Abstract:564S everal studies have demonstrated that arterial spin labeling (ASL)-perfusion-weighted imaging (PWI) can detect hypoperfusion and perfusion-diffusion mismatch in the setting of acute stroke, with good to modest correlation to dynamic susceptibility contrast perfusion MRI. [1][2][3][4] Recently, ASL-PWI has been incorporated as a part of the acute ischemic stroke evaluation in our institution, and with its increasing use, we have encountered patients with acute ischemic stroke in whom a characteristic brigh… Show more
“…9 ABS can also be seen without an occlusion and may then be because of a stagnant flow upstream of a stenosis. Our data are in agreement with the recent work of Yoo et al, 10 which highlights that the bright intravascular signal, attributable to slowflowing blood on ASL imaging, may facilitate the detection and localization of arterial occlusion in acute IS. The authors moreover affirm that 10 occlusions could solely be detected by the ASL bright vessel appearance, whereas no occlusion case could be exclusively identified by the susceptibility vessel sign on susceptibility weighted imaging.…”
Section: Majer Et Al Use Of Raw Asl Data In Patients With Ischemic Stsupporting
confidence: 93%
“…The authors moreover affirm that 10 occlusions could solely be detected by the ASL bright vessel appearance, whereas no occlusion case could be exclusively identified by the susceptibility vessel sign on susceptibility weighted imaging. In accordance with these observations, we found that the ABS had a high sensitivity (100% in our study compared with 94% for Yoo et al 10 ). However, unlike them, occlusions assessed by EPI T2* showed less sensitivity than susceptibility weighted imaging in our patient sample.…”
Section: Majer Et Al Use Of Raw Asl Data In Patients With Ischemic Stsupporting
A rterial spin labeling (ASL) is one of the most recent magnetic resonance imaging (MRI) sequences used to assess brain perfusion noninvasively. It can be used in the acute phase of ischemic stroke (IS) to identify ischemic penumbra. 1 In patients in acute phase of IS, thrombus assessment is of major clinical relevance because the presence and location of the thrombus may determine therapeutic strategy. 2 An arterial bright signal (ABS), at the level of vascular occlusions, can be observed on raw data of ASL sequence performed for stroke.The aim of this study is to evaluate the relevance of this MRI sign in patients admitted for IS.
Patients and MethodsWith the approval of the local ethics committee, we retrospectively analyzed MRI sequences of patients with an IS suspicion admitted in the Department of Neuroradiology (University Hospital of Martinique) from December 2011 to August 2014. MRI (GE Optima MR450W 1.5 T) was performed within 6 hours from stroke onset and included diffusion weighted imaging sequence, echo planar imaging T2* (EPI T2*), fluid attenuated inversion recovery (FLAIR) and MR angiography (Willis time of flight (TOF)). ASL sequence was performed only in case of doubtful diffusion weighted imaging or to highlight a mismatch before a thrombolytic treatment.ASL scans were performed using a pseudocontinuous mode with a repetition time of 4554 ms, an echo time of 10 ms, a postlabeling delay of 1525 ms, and a total acquisition time of 4 minutes.Main judgment criteria were the assessment and the concordance of ABS compared with other sequences (TOF, EPI T2*, and FLAIR).Moreover, a vessel occlusion was diagnosed if an artery was missing on Willis TOF. An intra-arterial clot could be diagnosed on T2* (as a focal hyposignal) and on FLAIR sequences (as a focal hypersignal). ABS was diagnosed according to 2 different patterns upstream of a hypoperfused territory: spot-like (rounded or oval, with sharp edges, on a vascular path) or vessel-like (linear hypersignal on an artery path).One neuroradiologist (AA), with 11 years of experience, first analyzed ASL data while being blinded to clinical data and other sequences. After this first analysis, ABS was definitely graded as 0 if absent or 1 if present and its grading remained unmodified thereon. Other MRI sequence findings (diffusion weighted imaging, occlusion on Willis TOF, clot on T2*, clot on FLAIR) were also studied and graded in a similar manner.A radiology resident, with a 6-month experience in neuroradiology, independently repeated the whole data analysis process in the same conditions.A stroke was considered ongoing in case of the detection of an area of restricted diffusion, identified while being blinded to ASL results.The absence of stroke diagnosis was made if no restricted diffusion area was observed, while still blinded to ASL results. This was further corroborated by clinical data and computed tomography or MRI follow-up for 1 week after patient admission for IS suspicion.
Statistical AnalysisInterobserver variability for ABS was assessed usi...
“…9 ABS can also be seen without an occlusion and may then be because of a stagnant flow upstream of a stenosis. Our data are in agreement with the recent work of Yoo et al, 10 which highlights that the bright intravascular signal, attributable to slowflowing blood on ASL imaging, may facilitate the detection and localization of arterial occlusion in acute IS. The authors moreover affirm that 10 occlusions could solely be detected by the ASL bright vessel appearance, whereas no occlusion case could be exclusively identified by the susceptibility vessel sign on susceptibility weighted imaging.…”
Section: Majer Et Al Use Of Raw Asl Data In Patients With Ischemic Stsupporting
confidence: 93%
“…The authors moreover affirm that 10 occlusions could solely be detected by the ASL bright vessel appearance, whereas no occlusion case could be exclusively identified by the susceptibility vessel sign on susceptibility weighted imaging. In accordance with these observations, we found that the ABS had a high sensitivity (100% in our study compared with 94% for Yoo et al 10 ). However, unlike them, occlusions assessed by EPI T2* showed less sensitivity than susceptibility weighted imaging in our patient sample.…”
Section: Majer Et Al Use Of Raw Asl Data In Patients With Ischemic Stsupporting
A rterial spin labeling (ASL) is one of the most recent magnetic resonance imaging (MRI) sequences used to assess brain perfusion noninvasively. It can be used in the acute phase of ischemic stroke (IS) to identify ischemic penumbra. 1 In patients in acute phase of IS, thrombus assessment is of major clinical relevance because the presence and location of the thrombus may determine therapeutic strategy. 2 An arterial bright signal (ABS), at the level of vascular occlusions, can be observed on raw data of ASL sequence performed for stroke.The aim of this study is to evaluate the relevance of this MRI sign in patients admitted for IS.
Patients and MethodsWith the approval of the local ethics committee, we retrospectively analyzed MRI sequences of patients with an IS suspicion admitted in the Department of Neuroradiology (University Hospital of Martinique) from December 2011 to August 2014. MRI (GE Optima MR450W 1.5 T) was performed within 6 hours from stroke onset and included diffusion weighted imaging sequence, echo planar imaging T2* (EPI T2*), fluid attenuated inversion recovery (FLAIR) and MR angiography (Willis time of flight (TOF)). ASL sequence was performed only in case of doubtful diffusion weighted imaging or to highlight a mismatch before a thrombolytic treatment.ASL scans were performed using a pseudocontinuous mode with a repetition time of 4554 ms, an echo time of 10 ms, a postlabeling delay of 1525 ms, and a total acquisition time of 4 minutes.Main judgment criteria were the assessment and the concordance of ABS compared with other sequences (TOF, EPI T2*, and FLAIR).Moreover, a vessel occlusion was diagnosed if an artery was missing on Willis TOF. An intra-arterial clot could be diagnosed on T2* (as a focal hyposignal) and on FLAIR sequences (as a focal hypersignal). ABS was diagnosed according to 2 different patterns upstream of a hypoperfused territory: spot-like (rounded or oval, with sharp edges, on a vascular path) or vessel-like (linear hypersignal on an artery path).One neuroradiologist (AA), with 11 years of experience, first analyzed ASL data while being blinded to clinical data and other sequences. After this first analysis, ABS was definitely graded as 0 if absent or 1 if present and its grading remained unmodified thereon. Other MRI sequence findings (diffusion weighted imaging, occlusion on Willis TOF, clot on T2*, clot on FLAIR) were also studied and graded in a similar manner.A radiology resident, with a 6-month experience in neuroradiology, independently repeated the whole data analysis process in the same conditions.A stroke was considered ongoing in case of the detection of an area of restricted diffusion, identified while being blinded to ASL results.The absence of stroke diagnosis was made if no restricted diffusion area was observed, while still blinded to ASL results. This was further corroborated by clinical data and computed tomography or MRI follow-up for 1 week after patient admission for IS suspicion.
Statistical AnalysisInterobserver variability for ABS was assessed usi...
“…The postlabeling delay (time between labeling and readout) is set to be longer than the arterial transit time; therefore, all blood has entered the tissue and no blood remains visible in large vessels (Alsop et al, 2015). However, due to pathological changes and also to anesthesia, blood flow velocities might slow down and blood potentially remaining inside the vessels can be misinterpreted as areas of elevated perfusion (overshoot) (Yoo et al, 2015). …”
ObjectivesIntraoperative magnetic resonance imaging is a unique tool for visualizing structures during resection and/or for updating any kind of neuronavigation that might be hampered as a result of brain shift during surgery. Advanced MRI techniques such as perfusion-weighted imaging have already proven to be important in the initial diagnosis preoperatively, but can also help to differentiate between tumor and surgically induced changes intraoperatively. Commonly used methods to visualize brain perfusion include contrast agent administration and are therefore somewhat limited. One method that uses blood as an internal contrast medium is arterial spin labeling (ASL), which might represent an attractive alternative.Materials and methodsTen healthy volunteers were examined using three different scanners and coils within 1 h (3T Achieva MRI using 32-channel head coil, 1.5T Achieva MRI using a 6-channel head coil, 1.5 Intera Scanner using 2 surface coils, Philips, Best, The Netherlands) and quantitative CBF values were calculated and compared between the different setups. Additionally, in eight patients with glioblastoma multiforme, ASL was used pre-, intra-, and postoperatively to define tumor tissue and the extent of resection in comparison to structural imaging.ResultsA high correlation (r = 0.91–0.96) was found between MRI scanners and coils used. ASL was as reliable as conventional MR imaging if complete resection was already achieved, but additionally provided valuable information regarding residual tumor tissue in one patient.ConclusionsIntraoperative arterial spin-labeling is a feasible, reproducible, and reliable tool to map CBF in brain tumors and seems to give beneficial information compared to conventional intraoperative MR imaging in partial resection.
“…This bright vessel sign corresponds to an accumulation of protons in labelled arterial blood immediately upstream from the arterial occlusion. The sensitivity of the bright vessel sign would be superior to that of the susceptibility vessel sign [36–38]. The bright vessel sign can also reveal certain distal arterial occlusions not initially detected on the vascular sequences, e.g.…”
Section: Arterial Spin Labellingmentioning
confidence: 99%
“…The bright vessel sign can also reveal certain distal arterial occlusions not initially detected on the vascular sequences, e.g. 3D TOF sequences [38]. Fig.…”
Magnetic resonance imaging (MRI) plays a central role in the early diagnosis of cerebral vascular events. Today, MRI is used not only for the detection of acute ischaemic lesions, but also to fine tune the diagnosis and improve patient selection for early therapeutic decision-making. In this perspective, new tools such as arterial spin labelling (ASL) and susceptibility-weighted imaging (SWI) sequences have been developed. These MRI sequences enable noninvasive assessment of brain damage, providing important diagnostic and prognostic information: evaluation of cerebral parenchymal perfusion; detection and aetiological assessment of thrombi; ruling out differential diagnoses. After a brief recall of the fundamental basis of these sequences, this article proposes an update on their current contribution to the early management of stroke victims.Teaching Points• These noninvasive sequences provide essential information for early management of acute stroke.
• They can detect zones of parenchymal hypoperfusion.
• Susceptibility-weighted sequences provide information on thrombus localisation and composition.
• ASL can identify certain aetiologies of stroke mimics.
• Post-therapeutic ASL perfusion status predicts outcome.
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