| Part I Anatomy of the retronasopharyngeal spaceObjective: To further investigate the Magnetic Resonance Imaging(MRI)manifestations of the posterior wall of the nasopharyngeal.Methods:(1)Twenty volunteers without head and neck lesions were examined by MRI scan,including axial T1-Weighted Imaging(T1WI)and T2-Weighted Imaging(T2WI)plain scan,observe MRI manifestations of the posterior wall of the nasopharyngeal.(2)Five formalin-fixed head and neck of adult cadavers were first evaluated by MRI manifestation.They were frozen,cut into cross section and stained with hematoxylin-eosin,while the manifestations of the posterior wall of the nasopharyngeal were observed contrastively between MRI and microscopic examination.Results: MRI that obtained from 20 normal adults and 5 cadavers showed the following results.At the upper 1/2 level of nasopharyngeal,the posterior wall of nasopharynx consisted of four layers from the outside: nasopharyngeal mucosa,fascia,prevertebral muscle and clivus.Bilateral anterior edge of the prevertebral muscle was smooth and continuous low signal fascia shadow by gross observation,which was the fascia layer that consisted of the pharyngobasilar fascia,the buccopharyngeal fascia,the alar fascia and the prevertebral fascia at the microscopic level.The heterogeneous signal was detected in bilateral prevertebral muscle,which was unable to clearly distinguish the posterior boundary of bilateral prevertebral muscle from the basilar clivus.At the lower 1/2 level of nasopharyngeal,the homogeneous signal was detected in bilateral prevertebral muscle,and its anterior edge was smooth while the shadow of the fascia was ambiguous,where the fibrous membranes of the pharyngeal constrictor turned thin distinctly and the pharyngeal constrictor separated it from the posterior fascia(consist of buccopharyngeal fascia,alar fascia and prevertebral fascia)at the microscopic level,furthermore,there was high signal of the fat strip between posterior edge of bilateral prevertebral muscle and the lower clivus.The inferior edge of the anterior arch of the atlas and the soft palate were approximately at the same level.Conclusion: MR can show clearly the structure of fascia,Prevertebral muscle and fat space in the posterior wall of nasopharynx,and inferior edge of the atlas’ anterior arching can be used as a radiographic boundary sign of nasopharynx and oropharynx.Part Ⅱ The routine MR and DWI manifestations of the benign and malignant retropharyngeal lymph nodesObjective: To explore the MR manifestations of retropharyngeal lymph nodes and its value in the differential diagnosis of nasopharyngeal diseases.Methods: The clinical and MRI data in 117 patients with retropharyngeal lymph nodes(RLN)were collected.Their nasopharyngeal diseases were confirmed by clinical or pathology,and 49 cases were divided into benign group and 68 cases were divided into malignant group.We analysized some indicators of the RLN,such as single or bilateral,the signal,the boundary,the minimum and the maximum size,using Bayes discriminant analysis to establish discriminant function and make further judgment on the diagnostic value of its MRI signs.The difference of the diffusion weighted imaging(DWI)signal and apparent diffusion coefficient(ADC)were analysized in the lymph nodes between benign and malignant groups.Using the receiver-operating characteristic curve(ROC)analysis,the minimum and maximum diameter and ADC values of RLN were obtained and the best diagnostic cut-off point was evaluated.Results: There was significant difference in single or bilateral,the signal,the boundary,the path and the minimum and maximum diameter of the RLN between benign group and malignant group(P<0.05).The minimum diameter of the benign and malignant lymph nodes were 6.68±1.59 mm and11.28±4.37 mm respectively,The minimum diameter of the lymph nodes in the judgment of benign or malignant was set at the point where ROC area under the curve was 0.827 with 8.05/8.20 mm as the threshold,thus the sensitivity was 70.1% and specificity was 84.7%.The maximum diameter of the benign and malignant lymph nodes were 8.99±2.31 mm and14.52±5.35 mm respectively,the maximum diameter of the lymph nodes in the judgment of benign or malignant was set at the point where ROC area under the curve was 0.819 with 12.10 mm as the threshold,thus the sensitivity was 63.9% and specificity was 93.9%.With the Bayes step wise discriminant and F test,the variables of the RLN such as single or bilateral,the signal and minimum diameter variables play a significant role in the judgment of the properties of lymph nodes.We established the discriminant function according to these features,the overall diagnostic accuracy was 87% by retrospective analysis and cross checking method.(2)The ADC values of RLN significantly differ between benign and malignant groups and the values were(0.833±0.095)×10-3mm2/s and(0.663±0.070)×10-3mm2/s respectively,(P = 0.000).the ADC value of the lymph nodes in the judgment of benign or malignant was set at the point that ROC area under the curve was 0.959 with 0.767×10-3mm2/s as the threshold value,thus the sensitivity was 78.3% and specificity was 100%.Conclusion: The manifestations of RLN in the routine MRI and DWI was significant difference,which played a indicative role in the judgment of distinguishing nature of nasopharyngeal diseases;and discriminant function can further improve the accuracy of the nature of the lymph node.Part Ⅲ Study on the correlation between the invas ion of retronasopharyngeal space and the occipital skull base in the patients with nasopharyngeal carc inomaObjective: To analyze the correlation between the invasion of retronasopharyngeal space and the occipital skull base in patients with nasopharyngeal carcinoma(NPC),and explore the value of the invasion of the retronasopharyngeal space in staging of NPC.Methods: A group of 152 new NPC patients without treatment examined by MRI were collected.The regularities of surrounding tissue invasion and cervical lymph node metastasis in NPC patients were summarized,meanwhile the relationship between the RLN metastasis and invasion of prevertebral muscle,invasion of prevertebral muscle and occipital skull base invasion were analyzed respectively.Results:(1)The most common lymph nod earea invasioned by NPC was the Ⅱ area neck lymph node(97.36%),followed by Ⅲ area(85.52%)and RLN(68.42%).Using relevance of the chi square test,Spearman rank correlation coefficient of the RLN metastasis and invasion of prevertebral muscle was-0.088(P=0.283),which showed no significant correlation between the RLN metastasis and the invasion of prevertebral muscle in NPC.(2)The most common muscle invasioned by NPC was the prevertebral muscle(59.21%),followed by pharynx s ide clearance(52.63%)and the base of the occipital(36.84%).Spearman rank correlation coefficient between the invasion of prevertebral muscle and occipital skull base invasion in NPC patients was 0.507(P=0.000),which indicated to have a significant correlation between the invasion of prevertebral muscle and occipital skull base bone invasion.Conclusion: The invasion of prevertebral muscle and occipital skull base bone have a significant correlation,which indicated to the clinical value of prevertebral muscle invasion and occipital skull invasion may were similar,The invasion of prevertebral muscle should be considered in the further study.Part Ⅳ The survival analysis of posterior fascia space invasion and retropharyngeal lymph node metastasis in NPC PatientsObjective: To investigate the effect of invasion of posterior fascia space and RLN metastasis on the prognosis of patients with NPC.Methods: A group of 108 new NPC patients without treatment were examined by MR,using COX proportional hazards regression model to conduct a multi factorial analysis on the prognosis of patients with NPC,including sex,age,the invasion of parapharyngeal space,prevertebral muscle,medial pterygoid muscle,skull base bone and the lymph node metastasis of the lateral pterygoid muscle,cavernous sinus invasion and RLN,I,II,III IV,V area.All the patients were divided into retropharyngeal lymph metastasis group and non-retropharyngeal lymph node metastasis group,invasion of prevertebral muscle group and non-invasion group,invasion of prevertebral muscle group and invasion of prevertebral muscle accompanying with occipital skull base invasion group.All cases were definited into the different TMN stage according to NPC staging criteria,the Local recurrence-free(LRFS),Distant metastasis-free Survival(DMFS)and O verall S urvival(OS)were calculated by Kaplan-Meier method and conducted by Log-rank test in every group.Results:(1)The prevertebral muscle invasion was one of independent prognostic factors for LRFS(P=0.045)and OS(P=0.004)using COX regression multi-available analysis,and age was one of independent prognostic factors for OS(P=0.027);(2)There were significant difference in LRFS(P=0.042),DMFS(P=0.012)and OS(P=0.030)between the prevertebral muscle invasion group and non-invasion group using Kaplan-Meier calculation and Log-rank test.However,there were no significant difference in LRFS,DMFS and OS between RLN metastasis group and non-metastasis group,prevertebral muscle invasion group and prevertebral muscle accompanying occipital skull base invasion group(P>0.05).(3)There were significant difference in DMFS(P = 0.040)and OS(P = 0.048)among different N staging NPC patients groups while there was no statistically significant difference in LRFS(P = 0.310)among groups.Otherwise,LRFS,DMFS and OS had no statistically significant difference(P>0.05)among different T stage and clinical staging for NPC patients.Conclusion: The prevertebral muscle invasion was one of independent prognostic factors for DFMF and OS in NPC patients,and age was one of independent prognostic factors for OS.The clinical value of prevertebral muscle invasion and occipital skull invasion were similar in NPC patients.Patients with prevertebral muscle invasion were classified as T3 stage may be more reasonable. |
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