Implementation of the QRAPMASTER data analysis using dictionary matching and quantitative evaluation of the...

To clarify the magnetization transfer (MT) effect on T₁ and T₂ values obtained with the QRAPMASTER sequence.

A phantom consisting of MnCl₂ aqueous solution with various proton relaxation times and a chicken breast sample was imaged with the QRAPMASTER sequence and a multislice multiple spin-echo (MSMSE) sequence that was the basis of the QRAPMASTER sequence using a 1.5 T MRI system. T₁ values were calculated by data matching using the dictionary dataset created by a Bloch image simulation of the QRAPMASTER sequence. T₂ values were calculated by data matching using the dictionary dataset created by a Bloch image simulation of the MSMSE sequence. The MT effect on the images acquired with the QRAPMASTER and MSMSE sequences was calculated by numerically solving Bloch equations using a two-pool model.

The linearity and accuracy of the regression lines between the T₁ values measured by the QRAPMASTER sequence and those measured by the standard method excluding the T₁ values of the chicken breast sample was excellent (R = 0.9969-0.9986, slope = 1.0065-1.016) for consecutive four slices including the central slice. The linearity of the regression lines for the T₂ values of all samples was good (R = 0.963-0.985) for the four slices. The accuracy of the regression line was not good (slope = 0.674-0.758), which was mainly due to the effect of eddy currents. The large deviation of the T₁ values of the chicken breast sample from the regression line was semi-quantitatively reproduced by the Bloch simulation for the two-pool model.

This study demonstrated that the T₁ value of a biological sample obtained by the QRAPMASTER sequence was shortened by the MT effect.