THE ROLE OF TIME TO MAXIMUM PARAMETER IN THE QUANTIFICATION OF THE ISCHEMIC PENUMBRA FOR DSC-MRI IMAGING

Background: The time to maximum of the tissue residue function (Tmax) is commonly used parameter to determine hypoperfused cerebral parenchyma .However, the post-processing software to calculate Tmax is problematic since it is optional, expensive and requires a powerful workstation.

Methods: The purpose of this study was to present the development of a perfusion imaging analysis workflow that creates reliable and reproducible Tmax maps. The quantification procedure begins by estimating the perfusion signal from the data provided by the MRI system. The curve is then converted into a concentration curve. The next step is the determination of the Arterial Input Function (AIF) by an automatic method followed by deconvolution using the Singular Value Decomposition (SVD). Finally, we calculated the parameter Tmax and generated the mapping of this parameter by applying thresholds.

The clinical utility was tested in healthy subjects, in patients with confirmed brain infarction and two patients with no mismatch. Performance of the Tmax parameter was also assessed by comparison with the usual semi-quantitative analysis (time-to-peak (TTP) parameter).

Results and Conclusion: The obtained results show that the Tmax map offers a rapid and accurate estimation of the hypoperfused cerebral parenchyma. It provides a much better solution with clearer edges and more detailed information achieved by the TTP parameter.