| Part one:The microstructure characteristics of temporal lobes white mater after radiation therapy for nasopharyngeal carcinomaObjective:To detect the microstructure characteristics of temporal lobes white mater after radiation therapy (RT) for nasopharyngeal carcinoma (NPC) using diffusion tensor imaging.Materials and methods:The study included64subjects (46male,18female, aged18-65years mean:44years), who had or had not undergone radiotherapy for nasopharyngeal carcinoma. All diagnoses were confirmed by histopathology. Of the64subjects,16were pre-treatment patients; the remaining48were post-radiation patients. The time from radiotherapy to imaging ranged from several days to4years. Three-dimensional conformal radiation therapy was used in the protocol for nasopharynx and neck radiotherapy. Nasopharynx radiotherapy involved a total dose of66-72Gy divided into33to36fractions, and was performed over a course of43to51days. Before patients underwent MRI examination, we confirmed that there were no signs of intracranial invasion of nasopharyngeal carcinoma or of intracranial tumor. Patients with white matter degeneration, vascular lesions, high blood pressure, diabetes, or heart disease were excluded from the study, as these lesions or diseases affect the DTI data measurements.The pre-radiation subjects constituted the control group. The post-radiation patients were divided into three groups according to the domestic and international staging systems for classifying radiation-induce brain injury. Group I included patients who had undergone radiation therapy less than6months prior, representing an acute response in the early period after radiation therapy. Post-radiation patients in the late delayed reaction period were divided into2groups:Group II included cases who had undergone radiotherapy6-12months prior while Group III included those who had undergone radiotherapy more than12months prior. Each group consisted of16subjects. There were no statistically significant differences between the groups with respect to age, gender, duration of education, cigarette smoking or alcohol consumption.MRI was performed using a Philips Achieva1.5-T Nova Dual MR scanner. DTI used a sixteen-channel head coil, obtaining DTI images. Diffusion imaging data were acquired using a32diffusion gradient direction scheme (b=800s/mm2) along32non-collinear directions plus b=0reference images acquired using a single-shot spin-echo planar sequence parallel to the AC-PC line to collect diffusion weighted images. Other imaging parameters were:TR=10793ms, TE=62ms, field of view=230×230mm2, matrix=128×128, slice thickness=2mm, with no slice gap, voxel size=2x2x2mm3.DTI post-processing used DTIStudio. After converting the raw perfusion data to the NIFTI format using MRIcro software, DTIStudio was applied to correct for head movement and eddy current. A fractional anisotropy (FA) map and eigenvalue images were generated based on the corrected DTI images. The FA value λ‖and λ⊥were calculated for each voxel.To find the layer of cerebral peduncle, one ROI were then marked on unilateral temporal lobe white matter in each subject. These ROIs were of equal area. The average of these values in the temporal lobes white matter was accepted as the final value.Statistical analysis was performed using SPSS version13.0software. One-way analysis of variance and two-sample t-tests were used to assess the differences in age, duration of education, cigarette smoking, and alcohol consumption across the groups. Pearson’sχtest was used to see the gender differences between the groups. All DTI data were examined for homogeneity of variance using one-way analysis of variance (ANOVA). The statistical differences between the groups were further examined using the Bonferroni method, with p<0.05accepted as statistically significant.Results:FA:Analysis of variance showed statistically significant differences between the groups with respect to FA value. Further group-wise comparisons showed that the FA value decreased significantly in the three post-radiation groups compared to the pre-radiation group; the FA value in Group Ⅱ increased significantly compared to Group Ⅰ; the FA value in Group Ⅲ was higher than that in Group Ⅱ, though with no significant difference, while it was significantly higher than in Group Ⅰλ‖:Analysis of variance showed statistically significant differences between the groups with respect to λ‖eigenvalue. Further group-wise comparisons showed that λ‖decreased significantly in the three post-radiation groups compared to the pre-radiation group; λ‖in Group Ⅲ was higher than that in Group Ⅱ, though with no significant difference, while it was significantly higher than in Group Ⅰ λ⊥:Analysis of variance showed statistically significant differences between the groups with respect to λ⊥. Further group-wise comparisons showed that λ⊥increased significantly in Group I compared to the pre-radiation group.Conclusion:The results of the present study illustrated microstructural changes occur in brain tissue that appears normal on routine MR imaging in patients with NPC after radiotherapy. The microscopic pathological changes in the early after irradiation of the brain improves some time after the cessation of radiotherapy. Radiation-induced brain injury of the temporal lobe exist for a considerable period of time, so making long-term clinical follow-up using DTI for dynamic monitoring of radioactive encephalopathy is of great clinical significance for radiotherapy patients who suffer from NPC. Part two:The hemodynamic characteristics of temporal lobes white mater after radiation therapy for nasopharyngeal carcinomaObjective:To detect the hemodynamic characteristics of temporal lobes white mater after radiation therapy (RT) for nasopharyngeal carcinoma (NPC) using dynamic susceptibility contrast-enhanced perfusion-weighted imaging.Materials and methods:The study included64subjects (46male,18female, aged18-65years mean:44years), who had or had not undergone radiotherapy for nasopharyngeal carcinoma. All diagnoses were confirmed by histopathology. Of the64subjects,16were pre-treatment patients; the remaining48were post-radiation patients. The time from radiotherapy to imaging ranged from several days to4years. Three-dimensional conformal radiation therapy was used in the protocol for nasopharynx and neck radiotherapy. Nasopharynx radiotherapy involved a total dose of66-72Gy divided into33to36fractions, and was performed over a course of43to51days. Before patients underwent MRI examination, we confirmed that there were no signs of intracranial invasion of nasopharyngeal carcinoma or of intracranial tumor. Patients with white matter degeneration, vascular lesions, high blood pressure, diabetes, or heart disease were excluded from the study, as these lesions or diseases affect the DSC-PWI data measurements.The pre-radiation subjects constituted the control group. The post-radiation patients were divided into three groups according to the domestic and international staging systems for classifying radiation-induce brain injury. Group Ⅰ included patients who had undergone radiation therapy less than6months prior, representing an acute response in the early period after radiation therapy. Post-radiation patients in the late delayed reaction period were divided into2groups:Group Ⅱ included cases who had undergone radiotherapy6-12months prior while Group Ⅲ included those who had undergone radiotherapy more than12months prior. Each group consisted of16subjects. There were no statistically significant differences between the groups with respect to age, gender, duration of education, cigarette smoking or alcohol consumption.MRI was performed using a Philips Achieva1.5-T Nova Dual MR scanner. Perfusion imaging used a sixteen-channel head coil, obtaining PWI images. Perfusion imaging of the temporal lobe was performed using a single-shot spin-echo version of an echo planar (SE-EPI) pulse sequence, parallel to the AC-PC line, with the following imaging parameters:TR=1000ms, TE=30ms, field of view=202×202mm2, matrix=115×116, voxel size=1.9×1.9×1.9mm3, slice thickness=5mm, slice gap=0.30mm, slice=11,45phases. A total of495images was acquired after an intravenous injection of0.2mmol/kg body weight of Gd-GTPA, with a5mL/s injection rate followed by a saline flush of20mL with the same injection rate using an automatic power injector. The acquisition time was89s.The Extended MR workspace was used for post-processing of PWI images. Software developed in-house (Neuro Perfusion software) was used to open the PWI scan data in the Extended MR workspace; the T2W imaging position image and the rCBF map were received automatically. Next, one ROI were drawn on unilateral temporal lobe in the layer of cerebral peduncle in each subject. These ROIs were of equal area. The average of the ROIs’ parameters’ values in the bilateral temporal lobe white matter was accepted as the final rCBF value.Statistical analysis was performed using SPSS version13.0software. One-way analysis of variance and two-sample t-tests were used to assess the differences in age, duration of education, cigarette smoking, and alcohol consumption across the groups. Pearson’s x test was used to see the gender differences between the groups. All DSC-PWI data were examined for homogeneity of variance using one-way analysis of variance (ANOVA). The statistical differences between the groups were further examined using the Bonferroni method, with p<0.05accepted as statistically significant.Results:The differences between the groups with respect to rCBF were statistically significant. Further group-wise comparisons showed that the rCBF in each post-radiation group decreased significantly compared to the pre-radiation group. The decrease was greatest in Group Ⅰ (0-6months after radiotherapy); the rCBF in Groups Ⅱ and Ⅲ was higher than that in Group Ⅰ but without significance; the rCBF was higher in Group Ⅲ than in Group Ⅱ but without significance. Conclusions:The results of the present study illustrated circulatory changes occur in brain tissue that appears normal on routine MR imaging in patients with NPC after radiotherapy. Vascular damage and the resulting decrease in blood flow may play a significant role in neural tissue injury in the early stages after radiotherapy. In later stages, improvement of the vascular damage may contribute to the recovery of radiation-induced brain injury. Vascular damage may play a significant role in radiation-induced brain injury. Radiation-induced brain injury of the temporal lobe exist for a considerable period of time, so making long-term clinical follow-up using PWI for dynamic monitoring of radioactive encephalopathy is of great clinical significance for radiotherapy patients who suffer from NPC. Part three:To explore the Gary Matter volume abnormalities after radiation therapy for nasopharyngeal carcinomaObjective:To explore the Gary Matter (GM) volume abnormalities in after radiation therapy (RT) for nasopharyngeal carcinoma by using high resolution MRI and DARTEL-VBM.Materials and methods:This study was carried out in8patients (12male,3female; age range,34-54years; mean age,44years) with a histopathologically established diagnosis of NPC, who received fractionated radiation therapies with3D conformal techniques (total doses/daily fraction/exposures/,68-70GY/2.0GY/34-35times). Each patient received MRI examinations before and1-2months after completion of the radiotherapy. No patient exhibited distinct neurological symptoms or showed signs of intracranial invasion or intracranial tumors before imaging. Patients were excluded from the study who presented with white matter degeneration, vascular lesions, hypertension, heart disease or diabetes.MRI was performed using a Philips Achieva1.5-T Nova Dual MR scanner. Perfusion imaging used a sixteen-channel head coil, obtaining3D-T1images.3D-T1imaging was performed using a three-dimensional fast field echo (FFE) pulse sequence, parallel to the AC-PC line, with the following imaging parameters:TR=4.1ms, TE=25ms, field of view=230×230mm2, matrix=231×231, slice thickness=1mm, slice gap=0mm, slice=1mm.The DARTEL tool, a extention tool of SPM, was used to perform anatomical images analysis. the main procedures include:(1) the naive image of all the subjects were segmented to obtain the*seg.sn.mat profile, which was then imported to DARTEL for calculateing and getting GM image for each participant.(2) create GM template using DARTEL.(3) use the GM template to normalize each participant’s GM with.(4) modulate the resulting GM images with a Jacobian determinant, then the voxel’s values indicate the absolute volume of the local GM.(5) use a12-mm full width at half maximum (FWHM) isotropic Gaussian kernel to smooth resulting images.(6) the GM was transformed to the MNI coordinate for SPM analysis. And then these preprocessed GM data was analysised by using SPM8through GLM and random field theory. The differences between two group was determined by a voxel based comparison. a cluster-level threshold of p<.05were set to produce statistical maps, which was corrected for multiple comparisons using false discovery rate (FDR).Results: The right hippocampus volume was significantly increased in patients with nasopharyngeal carcinorma compare with before radiotherapy (p<0.05, FDR correction, corrected, clusters=100mm3). No GM volume increased.Conclusions:The significantly increase of right hippocampus volume may be attributed to functional compensatory hypertrophy under the condition of temporal white matter injury, or damage of grey matter and inflammatory reaction. Radiotherapy may also have an effect on gray matter. High resolution imaging and VBM-DARTEL can detect radiation induced grey matter injury. |
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