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    CT Angiography Source Images with Modern Multisection CT Scanners: Delay Time from Contrast Injection to Imaging Determines Correlation with Infarct Core | American Journal of Neuroradiology  
    


















    


























    
  
  




    
    

  

      


    

      

  
  
  

    

  

    

  

                
    

      

  

    

  
      
  
  

    


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CT Angiography Source Images with Modern Multisection CT Scanners: Delay Time from Contrast Injection to Imaging Determines Correlation with Infarct Core
  
    	
B. Pulli and A.J. Yoo

  
    	
American Journal of Neuroradiology April 2012,  33 (4) E61; DOI: https://doi.org/10.3174/ajnr.A3039 

  
  
  



  


  
  



  
      
  
  

    
We have read with great interest the letter by Dr Kloska1 and a subsequent reply2 concerning a study by Sharma et al,3 investigating the perfusion imaging correlate of CTA source image (CTA-SI) lesions and would like to share our own data on this subject. On the basis of our findings, we agree with Dr Kloska that evaluation of acute ischemia with CTA-SI on state-of-the-art multisection CT scanners depends primarily on the imaging protocol.
In a recent investigation at our institution,4 we analyzed 100 patients with acute ischemic stroke who underwent CTA-SI by using 2 different acquisition protocols with close follow-up DWI. We correlated CTA-SI hypoattenuation volumes with concurrent DWI hyperintense volumes and found that with the older protocol designed for a 4- or 16-section CT scanner (Table), CTA-SI volume correlated well with DWI volume. When a 64-section scanner was installed at our medical center, we modified our CTA acquisition protocol to improve arterial phase opacification (Table), and this was associated with significant overestimation of concurrent DWI volumes. Analysis of the CTA protocol parameters revealed that a shorter time from contrast injection to imaging of the ischemic territory was the single best predictor of CTA-SI overestimation of the infarct core on DWI. Imaging too soon likely prevented the contrast from traversing the collaterals and reaching the infarct bed. Most interesting, atrial fibrillation was associated with CTA-SI overestimation with the older protocol, which used a fixed delay, presumably related to delayed contrast-arrival time from reduced cardiac output.
View this table:
Overview of CTA protocols used in previous CTA-SI studies of acute stroke
Given these data, we conclude that CTA-SI, just like CT perfusion, requires protocol validation before being used to assess acute infarct size in clinical practice. Moreover, protocol parameters should be standardized. The Table illustrates the variable parameters that have been used in studies evaluating CTA-SI for acute ischemic stroke. Until these issues are fully addressed, CTA-SI should be used cautiously to inform treatment decisions in patients with acute ischemic stroke.
References
  1. 1.


    1. Kloska  SP
    . CT angiographic source images with modern multisection CT scanners: appropriate injection protocol is crucial. AJNR Am J Neuroradiol 2011;32: E93

  2. 2.


    1. Aviv  RI, 
    2. Sharma  M, 
    3. Lee  TJ
    . Reply. AJNR Am J Neuroradiol 2011;32: E94

  3. 3.


    1. Sharma  M, 
    2. Fox  AJ, 
    3. Symons  S, 
    4. et al
    . CT angiographic source images: flow- or volume-weighted?
AJNR Am J Neuroradiol 2011;32: 359–64
  4. 4.


    1. Pulli  B, 
    2. Schaefer  PW, 
    3. Hakimelahi  R, 
    4. et al
    . Acute ischemic stroke: infarct core estimation on CT angiography source images depends on CT angiography protocol. Radiology 2012;262: 593–604
  5. 5.


    1. Schramm  P, 
    2. Schellinger  PD, 
    3. Fiebach  JB, 
    4. 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: 2426–32
  6. 6.


    1. Schramm  P, 
    2. Schellinger  PD, 
    3. Klotz  E, 
    4. 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: 1652–58
  7. 7.


    1. Wittkamp  G, 
    2. Buerke  B, 
    3. Dziewas  R, 
    4. et al
    . Whole brain perfused blood volume CT: visualization of infarcted tissue compared to quantitative perfusion CT. Acad Radiol 2010;17: 427–32
  


  
  



  



    

  



  

                
    

      

  

    

  
      
  
  

    


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