正常胸腺及胸腺病变的ct表现

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1、正常胸腺及胸腺病变—CT表现TheNormalandAbnormalThymus——CTimagingfinding南方医院影像中心2009级博士研究生吕晓飞Content胸腺病变的CT表现3正常胸腺的CT表现2概述1胸腺是一种复杂的淋巴上皮器官，具有调节细胞免疫的功能，在人类正常免疫中是不可缺少的。CT及MR在胸腺异常的诊断中有重要作用，有利于评价是否正常及胸腺病变的范围。概述1正常CT表现（形态、大小、密度）胚胎发育正常胸腺解剖位置及异位胸腺正常胸腺的CT表现2胎儿第6周，胸腺起源于第三及第四咽囊；第7周，胸腺始基延长并呈圆柱状形态，形成胸腺咽管，逐渐移行

2、至前纵隔；第8周，胸腺始基于下极融合；第10周，肝脏组织及骨髓内的小淋巴样细胞移行至胸腺始基；第14~16周，胸腺进一步分化形成皮质及髓质成分。胚胎发育正常胸腺解剖位置位于前上纵隔，上达胸廓入口（甚至突入颈部接近甲状腺下缘），下至心包前面上部，两侧临近纵隔胸膜，后面贴附心包及左头臂静脉及主动脉弓。胸腺的位置上界不超过胸骨柄上缘，下缘不超过左心室上缘或主动脉根部层面，外缘不超过上腔静脉、主动弥弓外缘．其前缘位置正常可随周围结构改变而向左或向右移位。正常胸腺解剖AB异位胸腺Ectopicandaccessorythymictissuemayoccuranywher

3、ealongthepathofdescent(thymopharyngealduct)astheresultoffailureofdescent,sequestration,orfailuretoinvolute.Ectopicoraccessorythymictissuemaybefoundinthevicinityofthesuperiorvenacava,brachiocephalicvessels,andaorta.Rarely,itmaybefoundintheposteriormediastinumoreveninthedermis.异位胸腺Fig

4、ure1.Normalthymuswithacervicalcomponentina12-year-oldboy.(a)Sagittalultrasonographic(US)imageshowsthemediastinalandcervicalcomponentsofthethymus(blackarrows)attachedtothelowerpoleofthethyroid(whitearrow)viathethyrothymicligament(arrowhead).Notethe“starrysky”appearanceofthethymus;thi

5、siscreatedbyhyperechoicfatagainstthebackgroundoftheremaininghypoechoiclymphoidtissue.(b)Correspondinganatomicdrawingshowsthemediastinal(arrowheads)andcervical(arrows)componentsofthethymus.AB异位胸腺Figure2.Cervicalcomponentofthethymusina3-year-oldboywithastrongmaternalfamilyhistoryofpap

6、illarythyroidcarcinoma.Thecervicalcomponentwasmisinterpretedasan“exophytictumorofthethyroidgland.”Contrast-enhancedCTscansshowanormalmediastinalthymus(arrowsinA)anditscervicalcomponent(arrowsinB).Follow-upstudies2yearslatershowednochange,andthepatientremainedasymptomatic.AB异位胸腺Figur

7、e3.Ectopicparapharyngealthymusina7-week-oldboywitha“mass”intherightmandib-ularangle.Coronalcontrastmaterial–enhancedT1-weightedmagneticresonance(MR)imageshowsanenhancingparapharyngealmass(arrow),whichisisointenserelativetothemediastinalthymus(arrowhead).Atneedlebiopsy,themasswasprov

8、edtobeectopicthymic