and is primarily managed with cerebral revascularization surgery. A quantitative assessment of preoperative and postoperative collateral flow using quantitative magnetic resonance angiography with noninvasive optimal vessel analysis (NOVA) was used to illustrate the impact of revascularization on cerebral flow distribution. A retrospective review of patients with unilateral MMD who underwent direct, indirect, or combined direct/indirect cerebral revascularization surgery was conducted between 2011 and 2020. Using NOVA, flow was measured at the anterior cerebral artery (ACA), ACA distal to the anterior communicating artery (A2), middle cerebral artery (MCA), posterior cerebral artery (PCA), and PCA distal to the posterior communicating artery (P2). Pial flow (A2 + P2) and collateral flow (ipsilateral [A2 + P2])-(contralateral [A2 + P2]) were measured and compared before and after revascularization surgery. Total hemispheric flow (MCA + A2 + P2) with the addition of the bypass graft flow postoperatively was likewise measured. Thirty-four patients with unilateral MMD underwent cerebral revascularization. Median collateral flow significantly decreased from 68 to 39.5 mL/min (P = .007) after bypass. Hemispheres with maintained measurable bypass signal on postoperative NOVA demonstrated significant reduction in median collateral flow after bypass (P = .002). Median total hemispheric flow significantly increased from 227 mL/min to 247 mL/min (P = .007) after bypass. Only one patient suffered an ipsilateral ischemic stroke, and no patients suffered a hemorrhage during follow-up. NOVA measurements demonstrate a reduction in pial collateral flow and an increase in total hemispheric flow after bypass for MMD, likely representing a decrease in leptomeningeal collateral stress on the distal ACA and PCA territories. Further studies with these measures in larger cohorts may elucidate a role for NOVA in predicting the risk of ischemic and hemorrhagic events in MMD.

Epidemiology, Pathophysiology, and Imaging of Atherosclerotic Intracranial Disease.

Intracranial atherosclerotic disease (ICAD) is one of the most common causes of stroke worldwide. Among people with stroke, those of East Asia descent and non-White populations in the United States have a higher burden of ICAD-related stroke compared with Whites of European descent. Disparities in the prevalence of asymptomatic ICAD are less marked than with symptomatic ICAD. In addition to stroke, ICAD increases the risk of dementia and cognitive decline, magnifying ICAD societal burden. The risk of stroke recurrence among patients with ICAD-related stroke is the highest among those with confirmed stroke and stenosis ≥70%. In fact, the 1-year recurrent stroke rate of >20% among those with stenosis >70% is one of the highest rates among common causes of stroke. The mechanisms by which ICAD causes stroke include plaque rupture with in situ thrombosis and occlusion or artery-to-artery embolization, hemodynamic injury, and branch occlusive disease. The risk of stroke recurrence varies by the presumed underlying mechanism of stroke, but whether techniques such as quantitative magnetic resonance angiography, computed tomographic angiography, magnetic resonance perfusion, or transcranial Doppler can help with risk stratification beyond the degree of stenosis is less clear. The diagnosis of ICAD is heavily reliant on lumen-based studies, such as computed tomographic angiography, magnetic resonance angiography, or digital subtraction angiography, but newer technologies, such as high-resolution vessel wall magnetic resonance imaging, can help distinguish ICAD from stenosing arteriopathies.

Flow-augmentation STA-MCA bypass for acute and subacute ischemic stroke due to internal carotid artery occlusion and the role of advanced neuroimaging with hemodynamic and flow-measurement in the decision-making: preliminary data.

A major clinical challenge is the adequate identification of patients with acute (<1 week) and subacute (1-6 weeks) ischemic stroke due to internal carotid artery (ICA) occlusion who could benefit from a surgical revascularization after a failure of endovascular and/or medical treatment. Recently, two novel quantitative imaging modalities have been introduced: (I) quantitative magnetic resonance angiography (qMRA) with non-invasive optimal vessel analysis (NOVA) for quantification of blood flow in major cerebral arteries (in mL/min), and (II) blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging to assess cerebrovascular reactivity (CVR). The aim of this study is to present our cohort of patients who underwent surgical revascularization in the acute and subacute phase of ischemic stroke as well as to demonstrate the importance of hemodynamic and flow assessment for the decision-making regarding surgical revascularization in patients with acute and subacute stroke and ICA-occlusion. Symptomatic patients with acute and subacute ischemic stroke because of persistent ICA-occlusion despite optimal medical/endovascular recanalization therapy who were treated at the Neuroscience Clinical Center of the University Hospital Zurich underwent both BOLD-CVR and qMRA-NOVA to study the hemodynamic and collateral vessel status. Patients selected for surgical revascularization according to our previously published flowchart were included in this prospective cohort study. Repeated NOVA and BOLD-CVR investigations were done after bypass surgery as follow up as well as clinical follow up. Continuous BOLD-CVR and qMRA-NOVA variables were compared using paired Student t-test. Between May 2019 and September 2022, superficial temporal artery-middle cerebral artery (STA-MCA) bypass surgery was performed in 12 patients with acute and subacute stroke because of ICA-occlusion despite of optimal endovascular and/or medical treatment prior to the surgery. Impaired BOLD-CVR in the occluded vascular territory [MCA territory: ipsilateral vs. contralateral: -0.03±0.07 vs. 0.11±0.07 %BOLD/mmHgCO2, P<0.001] as well as reduced hemispheric flow with qMRA-NOVA (ipsilateral vs. contralateral: 228.00±54.62 vs. 384.50±70.99 mL/min, P=0.01) were measured indicating insufficient collateralization. Post-operative qMRA-NOVA showed improved hemispheric flow (via bypass) (pre-bypass vs. post-bypass: 236.60±76.45 vs. 334.20±131.33 mL/min, P=0.02) and the 3-month-follow-up with BOLD-CVR showed improved cerebral hemodynamics (MCA territory: pre-bypass vs. post-bypass: -0.01±0.05 vs. 0.06±0.03 %BOLD/mmHgCO2, P=0.02) in all patients studied. Quantitative assessment with BOLD-CVR and qMRA-NOVA allows us to evaluate the pre- and post-operative cerebral hemodynamics and collateral vessel status in patients with acute/subacute stroke due to ICA occlusion who may benefit from surgical revascularization after failure of endovascular/medical treatment.

Stroke mechanisms in adult moyamoya disease: The association between infarction patterns and quantitative magnetic resonance angiography flow state

IntroductionFlow augmentation is the mainstay treatment for moyamoya disease as hemodynamic failure is believed to be the dominant mechanism. We aimed to investigate the mechanisms of stroke in moyamoya disease by assessing the relationship between infarction patterns and quantitative magnetic resonance angiography flow state. MethodsA retrospective study of adult patients with suspected MMD who presented with MRI confirmed acute ischemic stroke predating or following QMRA by a maximum of six months between 2009 and 2021 was conducted. Of the 177 consecutive patients with MMD who received QMRA, 35 patients, consisting of 41 hemispheres, met inclusion criteria. Flow-status was dichotomized into low-flow and normal-flow state based on previously established criteria. ResultsMixed infarction pattern was the most frequent finding (70.7 %), followed by embolic (17.1 %), perforator (7.3 %), and internal borderzone (IBZ) (4.9 %). Infarction patterns were further dichotomized into IBZ+ (internal borderzone alone or mixed) and IBZ− (no internal borderzone constituent). Low-flow states were not significantly more frequent in the IBZ+ compared to IBZ− population (48.4 % vs. 20.0 %, p = 0.14). Ipsilateral posterior cerebral artery fractional flow was significantly higher with IBZ+ compared to IBZ− (345.0 % vs. 214.7 %, p = 0.04). ConclusionMixed infarction pattern was the most common pattern of infarction in patients with moyamoya disease, implying hypoperfusion and thromboembolism are codominant stroke mechanisms. An association between ICA flow status and infarction pattern was not found, although QMRA evidence of more robust posterior cerebral artery leptomeningeal collaterals was found in patients with a hypoperfusion contribution to their stroke mechanism.

Quantitative Blood Flow Reduction in Selective Embolization of Intranidal Fistula of Cerebral Arteriovenous Malformations: Case Series.

Arteriovenous malformations (AVMs) are often associated with high-flow intranidal fistulas (INFs). Although INF embolization has been suggested to provide higher reduction of total AVM flow compared with regular pedicle embolization, this effect has not previously been quantified. The aim of this study was to characterize the effect of AVM INF embolization on total AVM flow. This study is an Institutional Review Board-approved, retrospective case series of patients from 2010 to 2022 with AVMs, both with and without INFs, who underwent quantitative magnetic resonance angiography and endovascular embolization. Twenty patients accounted for 35 separate embolization sessions: 13 patients with INFs underwent a total 21 embolizations and 12 patients without INFs had 14 embolizations. No significant differences were found between groups on age, sex, laterality, drainage pattern, and Spetzler-Martin grade. However, AVMs with INFs were larger than the control group (12.7 vs 8.37 cm 3 , P = .049). Baseline pre-embolization AVM flow significantly differed between AVM with INF vs control groups (522 vs 320 cc/min, P = .005). Similarly, postembolization AVM flow also differed between AVM with INF and control groups (392 vs 224 cc/min, P = .008), with a larger decrease in flow per vessel per embolization session within the AVM INF group compared with controls (101.5 vs 33.2 cc/min, P < .001). Repeated measure analysis of variance showed significant differences pre-embolization and postembolization AVM flow between those with INFs vs controls ( P < .001). This study represents the first to examine the effect of INF embolization on total AVM flow. AVMs with INFs showed higher baseline flow, and targeted embolization toward INFs significantly lowered AVM flow in comparison with controls without INFs. The results of this study emphasize the importance of recognizing the presence of INFs within AVMs and their embolization to reduce AVM flow as part of a multistep management paradigm.

Preoperative embolization of brain arteriovenous malformation and efficacy in intraoperative blood loss reduction: a quantitative study

BackgroundEmbolization of brain arteriovenous malformations (bAVMs) is often used as adjuvant therapy to microsurgical resection to reduce the high-risk features of bAVMs such as large size and high flow. However,...

Association between the degree of vertebrobasilar stenosis, location, infarction pattern, and QMRA flow state.

We aimed to investigate the relationship between the degree and location of vertebrobasilar stenosis and quantitative magnetic resonance angiography (QMRA) distal flow. We retrospectively reviewed patients who presented with acute ischemic stroke with ≥50% stenosis of the extracranial or intracranial vertebral or basilar arteries, and QMRA performed within 1year of stroke. Standardized techniques were used to measure stenosis and to dichotomize vertebrobasilar distal flow status. Patients were grouped based on the involved artery and the severity of disease. All p-values were calculated using chi-squared analysis and Fisher exact test with statistical significance defined as p<.05. Sixty-nine patients met study inclusion, consisting of 31 with low distal flow and 38 with normal distal flow. The presence of severe stenosis or occlusion was 100% sensitive, but only 47% predictive and 26% specific of a low distal flow state. Bilateral vertebral disease was only 55% sensitive but was 71% predictive and 82% specific of a low-flow state and was five times and nearly three times more likely to result in a low-flow state compared to unilateral vertebral disease (14%) and isolated basilar disease (28%), respectively. Severe stenosis of ≥70% may mark the minimal threshold required to cause hemodynamic insufficiency in the posterior circulation, but nearly half of these patients may remain hemodynamically sufficient. Bilateral vertebral stenosis resulted in a fivefold increase in QMRA low distal flow status compared to unilateral vertebral disease. These results may have implications in the design of future treatment trials of intracranial atherosclerotic disease.

Abstract Number ‐ 248: Association Between Vertebrobasilar Stenosis, Location, and Quantitative Magnetic Resonance Angiography Flow State

Introduction The relationship between the degree of vertebrobasilar stenosis and QMRA distal‐flow status is uncertain. Our aim was to investigate this relationship. Methods We retrospectively reviewed patients who presented with acute ischemic stroke, had neurovascular imaging demonstrating ≥ 50% stenosis of extracranial or intracranial vertebral or basilar arteries, and QMRA within one year of stroke, between 2009 and 2021 at two institutions. The WASID and CAVATAS methods were used to measure the degree of intracranial and extracranial vertebrobasilar stenosis, respectively. Patients were grouped as: high‐grade (≥ 70% stenosis) in (1) one vertebral artery; (2) two vertebral arteries; or (3) basilar artery; and (4) moderate grade (≤70% stenosis) in either intracranial vertebral and basilar arteries or exclusive extracranial vertebral stenosis or occlusion. QMRA distal‐flow status was used to dichotomize patients into low‐flow and normal‐flow states based on VERiTAS criteria. P‐values were calculated using chi‐squared analysis and Fisher exact test with statistical significance defined as p &lt; 0.05. Results Of the 303 patients undergoing QMRA for vertebrobasilar disease, 69 met study inclusion, consisting of 31 patients with low‐flow and 38 patients with normal‐flow states. High‐grade stenosis was most commonly found in one vertebral artery (34.8%), followed by both vertebral arteries (29.0%), and the basilar artery (27.5%), and moderate stenosis or exclusive extracranial disease made up 21.7% of patients. High‐grade stenosis in at least one vertebral or basilar artery was significantly associated with low‐flow states compared to patients with moderate‐grade stenosis or exclusive extracranial disease (53.7% versus 13.3%, p = 0.007). High‐grade stenosis in both vertebral arteries was significantly more likely to result in a low‐flow state compared to high‐grade stenosis in one vertebral artery (75.0% versus 41.7%, p = 0.001) or to high‐grade stenosis in the basilar artery (75.0% versus 42.1%, p = 0.040). Conclusions Low distal flow status on QMRA is strongly associated with high‐grade intracranial stenosis compared to moderate‐grade or exclusive extracranial stenosis and is nearly twice as frequent with high‐grade intracranial stenosis of both vertebral arteries compared to one. The location, degree of stenosis, and distal‐flow status should be considered as possible entry points for future prospective treatment trials in intracranial atherosclerotic disease.

Abstract TMP71: Hypoperfusion And Thromboembolism Are Codominant Stroke Mechanisms In Adult Moyamoya Disease

Background: Treatment of moyamoya disease (MMD) has predominantly focused on flow augmentation since the mechanism of ischemic stroke has largely been attributed to hemodynamic failure. Recent studies have challenged this notion suggesting that thromboembolism may play a dominant role. The aim of our study was to investigate the mechanisms of ischemic stroke in MMD by assessing the relationship between infarction patterns and Quantitative Magnetic Resonance Angiography (QMRA) flow state. Methods and Results: This is a retrospective study of adult patients with suspected MMD that presented with MRI confirmed acute ischemic stroke predating or following QMRA by a maximum of six months, between 2009 and 2021. Of the 177 consecutive patients with MMD that underwent QMRA, 35 patients met inclusion, consisting of 41 hemispheres. Flow-status was dichotomized into low-flow and normal-flow based on published criteria. Mixed pattern was the most frequent finding (70.7%), followed by embolic (17.1%), perforator (7.3%), and internal borderzone (IBZ) (4.9%). Infarction patterns were then dichotomized into IBZ+ (internal borderzone alone or mixed) and IBZ- (no internal borderzone constituent) based on the constituents of the patterns. Low-flow states were insignificantly more frequent with IBZ+ compared to IBZ- (48.4% vs. 20.0%, p = 0.14). Ipsilateral PCA fractional flow was significantly higher with IBZ+ compared to IBZ- (345.0% vs. 214.7%, p = 0.04). Conclusions: Mixed infarction pattern was the most common pattern of infarction in patients with MMD, implying that at least 2 interrelated stroke mechanisms of hypoperfusion and thromboembolism likely coincide. An association between ICA flow status and the pattern of infarction was not found. Prospective studies evaluating the utility of antithrombotic agents in MMD are needed.

Abstract WP136: Cerebral Blood Flow Correlates Of Brain Arterial Dilatation

Introduction: Based on the Poiseuille’s law (blood flow= [pressure gradient* [Pi*radius 4 ]]/[8*blood viscosity*length]) larger brain arterial diameter should associate with a proportional increase in cerebral blood flow. We have reported that larger brain arterial diameters are associated with higher risk of dementia and cerebrovascular disease, but the flow correlates of larger brain arterial diameters have not been studied. Methods: We leveraged an existing data repository of 325 unselected volunteers recruited to validate phase contrast quantitative magnetic resonance angiography (QMRA). Imaging was performed in a 3.0 Tesla MRI Scanner (Signa VHi to HDx, General Electric Medical Systems, later GE Healthcare, Milwaukee, WI, USA) using either a four-channel or eight-channel neurovascular coil. The volume flow rate measurements were acquired with the Noninvasive Optimal Vessel Analysis software (VasSol,Chicago, IL, USA). Brain arterial diameters of the circle of Willis were measured using LKEB Automated Vessel Analysis (LAVA) software. Adjusted models by age, sex, race/ethnicity and height were built to explore the association between blood flow and the diameters of the basilar, middle, and anterior cerebral arteries. Results: We include 325 participants (mean age 48 ± 15 years, 52% female, 64% non-Hispanic white). As expected, arterial luminal diameters are associated with proportionally higher cerebral blood flow. Among people with the largest diameters in this sample, however, the corresponding cerebral blood flow was lower than predicted[MRS1] and this non-linear association was significant in three out of the five arteries studied (Figure 1). Conclusions: In a sample of relatively healthy individuals, those with the largest diameters had lower-than-expected cerebral blood flow. Further studies are needed to better understand the physiopathology by which larger brain arterial diameters relate to cerebrovascular disease.

Quantitative magnetic resonance angiography as an alternative imaging technique in the assessment of cerebral vasospasm after subarachnoid hemorrhage.

The major mechanism of morbidity of delayed cerebral ischemia after subarachnoid hemorrhage (SAH) is considered to be severe vasospasm. Quantitative MRA (QMRA) provides direct measurements of vessel-specific volumetric blood flow and may permit a clinically relevant assessment of the risk of ischemia secondary to cerebral vasospasm. To evaluate the utility of QMRA as an alternative imaging technique for the assessment of cerebral vasospasm after SAH. QMRA volumetric flow rates of the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA) were compared with vessel diameters on catheter-based angiography. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of QMRA for detecting cerebral vasospasm was determined by receiver-operating characteristic curves. Spearman correlation coefficients were calculated for QMRA flow versus angiographic vessel diameter. Sixty-six vessels (10 patients) were evaluated with QMRA and catheter-based angiography. The median percent QMRA flow of all vessels with angiographic vasospasm (55.0%, IQR 34.3-71.6%) was significantly lower than the median percent QMRA flow of vessels without vasospasm (91.4%, IQR 81.4-100.4%) (p < 0.001). Angiographic vasospasm reduced QMRA-assessed flow by 23 ± 5 (p = 0.018), 95 ± 12 (p = 0.042), and 16 ± 4 mL/min (p = 0.153) in the ACA, MCA, and PCA, respectively, compared to vessels without angiographic vasospasm. The sensitivity, specificity, PPV, and NPV of QMRA for the discrimination of cerebral vasospasm was 84%, 72%, 84%, and 72%, respectively, for angiographic vasospasm >25% and 91%, 60%, 87%, and 69%, respectively, for angiographic vasospasm >50%. The Spearman correlation indicated a significant association between QMRA flows and vessel diameters (rs = 0.71, p < 0.001). Reduction in QMRA flow correlates with angiographic vessel narrowing and may be useful as a non-invasive imaging modality for the detection of cerebral vasospasm after SAH.

Natural History of Cerebrovascular Flow in Cervical Arterial Dissection Using Quantitative Magnetic Resonance Angiography

The degree to which cervical arterial dissection (CAD) limits cerebral blood flow and the change in flow over time is not well characterized. This study is the first to evaluate blood flow using quantitative magnetic resonance angiography (QMRA) in this patient population. A retrospective chart review was completed in patients CAD between 2009 and 2019. Inclusion criteria were adults with dissection of internal carotid artery or vertebral artery, who underwent QMRA. Cases were reviewed for presentation, management, and imaging findings. Patients treated endovascularly were excluded. Flow index was calculated using ipsilateral vessel flow divided by contralateral flow. A total of 36 patients were included, mean age 44.8 +/- 11.1 years. 21 patients (51.2%) had internal carotid artery (ICA) dissections, 19 (46.3%) with vertebral artery (VA) dissections, and 1 with both. 6 patients (14.6%) had bilateral or multiple vessels involved. Although flow tended to improve over time in the affected vessel, patients with the lowest flow index on presentation continued to have low flow at follow-up (p<0.001). In addition, cerebral blood flow was shown to be associated with the degree of vessel narrowing, particularly in the ICA (p<0.001, R=0.891, R 2 =0.794), although this effect was not significant in the VA (p=0.237). This study represents the first to assess vessel flow in CAD using QMRA and to describe its patterns over time. Flow tended to improve in all patients over time in the dissected vessel, although patients with low flow on presentation continued to have low flow at follow-up.

Brain arteriovenous malformation flow after stereotactic radiosurgery: Role of quantitative MRA.

Stereotactic radiosurgery (SRS) is a current therapeutic option for treatment of arteriovenous malformations (AVMs) located in deep or eloquent brain regions. Obliteration usually occurs in a delayed fashion, with an expected latency of 3-5 years. Here, we assess how AVM flow correlates with volume before and after SRS treatment. Patients with supratentorial AVM treated with SRS at our institution between 2012-2022 were retrospectively reviewed. Patients were included if Quantitative Magnetic Resonance Angiography (QMRA) study was performed at baseline and at least at the first follow-up. Correlation between AVM flow and volume before and after treatment was evaluated. AVM flow and volume were additionally assessed for obliteration using the non-parametric receiver operating characteristic (ROC) curve. Twelve patients with radiologic follow-up imaging were included. Eight patients presented AVM rupture, one of which occurred after radiosurgical treatment. Three patients underwent embolization prior SRS. Mean AVM initial volume was 3.8 cc (0.1-12.4 cc), mean initial flow 174 ml/min (11-604 ml/min), both variables showed progressive reduction at follow-up (range 3-57 months); and flow decreased with volume reduction (p < 0.001). Area under the ROC was 0.914 for both AVM flow and volume with obliteration (p = 0.019). AVM flow significantly decreased after SRS treatment, reflecting volume reduction. Baseline AVM flow and volume both predicted obliteration. QMRA provides additional non-invasive information to monitor patients after radiosurgical treatment.

Impact of Vessel Narrowing and Changes in Blood Flow on the Development of Ischemia in Cervical Arterial Dissection Using Quantitative Magnetic Resonance Angiography

Background Up to 3% of all ischemic strokes are secondary to dissections; however, cerebral hemodynamic patterns in cervical arterial dissection and their association with cerebral ischemia are unknown. This study represents the first to assess blood flow using quantitative magnetic resonance angiography in patients with cervical arterial dissection and their presentation with ischemia. Methods Retrospective chart review was completed in patients with cervical arterial dissection between 2009 and 2019. Inclusion criteria were adults with dissection of internal carotid artery or vertebral artery who underwent baseline magnetic resonance imaging (MRI) and quantitative magnetic resonance angiography. Cases were reviewed for presentation, management, and imaging findings. Flow index was calculated using ipsilateral vessel flow divided by contralateral flow. Results A total of 37 patients with a mean age of 45.95±11.95 years were included. Of the patients, 19 (51.2%) had internal carotid artery dissections, 17 (45.9%) with vertebral artery dissections, and 1 with both. Patients with ischemia on MRI demonstrated lower flow in the ipsilateral vessel when compared with those patients without ischemia ( P =0.003). Using the flow index in receiver operating characteristic analysis to predict ischemia on MRI yielded an area under the curve of 0.833 ( P =0.002); receiver operating characteristic analysis of the percent of total flow for ischemia on MRI found an area under the curve of 0.895 ( P =0.000), and receiver operating characteristic analysis of percent vessel narrowing calculated an area under the curve of 0.887 ( P =0.000). Multivariate analysis identified vessel narrowing as significantly associated with ischemia on MRI ( P =0.03). Conclusion This study represents the first to evaluate blood flow in patients with cervical arterial dissection using quantitative magnetic resonance angiography and its relationship with cerebral ischemia. Patients with lower flow as a result of dissection appear to be at higher risk of ischemia on presentation, emphasizing the role of hemodynamics in underlying pathophysiology, and vessel narrowing appears paramount in the association with developing ischemia.

Prediction of Long-Term Restenosis After Carotid Endarterectomy Using Quantitative Magnetic Resonance Angiography.

BackgroundTo detect restenosis after carotid endarterectomy (CEA), long-term monitoring is required. However, non-selective follow-up is controversial and can be limited by costs and logistical considerations.ObjectiveTo examine the value of immediate perioperative vessel flow measurements after CEA using quantitative magnetic resonance angiography (QMRA) to detect patients at risk of long-term restenosis.MethodsA prospective cohort study with long-term sonographic follow-up after CEA for symptomatic internal carotid artery stenosis (ICAs) > 50%. In all patients, vessel flow has been assessed both pre- and postoperatively using QMRA within ±3 days of surgery. Data on QMRA assessment were analyzed to identify patients at risk of restenosis for up to 10 years.ResultsRestenosis was recorded in 4 of 24 patients (17%) at a median follow-up of 6.8 ± 2.6 years. None of them experienced an ischemic event. Perioperative flow differences were significantly greater in patients without long-term restenosis, both for the ipsilateral ICA (p < 0.001) and MCA (p = 0.03), compared to those with restenosis (p = 0.22 and p = 0.3, respectively). The ICA mean flow ratio (p = 0.05) tended to be more effective than the MCA ratio in predicting restenosis over the long term (p = 0.35).ConclusionOur preliminary findings suggest that QMRA-based mean flow increases after CEA may be predictive of restenosis over the long term. Perioperative QMRA assessment could become an operator-independent screening tool to identify a subgroup of patients at risk for restenosis, in whom long-term monitoring is advised.

Selective endovascular treatment of cervical arterial dissection using quantitative magnetic resonance angiography.

The role of endovascular treatment in cervical artery dissection (CAD) is equivocal. This study compared cerebral blood flow in CAD between medically and endovascularly treated patients using quantitative magnetic resonance angiography (QMRA). Retrospective chart review was completed for patients with CAD. Inclusion criteria were adults (>18 years) with diagnosis of dissection of the internal carotid artery or vertebral artery who received QMRA. The cases were reviewed for clinical presentation, diagnosis, management, and imaging, and in particular, patients who underwent endovascular treatment were evaluated. Forty-one patients were included, 46.3% female and mean age 46.0+/- 11.9 years. 21 patients (51.2%) had contralateral (ICA) dissections while 19 (46.3%) had vertebral artery (VA) dissections, and 1 had both involved. Five patients underwent stenting, angioplasty, or both. Baseline characteristics between patients who underwent medical versus endovascular treatment were similar, although patients undergoing stenting/angioplasty were more likely to have diabetes (p = 0.015) and prior anticoagulation use (p = 0.007). All endovascular patients demonstrated ischemia on MRI versus 53.1% of those undergoing medical management (p = 0.047). Comparing ipsilateral vessel flow over time in these two patient groups showed those who underwent stenting or angioplasty had lower baseline flows, albeit non-significant (p = 0.629). Patients who underwent endovascular treatment had lower distal flow compared to the medical management group. This study represents the first to assess vessel flow using QMRA in patients who underwent endovascular treatment of CAD. In combination with progressive symptoms, QMRA may serve as a useful adjunct in the selection of patients for endovascular intervention in arterial dissections.

Abstract No. 235 Immediate effect of pipeline embolization on intracranial hemodynamics studied using non-invasive optimal vessel analysis software

Non-invasive Optimal Vessel Analysis (NOVA) is a software that can process Quantitative magnetic resonance angiography (QMRA) to collect and analyze hemodynamic data from Pipeline embolization patients. At our institution, every patient receives post-embolization QMRA within 24 hours of treatment to evaluate Pipeline patency, and many patients received QMRA before the treatment as baseline. Here, we aim to elucidate the short-term hemodynamic changes following Pipeline embolization device (PED) placement.

Vertebrobasilar Stroke: Association Between Infarction Patterns and Quantitative Magnetic Resonance Angiography Flow State.

BackgroundTreatment and prognosis of vertebrobasilar atherosclerotic disease differs depending on stroke mechanism, such as artery‐to‐artery embolism, branch atheromatous disease, and hemodynamic ischemia. Our aim was to investigate the relationship between infarction pattern and flow status using quantitative magnetic resonance angiography (QMRA), to determine the validity of using infarction patterns to infer stroke mechanism.Methods and ResultsThis is a retrospective study of patients with ischemic stroke with intra‐ or extracranial vertebrobasilar atherosclerotic stenosis, who underwent magnetic resonance imaging of the brain, neurovascular imaging, and QMRA, between 2009 and 2021. Patients with cerebral infarction predating or following QMRA by ≥1 year, or QMRA studies performed for basilar thrombosis, vertebral dissection, or only postangioplasty/stenting, were excluded. Poststenotic flow (basilar and posterior cerebral arteries) was dichotomized as low‐flow or normal‐flow based on published criteria. Of 1211 consecutive patients who underwent QMRA noninvasive optimal analysis, 69 met inclusion. Mixed patterns were most common (46.4%), followed by perforator (23.2%), borderzone (14.5%), and territorial (15.9%). Patients with low‐flow had a significantly higher rate of borderzone+ patterns (borderzone alone or in mixed pattern) compared with patients with normal‐flow (77.4% low‐flow versus 39.5% normal‐flow, P=0.002). Borderzone+ patterns were associated with 61.5% probability of low‐flow state, while no borderzone (perforator/territorial) patterns were associated with 76.7% probability of normal‐flow state.ConclusionsBorderzone infarction pattern (alone or mixed) was associated with low poststenotic posterior circulation flow by QMRA. However, borderzone pattern only moderately predicted low‐flow state, and may be an unreliable flow marker. Therefore, infarct topography may complement, but should not replace hemodynamic studies to establish flow status.