The ADC value fluctuated when the b values used for calculation were higher than the fractional b value. Therefore, it is important to determine the fractional b value of the target tissue.

The diffusion weighted images (DWIs) are used widely in clinical practice. Recently, the gradient overplus imaging was developed in addition to orthogonal technique for the duration method of motion-probing gradient pulses. The gradient overplus technique can reduce the load of a gradient strength, and enables setting of the shortest TE compared with the orthogonal gradients, and moreover it has the information on diffusion tensor. The apparent diffusion coefficient (ADC) values, signal-to-noise ratio (SNR), and geometric distortion were compared for the two duration methods of DWI using four different phantoms of coefficient of viscosity. In the gradient overplus, the time of smallest TE became smaller than the orthogonal gradients according to the increase of the b value. As a result, SNR increased by shortening of TE, and thus the geometric distortion was improved. Moreover, the ADC value did not show any difference in the two duration methods of DWI. The gradient overplus technique is a more useful technique in a clinical study than the orthogonal gradients because the quality of image is improved, and the ADC value is the same as the orthogonal gradients.

Optimal b values should be considered when acquiring images for the derivation of computed DW images.

No abstract