Abstract
PurposeComputed tomography perfusion (CTP) imaging in acute ischemic stroke (AIS) suffers from measurement errors due to image noise. The purpose of this study was to investigate if iterative reconstruction (IR) algorithms can be used to improve the diagnostic value of standard-dose CTP in AIS.MethodsTwenty-three patients with AIS underwent CTP with standardized protocol and dose. Raw data were reconstructed with filtered back projection (FBP) and IR with intensity levels 3, 4, 5. Image quality was objectively (quantitative perfusion values, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR)) and subjectively (overall image quality) assessed. Ischemic core and perfusion mismatch were visually rated. Discriminative power for tissue outcome prediction was determined by the area under the receiver operating characteristic curve (AUC) resulting from the overlap between follow-up infarct lesions and stepwise thresholded CTP maps.ResultsWith increasing levels of IR, objective image quality (SNR and CNR in white matter and gray matter, elimination of error voxels) and subjective image quality improved. Using IR, mean transit time (MTT) was higher in ischemic lesions, while there was no significant change of cerebral blood volume (CBV) and cerebral blood flow (CBF). Visual assessments of perfusion mismatch changed in 4 patients, while the ischemic core remained constant in all cases. Discriminative power for infarct prediction as represented by AUC was not significantly changed in CBV, but increased in CBF and MTT (mean (95% CI)): 0.72 (0.67–0.76) vs. 0.74 (0.70–0.78) and 0.65 (0.62–0.67) vs 0.67 (0.64–0.70).ConclusionIn acute stroke patients, IR improves objective and subjective image quality when applied to standard-dose CTP. This adds to the overall confidence of CTP in acute stroke triage.
Highlights
In acute stroke triage, computed tomography perfusion (CTP) imaging provides clinically relevant information about the infarct core and tissue at risk for treatment decisions [1]
Using iterative reconstruction (IR), mean transit time (MTT) was higher in ischemic lesions, while there was no significant change of cerebral blood volume (CBV) and cerebral blood flow (CBF)
Visual assessments of perfusion mismatch changed in 4 patients, while the ischemic core remained constant in all cases
Summary
In acute stroke triage, computed tomography perfusion (CTP) imaging provides clinically relevant information about the infarct core and tissue at risk for treatment decisions [1]. For detection of infarct core, CTP suffers from large measurement errors due to image noise compared to diffusion weighted magnetic resonance imaging [2]. Different perfusion processing algorithms and vendor specific software are known to produce different perfusion values with variable sensitivity and specificity to detect ischemia and infarct [3]. Combined with IR algorithms, the effectiveness of lowdose CTP was demonstrated in a clinical setting for a majority of acute stroke patients [5]. It has not been examined whether IR leads to better identification of ischemic tissue in standard-dose CTP, and how IR performs across different CTP processing algorithms to predict infarct
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