[The Measurement Precision and Accuracy of T1 Mapping Using Polarity Corrected (PC) TI Prep Tool].

The aim of this study was to evaluate the measurement precision and accuracy of T1 mapping using a polarity corrected (PC) TI prep tool, which was based on fast field echo (FFE) and obtained one data point with one inversion recovery (IR) pulse. A phantom was used consisting of eight materials with different Gd concentrations. T1 mappings were measured by changing the trigger interval and the inversion time (TI) interval. The T1 mapping measurement precision using the PC TI prep tool increased as the trigger interval was made longer. The measurement precision didn't depend on the interval of TI. On the other hand, when the trigger intervals are more than 1000 ms, the measurement accuracy was less than approximately 8%. By setting the optimal end of TI, the T1 mapping using a PC TI prep tool could measure the T1 value precisely and accurately.

[Evaluation of the accuracy of line spread function (LSF) and point spread function (PSF) measured in the computed tomography.].

We propose a method to estimate the accuracy of the line spread function (LSF) in computed tomography (CT). When we assume an object for scanning has a shape and CT-value in the x-y scan-plane that are constant in the z-direction perpendicular to the scan-plane, blurring in the image of the object is predicted with calculation by the LSF measured in the scanner. When using the precise LSF, the calculated image must agree well with the scanned image of the phantom corresponding to the object. Then, verification of LSF is performed by comparing the calculated image with the scanned image. We measured the LSF in our scanner, and scanned a cylindrical phantom with constant diameter and CT-value in which the direction of cylinder was parallel to the z-direction, as mentioned above. Images calculated by using the LSF corresponded well to scanned images, indicating the validity of the LSF. We obtained another LSF by an inappropriate manner, and calculated images using it. Those images showed an apparent difference with scanned images, indicating the inaccuracy of the LSF. Our technique is effective to evaluate the accuracy of LSF, PSF, and also modulation transfer function (MTF) derived from the LSF or PSF.