Potential of transcranial ultrasound- and near-infrared spectroscopy-based acute stroke imaging for decision-making on intravenous thrombolysis treatment

Abstract

Background: Mobile Stroke Units (MSU) shorten time to intravenous thrombolysis (IVT) and improve functional outcome, but they rely on computed tomography (CT) making them highly specialized and costly. Alternative technologies can potentially identify imaging-based IVT contraindications like intracranial hemorrhage (ICH) or malignancies (IM), e.g., by transcranial color-coded sonography (TCCS) and near-infrared spectroscopy (NIRS).

Methods: Using a simulation approach, we analyzed magnetic resonance imaging (MRI) scans of stroke-suspected patients within 4.5 h of symptom onset to assess TCCS and NIRS for identifying imaging-based IVT contraindications. Our study included both primary and sensitivity analyses, each employing conservative and optimistic scenarios. The primary analysis integrated clinical information from the emergency department, while the sensitivity analysis evaluated overall performance across all patients, regardless of clinical information. The conservative scenario defined TCCS detecting acute deep-brain hemorrhages or tumors >20 mm from scalp surface or > 10 mL in volume or causing >4 mm midline-shift, while NIRS was defined detecting them <20 mm from scalp surface with a volume > 3.5 mL. The optimistic scenario defined TCCS detecting intracranial or subarachnoid acute/subacute hematoma or tumors >20 mm from scalp surface or > 5 mL in volume or causing >2 mm midline-shift, while NIRS was defined detecting them <35 mm from the scalp surface with volume > 3.5 mL.

Results: We assessed 1,089 consecutive patients undergoing acute MRI, identifying 69 with imaging-based IVT contraindications, of which 40 had additional non-imaging contraindications. In the primary analysis, among those 29 patients without non-imaging-based contraindications, TCCS/NIRS would have detected 15 of 25 ICH and 3 of 4 malignant tumors in the conservative scenario. In the optimistic scenario, 18 of 25 ICH and all malignant tumors would have been detected. In the sensitivity analyses, the conservative scenario would have detected 30 of 52 ICH and 8 of 17 malignant tumors, while the optimistic scenario would have identified 37 of 52 ICH and 12 of 17 malignant tumors.

Conclusion: While TCCS and NIRS technologies exhibit potential for identifying IVT contraindications in pre-hospital settings, comprehensive evaluation in real-world scenarios is imperative to ascertain their operational constraints.

Keywords: MRI; NIRS (near infrared spectroscopy); TCCS; intracranial haematoma; intravenous thrombolysis; stroke.

Figure 1

Participant enrollment.

Figure 2

The heatmaps visualize the spatial distribution of all 25 ICH and 4 IM across different sections of the brain in the primary population. The color scale represents lesion frequency, with brighter colors indicating higher densities. The highest concentrations are observed in the deep basal ganglia, parietal lobes, and parieto-occipital regions. These heatmaps provide insights into the lesion locations, helping to understand their spatial distribution within the studied cohort.

Figure 3

This figure extends the analysis from Figure 2 to the total population. The distribution patterns remain similar but reflects the larger dataset including all 52 ICH and 17 IM.

Figure 4

The heatmaps displays the spatial distribution of undetected ICH and IM in the primary population that were not detected by TCCS and NIRS in the conservative scenario. One brain tumor was undetected, located in the left temporal lobe, while all other lesions are ICH smaller than 10 mL. Additionally, two ICH are located in the pons and right cerebellar region.

Figure 5

Similar to Figure 4, this figure presents the undetected ICH under the primary population for the optimistic scenario.