Is it possible to define salvageable ischemic penumbra using semiquantitative rCBF levels derived from MR perfusion-weighted imaging?

Predictive value of perfusion weighted imaging for early new lesions after stroke patients receive endovascular treatment

Background

Previous studies have focused on early new lesion-associated factors, but the differences in the perfusion status between the at-risk hypoperfusion areas with new lesions and the other hypoperfusion areas in stroke patients before thrombectomy is not clear. We investigated the value of perfusion-weighted imaging (PWI) in predicting early new lesions in patients after stroke.

Methods

Fifty-five acute stroke patients who underwent diffusion-weighted imaging (DWI) and PWI before and after thrombectomy within 24 h were eligible. The PWI parameters of the core infarct areas (high signal tissue on the DWI), the at-risk hypoperfusion areas (hypoperfusion area with new lesions at follow-up PWI) and the other hypoperfusion areas of patients with new lesions were collected. Statistical analysis was performed to predict new lesions after stroke. The differences in the PWI parameters of the core infarct areas, the at-risk hypoperfusion areas and the other hypoperfusion areas were compared. Receiver operating characteristic (ROC) curve analysis was used to assess the predictive value of the PWI parameters (P<0.05) for the occurrence of new lesions in patients with acute stroke after thrombectomy.

Results

Fifty-five stroke patients were analyzed, including forty patients (72.73%) with new lesions and fifteen patients (27.27%) without new lesions. Acute stroke patients with new lesions had a longer mean transit time (MTT) and time to peak (TTP) in the at-risk hypoperfusion areas (11.95±3.29; 38.30±11.39) than in the other hypoperfusion areas (8.68±2.08; 29.76±6.86), both of which were significantly different (P<0.0001; P<0.0001, respectively). The ROC analysis showed that the sensitivity and specificity of MTT for predicting the occurrence of new lesions after stroke were 70.00% and 87.50%, respectively; the sensitivity and specificity of TTP were 70.00% and 80.00%, respectively.

Conclusions

MTT and TTP may be useful in predicting early new lesions in acute stroke patients after thrombectomy.

(18)F-fluoromisonidazole (FMISO) Positron Emission Tomography (PET) Predicts Early Infarct Growth in Patients with Acute Ischemic Stroke

BACKGROUND AND PURPOSE

(18) F-fluoromisonidazole (FMISO) positron emission tomography (PET) is used to image metabolically compromised but viable hypoxic tissue. We hypothesized that FMISO PET might predict early infarct growth in acute ischemic stroke patients with perfusion-diffusion mismatch in magnetic resonance imaging (MRI).

METHODS

We prospectively enrolled acute ischemic stroke patients who visited the emergency room within 48 hours after stroke onset and had perfusion-diffusion mismatch (>20%), as shown MRI. Infarct growth was defined as >20% increase of initial infarct volume or >5 mL in follow-up diffusion-weighted image 5 ± 2 days after stroke. The association between FMISO uptake and infarct growth was explored.

RESULTS

Of 19 enrolled patients, 10 (52.6%) showed increased FMISO uptake, with 8 of the latter showing infarct growth. None of the 9 patients who did not show FMISO uptake had infarct growth. FMISO uptake was significantly associated with infarct growth (Fisher's exact test; P < .01). FMISO PET scan had a sensitivity of 100% and a specificity of 82% (AUC = .909) in predicting infarct growth.

CONCLUSIONS

FMISO PET scan can predict early infarct growth in acute ischemic stroke patients with perfusion-diffusion mismatch in MRI.

Estimation of the ischemic penumbra based on CT perfusion a pilot study

RATIONALE AND OBJECTIVES

Ischemic penumbra (IP), the target of thrombolytic therapies, could be estimated by the mismatch region between magnetic resonance imaging (MRI) diffusion- and perfusion-defined abnormalities; however, the accuracy of this method has been challenged recently. In this study, we try to establish a method for calculating IP size based on computed tomography perfusion (CTP) and to observe the early evolution of IP in detail.

MATERIALS AND METHODS

The middle cerebral artery occlusion (MCAO) model in monkey was used to compare the accuracy in estimating the IP between CTP and MRI methods. A receiver operating characteristic (ROC) curve was performed to calculate the IP threshold of the different CTP parameters, and then the best parameter was obtained. The dynamic evolutions of estimated size of IP by these two methods were compared.

RESULTS

Among the three CTP parameters, relative cerebral blood flow (rCBF) had the highest sensitivity (83.3%) and specificity (98.5%) in estimating the IP. The optimal cutoff threshold of rCBF was 0.203. During the first 15 hours of the MCAO model, the estimated size of IP by the rCBF was larger than that of the MRI method; however, this relationship was reversed 15 hours later.

CONCLUSION

This study suggests that the rCBF method is more accurate in estimating the IP since previous studies have reported that the MRI method underestimated the exact IP in the early stage of ischemia and overestimated the exact IP in the later stages. Further experimental and clinical studies are needed to validate the conclusion.