Published Online:https://doi.org/10.1148/radiol.11110896

CT angiography protocol changes designed to speed imaging and optimize arterial opacification are associated with significant overestimation on CT angiography source images of the region of restricted diffusion on concurrently obtained diffusion-weighted images, which may lead to inappropriate exclusion of patients who may benefit from treatment.

Purpose

To test whether the relationship between acute ischemic infarct size on concurrent computed tomographic (CT) angiography source images and diffusion-weighted (DW) magnetic resonance images is dependent on the parameters of CT angiography acquisition protocols.

Materials and Methods

This retrospective study had institutional review board approval, and all records were HIPAA compliant. Data in 100 patients with anterior-circulation acute ischemic stroke and large vessel occlusion who underwent concurrent CT angiography and DW imaging within 9 hours of symptom onset were analyzed. Measured areas of hyperintensity at acute DW imaging were used as the standard of reference for infarct size. Information regarding lesion volumes and CT angiography protocol parameters was collected for each patient. For analysis, patients were divided into two groups on the basis of CT angiography protocol differences (patients in group 1 were imaged with the older, slower protocol). Intermethod agreement for infarct size was evaluated by using the Wilcoxon signed rank test, as well as by using Spearman correlation and Bland-Altman analysis. Multivariate analysis was performed to identify predictors of marked (≥20%) overestimation of infarct size on CT angiography source images.

Results

In group 1 (n = 35), median hypoattenuation volumes on CT angiography source images were slightly underestimated compared with DW imaging hyperintensity volumes (33.0 vs 41.6 mL, P = .01; ratio = 0.83), with high correlation (ρ = 0.91). In group 2 (n = 65), median volume on CT angiography source images was much larger than that on DW images (94.8 vs 17.8 mL, P < .0001; ratio = 3.5), with poor correlation (ρ = 0.49). This overestimation on CT angiography source images would have inappropriately excluded from reperfusion therapy 44.4% or 90.3% of patients eligible according to DW imaging criteria on the basis of a 100-mL absolute threshold or a 20% or greater mismatch threshold, respectively. Atrial fibrillation and shorter time from contrast material injection to image acquisition were independent predictors of marked (≥20%) infarct size overestimation on CT angiography source images.

Conclusion

CT angiography protocol changes designed to speed imaging and optimize arterial opacification are associated with significant overestimation of infarct size on CT angiography source images.

© RSNA, 2011

Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11110896/-/DC1

References

  • 1 Chalela JA, Kidwell CS, Nentwich LM, et al.. Magnetic resonance imaging and computed tomography in emergency assessment of patients with suspected acute stroke: a prospective comparison. Lancet 2007;369(9558):293–298. Crossref, MedlineGoogle Scholar
  • 2 Latchaw RE, Alberts MJ, Lev MH, et al.. Recommendations for imaging of acute ischemic stroke: a scientific statement from the American Heart Association. Stroke 2009;40(11):3646–3678. Crossref, MedlineGoogle Scholar
  • 3 Schellinger PD, Bryan RN, Caplan LR, et al.. Evidence-based guideline: the role of diffusion and perfusion MRI for the diagnosis of acute ischemic stroke—report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Neurology 2010;75(2):177–185. Crossref, MedlineGoogle Scholar
  • 4 Hacke W, Albers G, Al-Rawi Y, et al.. The Desmoteplase in Acute Ischemic Stroke Trial (DIAS): a phase II MRI-based 9-hour window acute stroke thrombolysis trial with intravenous desmoteplase. Stroke 2005;36(1):66–73. Crossref, MedlineGoogle Scholar
  • 5 Furlan AJ, Eyding D, Albers GW, et al.. Dose Escalation of Desmoteplase for Acute Ischemic Stroke (DEDAS): evidence of safety and efficacy 3 to 9 hours after stroke onset. Stroke 2006;37(5):1227–1231. Crossref, MedlineGoogle Scholar
  • 6 Wintermark M, Meuli R, Browaeys P, et al.. Comparison of CT perfusion and angiography and MRI in selecting stroke patients for acute treatment. Neurology 2007;68(9):694–697. Crossref, MedlineGoogle Scholar
  • 7 Wintermark M, Flanders AE, Velthuis B, et al.. Perfusion-CT assessment of infarct core and penumbra: receiver operating characteristic curve analysis in 130 patients suspected of acute hemispheric stroke. Stroke 2006;37(4):979–985. Crossref, MedlineGoogle Scholar
  • 8 von Kummer R, Bourquain H, Bastianello S, et al.. Early prediction of irreversible brain damage after ischemic stroke at CT. Radiology 2001;219(1):95–100. LinkGoogle Scholar
  • 9 Camargo EC, Furie KL, Singhal AB, et al.. Acute brain infarct: detection and delineation with CT angiographic source images versus nonenhanced CT scans. Radiology 2007;244(2):541–548. LinkGoogle Scholar
  • 10 Schramm P, Schellinger PD, Fiebach JB, et al.. Comparison of CT and CT angiography source images with diffusion-weighted imaging in patients with acute stroke within 6 hours after onset. Stroke 2002;33(10):2426–2432. Crossref, MedlineGoogle Scholar
  • 11 Schramm P, Schellinger PD, Klotz E, et al.. Comparison of perfusion computed tomography and computed tomography angiography source images with perfusion-weighted imaging and diffusion-weighted imaging in patients with acute stroke of less than 6 hours’ duration. Stroke 2004;35(7):1652–1658. Crossref, MedlineGoogle Scholar
  • 12 Lev MH, Segal AZ, Farkas J, et al.. Utility of perfusion-weighted CT imaging in acute middle cerebral artery stroke treated with intra-arterial thrombolysis: prediction of final infarct volume and clinical outcome. Stroke 2001;32(9):2021–2028. Crossref, MedlineGoogle Scholar
  • 13 Hamberg LM, Hunter GJ, Kierstead D, Lo EH, Gilberto González R, Wolf GL. Measurement of cerebral blood volume with subtraction three-dimensional functional CT. AJNR Am J Neuroradiol 1996;17(10):1861–1869. MedlineGoogle Scholar
  • 14 Hunter GJ, Hamberg LM, Ponzo JA, et al.. Assessment of cerebral perfusion and arterial anatomy in hyperacute stroke with three-dimensional functional CT: early clinical results. AJNR Am J Neuroradiol 1998;19(1):29–37. MedlineGoogle Scholar
  • 15 Smith WS, Roberts HC, Chuang NA, et al.. Safety and feasibility of a CT protocol for acute stroke: combined CT, CT angiography, and CT perfusion imaging in 53 consecutive patients. AJNR Am J Neuroradiol 2003;24(4):688–690. MedlineGoogle Scholar
  • 16 Murphy BD, Fox AJ, Lee DH, et al.. Identification of penumbra and infarct in acute ischemic stroke using computed tomography perfusion-derived blood flow and blood volume measurements. Stroke 2006;37(7):1771–1777. Crossref, MedlineGoogle Scholar
  • 17 Konstas AA, Goldmakher GV, Lee TY, Lev MH. Theoretic basis and technical implementations of CT perfusion in acute ischemic stroke. I. Theoretic basis. AJNR Am J Neuroradiol 2009;30(4):662–668. Crossref, MedlineGoogle Scholar
  • 18 Sharma M, Fox AJ, Symons S, Jairath A, Aviv RI. CT angiographic source images: flow- or volume-weighted? AJNR Am J Neuroradiol 2011;32(2):359–364. Crossref, MedlineGoogle Scholar
  • 19 Albers GW, Thijs VN, Wechsler L, 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(5):508–517. Crossref, MedlineGoogle Scholar
  • 20 Schellinger PD, Thomalla G, Fiehler J, et al.. MRI-based and CT-based thrombolytic therapy in acute stroke within and beyond established time windows: an analysis of 1210 patients. Stroke 2007;38(10):2640–2645. Crossref, MedlineGoogle Scholar
  • 21 Köhrmann M, Jüttler E, Fiebach JB, et al.. MRI versus CT-based thrombolysis treatment within and beyond the 3 h time window after stroke onset: a cohort study. Lancet Neurol 2006;5(8):661–667. Crossref, MedlineGoogle Scholar
  • 22 Sanák D, Nosál’ V, Horák D, et al.. Impact of diffusion-weighted MRI-measured initial cerebral infarction volume on clinical outcome in acute stroke patients with middle cerebral artery occlusion treated by thrombolysis. Neuroradiology 2006;48(9):632–639. Crossref, MedlineGoogle Scholar
  • 23 Yoo AJ, Verduzco LA, Schaefer PW, Hirsch JA, Rabinov JD, González RG. MRI-based selection for intra-arterial stroke therapy: value of pretreatment diffusion-weighted imaging lesion volume in selecting patients with acute stroke who will benefit from early recanalization. Stroke 2009;40(6):2046–2054. Crossref, MedlineGoogle Scholar
  • 24 Yoo AJ, Barak ER, Copen WA, et al.. Combining acute diffusion-weighted imaging and mean transmit time lesion volumes with National Institutes of Health Stroke Scale Score improves the prediction of acute stroke outcome. Stroke 2010;41(8):1728–1735. Crossref, MedlineGoogle Scholar
  • 25 Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;1(8476):307–310. Crossref, MedlineGoogle Scholar
  • 26 Fiebach JB, Schellinger PD, Jansen O, et al.. CT and diffusion-weighted MR imaging in randomized order: diffusion-weighted imaging results in higher accuracy and lower interrater variability in the diagnosis of hyperacute ischemic stroke. Stroke 2002;33(9):2206–2210. Crossref, MedlineGoogle Scholar
  • 27 Luby M, Bykowski JL, Schellinger PD, Merino JG, Warach S. Intra- and interrater reliability of ischemic lesion volume measurements on diffusion-weighted, mean transit time and fluid-attenuated inversion recovery MRI. Stroke 2006;37(12):2951–2956. Crossref, MedlineGoogle Scholar
  • 28 Warach S. New imaging strategies for patient selection for thrombolytic and neuroprotective therapies. Neurology 2001;57(5,Suppl 2):S48–S52. Crossref, MedlineGoogle Scholar
  • 29 Wang Y, Liao X, Zhao X, et al.. Imaging-based thrombolysis trial in acute ischemic stroke-II (ITAIS-II). Int J Stroke 2009;4(1):49–53; discussion 49. Crossref, MedlineGoogle Scholar
  • 30 Imaging-based Thrombolysis trial in Acute Ischemic Stroke-II. ISRCTN#: 12033002. Stroke Trials Registry. Internet Stroke Center Web site. http://www.strokecenter.org/. Accessed April 30, 2011. Google Scholar
  • 31 Imaging-based Thrombolysis trial in Acute Ischemic Stroke-III. ISRCTN#: 03887874. Stroke Trials Registry. Internet Stroke Center Web site. http://www.strokecenter.org/. Accessed April 30, 2011. Google Scholar
  • 32 Bartlett ES, Walters TD, Symons SP, Fox AJ. Quantification of carotid stenosis on CT angiography. AJNR Am J Neuroradiol 2006;27(1):13–19. MedlineGoogle Scholar
  • 33 Wittkamp G, Buerke B, Dziewas R, et al.. Whole brain perfused blood volume CT: visualization of infarcted tissue compared to quantitative perfusion CT. Acad Radiol 2010;17(4):427–432. Crossref, MedlineGoogle Scholar
  • 34 Jovin TG, Yonas H, Gebel JM, et al.. The cortical ischemic core and not the consistently present penumbra is a determinant of clinical outcome in acute middle cerebral artery occlusion. Stroke 2003;34(10):2426–2433. Crossref, MedlineGoogle Scholar
  • 35 Kidwell CS, Saver JL, Starkman S, et al.. Late secondary ischemic injury in patients receiving intraarterial thrombolysis. Ann Neurol 2002;52(6):698–703. Crossref, MedlineGoogle Scholar
  • 36 Schaefer PW, Hassankhani A, Putman C, et al.. Characterization and evolution of diffusion MR imaging abnormalities in stroke patients undergoing intra-arterial thrombolysis. AJNR Am J Neuroradiol 2004;25(6):951–957. MedlineGoogle Scholar
  • 37 Fiehler J, Knudsen K, Kucinski T, et al.. Predictors of apparent diffusion coefficient normalization in stroke patients. Stroke 2004;35(2):514–519. Crossref, MedlineGoogle Scholar
  • 38 Kidwell CS, Saver JL, Mattiello J, et al.. Thrombolytic reversal of acute human cerebral ischemic injury shown by diffusion/perfusion magnetic resonance imaging. Ann Neurol 2000;47(4):462–469. Crossref, MedlineGoogle Scholar
  • 39 Chemmanam T, Campbell BC, Christensen S, et al.. Ischemic diffusion lesion reversal is uncommon and rarely alters perfusion-diffusion mismatch. Neurology 2010;75(12):1040–1047. Crossref, MedlineGoogle Scholar
  • 40 Chalela JA, Kang DW, Luby M, et al.. Early magnetic resonance imaging findings in patients receiving tissue plasminogen activator predict outcome: insights into the pathophysiology of acute stroke in the thrombolysis era. Ann Neurol 2004;55(1):105–112. Crossref, MedlineGoogle Scholar
  • 41 Neumann-Haefelin T, Kastrup A, de Crespigny A, et al.. Serial MRI after transient focal cerebral ischemia in rats: dynamics of tissue injury, blood-brain barrier damage, and edema formation. Stroke 2000;31(8):1965–1972; discussion 1972–1973. Crossref, MedlineGoogle Scholar
  • 42 Li F, Liu KF, Silva MD, et al.. Transient and permanent resolution of ischemic lesions on diffusion-weighted imaging after brief periods of focal ischemia in rats: correlation with histopathology. Stroke 2000;31(4):946–954. Crossref, MedlineGoogle Scholar
  • 43 Guadagno JV, Warburton EA, Jones PS, et al.. The diffusion-weighted lesion in acute stroke: heterogeneous patterns of flow/metabolism uncoupling as assessed by quantitative positron emission tomography. Cerebrovasc Dis 2005;19(4):239–246. Crossref, MedlineGoogle Scholar
  • 44 Guadagno JV, Warburton EA, Jones PS, et al.. How affected is oxygen metabolism in DWI lesions? a combined acute stroke PET-MR study. Neurology 2006;67(5):824–829. Crossref, MedlineGoogle Scholar
  • 45 Kohno K, Hoehn-Berlage M, Mies G, Back T, Hossmann KA. Relationship between diffusion-weighted MR images, cerebral blood flow, and energy state in experimental brain infarction. Magn Reson Imaging 1995;13(1):73–80. Crossref, MedlineGoogle Scholar
  • 46 Busza AL, Allen KL, King MD, van Bruggen N, Williams SR, Gadian DG. Diffusion-weighted imaging studies of cerebral ischemia in gerbils: potential relevance to energy failure. Stroke 1992;23(11):1602–1612. Crossref, MedlineGoogle Scholar
  • 47 Lin W, Lee JM, Lee YZ, Vo KD, Pilgram T, Hsu CY. Temporal relationship between apparent diffusion coefficient and absolute measurements of cerebral blood flow in acute stroke patients. Stroke 2003;34(1):64–70. Crossref, MedlineGoogle Scholar
  • 48 Sobesky J, Zaro Weber O, Lehnhardt FG, et al.. Does the mismatch match the penumbra? magnetic resonance imaging and positron emission tomography in early ischemic stroke. Stroke 2005;36(5):980–985. Crossref, MedlineGoogle Scholar
  • 49 Frykholm P, Andersson JL, Valtysson J, et al.. A metabolic threshold of irreversible ischemia demonstrated by PET in a middle cerebral artery occlusion-reperfusion primate model. Acta Neurol Scand 2000;102(1):18–26. Crossref, MedlineGoogle Scholar
  • 50 Powers WJ, Grubb RL, Darriet D, Raichle ME. Cerebral blood flow and cerebral metabolic rate of oxygen requirements for cerebral function and viability in humans. J Cereb Blood Flow Metab 1985;5(4):600–608. Crossref, MedlineGoogle Scholar
  • 51 de Ipolyi AR, Wu O, Schaefer PW, et al.. Cerebral blood volume measurements in acute ischemic stroke are technique-dependent and cannot substitute for DW imaging. Boston, Mass: American Society of Neuroradiology, 2010. Google Scholar
  • 52 Heiss WD, Sobesky J, Smekal U, et al.. Probability of cortical infarction predicted by flumazenil binding and diffusion-weighted imaging signal intensity: a comparative positron emission tomography/magnetic resonance imaging study in early ischemic stroke. Stroke 2004;35(8):1892–1898. Crossref, MedlineGoogle Scholar
  • 53 Heiss WD, Grond M, Thiel A, et al.. Permanent cortical damage detected by flumazenil positron emission tomography in acute stroke. Stroke 1998;29(2):454–461. Crossref, MedlineGoogle Scholar
  • 54 Hermier M, Nighoghossian N, Adeleine P, et al.. Early magnetic resonance imaging prediction of arterial recanalization and late infarct volume in acute carotid artery stroke. J Cereb Blood Flow Metab 2003;23(2):240–248. Crossref, MedlineGoogle Scholar
  • 55 Copen WA, Rezai Gharai L, Barak ER, et al.. Existence of the diffusion-perfusion mismatch within 24 hours after onset of acute stroke: dependence on proximal arterial occlusion. Radiology 2009;250(3):878–886. LinkGoogle Scholar
  • 56 Bhatia R, Hill MD, Shobha N, et al.. Low rates of acute recanalization with intravenous recombinant tissue plasminogen activator in ischemic stroke: real-world experience and a call for action. Stroke 2010;41(10):2254–2258. Crossref, MedlineGoogle Scholar

Article History

Received May 2, 2011; revision requested June 1; revision received July 27; accepted August 11; final version accepted August 30. A.J.Y.
Published online: Feb 2012
Published in print: Feb 2012