Successfully reported this slideshow.

Stroke

482 views

Published on

perfusion imaging of stroke for early detection and selectiong appropriate patients for thrombolytic therapy

Published in: Health & Medicine
  • Be the first to comment

Stroke

  1. 1. Adila Iqbal R-3, NRD, SHL.
  2. 2. LEARNING OBJECTIVES  Brief review of vascular territories  Early CT and MR signs of infarction  How to identify patients with tissue at risk for guidance in selecting the appropriate therapy
  3. 3. Penumbra
  4. 4. Rai AT, Carpenter JS, Peykanu JA, Popovich T, Hobbs GR, Riggs JE. The role of CT perfusion imaging in acute stoke diagnosis: a large single- center experience. J Emerg Med 2008; 35:287–292
  5. 5. STANDARD WINDOW SETTING (W80 C 20) – SENSITIVITY 57% SPECIFICITY 100% STROKE WINDOW SETTING (W8 C 32) SENSITIVITY 71% SPECIFICITY 100%
  6. 6. Alberta Stroke Program Early CT Score (ASPECTS)  Proposed in 2001 as a means of quantitatively assessing acute ischemia on CT images.  MCA territory is divided into 10 regions, each of which accounts for one point in the total score. Silvennoinen HM, Hamberg LM, Lindsberg PJ, Valanne L, Hunter GJ. CT perfusion identifies increased salvage of tissue in patients receiving intravenous recombinant tissue plasminogen activator within 3 hours of stroke onset. Am J Neuroradiol 2008; 29:1118–1123
  7. 7. 10 regions of the MCA distribution, each of which accounts for one point in the ASPECTS system: M1, M2, M3, M4, M5, M6, the caudate nucleus (C), the lentiform nucleus (L), the internal capsule (IC), and the insular cortex (I). For each area involved in ischemia depicted at unenhanced CT, one point is subtracted from the total score of 10. Silvennoinen HM, Hamberg LM, Lindsberg PJ, Valanne L, Hunter GJ. CT perfusion identifies increased salvage of tissue in patients receiving intravenous recombinant tissue plasminogen activator within 3 hours of stroke onset. Am J Neuroradiol 2008; 29:1118–1123
  8. 8. Normal symmetric brain perfusion. All color maps are coded red for higher values and blue for lower values. PERFUSION CT BRAIN Healthy 53-year-old man Unenhanced CT scan Perfusion CT cerebral blood volume Perfusion CT cerebral blood flow Perfusion CT mean transit time
  9. 9. Perfusion CT maps cerebral blood volume CBV: Total volume of blood within an imaging voxel including blood in the tissues and blood vessels. CBV is measured in units of milliliters of blood per 100 g of brain. Hopyan J, Ciarallo A, Dowlatshahi D, et al. Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography. Radiology 2010; 255:142–153
  10. 10. Perfusion CT cerebral blood flow CBF: Total volume of blood moving through a voxel in a given unit of time and is commonly measured in units of milliliters of blood per 100 g of brain tissue per minute. After a bolus of contrast material is injected, time is required for each individual molecule of contrast material to circulate. Hopyan J, Ciarallo A, Dowlatshahi D, et al. Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography. Radiology 2010; 255:142–153
  11. 11.  MTT:  Average transit time of all the molecules of contrast medium with the bolus through a given volume of brain measured in seconds.  MTT can be approximated according to the central volume principle: MTT = CBV / CBF. Perfusion CT mean transit time Hopyan J, Ciarallo A, Dowlatshahi D, et al. Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography. Radiology 2010; 255:142–153
  12. 12. CBF maps show flow reduction in nearly the whole cortical territory of the left MCA. Temporal (B2), severe; parietal (B1), moderate to severe. Color code: red, blood vessels; green, normal cortex; blue, normal white matter; violet, low flow area). 61-year-old woman experienced acute right hemiplegia and global aphasia during coronary angiography. Hopyan J, Ciarallo A, Dowlatshahi D, et al. Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography. Radiology 2010; 255:142–153
  13. 13. TTP concentration of contrast enhancement maps show time delay in the cortical territory of the left MCA and artifact in areas where no peak is discernible. Color code: blue, segmented blood vessels, normal cortex; dark green, normal white matter; light green, yellow, and red, low flow area). 61-year-old woman experienced acute right hemiplegia and global aphasia during coronary angiography. Hopyan J, Ciarallo A, Dowlatshahi D, et al. Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography. Radiology 2010; 255:142–153
  14. 14. CT PERFUSION PROTOCOL  Arterial and venous regions of interest (ROIs) and pre- and postenhancement cutoff values are selected from the perfusion CT source images to generate representative arterial input and venous outflow time-attenuation curves.  The A2 segment of the anterior cerebral artery is commonly used to obtain the arterial input function (AIF) ROI because it travels perpendicular to the axial plane.  Similarly, the superior sagittal sinus can be used to obtain the venous output function (VOF) ROI. Murayama K, Katada K, Nakane M, et al. Whole brain perfusion CT performed with a prototype 256-detector row CT system: initial experience. Radiology 2009; 250:202–211
  15. 15. Figure 3b. Perfusion CT software. (a) CT scan with superimposed labels illustrates semiautomatic selection of arterial (ACA or contralateral MCA) and venous ROIs. (b) Graph illustrates time-attenuation curves for arterial (red) and venous (blue) ROIs. RadioGraphics, http://pubs.rsna.org/doi/abs/10.1148/rg.286085502 Published in: Enrique Marco de Lucas; Elena Sánchez; Agustín Gutiérrez; Andrés González Mandly; Eva Ruiz; Alejandro Fernández Flórez; Javier Izquierdo; Javier Arnáiz; Tatiana Piedra; Natalia Valle; Itziar Bañales; Fernando Quintana; RadioGraphics 2008, 28, 1673-1687. DOI: 10.1148/rg.286085502 © RSNA, 2008 One PowerPoint slide of each figure may be downloaded and used for educational, non-promotional purposes by an author for slide presentations only. The RSNA citation line must appear in at least 10-point type on all figures in all presentations. Pharmaceutical and Medical Education companies must request permission to download and use slides, and authors and/or publishing companies using the slides for new article creations for books or journals must apply for permission. For permission requests, please contact the publisher at permissions@rsna.org Perfusion CT software : Graph illustrates time-attenuation curves for arterial (red) and venous (blue) ROIs. Mathematical modeling can be then used to calculate perfusion parameters and generate color coded perfusion maps (deconvolution analysis)
  16. 16. CT PERFUSION INTERPRETATION Acute Infarction  Areas of decreased CBF and CBV, and increased MTT and TTP.  Matched perfusion abnormalities on CBV and MTT maps correspond to areas of nonsalvageable brain tissue and neuronal death, also known as “core infarct”.  Mismatched areas of prolonged MTT and diminished CBF where CBV is relatively preserved correspond to areas of salvageable tissue, also called “ischemic penumbra”. Murayama K, Katada K, Nakane M, et al. Whole brain perfusion CT performed with a prototype 256-detector row CT system: initial experience. Radiology 2009; 250:202–211
  17. 17. CT PERFUSION INTERPRETATION Acute Infarction  Because of compensatory cerebrovascular mechanisms, many patients are able to preserve CBV within an area at risk for ischemic injury shortly after the initial insult.  Patients with areas of CBV-MTT mismatch that are large or that involve eloquent areas of brain may be good candidates for reperfusion therapy.  CBF may also be decreased to a lesser degree within ischemic penumbra. Murayama K, Katada K, Nakane M, et al. Whole brain perfusion CT performed with a prototype 256-detector row CT system: initial experience. Radiology 2009; 250:202–211
  18. 18. Murayama K, Katada K, Nakane M, et al. Whole brain perfusion CT performed with a prototype 256-detector row CT system: initial experience. Radiology 2009; 250:202–211
  19. 19. Mean transit time reveals prolongation within same region (arrows) 51-year-old man who presented with right facial droop and acute aphasia. Cerebral blood flow reveals region of decreased perfusion within left middle cerebral artery (MCA) territory Cerebral blood volume shows relative symmetric maintenance of blood volume.
  20. 20. An example of applying the CT protocol to triage patients with acute ischemic stroke for endovascular therapy-mm clot on the coronal ultrathin noncontrasted CT (middle). Shang T , and Yavagal D R Neurology 2012;79:S86-S94 Copyright © 2012 by AAN Enterprises, Inc.
  21. 21. Acute stroke–induced cytotoxic edema in posterior, anterior and middle cerebral infarction
  22. 22. Any abnormality???
  23. 23. CLINICAL APPLICATION OF DWI  More sensitive for detection of hyperacute ischemia  becomes abnormal within 30 minutes  Distinguish b/w old and new stroke  DWI should always be used with ADC to assess AGE OF INFARCT
  24. 24. Pseudo-normalization of DWI in a 2 weeks old posterior infarction normal DWI. On T2WI there is some subtle hyperintensity in the right occipital lobe in the vascular territory of the posterior cerebral artery. The T1WI after the administration of Gadolinium shows gyral enhancement
  25. 25. Time course of an ischemic infarction
  26. 26. large area with restricted diffusion in the territory of the right MCA with involvement of the basal ganglia. There is a perfect match with the perfusion images, so this patient should not undergo any form of thrombolytic therapy
  27. 27. g Acute stroke (6 hours evolution) in a 46-year-old woman with left hemiplegia
  28. 28. Acute stroke (2 hours evolution) in a 46-year-old man with left hemiparesis.
  29. 29. SUMMARY The on-call radiologist has a key role in the management of acute stroke. A complete CT study (nonenhanced CT, perfusion CT, and CT angiography) may be performed and analyzed rapidly and easily by general radiologists using a simple standardized protocol. Hemorrhages should be ruled out at nonenhanced CT, but time should not be lost in puzzling over subtle early ischemic signs. Perfusion CT can delineate the salvageable brain tissue (mismatch), and CT angiography helps detect vessel occlusion and collateral flow.
  30. 30. What do you see here? What do you expect on CTA?
  31. 31. ?

×