1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [69def1be-2fdd-48a7-86e0-ca00fddfe59f] => Array
        (
            [runtime-id] => 69def1be-2fdd-48a7-86e0-ca00fddfe59f
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [71a420c6-e89c-483f-abe3-6cc0ec68eed4] => Array
                        (
                            [runtime-id] => 71a420c6-e89c-483f-abe3-6cc0ec68eed4
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;78903f018fbc5f00dba16716c554b06ffc6c42d5
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [b32446ac-abf5-49b7-a08a-4a3c92ed1dae] => Array
        (
            [runtime-id] => b32446ac-abf5-49b7-a08a-4a3c92ed1dae
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [72a1bbae-a969-4cd2-8ff5-f4413cf564a7] => Array
                        (
                            [runtime-id] => 72a1bbae-a969-4cd2-8ff5-f4413cf564a7
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;78903f018fbc5f00dba16716c554b06ffc6c42d5
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [b32446ac-abf5-49b7-a08a-4a3c92ed1dae] => Array
        (
            [runtime-id] => b32446ac-abf5-49b7-a08a-4a3c92ed1dae
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [72a1bbae-a969-4cd2-8ff5-f4413cf564a7] => Array
                        (
                            [runtime-id] => 72a1bbae-a969-4cd2-8ff5-f4413cf564a7
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;78903f018fbc5f00dba16716c554b06ffc6c42d5
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [b32446ac-abf5-49b7-a08a-4a3c92ed1dae] => Array
        (
            [runtime-id] => b32446ac-abf5-49b7-a08a-4a3c92ed1dae
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [72a1bbae-a969-4cd2-8ff5-f4413cf564a7] => Array
                        (
                            [runtime-id] => 72a1bbae-a969-4cd2-8ff5-f4413cf564a7
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;78903f018fbc5f00dba16716c554b06ffc6c42d5
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [b32446ac-abf5-49b7-a08a-4a3c92ed1dae] => Array
        (
            [runtime-id] => b32446ac-abf5-49b7-a08a-4a3c92ed1dae
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [72a1bbae-a969-4cd2-8ff5-f4413cf564a7] => Array
                        (
                            [runtime-id] => 72a1bbae-a969-4cd2-8ff5-f4413cf564a7
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;78903f018fbc5f00dba16716c554b06ffc6c42d5
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [b32446ac-abf5-49b7-a08a-4a3c92ed1dae] => Array
        (
            [runtime-id] => b32446ac-abf5-49b7-a08a-4a3c92ed1dae
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => Controlled
            [privilege] => Array
                (
                    [72a1bbae-a969-4cd2-8ff5-f4413cf564a7] => Array
                        (
                            [runtime-id] => 72a1bbae-a969-4cd2-8ff5-f4413cf564a7
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;78903f018fbc5f00dba16716c554b06ffc6c42d5
                )

        )

)
1naresh2naresh
Array
(
    [urn:ac.highwire.org:guest:identity] => Array
        (
            [runtime-id] => urn:ac.highwire.org:guest:identity
            [type] => guest
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [urn:ac.highwire.org:guest:privilege] => Array
                        (
                            [runtime-id] => urn:ac.highwire.org:guest:privilege
                            [type] => privilege-set
                            [privilege-set] => GUEST
                        )

                )

            [credentials] => Array
                (
                    [method] => guest
                )

        )

    [773d300e-2b30-4321-8000-1110f9d8e330] => Array
        (
            [runtime-id] => 773d300e-2b30-4321-8000-1110f9d8e330
            [type] => toll-free-key
            [service-id] => ajnr-ac.highwire.org
            [access-type] => FreeToRead
            [privilege] => Array
                (
                    [8662c037-a097-4648-bd06-c977f765c6a7] => Array
                        (
                            [runtime-id] => 8662c037-a097-4648-bd06-c977f765c6a7
                            [type] => toll-free-key
                        )

                )

            [credentials] => Array
                (
                    [method] => toll-free-key
                    [value] => tf_ipsecsha;78903f018fbc5f00dba16716c554b06ffc6c42d5
                )

        )

)


  
    











    Reply | American Journal of Neuroradiology  
    


















    


























    
  
  




    
    

  

      


    

      

  
  
  

    

  

    

  

                
    

      

  

    

  
      
  
  

    


Advertisement



  



  


  
  



  



    

  


  


  


  
  
  
  
  
  

  	      



          


    
      

    
  
    
        
    

  

    
                        

  

                
    

      

  

    

  
      
  
  

    

  
  
      
ReplyLetter

  
      

  
      
Reply
  
    	
R. Aviv, T.Y. Lee and M. Sharma

  
    	
American Journal of Neuroradiology April 2012,  33 (4) E62; DOI: https://doi.org/10.3174/ajnr.A3051 

  
  
  



  


  
  



  
      
  
  

    
We thank Drs Pulli and Yoo for their interest in our results and their subsequent confirmation of our study findings.1 Our work highlighted the danger of extrapolating findings from previous-generation scanners to newer, faster scanners. In particular, before our publication, there was an established opinion that CTA-signal intensities (SIs) were CBV-weighted and could, in addition to providing vascular data, provide an estimate of infarct core. This observation was true for older-generation scanners and was likely due to the increased scanning time required to cover the region of interest. Slower scanning times allowed contrast to reach the blood vessels in the ischemic/infarct region associated with prolonged transit time.
With the advent of modern scanners, the observation is no longer true. The role of CTA, in our opinion, remains the delineation of vascular anatomy, including the site of occlusion and presence of collaterals. CTA protocols should be optimized for vascular, not parenchymal, imaging. Estimation of infarct volume on CTA-SI was useful when CTP was not widely available but should be relegated to the history books. CTP studies provide outstanding estimates of core and tissue at risk with the area under the curve associated with thresholded parameters approaching 0.90 for core determination.2 For those centers where CTP is unavailable, we have shown that a postcontrast CT (PCT) following CTA demonstrates hypoattenuation that closely estimates core. PCT can be obtained at a lower dose than CTP. We strongly favor CTP over a PCT approach and have previously shown that infarct can be more confidently and correctly diagnosed by using CTP than noncontrast CT or CTA source images.3
References
  1. 1.


    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
  2. 2.


    1. Bivard  A, 
    2. Spratt  N, 
    3. Levi  C, 
    4. et al
    . Perfusion computer tomography: imaging and clinical validation in acute ischaemic stroke. Brain 2011;134: 3408–16
  3. 3.


    1. Hopyan  J, 
    2. Ciarallo  A, 
    3. Dowlatshahi  D, 
    4. et al
    . Certainty of stroke diagnosis: incremental benefit with CT perfusion over noncontrast CT and CT angiography. Radiology 2010;255: 142–53
  


  
  



  



    

  



  

                
    

      

  

    

  
      
  
  

    


Advertisement