Identifying perfusion deficits on CT perfusion images using temporal similarity perfusion (TSP) mapping

Abstract

Objectives: Deconvolution-derived maps of CT perfusion (CTP) data may be confounded by transit delays. We propose temporal similarity perfusion (TSP) analysis to decrease CTP maps' dependence on transit times and investigate its sensitivity to detect perfusion deficits.

Methods: CTP data of acute stroke patients obtained within 9 h of symptom onset was analyzed using a delay-insensitive singular value decomposition method and with TSP. The TSP method applies an iterative process whereby a pixel's highest Pearson's R value is obtained through comparison of a pixel's time-shifted signal density time-series curve and the average whole brain signal density time-series curve. Our evaluation included a qualitative and quantitative rating of deconvolution maps (MTT, CBV, and TTP), of TSP maps, and of follow-up CT.

Results: Sixty-five patients (mean 68 (SD 13) years, 34 male) were included. A perfusion deficit was identified in 90%, 86%, 65%, and 84% of MTT, TTP, CBV, and TSP maps. The agreement of MTT, TTP, and TSP with CT follow-up was comparable but noticeably lower for CBV. CBV had the best relationship with final infarct volume (R² = 0.77, p < 0.001), followed by TSP (R² = 0.63, p < 0.001). Intra-rater agreement of an inexperienced reader was higher for TSP than for CBV/MTT maps (kappa's of 0.79-0.84 and 0.63-0.7). Inter-rater agreement for experienced readers was comparable across maps.

Conclusions: TSP maps are easier to interpret for inexperienced readers. Perfusion deficits detected by TSP are smaller which may suggest less dependence on transit delays although more investigation is required.

Key points: • Temporal similarity perfusion mapping assesses CTP data based on similarities in signal time-curves. • TSP maps are comparable in perfusion deficit detection to deconvolution maps. • TSP maps are easier to interpret for inexperienced readers.

Keywords: Brain ischemia; Humans; Perfusion; Stroke; Tomography, X-ray computed.

Fig. 1

CTP images and follow-up NCCT image of a 69-year-old male patient with a right MCA infarction. The patient arrived at the hospital with an NIHSS of 15 and was treated with IV-rTPA. Within the MCA territory, a perfusion deficit was visible at admission on both the conventional perfusion images (MTT, TTP, and CBV images) as well as the TSP

Fig. 2

MTT and TSP images of a 74-year-old male patient who was admitted to the hospital with an NIHSS of 13 and was treated with IV-rTPA. A perfusion deficit was visible posteriorly in the left hemisphere on the MTT images but not on the TSP images. CT follow-up did not demonstrate infarction

Fig. 3

Example images of a 56-year-old male patient with an infarction in both the right and left cerebellum on NC CT (follow-up) image. The patient had an NIHSS of 4 at admission and no treatment was given. The perfusion deficit in the right cerebellum is well visible on both the TSP, MTT, and TTP images but more subtle on the CBVimages. The area of infarction as seen on the NCCT in the left cerebellum shows only a very small perfusion lesion on the TSP, MTT, and TTP images but is not visible on the CBV images

Fig. 4

Images of a 50-year-old female patient who presented with an NIHSS of 12 at admission. The patient was treated with IA therapy. Infarction is seen within the right basal ganglia area on the NCCT (follow-up) images. The perfusion deficit as visualized on the TSP images is smaller than the area with increased transit time on the MTT and TTP images. No clear lesion is visible on the CBV images