PubMed Health⌕ Search

Biomedical subjects

Masaaki Shinohara

Publications and source records attributed to Masaaki Shinohara.

2 recordsLinked to original sources

Autoregressive moving average (ARMA) model applied to quantification of cerebral blood flow using dynamic susceptibility contrast-enhanced magnetic resonance imaging.

PURPOSE: To investigate the feasibility of the autoregressive moving average (ARMA) model for quantification of cerebral blood flow (CBF) with dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI) in comparison with deconvolution analysis based on singular value decomposition (DA-SVD). METHODS: Using computer simulations, we generated a time-dependent concentration of the contrast agent in the volume of interest (VOI) from the arterial input function (AIF) modeled as a gamma-variate function under various CBFs, cerebral blood volumes and signal-to-noise ratios (SNRs) for three different types of residue function (exponential, triangular, and box-shaped). We also considered the effects of delay and dispersion in AIF. The ARMA model and DA-SVD were used to estimate CBF values from the simulated concentration-time curves in the VOI and AIFs, and the estimated values were compared with the assumed values. RESULTS: We found that the CBF value estimated by the ARMA model was more sensitive to the SNR and the delay in AIF than that obtained by DA-SVD. Although the ARMA model considerably overestimated CBF at low SNRs, it estimated the CBF more accurately than did DA-SVD at high SNRs for the exponential or triangular residue function. CONCLUSION: We believe this study will contribute to an understanding of the usefulness and limitations of the ARMA model when applied to quantification of CBF with DSC-MRI.

Blood Flow Velocity↗

Quantitative mapping of cerebral deoxyhemoglobin content using MR imaging.

In this study, we present a magnetic resonance imaging (MRI) method for quantifying cerebral deoxyhemoglobin content that is based on a measurement of the reversible contribution (R'2) of the transverse relaxation rate under the assumption of a quantitative relationship between R'2 and deoxyhemoglobin content. A numerical simulation was performed assuming a specific pulse sequence conventionally employed for R'2 measurement. The results showed a near linear relationship between R'2 and deoxyhemoglobin content in the physiological range of oxygen extraction for almost all sized vessels, although a large diffusion effect for capillary sized vessels compromised the relationship. Concerning the methodology for R'2 measurement, a theoretical analysis showed that multiexponential transverse signal decay of brain parenchyma may result in a considerable underestimation or overestimation of R'2, if a conventional method is employed for R'2 quantification. A modified method for correcting the effect of multiexponential signal decay was employed for R'2 measurement of the brain in normal volunteers. The results showed a high level of agreement between the R'2 values measured in our study and those estimated from physiological parameters obtained using other modalities such as PET. In the context of BOLD contrast-based functional MRI, the method proposed provides a quantitative mapping of baseline cerebral deoxyhemoglobin content, which is the essential physiological parameter for calibrating the stimulation-induced BOLD signal change and mapping neuronal activity in a quantitative manner by functional MRI.

Adult↗