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CT angiographic source images: flow- or volume-weighted?
1Department of Medical Imaging, University of Toronto, Sunnybrook Health Sciences Centre, Ontario, Canada.
Insights
CT angiography with iodine concentration (CTA-SI) in stroke patients is weighted by cerebral blood flow (CBF), not cerebral blood volume (CBV). This finding impacts how stroke imaging is interpreted.
Area of Science:
- Neuroimaging
- Radiology
- Stroke Imaging
Background:
- Cerebral blood volume (CBV) has been the assumed correlate of CT angiography with iodine concentration (CTA-SI).
- Modern multisection CT scanners may alter the weighting of CTA-SI.
Purpose of the Study:
- To investigate whether CTA-SI performed with modern CT scanners reflects cerebral blood flow (CBF) or CBV.
- To compare the correlation of CTA-SI with CBF and CBV.
Main Methods:
- Sixty-four anterior circulation stroke patients were analyzed.
- Defect volumes from CTA-SI, perfusion CT (PCCT), CBF, and CBV images were calculated by blinded readers.
- Spearman correlation and linear regression were used to analyze lesion volumes and identify outliers.
Main Results:
- CTA-SI showed a strong positive correlation with CBF (r = 0.89, P < .0001).
- CTA-SI had a weaker correlation with CBV (r = 0.5, P < .0001).
- Perfusion CT (PCCT) correlated strongly with CBV (r = 0.79, P < .0001) and less strongly with CBF (r = 0.52, P < .0001).
Conclusions:
- CTA-SI is predominantly CBF-weighted, not CBV-weighted.
- This suggests a shift in understanding CTA-SI's role in stroke assessment.
Background And Purpose:
CTA-SI have been previously reported to correlate with CBV. We hypothesized that CTA-SI performed by modern multisection CT scanners are CBF-, not CBV-weighted.
Materials And Methods:
Sixty-four consecutive patients with anterior circulation stroke symptoms were selected from a stroke data base between June 2007 and January 2009. Two independent blinded readers calculated defect volumes of CTA-SI and PCCT, CBF, and CBV images. Spearman correlation of lesion volumes was performed. Linear regression and residual analysis demonstrated factors associated with outliers for CTA or PCCT for CBF and CBV volumes.
Results:
We found a strong positive correlation between CTA with CBF (r = 0.89, P < .0001) and between PCCT and CBV (r = 0.79, P < .0001). CTA to CBV (r = 0.5, P < .0001) and PCCT to CBF (r = 0.52, P < .0001) correlations were weaker. Positive CTA outliers had lower ASPECTS (P = .01), larger baseline CTA (149 ± 46 cm(3) versus 83 ± 32 cm(3); P = .002, respectively), and final infarct (190 ± 100 cm(3) versus 80 ± 50 cm(3); P = .09, respectively) volumes than nonoutliers. No baseline features were significantly related to PCCT outliers. There was no difference in the vessel occlusion sites for positive or negative outliers for CTA or PCCT (P = .55 and P = 1.00, respectively).
Conclusions:
Our results indicate that CTA-SI are CBF- rather than CBV-weighted.
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