Liu Yi-Jui, Lee Yi-Hsiung, Chang Hing-Chiu, Huang Teng-Yi, Chiu Hui-Chu, Wang Chih-Wei, Chiou Ta-Wei, Hsu Kang, Juan Chun-Jung, Huang Guo-Shu, Hsu Hsian-He
Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan, Republic of China.
Ph.D. program in Electrical and Communication Engineering in Feng Chia University, Taichung, Taiwan, Republic of China; Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, Republic of China.
PLoS One. 2015 Apr 29;10(4):e0124118. doi: 10.1371/journal.pone.0124118. eCollection 2015.
To investigate transient signal loss on diffusion weighted images (DWI) and overestimation of apparent diffusion coefficient (ADC) in parotid glands using single shot echoplanar DWI (EPDWI).
This study enrolled 6 healthy subjects and 7 patients receiving radiotherapy. All participants received dynamic EPDWI with a total of 8 repetitions. Imaging quality of DWI was evaluated. Probability of severe overestimation of ADC (soADC), defined by an ADC ratio more than 1.2, was calculated. Error on T2WI, DWI, and ADC was computed. Statistical analysis included paired Student t testing and Mann-Whitney U test. A P value less than 0.05 was considered statistically significant.
Transient signal loss was visually detected on some excitations of DWI but not on T2WI or mean DWI. soADC occurred randomly among 8 excitations and 3 directions of diffusion encoding gradients. Probability of soADC was significantly higher in radiotherapy group (42.86%) than in healthy group (24.39%). The mean error percentage decreased as the number of excitations increased on all images, and, it was smallest on T2WI, followed by DWI and ADC in an increasing order.
Transient signal loss on DWI was successfully detected by dynamic EPDWI. The signal loss on DWI and overestimation of ADC could be partially remedied by increasing the number of excitations.
利用单次激发平面回波扩散加权成像（EPDWI）研究腮腺在扩散加权图像（DWI）上的短暂信号丢失及表观扩散系数（ADC）的高估情况。
本研究纳入了6名健康受试者和7名接受放疗的患者。所有参与者均接受了共8次重复的动态EPDWI检查。对DWI的成像质量进行评估。计算ADC严重高估（soADC）的概率，其定义为ADC比值大于1.2。计算T2WI、DWI和ADC上的误差。统计分析包括配对t检验和Mann-Whitney U检验。P值小于0.05被认为具有统计学意义。
在DWI的某些激发上可肉眼观察到短暂信号丢失，但在T2WI或平均DWI上未观察到。soADC在8次激发和3个扩散编码梯度方向上随机出现。放疗组soADC的概率（42.86%）显著高于健康组（24.39%）。所有图像上，平均误差百分比随激发次数增加而降低，且在T2WI上最小，其次是DWI，ADC上的误差百分比按升序排列。
通过动态EPDWI成功检测到DWI上的短暂信号丢失。增加激发次数可部分纠正DWI上的信号丢失和ADC的高估。
