Optimization of magnetic resonance sequences in lymph node staging of nasopharyngeal carcinoma / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Detection rate of retropharyngeal lymph node metastasis in patients with nasopharyngeal carcinoma (NPC) needs to be improved. The purpose of this study was to compare three magnetic resonance (MR) sequences for detecting lymph nodes in patients with NPC.</p><p><b>METHODS</b>Between July 2007 and March 2008, MR staging of pre-treated tumor was conducted on 120 patients with pathologically confirmed NPC. The outcome of three different sequences for MR NPC staging were compared: coronal short TI inversion recovery (STIR), axial proton density fat-suppressed (PDWI fs), and coronal contrast enhanced fast spin echo T1 weighted fat-suppressed (CE FSE T1WI fs). Nodal classification method (1999) was applied to count the number of retropharyngeal and cervical lymph nodes discovered by each MR sequence. Paired t tests were used for statistical analysis.</p><p><b>RESULTS</b>A total of 2575 lymph nodes were found using coronal STIR sequence; 1816 lymph nodes for coronal CE FSE T1WI fs sequence and 2638 lymph nodes for axial PDWI fs sequence. Significant differences existed in the number of lymph nodes detected by axial PDWI fs and coronal CE FSE T1WI fs sequence (paired t test, P < 0.05), with the former sequence getting higher numbers. Statistical differences also existed between coronal STIR and coronal CE FSE T1WI fs sequence (paired t test, P < 0.05), with the former sequence getting higher numbers. No significant difference was found between coronal STIR sequence and axial PDWI fs sequence (paired t test, P > 0.05).</p><p><b>CONCLUSIONS</b>For the detection of retropharyngeal and cervical lymph nodes, coronal STIR sequence and axial PDWI fs sequence have similar performance and both sequences showed better detection than CE FSE T1WI fs sequence. Furthermore, by combining coronal STIR sequence and axial PDWI fs sequence, we can improve the detection of lymph nodes in NPC N-staging before treatment, especially for lymph nodes located in the thoracic entrance.</p>

Image quality stability of whole-body diffusion weighted imaging / 中国医学科学杂志(英文版)

<p><b>OBJECTIVE</b>To assess the reproducibility of whole-body diffusion weighted imaging (WB-DWI) technique in healthy volunteers under normal breathing with background body signal suppression.</p><p><b>METHODS</b>WB-DWI was performed on 32 healthy volunteers twice within two-week period using short TI inversion-recovery diffusion-weighted echo-planar imaging sequence and built-in body coil. The volunteers were scanned across six stations continuously covering the entire body from the head to the feet under normal breathing. The bone apparent diffusion coefficient (ADC) and exponential ADC (eADC) of regions of interest (ROIs) were measured. We analyzed correlation of the results using paired-t-test to assess the reproducibility of the WB-DWI technique.</p><p><b>RESULTS</b>We were successful in collecting and analyzing data of 64 WB-DWI images. There was no significant difference in bone ADC and eADC of 824 ROIs between the paired observers and paired scans (P>0.05). Most of the images from all stations were of diagnostic quality.</p><p><b>CONCLUSION</b>The measurements of bone ADC and eADC have good reproducibility. WB-DWI technique under normal breathing with background body signal suppression is adequate.</p>