Effect of concentration of contrast agent on the inflow effect for measuring absolute perfusion by use of inversion recovery T₁-weighted TurboFLASH images.

Previous studies have shown that the organ blood flow (OBF) calculated from the T₁-weighted MRI technique was lower than expected. The inflow correction was one of the main corrections for measuring the absolute OBF. Our aim in this study was to investigate the influence of the contrast agent concentration on inflow effect on signal intensity (SI) and to find the gradient of different flow rates at different concentrations by use of inversion recovery T₁-weighted turbo fast low angle shot (TurboFLASH) MRI images. We performed these studies at six different concentrations of gadolinium-diethylenetriamine-pantaacetic acid (Gd-DTPA) to find the inflow effect on the SI. A flow phantom made of Perspex was designed that produced four different flow rates at the same time. The non-uniformity of the clinical head and neck coil was measured and applied to the SI for measuring the corrected SI. The corrected SI was measured at different flow rates and concentrations. The results indicated that an increase in the flow rate and in the concentration of the contrast agent was associated with an increase in the gradient of the flow rate. The results also indicated that the inflow correction could be ignored when the concentration was low for measurement of the absolute OBF. At high concentrations, the inflow effect should be considered in calculations of the absolute OBF.