Synopsis

Keywords: Stroke, Ischemia, T2 Star

Multiple parametric (MTP) is a novel quantitative MRI technique that allows the generation of quantitative maps as well as synthetic weightings from a single acquisition. Preliminary results show that MTP synthetic sequence can effectively distinguish infarcted brain from normal tissue with a good diagnostic performance. MTP imaging offers the potential to create a standardized brain imaging protocol providing multiple types of quantitative tissue property information and qualitative information in just a few minutes. The aim of this study is to evaluate the potential of MTP in the mapping-based identification of acute ischemic stroke.

Introduction

Acute ischemic stroke is the most common serious manifestation of cerebrovascular disease and a major cause of severe disability¹. A patient presenting with acute onset of a focal neurologic deficit should undergo a rapid, focused history and examination. However, fast imaging or high-resolution achievement often lead to great noise artifacts in reconstructed magnetic resonance images, which interfere with subsequent clinical diagnosis. Additionally, conventional MR imaging does not include quantitative assessment for the prohibitively long acquisition time in most cases. MTP synthetic sequence allows rapid simultaneous quantification of multiple tissue characteristics, including T1, T2 Star, R2 star, proton density (PD), and quantitative susceptibility mapping (QSM) with one acquisition². This study was conducted to investigate the value of MTP in the diagnosis of acute cerebral infarction.

Methods

Twenty patients with acute or subacute cerebral MCA infarction were scanned by conventional MR imaging as well as MTP. The clinical base data of all patients were recorded including National Institute of Health Stroke Scale (NIHSS) score on admission. To quantify MTP-derived T1, PD, R2 Star, T2 Star and QSM values in ischemic lesion, ROIs were manually drawn to outline the lesions on the infarct core (IC) and mirror area. The ratio of the quantitative parameters between the lesion and the contralateral normal tissue were calculated. Statistical analysis of the obtained T1, PD, R2 Star, T2 Star and QSM values between lesions and contralateral side were compared by the independent sample t-test or Mann-Whitney U test. Receiver operating characteristic (ROC) curves, wherein areas under the curves (AUCs) and 95% confidence intervals were calculated to compare the discriminatory power of quantitative parameters of MTP for predicting infarction. Spearman correlation analysis were separately used to analyze the relationships between the NIHSS score and the ratio of MTP quantitative parameters.

Results

A total of 20 patients (age 68.60±13.96, 70% men) were analyzed and divided into lesion group and contralateral group. The value of ADC and R2 Star of ischemic lesion area were significantly lower than those of the mirror area of the opposite healthy side, while the value of T1 Map and T2 Star was higher in lesion group (p<0.05). There were no differences in the value of PD Map and QSM between lesion group and contralateral group (Table 1, Figure 1). The AUC of the MTP-derived ADC, T1 Map, PD Map, R2 Star, T2 Star to predict acute ischemic stroke was 0.95, 0.69, 0.67, 0.81, 0.83, respectively (p < 0.05, Figure 2). Among these parameters, ADC and T2 Star have produced best performances, while the difference of QSM values did not reach statistical significance (p >0.05). NIHSS score on admission was negatively correlated with the rADC (R=0.-0.50, p=0.02, Figure 3), but other quantitative ratios have no correlation with NIHSS score (p >0.05).

Discussion

One major thrust in radiology today is image standardization with a focus on rapidly acquired quantitative multi-contrast information. This is critical for multi-center trials, for the collection of big data and for the use of artificial intelligence in evaluating the data³. MTP offers multiple sets of qualitative images and parametric maps with high SNR, quantitative accuracy, and acquisition/reconstruction efficiency. SWI and QSM have great application value in the diagnosis of cerebral micro hemorrhage⁴, however, these approaches are relatively time-consuming. T2 Map has been assessed in acute stroke in a previous study focused on ischemic lesion with a known time of symptom onset⁵. This study also confirmed that T2 Map can effectively distinguish infarction areas and is very sensitive to brain edema. MTP is capable of achieving a better balanced performance on imaging efficiency, resolution and SNR, these advantages are very useful for patients with acute cerebral infarction.

Conclusion

The application of MTP synthetic sequence can shorten the examination time of patients and obtain routine and quantitative MRI images. MTP synthetic sequence can effectively distinguish infarcted brain tissue from normal tissue with a good diagnostic performance.

Acknowledgements

No acknowledgement found.

References

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