A Relative Noncontrast CT Map to Detect Early Ischemic Changes in Acute Stroke

Abstract

BACKGROUND AND PURPOSE Early ischemic changes on noncontrast computed tomography (NCCT) are often subtle. We developed a novel postprocessing technique that aids in detecting such changes. METHODS NCCT maps were generated that display the relative density difference between corresponding voxels in contralateral hemispheres (ratio maps of the NCCT [rNCCT]). Voxels with a relative density difference below .95 were designated as infarct. We pilot tested the rNCCT for infarct segmentation on 6 consecutive subjects enrolled in the CT Perfusion to predict Response in Ischemic Stroke Project (CRISP) study and applied the inclusion criteria of an adequate quality NCCT and successful endovascular reperfusion. rNCCT infarct segmentation was compared to baseline NCCT, baseline CTP, and day‐5 follow‐up fluid‐attenuated inversion recovery (FLAIR). RESULTS Five of the six selected cases met the inclusion criteria. Their median time from symptom onset to CT was 4.95 hours (standard deviation [SD], ±3.5; range, 1.05‐10.45), and median NIHSS was 13. Early ischemic changes were identified on the rNCCT in all five cases and on the standard NCCT in three of the five cases. Lesions outlined by the rNCCT maps trended toward a better estimation of the day‐5 FLAIR volume (median difference = 6.2 mL) than the ischemic core volumes assessed on baseline CTP (median difference = 51.7 mL) in the four cases with a day‐5 FLAIR (P = .1). CONCLUSION In this proof‐of‐concept study, the rNCCT appears promising for detecting and quantifying early ischemic changes. These findings should be confirmed in a larger cohort.

Quantification of infarct core signal using CT imaging in acute ischemic stroke

“…As such, there is a need for accurate infarct core determinations using more widely available imaging modalities including Non-Contrast CT (NCCT) and CT Angiography (CTA). This problem has been pursued with automated machine learning approaches ( Hokkinen et al, 2021 , Hornung et al, 2020 , Kuang et al, 2021 , Lo et al, 2019 , Peter et al, 2017 , Qiu et al, 2020 , Sheth et al, 2019 , Srivatsan et al, 2019 , Wu et al, 2019 , Zhang et al, 2018 ) and visual semiquantitative inspection (NCCT / CTA-ASPECTS score) ( Coutts et al, 2004 , Lee et al, 2020 ).…”

Semiautomated Detection of Early Infarct Signs on Noncontrast CT Improves Interrater Agreement

“…4 To aid in the interpretation of the NCCT, including Alberta Stroke Program Early CT Score and acute infarct segmentation, we developed an algorithm that visualizes regions of hypodensity compared with contralateral regions, termed relative NCCT (rNCCT). 5 The rNCCT maps are displayed as an overlay on the NCCT. The rNCCT values are not specific for acute stroke since regions of hypodensity also occur for reasons other than an acute stroke, such as imaging artifacts and chronic strokes.…”

Detecting brain lesions in suspected acute ischemic stroke with CT-based synthetic MRI using generative adversarial networks

“…Many studies on stroke image analysis have attempted to improve lesion visibility on CT, such as lesion-totissue contrast amplification (22,23), voxelwise comparison (16,17,24,25), and texture analysis (26)(27)(28)(29)(30). Despite heterogeneous methodologies and sensitivities (31), substantial evidence indicates that certain radiological features, even if they are subtle or invisible, could be captured to improve human perception of the underlying pathologies.…”

“…Comparatively, our method has strengths in design concept, bias and risk control, and knowledge preparation. First, most methods assist in formal interpretation as contrast amplifiers (22,23) or density searchers (24,25). Our model targets early detection but not final diagnosis and probably better serves nonexperts onsite than radiologists in-door.…”