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SF 15 NR(NI)-01 Update of vessel wall imaging for cerebral arteries 14:00 - 14:30 208

Chairperson(s): Deok Hee Lee University of Ulsan College of Medicine, Asan Medical Center, Korea Chul Ho Sohn Seoul National University Hospital, Korea

Pathologic overview of extracranial and intracranial atherosclerosis - correlation of imaging

Hyo sung KwakChonbuk National University Hospital, Korea. kwakhs8140@gmail.com

Intracranial and extracranial vascular pathologies have been evaluated with angiography, whether conventional digital subtraction angiography or non-invasive (MR angiography or CT angiography) techniques. These techniques are limited by evaluation of the vessel lumen. In recent years, high resolution MR black-blood vessel wall imaging (VWl) techniques have been developed to subtract the signal of flowing blood in the vessel lumen. VWI has been extensively used for evaluation and characterization of extracranial carotid atherosclerosis, shedding light on vulnerable plaque characteristics that can be used for risk stratification beyond the traditional evaluation using luminal imaging. Intracranial VWI has also shown early promise in detecting plaque characteristics associated with culprit features.

Commonly used pathology nomenclature of atherosclerotic plaques

1. Intima: the region between the internal elastic lamina and the endothelial cell layer lining the surface of the blood vessel.

2. Diffuse intimal thickening: accumulation of smooth muscle cells in the intima in the absence of lipid or macrophage foam cells.

3. Fatty streak: luminal accumulation of foam cells without a necrotic core or fibrous cap.

4. Atheroma: an accumulation of cel ls, l ipids, extracellular matrix and necrotic debris within the intima. Atheroma is frequently referred to as “plaque”.

5. Necrotic core: a well-delineated region within the intima where the normal structural elements of the arterial wall are replaced by a core which can contain cholesterol esters, free cholesterol, phospholipids, triglycerides, inflammatory cells, red blood cells and fragments of an extracellular matrix (Fig. 1).

Fig. 1. Lipid-core without hemorrhage.

6. Lipid pool: dense accumulation of extracellular lipids occupying an extensive but well-defined region of the intima.

7. Fibrous cap: is the layer of connective tissue covering the lipid/necrotic core. It is located between the necrotic core and the lumen surface. The fibrous cap can contain a variety of cells, extracellular matrix and occasionally calcification.

8. Hemorrhage: a collection of red blood cells and red cell fragments into the necrotic core, depending on the age of hemorrhage and fibrin. Hemorrhage may occur from a disruption of the luminal surface or from neovasculature within the plaque.

9. Fibroatheroma: a lesion with a well-formed necrotic core that has an overlying fibrous cap.

10. Thin-cap fibroatheroma: a lesion with a thin fibrous cap (and underlying necrotic core) infiltrated by macrophages and lymphocytes with rare smooth muscle cells.

11. Plaque rupture: a fibroatheroma with fibrous cap disruption. The luminal thrombus communicates with the underlying necrotic core.

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12. Calcification: the dystrophic or ectopic calcium mineral deposition found in atherosclerotic plaque.

13. Calcified nodule: an eruptive nodular calcification with underlying fibrocalcific plaque.

Modified AHA classification for carotid plaque MRI

Type I-II near-normal wall thickness, no calcificationType III diffuse intimal thickening or small eccentric

plaque with no calcification

Type IV-V plaque with a l ipid or necrotic core surrounded by fibrous tissue with possible calcification

Type VI complex plaque with possible surface defects, hemorrhage, or thrombus

Type VII calcified plaqueType VIII fibrotic plaque without lipid core and with

possible small calcifications

The MRI appearance of plaque features

1. Calcification: Calcification is detected by well-defined areas of hypo-intense signals on all five weightings. Calcifications range in size from microscopic granules through varying sizes or fragments to large solid calcifications that can extend the length and breadth of the artery wall. Most calcifications are contained within the vessel wall, but the calcified nodule protrudes into the lumen, creating disturbances in flow (Fig. 2).

Fig. 2. The appearance of the superficial calcification, which gives hypointense signals on TOF, T1W, T2W, PDW and post-contrast T1W images.

2. Hemorrhage: MRI is able to differentiate the degrading stages of intraplaque hemorrhage (based on the signal intensity of MRI in the brain) (Fig. 3).

MRITOF T1 T2 PD CE-T1

Type I + +/o - - o/-Type II + +/o o/+ o/+ o/-

Fig. 3. I l lustrates the signal pattern of Type-I hemorrhage: the area of intraplaque hemorrhage is hyper-intense on TOF images, hyper-intense on the T1W, and hypo-intense on T2W and PDW. The signal pattern of Type-II hemorrhage shows the hyper-intense on all sequences.

3. Lipid rich necrotic core: The predominant lipids are cholesterol and ester of cholesterol. Because the lipid core does not contain triglycerides, it is not suppressed with fat-suppression techniques, which are often coupled with black-blood techniques. The lipid core has a short T2, which is due to the micellar structure of the lipoprotein, their destruction by oxidation, and exchanges between ester of cholesterol and eater. Necrotic Core shows a hypo signal on PD/T2W , but an iso- or slight hyper-signal intensity on T1W and TOF. The LR/NC shows a relatively lower signal than adjacent fibrous tissue on the CE T1W, due to the reduction or absence of enhancement. Draw Necrotic Core area on CE T1W, but exclude the calcification area (Fig. 4).

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Fig. 4. Illustrates the signal intensity of a necrotic core. The core is distinctly hypo-intense on the CE-T1W.

4. Loose matrix (LM): The loose matrix should instead be called a “T2 high” region. The “T2 high” area is composed of water rich tissues that include thrombus-fibrin, organizing thrombus, hyaluronan (HA), proteoglycans and occasionally collagen. Below is a schematic diagram showing the progression of matrix repair from fibrin and thrombus deposition to organizing thrombus -- which may include early hyaluronan and proteoglycan matrix deposition -- to the mature loose matrix and then finally to collagen. The healing cascade is present in all injuries, such as repeated plaque ruptures and subsequent plaque healing (Fig. 5).

Fig. 5. The “loose matrix” or “T2 high” area is characterized by areas of hyper intensity of T2W, PDW, and occasionally on CE-T1. The signal intensity may range from very bright to moderate with iso-hypo intensity on T1W and TOF.

5. Fibrous cap: The fibrous cap is an important plaque feature. It is the boundary between the necrotic core and flowing blood. Studies by this lab and others have designated a cap to be intact and thick if it is >0.25 mm. In MR images, a thick intact cap may appear as a juxtaluminal band of low signal intensity in TOF images. The absence of this hypo-

intense band indicates the possibility of a thin, absent, or remodeling cap. A rupture is suspected when the band is absent on TOF and a region of high SI is adjacent to the lumen due to juxtaluminal hemorrhage or mural thrombus, and/or luminal surface irregularity (Fig. 6).

Fig. 6. Intact fibrous cap on CT-T1W.

Histological findings of intracranial atherosclerosis

Unique structural features of intracranial vessels and nourishment from the surrounding cerebrospinal fluid environment may account for the relative lack of intracranial vasa vasorum early in life. However, with advancing age and with the development of vascular disease, vasa vasorum are known to develop. Advanced contrast material-enhanced imaging techniques are capable of helping detect and even grade intracranial vasa vasorum. Although it is traditionally believed that atherosclerosis begins in the intima and progresses outward, recent evidence suggests that the adventitia plays an init iatory role in the disease process. Vasa vasorum may be responsible for transporting inflammatory cells into the adventitia, which initiates an inflammatory cascade that progress inward. These inflammatory processes are believed to promote proliferation of the vasa vasorum, as well. The presence of vasa vasorum is strongly associated with intracranial atherosclerotic plaques, especially with more advanced lesions that exhibit thicker walls (Fig. 7).

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Fig. 7. Photomicrography shows basilar artery with eccentr ic luminal narrowing secondary to atherosclerosis. Higher magnification photomicrograph of adventitia demonstrates presence of vasa vasorum with neovascularity.

Also, severe intracranial atherosclerotic plaques had necrotic core. Contrast agent-enhanced MR imaging, which is capable of delineating plaque components, is another promising modality for studying vasa vasorum. Gadolinium chelates have been shown to preferentially enhance certain regions of plaque, such as sites of neovascularity and inflammation. Adventitial enhancement seen on MR images can be used to measure the density of vasa vasorum, which indicates plaque neovascularity and risk for disruption (Fig. 8).

Fig. 8. Contrast-enhanced T1 images with symptomatic basilar artery plaque. Contrast agent administration results in enhancement of vasa vasorum (lines) and fibrous cap (arrow) delineation lipid core (between adventitia and fibrous cap.

We performed the validation study for characterize intracranial atherosclerotic plaque components in a quantitative manner by obtaining the MR signal

characteristics at 3T in ex vivo circle of Willis specimens. Our study showed that most of intracranial plaques had a necrotic core. Necrotic core on T2 SPACE images showed the hypo-intense (Fig. 9).

Fig. 9. Histologic sections from the MCA specimens classified as type V with necrotic core. T2 SPACE shows hypo-intense of necrotic core.

Conclusion

Intracranial VWI can serve as a complementary tool to luminal imaging techniques in disease detection and differentiation. However, size of normal or disease vessels in the intracranial artery is very small. So, visualization of vessel wall such as inner and outer wall is not clear. Histological findings of intracranial atherosclerotic plaques are similar to that of extracranial carotid plaques. Therefore, plaque component on VWI of intracranial plaques will be similar findings of carotid atherosclerosis. Prospective longitudinal VWI investigation of individual atherosclerotic plaques would help to better describe imaging findings of plaque components.

References

1. Mossa-Basha M, Alexander M, Gaddikeri S, Yuan C, Gandhi D. Vessel wall imaging for intracranial vascular disease evaluation. J Neurointerv Surg 2016

2. Bhogal P, Navaei E, Makalanda HL, Brouwer PA, Sjostrand C, Mandell DM, et al. Intracranial vessel wall MRI. Clin Radiol 2016;71:293-303

3. Choi YJ, Jung SC, Lee DH. Vessel wall imaging of the intracranial and cervical carotid arteries. J Stroke 2015;17:238-255

4. Portanova A, Hakakian N, Mikulis DJ, Virmani R, Abdalla WM, Wasserman BA. Intracranial vasa vasorum: insights and implications for imaging. Radiology 2013;267:667-679

5. Harteveld AA, Denswil NP, Siero JC, Zwanenburg JJ, Vink A, Pouran B, et al. Quantitative intracranial atherosclerotic plaque characterization at 7T MRI: an ex vivo study with histologic validation. AJNR Am J Neuroradiol 2016;37:802-810

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6. Yamaguchi Oura M, Sasaki M, Ohba H, Narumi S, Oura K, Uwano I, et al. Carotid plaque characteristics

on magnetic resonance plaque imaging following long-term cilostazol therapy. J Stroke Cerebrovasc Dis 2014;23:2425-2430

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SF 15 NR(NI)-02 Update of vessel wall imaging for cerebral arteries 14:30 - 15:00 208

Chairperson(s): Deok Hee Lee University of Ulsan College of Medicine, Asan Medical Center, Korea Chul Ho Sohn Seoul National University Hospital, Korea

Intracranial vessel wall imaging: protocols and sequence optimization

Jihoon ChaSamsung Medical Center, Sungkyunkwan University School of Medicine, Korea.

kirinonakar@gmail.com

Intracranial magnetic resonance (MR) angiography is widely used to diagnose cerebrovascular diseases such as infarction, vasculitis, and moyamoya disease. MR angiography noninvasively shows luminal narrowing of the intracranial arteries. However, most vascular diseases, especially atherosclerosis, do not show luminal narrowing in early stage. Recently, high-resolution (HR) intracranial vessel wall imaging is used to demonstrate intracranial vessel wall abnormality. HR intracranial vessel wall imaging clearly shows vessel wall pathologies such as wall thickening or enhancement at the stenotic portion detected on MR angiography.

Intracranial vessel wall imaging has several characteristics. Intraluminal imaging such as angiography shows steno-occlusive lesion only, but vessel wall imaging shows vessel wall pathology directly, such as atherosclerotic

plaque, inflammation, smooth muscle proliferation, and vessel wall remodeling. Also, intracranial vessel wall imaging require high resolution, because the diameter of MCA is only 2-3 mm, and the thickness of normal vessel wall is less than 0.4 mm. Also, high resolution 3D imaging with multiplanar reconstruction is helpful, because intracranial artery is not straight. Next, angiography is white blood imaging but in the vessel wall imaging, the blood should be black to see the vessel wall, so special technique to suppress the blood signal is needed (spatial presaturation, double inversion recovery, iMSDE [improved motion-sensitized driven-equilibrium], DANTE [delay alternating with nutation for tailored excitation], etc.)

In this lecture, the strategy to optimize vessel wall imaging protocol will be discussed.

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SF 15 NR(NI)-03 Update of vessel wall imaging for cerebral arteries 15:00 - 15:30 208

Chairperson(s): Deok Hee Lee University of Ulsan College of Medicine, Asan Medical Center, Korea Chul Ho Sohn Seoul National University Hospital, Korea

Intracranial vessel wall imaging: various vascular disease

Seung Chai JungUniversity of Ulsan College of Medicine, Asan Medical Center, Korea. dynamics79@gmail.com

Angiography is a useful, important, common imaging method, with DSA remaining the gold standard for luminal imaging. CTA is minimally invasive and quite accurate in the evaluation of stenosis. MRA is a good screening tool with the least invasiveness. Angiography mostly represents intracranial artery disease as luminal stenosis, which is often not sufficient to evaluate intracranial vascular pathology. All of these modalities provide indirect information about vascular pathology because luminal change, such as stenosis, results from the changes of vessel walls. Noninvasive and direct in vivo assessment of vessel walls via imaging may provide better information about vascular pathology. Vessel wall imaging using high-resolution magnetic resonance imaging (HR-MRI) can convey the morphology of the vessel wall and surrounding structure

beyond just the luminal abnormalities. As such, vessel wall imaging was introduced as an emerging technique in cervical arteries and recently has been applied to intracranial artery diseases. HR-MRI enables us to observe vessel walls directly with high resolution and excellent soft tissue contrast without radiation hazard. HR-MRI for vessel walls can present the characteristic radiological findings for each intracranial artery disease such as atherosclerosis, dissection, moyamoya disease, vasculitis, and reversible cerebral vasoconstriction syndrome (RCVS). The radiological features are useful to differentiate among intracranial artery disease. Vessel wall imaging is expected to enhance the diagnostic performance of evaluations and the understanding of disease pathophysiology.

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Neurointervention 16:00-17:50 208Endovascular therapy of cerebrovascular

diseases

Chairperson(s)Tae Hong Lee Pusan National University Hospital,

KoreaHae Woong Jeong Inje University Busan Paik

Hospital, Korea

SS 37 NR(NI)-01 16:00 Computational fluid dynamics: comparison of prototype and commercial solutions for intracranial aneurysms with different entrance lengthJeong Hee Oh1, Sung Tae Park1, Young Bae Ko2 1Soonchunhyang University College of Medicine, 2Korea Institute of Industrial Technology, Korea. stpark@schmc.ac.kr

The aim of this study is to evaluate the influence of entrance length and compare the two different solutions of computational fluid dynamics (CFD) for distal internal cerebral artery (ICA) aneurysms. Siemens prototype SW (prototype, not commercially available) and the package of commercial CFD SW (commercials) were used. Twelve models of aneurysm at distal internal cerebral artery (ICA) were obtained from three dimensional angiography. The original models had longer entrance lengths from cervical segment of ICA. Intracranial (IC) models had shorter ones from proximal cavernous ICA. Prototype showed faster flow than commercials with comparison of the maximum value on velocity scale. Visualization of pathline within the aneurysm sac was well seen by prototype except one original model which showed pathline leak. With IC models, both tools showed high correlation with flow velocity.

SS 37 NR(NI)-02 16:10 Mid- to long-term result of stent assisted coil embolization of intracranial aneurysms using the low-profile visualized intraluminal support (LVIS™) deviceDong Hyun Yoo1, Young Dae Cho1, Hyun-Seung Kang1, O-Ki Kwon2, Moon Hee Han1 1Seoul National University Hospital, 2Seoul National University Bundang Hospital, Korea. aronnn@naver.com

We retrospectively examined the mid- to long-term results of the Low-profile Visualized Intraluminal Support

(LVIS™) device in stent-assisted coil embolization of intracranial aneurysms. Between October 2012 and February 2013, 55 patients with unruptured wide-necked intracranial aneurysms underwent coil embolization procedure using LVIS device. Aneurysm occlusion, stent deployment state, and delayed complications were evaluated. Follow-up imaging included digital subtraction angiography (DSA), magnetic resonance angiography (MRA), and plain radiography (PR). Lost to follow up occurred in three patients. Major recanalization occurred in one patient and the patient underwent additional coil embolization session 12 months after the initial procedure. Of the 52 patients, evaluation of recanalization after 6 months was possible in 37 patients using DSA and MRA, with mean follow up time of 27.1 months (range, 11-36 months). Only 1 patient (2.7%) showed minor recanalization and all other patients (97.3%) showed complete occlusion. Of remaining 15 patients, PR images with mean follow-up time of 34.1 months (range, 30-39 months) revealed stable coil configuration in all patients. There was no case of stent migration or alteration in stent expansion state in all 30 patients in whom DSA and/or PR images were available. Four patients (7.7%) suffered delayed cerebral ischemic symptom, all as transient ischemic attack without neurological sequelae. Three of the four cases were related to discontinuation of the anti-platelet medication. In conclusion, stent-assisted coil embolization of intracranial aneurysms using LVIS device provide excellent mid- to long-term aneurysm occlusion rate and with low rate of delayed complication.

SS 37 NR(NI)-03 16:20 Penetrable large shunting point in intracranial dural arteriovenous fistulas: providing alternative access route to transarterial intravenous embolizationDong-hyun Shim, Jieun Roh, Young Soo Kim, Seung Kug Baik Pusan National University Yangsan Hospital, Korea. skbaik9@gmail.com

PURPOSE: Transvenous and trasarterial embolization of the include affected venous outlet is the most common treatment method for the management of intracranial dural arteriovenous fistulas (DAVFs). However, such an approach is not always feasible such as dAVF involving an isolated sinus and multiple arterial feeder. We present dAVFs that were treated with transarterial intravenous embolization of the proximal venous outlet, as well as possible cases previously treated another route at out facility.MATERIALS AND METHODS: This study included 47 patients who had undergone endovascular treatment of the dAVF for treatment of dAVFs (4 cases of transarterial

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intravenous embolization). All clinical, angiographic, and procedural data were retrospectively collected from medical charts or the literature and recorded on standardized forms by a physician. The angiography was analyzed by two independent neurointerventionist. The dAVFs were classified according to the angiographic type and venous drainage pattern.RESULTS: In 47 patients, 17 (36%) cases have possible penetrable large shunting point with distal enlargement. Four cases was performed transarterial intravenous coil embolization of proximal venous site of the fistula was possible by using coils through the penetrable large shunting point; this resulted in complete obliteration in all patients. The access route for 12 of the 17 cases was the middle meningeal artery, and in 2 cases was the meningohypophyseal artery, each 1 case was deep temporal artery and occipital artery. Five of 17 cases have multiple possible penetrable large shunting point. Almost cases was restrictive type (mature type) of angiographic classfication.CONCLUSION: If a distally enlarged feeding artery is observed among the multiple feeding arteries, it suggests the existence of a large fistula and may serve as an access route for transarterial intravenous embolization. The penetrable large shunting point with distal enlargement should not be overlooked as a potential access route for transarterial intravenous embolization in cases where traditional endovascular access is limited; this approach does not carry the same risks that are generally associated with pure transarterial embolization along this pathway. Also it may offer a more treatment option for neurointerventionist.

SS 37 NR(NI)-04 16:30 Stenting as a rescue treatment after failure of mechanical thrombectomy for anterior circulation large artery occlusion Byung Moon Kim1, Jang-Hyun Baek2, Dong Joon Kim1 1Severance Hospital, 2National Medical Center, Korea. BMOON21@yuhs.ac

PURPOSE: We hypothesized that permanent stenting may be a rescue treatment for stentriever-failed anterior circulation large artery occlusion (AC-LAO). We compared the outcomes of the patients with permanent stenting and without stenting after stentriever failure.MATERIALS AND METHODS: We retrospectively evaluated 208 patients who underwent stentriever thrombectomy for AC-LAO between September 2010 and September 2015. Modified thrombolysis in cerebral ischemia (mTICI) 2b-3 recanalization was achieved with stentriever alone or combined with Penumbra in 155 (74.5%) patients. An additional 8 patients (3.8%) obtained mTICI 2b-3 with urokinase and/or glycoprotein

IIb/IIIa inhibitor infusion. Of the remaining 45 patients (21.6%), 17 underwent stenting (stenting group [SG]; mean age, 68 years), whereas 28 were left without stenting (non-stenting group [NSG]; mean age, 72 years). The rate of mTICI 2b-3 in SG was assessed and clinical outcomes were compared between SG and NSG.RESULTS: There were no differences in clinical and laboratory findings, initial NIHSS score, location of AC-LAO, and onset-to-puncture time between the 2 groups. mTICI 2b-3 was achieved in 14 (83.3%) of the SG. SG had more favorable outcomes (modified Rankin Scale [mRS] 0-2, 35.3%) and less cerebral herniation (CH, 11.8%) than NSG (mRS 0-2, 7.1%; CH, 42.9%) (p < 0.05 for both). Symptomatic intracranial hemorrhage (sICH) and mortality rates were not different between SG (sICH, 11.8%; mortality, 23.5%) and NSG (sICH, 14.3%; mortality, 39.3%).CONCLUSION: Among patients with stentriever-failed AC-LAO, SG had significantly more favorable outcomes than NSG. Permanent stenting may be a rescue modality for stentriever-failed AC-LAO.

SS 37 NR(NI)-05 16:40 Significance of truncal-type occlusion in stentriever-based thrombectomy for acute strokeByung Moon Kim1, Jang-Hyun Baek2, Dong Joon Kim1 1Severance Hospital, 2National Medical Center, Korea. BMOON21@yuhs.ac

PURPOSE: To investigate whether angiographically-defined occlusion type could predict of the etiology of acute intracranial large artery occlusion and the stentriever response.MATERIALS AND METHODS: We reviewed consecutive patients with acute intracranial large artery occlusion who underwent endovascu la r t rea tment and examined their work-ups for embolic sources. Patient demographics, laboratory findings, hyperdense artery sign, and angiographic occlusion type (truncal-type or branching-site occlusion) were compared between embolic sources (+) and (-) groups. These variables were also compared between stentriever failure and success groups. Details of endovascular procedures were also compared according to occlusion type.RESULTS: Two hundred fifty-nine patients (mean age, 70.3 years; M:F = 132:127) were finally included. Of these patients, 216 (83.4%) were assigned to embolic sources (+) group after thorough evaluation. Young age, no coronary artery disease, and truncal-type occlusion (odds ratio [OR] 9.07; 95% confidence interval [CI] 3.74-22.0) were independently associated with embolic source (-) group. Of the overall group, 224 patients (86.5%) underwent stentriever-based

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endovascular treatment. Hypertension, diabetes, high C-reactive protein level, and truncal-type occlusion (OR 32.2; 95% CI 7.78-133.0) were independent predictors of stentriever failure. Truncal-type occlusion was associated with more reocclusion (77.3% vs. 5.0%), resulting in recanalization failure by the stentriever (81.8% vs. 20.3%), a longer puncture-to-recanalization time (118.0 vs. 49.5 minutes), and more rescue treatment for final successful recanalization (78.9% vs. 7.0%).CONCLUSION: Angiographic occlusion type is an independent predictor of stentriever refractoriness and of the underlying stroke mechanism.

SS 37 NR(NI)-06 16:50 Permanent stenting with Solitaire FR as a rescue tool for reperfusion of acute intracranial artery occlusionHo Geol Woo, Cheolkyu Jung, Leonard Sunwoo, Yun Jung Bae, Byung Se Choi, Jae Hyoung Kim Seoul National University Bundang Hospital, Korea. jck0097@gmail.com

PURPOSE: Stent placement has been applied for a rescue therapy in combination with thrombolytic agent, mechanical thrombectomy and percutaneous balloon angioplasty in acute stroke treatment. Solitaire FR was able to be used for not only the tool of mechanical thrombectomy but also permanent stent which was detachable. Therefore, this case series assessed feasibility and safety of permanent stenting with Solitaire FR for intracranial artery recanalization for acute ischemic stroke.MATERIALS AND METHODS: Four hundred-thirty-four patients from January 2011 to January 2016 who had intracranial artery occlusion were treated by intra-arterial therapy (IAT). Among them, 13 patients (median NIHSS 16, mean age 67) were treated with permanent stenting with Solitaire FR as a rescue tool. TICI reperfusion grade at the end of procedure and instent restenosis or occlusion on follow up angiographic imaging were assessed as well as safety variables. Clinical outcome were assessed with mRS at 3 months.RESULTS: Intracranial occlusions were located at M1 middle cerebral artery (MCA) segment (n = 10), M2 MCA segment (n = 1), vertebral artery (n = 1), basilar artery (n = 1). Stent placement was successful in all procedures and resulted in successful reperfusion (mTICI 2b or 3) in 85%. GP IIb/IIIa inhibitors were administered in 8 of 13 cases (62%) during procedure. There was successful reperfusion in 7 of 8 patients (88%) in GP IIb/IIIa-treated patients, whilst no patient without treatment of GP IIb/IIA inhibitor. There was no complication related to the

procedure, symptomatic hemorrhagic transformation. During follow up period, 3 in hospital deaths occurred due to respiratory complication in advanced cancer patients. Four of 13 patients (31%) had mRS ≤ 2 at discharge and 3 of 10 patients (30%) had mRS ≤ 2 at 3 months. There was no patient with in stent restenosis more than 50% and reocclusion at 3 months.CONCLUSION: Our case series with permanent stenting of Solitaire FR showed high rate of successful stent placement, complete reperfusion, and low rate of restenosis or occlusion during short follow-up period at 3 months. Therefore, this technique seemed to be feasible and safe as a rescue tool for intra-arterial therapy of acute intracranial artery occlusion.

SS 37 NR(NI)-07 17:00 Clinical and procedural factors of good outcome and mortality after stent-retriever thrombectomy in acute anterior circulation strokeWoong Yoon, Seul Kee Kim, Byung Hyun Baek, Yun Young Lee Chonnam National University Hospital, Korea. radyoon@jnu.ac.kr

PURPOSE: Prognostic factors after stent-retriever thrombectomy in patients with acute anterior circulation stroke remain to be elucidated. This study aimed to investigate clinical and procedural factors leading to good outcome and mortality after stent-retriever thrombectomy in a large cohort of patients with acute anterior circulation stroke.MATERIALS AND METHODS: We analyzed clinical and procedural data in 335 patients with acute anterior circulation stroke treated with stent-retriever thrombectomy. A good outcome was defined as a modified Rankin Score of 0 to 2 at 3 months. The associations between clinical and procedural factors and each good out come and mortality were evaluated with logistic regression analysis.RESULTS: In a multivariate analysis, age (odds ratio [OR], 0.965; 95% confidence interval [CI], 0.944-0.986; p = 0.001), successful revascularization (OR, 4.658; 95% CI, 2.240-9.689; p < 0.001), baseline NIHSS score (OR, 0.908; 95% CI, 0.855-0.965; p = 0.002), and parenchymal hemorrhage (OR, 0.150; 95% CI, 0.049-0.460; p = 0.001) were independent predictors of good outcome at 3 months. Age (OR, 1.043; 95% CI, 1.002-1.086; p = 0.041), a history of previous stroke/TIA (OR, 3.124; 95% CI, 1.340-7.281; p = 0.008), successful revascularization (OR, 0.171; 95% CI, 0.079-0.370; p < 0.001), and parenchymal hemorrhage (OR, 2.961; 95% CI, 1.059-8.276; p = 0.038) were independent predictors of mortality.CONCLUSION: Age, revascularization status, and

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parenchymal hemorrhage are independent predictors of both good outcome and mortality after stent retriever thrombectomy in acute anterior circulation stroke. In addition, NIHSS score on admission is independently associated with good outcome whereas a history of previous stroke is independently associated with mortality.

SS 37 NR(NI)-08 17:10 The practical role of multiphase CTA in triage of acute ischemic stroke for intra-arterial treatment: to do or not to do?Ho Geol Woo1, Cheolkyu Jung1, Seunguk Jung2, Leonard Sunwoo1, Yun Jung Bae1, Byung Se Choi1, Jae Hyoung Kim1 1Seoul National University Bundang Hospital, 2Gyeongsang National University Hospital, Korea.jck0097@gmail.com

PURPOSE: Although recently, intra-arterial therapy (IAT) has been proven to play important role in acute ischemic stroke with large arterial occlusion, there would be controversy which one of multimodal CT neuroimaging would be suitable to select proper candidates for treatment. We hypothesized that multiphase CT angiography (mCTA) would be more beneficial than perfusion CT (PCT) or non-contrast CT (NCT) in determining the image triage of patients with acute ischemic stroke less than 4 hours from onset of event in daily practice in order to achieve the good functional outcomes at 3 months.MATERIALS AND METHODS: After retrospective review of our database for IAT from April 2015 to January 2016, patients to be treated by IAT were included in this study as the following criteria; (1) the stroke in anterior circulation; (2) NCT, PCT and mCTA within less than 4 hours between last normal time and arrival time were available. Pial arterial filling score using mCTA, the Alberta Stroke Program Early CT Score (ASPECTS) in NCT and PCT were semi-quantitatively assessed. Furthermore, mismatch ratio on PCT using CBV and MTT maps was measured. These parameters were evaluated to investigate the association of the clinical outcome using mRS at 3 months.RESULTS: Thirty nine patients (median, NIHSS 16; mean age, 72) were met for inclusion criteria. Functional clinical outcome was significantly associated with age (r2 = 0.317, p = 0.001), dichotomized pial arterial filing score (r2 = 0.282, p = 0.001), dichotomized ASPECTS in NCT (r2 = 0.10, p = 0.046) and PCT (r2 = 0.146, p = 0.019) and NIHSS before IAT (r2 = 0.175, p = 0.016). Mismatch ratio on perfusion CT (r2 = 0.052, p = 0.158) and successful reperfusion (mTICI 2b or 3, r2 = 0.052, p = 0.242) were not associated with functional outcome.

In multivariable analysis, age and pial arterial filling score remained strongly associated with good outcome (adjusted OR : 2.403, 95% CI : 1.10-5.24).CONCLUSION: Our study showed that age and pial arterial filling score using mCTA were strongly more associated with clinical outcome of stroke patient treated by IAT than ASPECTS of NCT or PCT as like previous studies. Therefore, it seemed that mCTA could be pragmatically used in daily practice to triage the patient of acute ischemic stroke with large vessel occlusion.

SS 37 NR(NI)-09 17:20 Optimizing clinical outcome prediction scores in acute ischemic stroke after intra-arterial thrombectomy using collateralization score on CT angiographyYe Na Son1, Chang-Woo Ryu1, Soonchan Park1, Eui Jong Kim2, Woo Suk Choi2, Kyung Mi Lee2 1Kyung Hee University Hospital at Gangdong, 2Kyung Hee University Medical Center, Korea. md.cwryu@gmail.com

PURPOSE: To evaluate whether additional use of the collateralization score on CT angiography (CTA) combined with other several outcome prediction scores can increase accuracy of clinical outcome prediction in acute ischemic stroke.MATERIALS AND METHODS: This retrospective study enrolled patients who underwent pre-procedural CT angiography and intra-arterial thrombectomy for acute ischemic stroke of anterior circulation within 8 hours. CTA was used to identify occlusion and grade the extent of collateralization vessel in the Sylvian fissure and leptomeningeal convexity. The CTA collateralization score (CTA-CS) classified: 0 = no collateralization filling, 1 = ≤ 50%, 2 = > 50% but < 100%, and 3 = 100% collateralization filling. We calculated three conventional outcome prediction scores (HIAT-2, SPAN-100, THRIVE) as an independent predictors of clinical outcome. Clinical outcome were assessed with modified Rankin scale (mRS) at discharge and mRS was classified as good outcome (mRS 0-2) and poor outcome (mRS 3-6). Three conventional prediction scores and these scores with additionally applying CTA-CS were assessed for the predictability of clinical outcome using receiver-operator characteristics (ROC) curve analysis.RESULTS: 68 patients (M:F = 44:24; mean age, 68.5 years) enrolled in this study. Mean symptom to puncture time were 3.8 hours. 53 cases were middle meningeal artery occlusion and 15 cases were internal carotid artery occlusion. Patients with good outcome were 29 (43%) and patients with poor outcome were 39 (57%). The predictability was increased after the added value

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of CTA-CS over predictive scores than predictive scores alone. AUC value of three predictive scores (HIAT-2, SPAN-100 and THRIVE) alone and added value of CTA-CS over predictive scores were 0.7 vs. 0.73, 0.723 vs. 0.777, and 0.630 vs. 0.682, respectively.CONCLUSION: The added value of The CTA-CS over conventional clinical outcome scoring system can improve predictability of clinical outcome after intra-arterial thrombectomy for anterior circulation large artery occlusions, compared with conventional scoring system alone.

SS 37 NR(NI)-10 17:30 The Alberta stroke program early CT score in the triage and prediction of outcomes after endovascular treatment for acute ischemic stroke: a meta-analysisChang-Woo Ryu1, Soonchan Park1, Eui Jong Kim2, Woo Suk Choi2, Kyung Mi Lee2 1Kyung Hee University Hospital at Gangdong, 2Kyung Hee University Medical Center, Korea. md.cwryu@gmail.com

PURPOSE: The Alberta Stroke Program Early CT Score (ASPECTS) was devised to quantify the extent of early ischemic changes in the middle cerebral artery territory on brain CT. We performed a systematic review and meta-analysis of studies that presented clinical outcomes and baseline ASPECTS in ischemic stroke patients managed with endovascular methods to validate the use of ASPECTS for risk prognostication and risk stratification.MATERIALS AND METHODS: We searched the MEDLINE, EMBASE, and Cochran databases for observational or interventional studies that reported the clinical outcomes and baseline ASPECTS in ischemic stroke patients treated with endovascular methods. Data were pooled to perform a meta-analysis for comparisons of clinical outcomes between high and low ASPECTS patients, and between endovascular and medical treatment in both high (> 7) and low (≤ 7) ASPECTS patients.RESULTS: A meta-analysis of 13 studies (s ix observational and seven interventional) revealed favorable outcomes (mRS sore 0-2 at 90 days) for high baseline ASPECTS (odds ratio = 2.22; 95% CI: 1.74-2.86). A meta-analysis of six randomized controlled trials revealed that endovascular treatment had a benefit in favorable outcomes for patients with high ASPECTS (1,317 patients; odds ratio = 2.13; 95% CI, 1.42-3.22), but not for patients with low ASPECTS (656 patients; odds ratio = 1.29; 95% CI, 0.92-1.81).CONCLUSION: High ASPECTS is a predictor of favorable outcome after endovascular therapy for

ischemic stroke, and benefits from endovascular therapy in comparison with standard medical treatment. The threshold of ASPECTS for candidates for endovascular therapy should be amended to increase the benefit of endovascular therapy.

SS 37 NR(NI)-11 17:40 Interobserver variability of aneurysm morphology: discrimination of the daughter sacWoo Sang Jung, Sang Hyun Suh Gangnam Severance Hospital, Korea. suhsh11@yuhs.ac

PURPOSE: Several definitions have been proposed to distinguish from the daughter sac in treatment decision of the unruptured intracranial aneurysms. The aim of this study was to evaluate interobserver variability of aneurysm morphology, including the daughter sac, from the international study of unruptured intracranial aneurysms (ISUIA) and the unruptured cerebral aneurysm study of Japan (UCAS).MATERIALS AND METHODS: After approval by the Institutional Review Board, we analyzed 4 morphological definitions (daughter sac, lobulation and irregular margin) from the ISUIA and UCAS using angiographic images of 102 saccular aneurysms. 4 independent readers interpreted each morphological criterion with the dichotomized scales (existence or not). The κ statistics were performed to measure interobserver agreement and κ > 0.6 was considered substantial agreement.RESULTS: In discrimination of the daughter sac, interobserver agreement among 4 readers was substantial for the UCAS (k = 0.626 in 2D and 0.659 in 3D images) and not for the ISUIA (k = 0.487 in 2D and 0.473 in 3D), which had a significant difference. Irrespective of the used images, pairwise pooled κ values for the UCAS were more than 0.6 except one case (score of 0.54 between reader A and B). In proportion of positive reads, there was significant difference between reads of daughter sac by the UCAS and those by the ISUIA.CONCLUSION: In discrimination of the daughter sac, the UCAS definition showed a higher reliability than the ISUIA. However, a further prospective study is necessary to validate this definition as treatment standard for the unruptured intracranial aneurysm.