Maekawa Tomoko, Hori Masaaki, Murata Katsutoshi, Feiweier Thorsten, Fukunaga Issei, Andica Christina, Hagiwara Akifumi, Kamagata Koji, Koshino Saori, Abe Osamu, Aoki Shigeki
Department of Radiology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.
Department of Radiology, Graduate School of Medicine and Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
Jpn J Radiol. 2018 Jul;36(7):415-420. doi: 10.1007/s11604-018-0737-0. Epub 2018 Apr 26.
Compared with the conventional pulsed gradient spin-echo (PGSE) sequence, diffusion-weighted imaging (DWI) with the oscillating gradient spin-echo (OGSE) sequence can shorten the diffusion time by changing the frequency. The purpose was to investigate whether n-alkanes are suitable as isotropic phantoms for estimating the diffusion coefficient with the OGSE sequence.
We investigated changes in the apparent diffusion coefficient (ADC) due to differences in the viscosities of nine n-alkane phantoms with different numbers of carbon atoms from CH to CH using OGSE and PGSE sequences at 21 °C. Effective diffusion times of 4.3, 5.1, 6.5, 9.3, 20, 40, and 60 ms were used. The T relaxation times of each n-alkane phantom were measured using quantitative synthetic magnetic resonance imaging (MRI). Circular regions of interest were placed manually within the alkane phantoms on ADC and T maps.
In each alkane phantom, changes in mean ADC values were almost constant with changes in diffusion times. Viscosities and ADC values showed inverse proportionality, as expected theoretically.
The ADC values of alkanes do not depend on diffusion times. The n-alkanes can be useful phantoms for assessing the accuracy of clinical protocols of DWI with the OGSE sequence.
与传统的脉冲梯度自旋回波（PGSE）序列相比，振荡梯度自旋回波（OGSE）序列的扩散加权成像（DWI）可通过改变频率来缩短扩散时间。本研究旨在探讨正构烷烃是否适合作为使用OGSE序列估算扩散系数的各向同性体模。
我们在21°C下，使用OGSE和PGSE序列研究了9种碳原子数从CH到CH的正构烷烃体模因粘度差异导致的表观扩散系数（ADC）变化。使用了4.3、5.1、6.5、9.3、20、40和60毫秒的有效扩散时间。使用定量合成磁共振成像（MRI）测量每个正构烷烃体模的T弛豫时间。在ADC和T图上手动在烷烃体模内放置圆形感兴趣区域。
在每个烷烃体模中，平均ADC值的变化随扩散时间的变化几乎保持恒定。正如理论预期，粘度和ADC值呈反比关系。
烷烃的ADC值不依赖于扩散时间。正构烷烃可作为有用的体模，用于评估使用OGSE序列的DWI临床方案的准确性。
