Better Late than Never
2012; Lippincott Williams & Wilkins; Volume: 43; Issue: 4 Linguagem: Inglês
10.1161/strokeaha.111.644344
ISSN1524-4628
Autores Tópico(s)MRI in cancer diagnosis
ResumoHomeStrokeVol. 43, No. 4Better Late than Never Free AccessEditorialPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessEditorialPDF/EPUBBetter Late than NeverThe Long Journey for Noncontrast Arterial Spin Labeling Perfusion Imaging in Acute Stroke Greg Zaharchuk Greg ZaharchukGreg Zaharchuk From the Department of Radiology, Stanford University, Stanford, CA. Originally published9 Feb 2012https://doi.org/10.1161/STROKEAHA.111.644344Stroke. 2012;43:931–932Other version(s) of this articleYou are viewing the most recent version of this article. Previous versions: January 1, 2012: Previous Version 1 See related article, p 1018.This report1 describes the authors' experience using a noncontrast brain perfusion method, arterial spin labeling (ASL), in patients with acute ischemic stroke and compares this with dynamic susceptibility contrast MRI. This latter technique is also sometimes referred to simply as perfusion-weighted imaging (PWI) to emphasize its complementary nature to diffusion-weighted imaging. The authors found excellent overlap between imaging information available with PWI and ASL with no measurable difference in perceived signal-to-noise ratio or lesion conspicuity. They also found that the effects of slow flow on the ASL signal, although present, were not an insurmountable impediment to image interpretation in that they correlated with the changes seen in the PWI time-to-maximum of the residue function (Tmax) and the nondelay-corrected cerebral blood flow maps. In particular, they point out that the parenchymal microvascular contrast afforded by the ASL images was particularly useful in visualizing hyperemia related to reperfusion, sometimes termed luxury perfusion.The basic ASL and PWI techniques were initially described >20 years ago,2,3 and both were applied to human patients with stroke relatively soon thereafter.4–6 PWI has become a mainstay of academic medical center MR stroke examinations. The dominant paradigm in the stroke imaging community is the PWI–diffusion-weighted imaging mismatch, which posits that patients with large perfusion lesions but small diffusion lesions have potentially salvageable tissue that can be "rescued" by prompt recanalization.7,8 ASL, despite the advantage of being a noncontrast perfusion technique, has not enjoyed widespread clinical use, however, because of 2 factors: first, the generally lower signal-to-noise ratio of the images; and second, the strong dependence of the ASL signal on delayed arterial transit times between the site of labeling and imaging. The first of these concerns is becoming alleviated with the adoption of higher field MR scanners9 and improved ASL pulse sequences that use pseudocontinuous labeling, background suppression, and optimized image readout.10 The second issue is more fundamental. Because the labeled water decays with the blood T1 time, which is on the order of 1 to 2 seconds, flow that arrives late, perhaps through collateral pathways, may be incorrectly interpreted as absence of flow. This is a critical distinction in acute ischemic stroke, in which collateral flow has been shown to be a key factor in patient outcome.11,12 Although current methods appear to yield information about collaterals,13,14 newer techniques such as velocity-selective ASL,15 which labels blood based on velocity rather than by position, and is theoretically insensitive to arrival time, will hopefully mitigate this issue. Finally, the recognition of the association between gadolinium contrast agents and nephrogenic systemic fibrosis has made bolus PWI a contraindication in some patients with stroke, making a noncontrast stroke protocol using ASL more clinically desirable because it eliminates the need to determine creatinine clearance before MR scanning.More MR vendors are developing product sequences and clinicians are gaining more experience with ASL in stroke. Because standard ASL does not typically yield information about arterial arrival times, future studies must determine the relationship between cerebral blood flow measures and Tmax regarding mismatch status and patient outcome. Another important focus will be the development of automated methods to assess lesion size,16 which is challenging for ASL due to the inherent cerebral blood flow differences between gray and white matter. Studies (such as this one) using both ASL and PWI, at least in the short term, will likely provide unique insights into the pathophysiology of the hemodynamic state in patients with acute stroke.DisclosuresDr Zaharchuk is a member of the neuroradiology advisory board for and receives research support from GE Healthcare.FootnotesThe opinions in this editorial are not necessarily those of the editors or of the American Heart Association.Oh Young Bang, MD, PhD, was the Guest Editor for this paper.Correspondence to Greg Zaharchuk, MD, PhD, Stanford University Medical Center, 1201 Welch Road, Mailcode 5488, Stanford, CA 94305-5488. E-mail gregz@stanford.eduReferences1. Wang D, Alger J, Qian J, Hou S, Fiaz R, Gunther M , et al. The value of arterial spin-labeled perfusion imaging in acute ischemic stroke—comparison with dynamic susceptibility contrast enhanced MRI. Stroke. 2012; 43:1018–1024.LinkGoogle Scholar2. Rosen BR, Belliveau JW, Vevea JM, Brady TJ. Perfusion imaging with NMR contrast agents. Magn Reson Med. 1990; 14:249–265.CrossrefMedlineGoogle Scholar3. Detre JA, Leigh JS, Williams DS, Koretsky AP. Perfusion imaging. Magn Reson Med. 1992; 23:37–45.CrossrefMedlineGoogle Scholar4. Sorensen AG, Buonanno FS, Gonzalez RG, Schwamm LH, Lev MH, Huang-Hellinger FR , et al. Hyperacute stroke: evaluation with combined multisection diffusion-weighted and hemodynamically weighted echo-planar MR imaging. Radiology. 1996; 199:391–401.CrossrefMedlineGoogle Scholar5. Siewert B, Schlaug G, Edelman RR, Warach S. Comparison of EPISTAR and T2*-weighted gadolinium-enhanced perfusion imaging in patients with acute cerebral ischemia. Neurology. 1997; 48:673–679.CrossrefMedlineGoogle Scholar6. Chalela JA, Alsop DC, Gonzalez-Atavales JB, Maldjian JA, Kasner SE, Detre JA. Magnetic resonance perfusion imaging in acute ischemic stroke using continuous arterial spin labeling. Stroke. 2000; 31:680–687.LinkGoogle Scholar7. Albers GW, Thijs VN, Wechsler L, Kemp S, Schlaug G, Skalabrin E , et al. Magnetic resonance imaging profiles predict clinical response to early reperfusion: the Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution (DEFUSE) study. Ann Neurol. 2006; 60:508–517.CrossrefMedlineGoogle Scholar8. Olivot JM, Albers GW. Diffusion-perfusion MRI for triaging transient ischemic attack and acute cerebrovascular syndromes. Curr Opin Neurol. 2011; 24:44–49.CrossrefMedlineGoogle Scholar9. Wang J, Alsop DC, Li L, Listerud J, Gonzalez-At JB, Schnall MD , et al. Comparison of quantitative perfusion imaging using arterial spin labeling at 1.5 and 4.0 Tesla. Magn Reson Med. 2002; 48:242–254.CrossrefMedlineGoogle Scholar10. Dai W, Garcia D, de Bazelaire C, Alsop DC. Continuous flow driven inversion for arterial spin labeling using pulsed radiofrequency and gradient fields. Magn Reson Med. 2008; 60:1488–1497.CrossrefMedlineGoogle Scholar11. Kucinski T, Koch C, Eckert B, Becker V, Kromer H, Heesen C , et al. Collateral circulation is an independent radiological predictor of outcome after thrombolysis in acute ischaemic stroke. Neuroradiology. 2003; 45:11–18.CrossrefMedlineGoogle Scholar12. Bang OY, Saver JL, Buck BH, Alger JR, Starkman S, Ovbiagele B , et al. Impact of collateral flow on tissue fate in acute ischaemic stroke. J Neurol Neurosurg Psychiatry. 2008; 79:625–629.CrossrefMedlineGoogle Scholar13. Chng SM, Petersen ET, Zimine I, Sitoh YY, Lim CC, Golay X. Territorial arterial spin labeling in the assessment of collateral circulation: comparison with digital subtraction angiography. Stroke. 2008; 39:3248–3254.LinkGoogle Scholar14. Zaharchuk G, Do HM, Marks MP, Rosenberg J, Moseley ME, Steinberg GK. Arterial spin-labeling MRI can identify the presence and intensity of collateral perfusion in patients with Moyamoya disease. Stroke. 2011; 42:2485–2491.LinkGoogle Scholar15. Wong EC, Cronin M, Wu W-C, Inglis B, Frank LR, Liu TT. Velocity-selective arterial spin labeling. Magn Reson Med. 2006; 55:1334–1341.CrossrefMedlineGoogle Scholar16. Straka M, Albers GW, Bammer R. Real-time diffusion-perfusion mismatch analysis in acute stroke. J Magn Reson Imaging. 2010; 32:1024–1037.CrossrefMedlineGoogle Scholar eLetters(0)eLetters should relate to an article recently published in the journal and are not a forum for providing unpublished data. Comments are reviewed for appropriate use of tone and language. Comments are not peer-reviewed. Acceptable comments are posted to the journal website only. Comments are not published in an issue and are not indexed in PubMed. Comments should be no longer than 500 words and will only be posted online. References are limited to 10. Authors of the article cited in the comment will be invited to reply, as appropriate.Comments and feedback on AHA/ASA Scientific Statements and Guidelines should be directed to the AHA/ASA Manuscript Oversight Committee via its Correspondence page.Sign In to Submit a Response to This Article Previous Back to top Next FiguresReferencesRelatedDetailsCited By Heit J, Zaharchuk G and Wintermark M (2018) Advanced Neuroimaging of Acute Ischemic Stroke, Neuroimaging Clinics of North America, 10.1016/j.nic.2018.06.004, 28:4, (585-597), Online publication date: 1-Nov-2018. Mandeville E, Ayata C, Zheng Y and Mandeville J (2016) Translational MR Neuroimaging of Stroke and Recovery, Translational Stroke Research, 10.1007/s12975-016-0497-z, 8:1, (22-32), Online publication date: 1-Feb-2017. Alves H, Pacheco F and Rocha A (2016) Collateral blood vessels in acute ischemic stroke: a physiological window to predict future outcomes, Arquivos de Neuro-Psiquiatria, 10.1590/0004-282X20160050, 74:8, (662-670) Majer M, Mejdoubi M, Schertz M, Colombani S and Arrigo A (2015) Raw Arterial Spin Labeling Data Can Help Identify Arterial Occlusion in Acute Ischemic Stroke, Stroke, 46:6, (e141-e144), Online publication date: 1-Jun-2015. Sheth S and Liebeskind D (2015) Collaterals in endovascular therapy for stroke, Current Opinion in Neurology, 10.1097/WCO.0000000000000166, 28:1, (10-15), Online publication date: 1-Feb-2015. Sheth S and Liebeskind D (2013) Imaging Evaluation of Collaterals in the Brain: Physiology and Clinical Translation, Current Radiology Reports, 10.1007/s40134-013-0029-5, 2:1, Online publication date: 1-Jan-2014. Hasan K, Ali H and Shad M (2013) Atlas-based and DTI-guided quantification of human brain cerebral blood flow: Feasibility, quality assurance, spatial heterogeneity and age effects, Magnetic Resonance Imaging, 10.1016/j.mri.2013.04.010, 31:8, (1445-1452), Online publication date: 1-Oct-2013. Sandhu G and Sunshine J (2012) Advanced Neuroimaging to Guide Acute Stroke Therapy, Current Cardiology Reports, 10.1007/s11886-012-0315-5, 14:6, (741-753), Online publication date: 1-Dec-2012. April 2012Vol 43, Issue 4 Advertisement Article InformationMetrics © 2012 American Heart Association, Inc.https://doi.org/10.1161/STROKEAHA.111.644344PMID: 22328550 Originally publishedFebruary 9, 2012 Keywordsneuroradiologyimagingbrain ischemiamagnetic resonanceischemiabrain infarctioncerebral hemodynamicscerebral blood flowbrain imagingPDF download Advertisement SubjectsComputerized Tomography (CT)Ischemic Stroke
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