Improving the Reliability and Accessibility of CT Perfusion Imaging in Acute Ischemic Stroke
Abstract
CT perfusion (CTP) imaging is a validated treatment decision support tool in acute ischemic stroke. Automated analysis of CTP cerebral blood flow (CBF) and Tmax maps produces estimates of ischemic core and penumbra volumes used to determine target mismatch profiles for treatment. However, availability and utilization of CTP is low due to diagnostic variability between CTP software and technical, logistical, and radiation dose considerations that may limit its routine adoption. The objective of this doctoral research was to improve the reliability and accessibility of CTP by (1) improving diagnostic agreement between CTP software, (2) enabling perfusion imaging with standard acute stroke CT studies, and (3) reducing CTP radiation dose.
Mismatch profiles may disagree between software due to different optimal stroke lesion thresholds. In Chapter 2, CTP thresholds were calibrated between software by quantifying the accuracy of each CTP software using simulated CTP data. With threshold calibration, mismatch profiles determined between three CTP software had 95% agreement. The proposed method may help systematically improve diagnostic agreement between CTP software.
Resource-limited hospitals may not have the capacity for routine CTP due to technical and logistical challenges. Non-contrast CT and multiphase CT angiography (mCTA) are widely available standard CT studies that together form a low temporal resolution CTP study. In Chapter 3, we demonstrated that mismatch profiles determined from mCTA perfusion maps had 82% concordance with that of standard CTP. Diagnostic agreement may improve with better optimized non-contrast CT and mCTA scan protocols. Our proposed technique may be a practical alternative to CTP when it is unavailable.
Sparse-view CT can reduce radiation dose by acquiring fewer x-ray projections but at the expense of streaking artifacts in the reconstructed image. In Chapter 4, we demonstrated that CTP is relatively insensitive to streaking artifacts and that radiation dose could be reduced by 50 to 66% compared to routine levels with sparse-view CTP. Low-dose CTP may improve the routine adoption of this useful diagnostic tool.
CTP plays an important role in the selecting patients with acute ischemic stroke for reperfusion treatment. The proposed improvements to CTP may allow wider adoption of this validated decision support tool.