Diffusion Kurtosis as an in vivo Imaging Marker of Early Radiation-Induced Changes in Radiation-Induced Temporal Lobe Necrosis in Nasopharyngeal Carcinoma Patients.

PURPOSE: Diffusion kurtosis imaging (DKI), an extension of the popular diffusion tensor imaging (DTI) model, has been applied in clinical studies of brain tissue changes. We explored the value of DKI for the early detection of radiation-induced changes in temporal lobe necrosis (TLN) after radiotherapy (RT) for nasopharyngeal carcinoma (NPC). METHODS: A total of 400 patients with NPC were retrospectively enrolled; all participants underwent MRI scans 0-7 days before RT, at 4 weeks during RT, and 1 month after completing RT. DKI-derived kurtosis parameters (mean kurtosis [MK], axial kurtosis [Ka], radial kurtosis [Kr]), and DKI-derived diffusion parameters (fractional anisotropy [FA], mean diffusivity [MD], axial diffusivity [λa], radial diffusivity [λr]) were assessed in temporal lobe white matter. RESULTS: Analysis was performed for 20 patients with temporal lobe necrosis following long-term follow-up. No brain abnormalities were visible on conventional MRI in any patient at 4 weeks during RT and 1 month after RT. Of all DKI-derived parameters, MK was significantly lower at 1 month after RT than before RT (P < 0.05). CONCLUSION: This study indicates DKI can detect the early presence of relatively subtle RT-induced brain abnormalities before TLN in patients with NPC and may provide a sensitive imaging technique for temporal white matter microstructural abnormalities that are silent on conventional modalities but precede TLN after RT.

Diffusion tensor imaging of association fiber tracts in amnestic mild cognitive impairment / 中国医学影像技术

Objective To investigate the characteristics of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of association fiber tracts in patients with amnestic mild cognitive impairment (aMCI), and to assess the application value of diffusion tensor imaging (DTI) in differential diagnosis of aMCI and AD. Methods DTI were performed in 20 patients of aMCI (aMCI group), 20 patients of AD (AD group) and 20 normal control subjects (control group). FA and ADC values were calculated in the regions of interest (ROI) in inferior fronto-occipital fasciculus (IFOF), genu and splenium of corpus callosum, superior longitudinal fasciclesⅡ (SLFⅡ) and cingulated bundles. Results There was significant difference of FA values in inferior fronto-occipital fasciculus and cingulate bundles between aMCI group compared with control group (P<0.05), as well as of FA values in cingulate bundles between aMCI group and AD group (P<0.05). Conclusion Abnormal FA values in inferior fronto-occipital fasciculus and cingulate bundles suggest that DTI can be used as a diagnosis index of aMCI. Furthermore, it is helpful in the differential diagnosis of aMCI and AD.

A new approach to research graphical performance of MRI RF coil based on the quantitative comparison method / 中国医疗器械杂志

<p><b>OBJECTIVE</b>To compare the performance of three different types of RF coil in 3.0T MRI, the signal-to-noise ratio (SNR) and image uniformity in 3.0 Tesla magnetic resonance imaging system have been studied.</p><p><b>MATERIALS AND METHODS</b>In addition to the measurement of SNR and Uniformity based on the protocol recommend by AAPM, the images had also been analyzed using SPSS and MATLAB to get the SNR distribution along two vertical direction and the whole imaging plane.</p><p><b>RESULTS</b>The SNR with T/R birdcage coil and 8-ch surface coil is seven and twelve times higher than surface coil in the region of interest (ROI), which was set in the center of the phantom images. With regard to the spatial variation of sensitivity, the uniformity of T/R birdcage coil and 8-ch surface coil are also much higher than that of surface coil.</p><p><b>CONCLUSION</b>The images from T/R birdcage and phased array coils are all better than those of surface coil. The SNR of the images from phased array coil is highest while the uniformity of the images from T/R birdcage coil is highest.</p>